Elucidating the Role of Plant Extracts Mediated Gold Nanoparticles as Smart Antimicrobials: Two-Way Attack

Balkrishna, Acharya; Rohela, Akansha; Kumar, Ashwani; Mishra, Shalini; Arya, Vedpriya; Kala, Vandana; Thakur, Naveen; Thakur, Nikesh; Kumari, Amita; Khan, Nazam

doi:https://doi.org/10.1155/2023/4085090

Journal of Nanomaterials

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Abstract Introduction Conclusion Data Availability Conflicts of Interest Authors’ Contributions Acknowledgments References Copyright Related Articles

Review Article | Open Access

Volume 2023 | Article ID 4085090 | https://doi.org/10.1155/2023/4085090

Elucidating the Role of Plant Extracts Mediated Gold Nanoparticles as Smart Antimicrobials: Two-Way Attack

Acharya Balkrishna,¹Akansha Rohela,²Ashwani Kumar,²Shalini Mishra,²Vedpriya Arya,^2,3Vandana Kala,²Naveen Thakur,⁴Nikesh Thakur,⁴Amita Kumari,⁵and Nazam Khan⁶

Academic Editor: Kaliannan Durairaj

Received09 Feb 2023

Revised03 Jul 2023

Accepted12 Jul 2023

Published10 Aug 2023

Abstract

Pathogenic bacteria remain the primary health concern even after developing a broad spectrum of antibiotics. The emergence of drug-resistant strains increased mortality, perhaps resulting in a never-ending future pandemic. The researchers are currently concentrating their efforts on nanotechnology-based therapies to counteract resistance. The present review focuses on the antimicrobial characteristics of plant-mediated gold nanoparticles (Au NPs). First, the methodology and importance of green synthesis are highlighted. Variability in NPs characterization methods was identified, with dynamic light scattering, zeta potential, and thermogravimetric analysis limited to a few investigations. Second, the Au NPs synthesized using different plant extracts were found to be broad-spectrum antimicrobial agents against Pseudomonas aeruginosa, Escherichia coli, Cryptococcus neoformans, Candida glabrata, Aspergillus niger, etc. The lowest minimum inhibitory concentrations range (1.95–15.62 µg/mL) was observed with Au NPs synthesized using Thymus vulgaris extract against Staphylococcus aureus, P. aeruginosa, Bacillus subtilis, and E. coli. The effect was more pronounced with smaller NPs (<10 nm). The activity of Au NPs might be mediated through a two-way attack which includes nanoparticles’ diverse mechanisms like reactive oxygen species generation, etc., and surface-attached phytocompounds such as flavonoids, alkaloids, phenolics, terpenoids, tannins, etc. The futuristic role of nanotechnology-based interventions in managing microbial infections is imperative. Synergistic interactions of Au NPs with antibiotics, toxicity profiling, stability, and bioavailability could be major areas of NPs research.

1. Introduction

Bacterial infections continue to be a leading cause of morbidity and mortality. The emergence of multidrug-resistant bacterial strains and biofilm-associated illnesses necessitates the development of new antimicrobials [1, 2]. Every year, more than 2 million antibiotic-resistant illnesses occur in the United States, resulting in 23,000 fatalities, according to the US Centers for Disease Control and Prevention [3]. Antibiotic-resistant pathogens are responsible for 25,000 deaths yearly in the European Union [4]. Antibiotic misuse and abuse greatly favor resistance among bacterial pathogens which is a prime cause of the lack of efficacy of existing antimicrobials. Unfortunately, more than 70% of all harmful microorganisms resist at least one standard antibiotic [5]. In addition, biofilm formation also makes it more challenging to treat various infections [6]. The development of new antimicrobials is the need of the hour; one of the most promising candidates in this setting could be the nanoparticles (NPs). Due to their high surface area-to-volume ratio and unique features, nanoscale materials have emerged as potential antimicrobial agents [7, 8]. The antimicrobial activity of NPs such as Ag, Au, Pt, MgO, CuO, Al, CdS, TiO₂, Cr₂O₃ NPs, and others has been reported against several drug-resistant bacterial and fungal species [9–17]. In continuation, NPs can replace antibiotics for treating bacterial infections caused by Enterococcus faecium, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus [18].

Toxic substances used in physical and chemical procedures may reside in the generated NPs, creating a concern for the environment and limiting their application in medicine [19]. So, now researchers are shifting toward synthesizing NPs using a green approach. Plant extracts, microorganisms, and other natural products are commonly used in the green synthesis of NPs [20–22]. Most of the NPs have been synthesized using plant materials, including leaves, flowers, bark, etc. Instead of using chemical reagents, all of these plant parts include polyphenols and proteins that can reduce metal ions into their lower valence states [23, 24]. Subsequently, bacteria, algae, and fungi are also employed because they have high concentrations of the reductase enzymes that transform the ionic form into its nano form [25]. Furthermore, the ease of growing and controlling the shape and size of synthesized NPs can drastically lower the cost of producing enormous amounts [26].

The processes of NPs synthesis from various sections of plants are cost-effective, environmentally benign, and simple [27, 28]. In addition, plant extracts also offer the benefit of reducing metal ions in less time [28]. Several nanoparticles, such as TiO₂ using Azadirachta indica [29], CuO using Ocimum tenuiflorum [30], and ZnO using Aloe vera [31] synthesized using the green approach were found to be effective antimicrobials. Among nanoparticles, metal and metal oxide NPs had remarkable biomedical activity [27]. Metallic NPs have also been shown to be efficient against diverse pathogens and their selectivity for bacterial strains [32]. Further, metallic NPs have been used in conjunction with antibiotics to overcome antibiotic resistance and improve the latter’s efficacy [33, 34]. Different NPs use diverse mechanisms to inhibit pathogens, and metallic NPs, in particular, have been found to penetrate the bacterial cell wall and create pores on the surface of the membrane, causing free radical production that damages the cell membrane [35]. Subsequently, NPs’ ions can inhibit enzyme production and produce reactive oxygen species (ROS). In addition, it has been shown that the transcription of DNA is affected [36].

Au NPs have many benefits over other NPs, and some of the advantages include easy synthesis using several methods [37]; exclusive chemical, physical, and optical properties because of size and shape [38]; a high surface area that provides compact drug loading and easily can reach to the target site through blood flow [39], and importantly, noncytotoxic to the normal cells [40]. Suchak et al. [41] reported that Au NPs were active at higher concentrations (0.005 M) against Gram-positive and negative bacterial strains. Likewise, the broad-spectrum antibacterial potential of Au NPs is also documented by other researchers [42]. Keeping in view the importance of Au NPs, the antimicrobial potential of plant-mediated Au NPs has been reviewed. The synthesis of Au NPs utilizing a plant-mediated green technique is thoroughly covered in this article, along with their broad-spectrum antibacterial activity. The significance of particle size, plant selection, and several other aspects have all been described in detail. Early reviews focused only on synthesis techniques or antibacterial potential; however, more thorough investigations highlighting the different research gaps are still necessary. The antibacterial mechanism of Au NPs is outlined in light of existing literature, and the mode of action of phytoconstituents against microbial pathogens is also illustrated.

2. Green Synthesis of NPs: Factors Affecting the Formation of NPs

Metallic NPs applications in healthcare have drawn a lot of attention. Scientists for synthesizing NPs have devised several methods, but their use is constrained by harmful chemicals, high-energy demands, and the release of toxic byproducts [43, 44]. For overcoming the drawbacks of physicochemically produced NPs, biological or green synthesis methods have proven to be effective solutions. Compared to other methods, NPs synthesized by biological means have enhanced characteristics for use in biomedical applications [45]. Green synthesis is an economical, easy, eco-friendly, and efficient approach to forming NPs through microorganisms and plants [46–48]. Microorganism-derived NPs are overwhelmed by plant-derived NPs owing to their single-step, nonhazardous process. Another downside of the microbial synthesis approach is time-consuming and expensive downstream processing [45, 49]. The biological synthesis precursors, the process, and the factors affecting NPs synthesis and characterization detail are depicted in Figure 1.

During the NPs synthesis process, it is crucial to consider the selection of a solvent, a safe reducing agent, and a nontoxic component for NPs stabilization [51]. Additionally, several parameters, including pH, salt content, incubation time, temperature, centrifugation, and reaction time, must be optimized to increase the effectiveness, size, and morphology of NPs generated using a green approach [50, 52]. To prevent the development of large aggregated NPs, the concentration of the reducing agent must be optimized. Thermal heating needs to be regulated simultaneously during synthesis; it can denature the bioactive molecules associated with the capping and stabilization of NPs. Altering the concentration of bioactive chemicals can improve the reaction rate. Subsequently, there are several drawbacks, such as the complexity of identifying the plant bioactive components responsible for the synthesis of NPs that influence their therapeutic effects [52, 53].

Additionally, temperature is one of the most significant factors for synthesizing NPs [53]. At higher temperatures (60°C), Mountrichas et al. [54] showed a faster and more uniform synthesis of NPs. The influence of pH on the synthesis of Ag NPs was studied by Gontijo et al. [55], who observed different-sized NPs (5–249 nm) at pH values between 2 and 9. The authors also observed fewer aggregated NPs at a pH <3 and >7. On the other hand, Traiwatcharanon et al. [56] used UV–Vis spectroscopy and transmission electron microscopy to study the impact of pH on the nature of Ag NPs. The authors noticed that when Ag NPs were synthesized in an acidic medium as opposed to a basic one, smaller size particles were produced. Optimizing the reducing agent’s concentration will help prevent the formation of large aggregated NPs. Ahmad et al. [57] used different concentrations of Au(III) (0.51–4.055 mM) for the synthesis of Au NPs using aqueous Elaeis guineensis (palm oil), where Au NPs were not formed at a concentration <1.53 mM. According to the authors, the reduction reaction is too weak because of the extremely low Au(III) concentration, which needs validation. The effects of pH, reaction medium, and reaction time on the synthesis of Ag NPs from mangosteen (Garcinia mangostana) leaf extract were investigated by Veerasamy et al. [58]. According to the authors, primary conditions promote the formation of Ag NPs, while acidic solutions hinder this process. Similarly, the author reported more NPs production at longer reaction times. At pH 4, the authors reported large-sized NPs, but at pH 8, they reported small-sized, extensively dispersed NPs. Different parameters need to be optimized for the synthesis of NPs as they affect reaction rate, size, shape, and biological potential.

3. Green Synthesis of Au NPs

Au NPs can be prepared by several physical and chemical approaches [43, 44]. However, their usage in biomedical applications is confined due to high energy consumption and the formation of hazardous byproducts [48]. Green synthesis, which includes plants, fungi, bacteria, actinomycetes algae, etc., could be utilized as a cost-effective, biocompatible, and eco-friendly approach [27, 59–62]. Diverse phytocompounds, like alkaloids, terpenoids, phenolics, etc., assist in metal ion reduction and stabilization during green synthesis [63]. The liquefied Au ions get condensed into Au NPs with the help of biological agents in the green approach. This approach led to various unique chemical and physical properties of Au NPs, such as a large surface-to-volume compared to bulk material with the same composition, with diverse applications like catalytic, drug delivery, anticancer, antibacterial, etc. [62]. The green approach can control the morphology (shape and size) of Au NPs that play a substantial role in diverse applications [64, 65].

To synthesize Au NPs, Au metal precursor solution is mixed with plant extract, a reducing and stabilizing agent [66]. Au NPs’ synthesis process consists of a three-phases, reduction, nucleation, and crystal nuclei growth [67, 68]. In the first phase (reduction), the precursor gets reduced while Au atoms continuously increase [69]. In the second phase (nucleation), the Au atoms form crystal nuclei when they reach the critical super-saturation, and the concentration of Au atoms starts to decrease [70, 71]. Crystal nuclei stop growing when the concentration falls below saturation, resulting in the formulation of pure Au NPs [72, 73]. An overview of various synthesis methods and the plant-mediated synthesis process is highlighted in Figures 2 and 3, respectively.

Plant extracts were used in several investigations to generate Au NPs, although the precise reaction mechanism is still unknown [74, 75]. Using a putative mechanism, Ahmad et al. [76] described how an extract from the leaves of E. guineensis might reduce Au³⁺ and stabilize Au NPs. The authors claim that most phenolic compounds, such as caffeic, ferulic, protocatechuic, and gallic acids, contain hydroxyl and carboxylic groups in their structure, which trigger the metallic ions to transform into metal particles [77]. Due to their exceptional binding potential, phenolic compounds (gallic acid) convert Au³⁺ into gold atoms by releasing electrons. Quinones and Au NPs are formed during the oxidation of gold intermediate complexes generated during the reduction reaction. Quinones create repulsive forces that inhibit aggregation and improve colloidal stability as they bind to the surfaces of Au NPs through carbonyl groups. In the literature, it has also been reported that quinones, which bind to Au NPs via negatively charged carbonyl groups, can serve as bio-capping agents similar to gallic acid. Catechin oxidation reduces Au ions, resulting in semiquinone, which is further oxidized to create stable quinones. Due to hydroxyl oxidation, stable quinones produce negatively charged carbonyl groups that cover reduced gold atoms [78]. During the conversion of enol to quinonoid, the generated electrons reduce Au³⁺ ions to gold atoms. The mechanistic component of creating NPs via environmentally friendly techniques requires more study [46].

3.1. Pros and Cons of Various Synthesis Methods

Several chemical, physical, and biological techniques have been used to create Au NPs. Some chemical processes utilized to create Au NPs include Turkevich, Brust, seed-mediated development, and digestive ripening [79]. The Turkevich method is quite simple and reproducible for producing spherical particles between 10 and 30 nm, but as the size increases, they become less spherical [80]. The burst approach produced heat and air-stable NPs and used organic solvents that were not water-miscible, limiting these materials’ applicability in biological systems [81]. Chemical processes have several benefits, including low cost, high yield, size controllability, and heat stability. These techniques have some drawbacks, including low purity, the usage of hazardous compounds, and organic solvents. Chemical techniques also have inherent limits, such as environmental issues and biocompatibility. Therefore, physical methods have numerous benefits, including rapid speed, no use of hazardous chemicals, and uniform size and shape. Limitations of this technique include high costs, radiation exposure, high energy requirements, temperature, and pressure requirements, decreased stability, changing surface chemistry, and altered physicochemical features of NPs [82].

Au NPs can now be produced biologically in a way that is easy, safe, environmentally friendly, nontoxic, and biocompatible [79]. There have been reports of employing fungi, plants, algae, and bacteria to synthesize Au NPs. Microbial methods necessitate time-consuming and expensive downstream processing. Additionally, because removing mycelia from culture filtrates is challenging, so fungus biomass preparation for the synthesis process necessitates cautious measures. Also, some species of microorganisms are pathogenic [83–85]. Algae require a long time to grow, making the process tedious and time-consuming. However, synthesizing Au NPs from algal biomass is very simple and easy. Plant-mediated synthesis is an eco-friendly approach and has several advantages over other methods. The drawback of employing plants for Au NPs formation is that it is challenging to identify the reactive components because plant biomass includes diverse components [86–88].

4. Antimicrobial Profile of Au NPs

Since the advent of nanotechnology, many Au NPs have been deployed in various fields because of their exceptional value. Because of its inertness and nontoxicity, gold can conjugate with multiple metals to generate highly stable alloys [89]. Due to their excellent therapeutic effectiveness and negligible side effects, Au NPs have recently piqued the interest of researchers intensely in treating clinically important bacteria, fungi, and parasites. Lately, the foremost concerns that imperil society’s health are emerging diseases and the surge in antibiotic resistance among microbes via different unknown pathways [90]. A range of studies has indicated that various green synthesized plant-based Au NPs played an essential role in protecting against various microbes.

In this context, Actinidia deliciosa fruit synthesized Au NPs damaged the cell membrane of P. aeruginosa, as evidenced by transmission electron microscopy [91]. Emmanuel et al. [92] revealed the remarkable antimicrobial effect of Justicia glauca leaves-mediated Au NPs (0.78–50 µg/mL) against Escherichia coli, Micrococcus luteus, S. aureus, Streptococcus mutans, Saccharomyces cerevisiae, Bacillus subtilis, Lactobacillus acidophilus, P. aeruginosa, and Candida albicans with minimum inhibitory concentrations (MIC) ranged between 6.2 and 25 µg/mL, where the lowest MIC value was observed against P. aeruginosa. However, the Rhazya stricta-mediated Au NPs displayed moderate activity against B. subtilis and E. coli with a MIC value of 50 µg/mL [93]. Additionally, Au NPs synthesized using the seeds of Embelia ribes exhibited strong activity against E. coli and S. aureus with a zone of inhibition range between 22 and 34 mm, where tetracycline (15 mg/mL) was used as a reference (17 and 11 mm against S. aureus and E. coli, respectively) [94]. In addition, Indigofera tinctoria leaf-mediated Au NPs, when investigated against Bacillus pumilus, Pseudomonas sp., E. coli, S. aureus, Aspergillus fumigatus, and Aspergillus niger exhibited inhibition of 10–30 mm. This efficacy might be due to the surface-functionalized biologically active compounds of I. tinctoria, such as alkaloids, flavonoids, and saponins [95]. Likewise, Stereospermum suaveolens (root bark) capped Au NPs at 50 µL showed inhibition (10–25 mm) against B. subtilis, S. aureus, E. coli, P. aeruginosa, Aspergillus flavus, and Aspergillus nidulans [96].

In another study, Origanum vulgare aerial parts mediated Au NPs (1 mL) were effective against Salmonella enteritidis, Listeria monocytogenes, E. coli, S. aureus, and C. albicans by using disc diffusion assay with inhibition zone diameter ranging between 8 and 28 mm [97]. Moreover, Hamelian et al. [98] found that Thymus vulgaris (Thyme) Au NPs inhibited P. aeruginosa, E. coli, B. subtilis, and S. aureus with MIC and MBC ranged between 3.9–15.62 and 15.62–62.5 µg/mL, respectively. The study also unveiled that the polyphenolic compounds of Thyme leaves could be responsible for inhibiting microorganisms. Subsequently, Au NPs synthesized using Alpinia nigra leaves (400 µg/mL) also inhibited both bacterial (B. subtilis, E. coli) and fungal pathogens (C. albicans) with IZD (inhibitory zone diameter) 15–18 mm when compared with standard antibacterial chloramphenicol (IZD 28–30 mm at 30 µg) and nystatin (50 µg), a standard antifungal drug with IZD 30 mm [99]. Also, the antibacterial activity of biosynthesized (using Nigella arvensis leaves) Au NPs was investigated against B. subtilis, Staphylococcus epidermidis, P. aeruginosa, E. coli, S. aureus, and Serratia marcescens. N. arvensis Au NPs displayed mild activity with inhibition zone diameters of 11, 10, and 11 mm, respectively, against E. coli, S. aureus, and B. subtilis, while showed complete inhibition against S. epidermidis. However, it showed an IZD of 6 mm against both S. marcescens and P. aeruginosa. Additionally, the MIC of Au NPs against all tested strains ranged between 62.5 and 250 µg/mL. It was hypothesized that metal NPs and secondary metabolites found in plant extract worked together to damage bacterial cell walls, causing cell respiration to be disrupted [100].

Subsequently, Dhayalan et al. [101] elucidated the antimicrobial status of Au NPs prepared using Coleus forskohlii roots (RECo-GNPs) against M. luteus and Proteus vulgaris by well diffusion method. The RECo-GNPs (250–1,000 µg/mL) showed mild antibacterial action with a 9–15 mm zone of inhibition and 1–11 mm against P. vulgaris and M. luteus, respectively. In contrast, positive control, tetracycline (30 µg/mL) showed IZD 19 and 15 mm, respectively. In another study, Amomum villosum fruits mediated Au NPs (45 µg/disc) demonstrated antibacterial activity with IZD of 17.66 and 18 mm against S. aureus and E. coli, respectively, where neomycin (30 µg/disc) was used as a positive control (IZD 15.33 and 15 mm, respectively) [102]. Concurrently, Bauhinia purpurea leaves mediated Au NPs (50 µL) were also ound to be effective antimicrobials against B. subtilis, P. aeruginosa, S. aureus, E. coli, A. flavus, and A. nidulans when evaluated using the agar well diffusion method with IZD ranging between 8 and 12 mm [103]. G. mangostana fruit rind-mediated Au NPs exhibited activity only against Pseudomonas sp. with 11 mm IZD in the disc diffusion method. However, they were inactive against Staphylococcus sp., Bacillus sp., and Klebsiella sp. [104].

Besides this, Au NPs synthesized using Peganum harmala (leaves and seeds) were investigated for antibacterial potential in agar and liquid media against E. coli and S. aureus. The seed extract-mediated NPs were found inactive in agar media up to 200 μg/mL while, in liquid media, they showed 15.5% and 10% inhibition against S. aureus, and E. coli, respectively. On the other hand, in agar media, leaves mediated Au NPs showed IZD 25 and 30 mm against E. coli and S. aureus at 200 μg/mL, while in liquid media, 20% and 91.8% inhibition was observed against E. coli and S. aureus, respectively [105]. Also, the Au NPs (90 μg/mL) prepared using Chenopodium formosanum shell and the positive control, streptomycin (40 μg/mL), displayed 84.44% and 98.45% inhibition, respectively, against E. coli, whereas 59.23% and 99.83% inhibition were observed against S. aureus [106]. In another study, Dillenia indica leaf synthesized Au NPs (1.5 mg/mL) exhibited IZD 25.5 and 28 mm against S. aureus and E. coli. However, the standard ciprofloxacin showed IZD 20 and 23 mm against S. aureus and E. coli [107]. Au NPs prepared using Musa acuminata flowers, when evaluated against P. aeruginosa, S. aureus, Proteus mirabilis, E. coli, Salmonella typhi, Enterococcus faecalis, and K. pneumoniae, were found active with IZD ranging between 7 and 11 mm [108]. Simultaneously, Coleus aromatics leaves mediated Au NPs coated cotton fabric, when investigated for antibacterial efficacy against S. epidermidis (Gram-positive) and E. coli (Gram-negative) strains, exerted remarkable sensitivity with IZD 22 and 27 mm, respectively [109].

Green synthesized Au NPs prepared using Clerodendrum inerme leaves were evaluated against various pathogens (E. coli, B. subtilis, Klebsiella sp., S. aureus, A. flavus, A. niger, and Trichoderma harzianum) and also for antibiofilm activity against S. aureus, B. subtilis, E. coli, and Klebsiella sp. in comparison to the standard antibacterial (Cephradine) and antifungal (Terbinafine hydrochloride) drugs. The resultant Au NPs (at 125–1,000 µg/mL) showed significant () activity against all the tested strains concerning their respective standards. Moreover, the nanoparticles revealed substantial () anti-biofilm activity. Thus, it can be said that C. inerme leaves biosynthesized Au NPs demonstrated microbicidal activity attributed to surface-functionalized alkaloids, flavonoids, saponins, phenolics, anthraquinones, terpenoids, and tannins [110].

The moderate antimicrobial effect of Mangifera indica seeds mediated Au NPs (10–50 mg/mL) was observed against fourteen microbial strains, Bacillus cereus, B. subtilis, S. aureus, E. coli, Corynebacterium rubrum, P. aeruginosa, Salmonella typhimurium, K. pneumoniae, Cryptococcus neoformans, Candida albicans, and C. glabrata as well as fungal clinical isolates (No.12, 15, 22) with a zone of inhibition ranging from 5 to 10 mm [111]. Also, a study showed that Au NPs synthesized using Solanum nigrum leaves (1.6–100 µg/mL) exerted antimicrobial efficacy against E. coli with IZD of 19.2–20 mm [112]. Boomi et al. [113] showed that the Acalypha indica leaves mediated Au NPs (10 µg/mL) strongly inhibited S. epidermidis (IZD 31 mm) as compared to E. coli (26 mm). A brief overview of the antimicrobial potential of Au NPs synthesized using various plant extracts is high. The Cynodon dactylon (plant) biosynthesized Au NPs exhibited antimicrobial efficacy against Enterobacter cloacae, Staphylococcus petrasii, S. haemolyticus, subsp. pragensis and B. cereus with IZD 13, 13, 12, and 12 mm, respectively, where standard, Ciprofoxacin (100 µg/mL) revealed a zone of inhibition of 19 mm against all the tested strains [114]. Green-synthesized Ricinus communis seeds gold nanoparticles showed activity against P. aeruginosa, B. cereus, K. pneumoniae, E. coli, Salmonella typhi, B. cereus, and methicillin-resistant S. aureus with inhibition zone diameters between 15.5 and 18.5 mm by using agar diffusion method where ampicillin (zone of inhibition range: 15.3–18.33 mm) served as a standard [115]. The MICs of Au NPs biosynthesized using Jatropha integerrima were 5.0, 10, 2.5, and 2.5 µg/mL against B. subtilis, S. aureus, E. coli, and K. pneumoniae, respectively [116]. Opuntia dillenii extract and its synthesized Au NPs showed inhibition against P. aeruginosa, E. coli, K. pneumoniae, and S. aureus [117]. However, the Au NPs (20 µL of 4.0 mM) synthesized using Capsicum chinense were found inactive against S. marcescens E. coli, S. aureus, and E. faecalis [118].

Au NPs in this study are primarily spherical (3–100 nm), in addition to hexagonal, cubic crystalline, and triangular (Table 1). Various morphologies have been reported for Au NPs, including spheres, rods, clusters, cubic, icosahedral, decahedral, nanocages, stars, triangular, prisms, hexagonal, and others [52, 73, 99, 103]. The alteration in the ratio of metal salts to apiin compound (derived from the leaves of Lawsonia inermis L.) resulted in the modulation of the size and form of the Au and Ag NPs [119]. According to Hussain et al. [120], when Au NPs were synthesized using the chemical reduction process with different solvent polarities, high solvent polarity resulted in spherical Au NPs, as compared to irregular Au NPs with low solvent polarity. The concentration of salts, phytoconstituents, and different parameters of distinct procedures utilized for NPs synthesis might influence the final shape of the NPs. In contrast to certain physicochemical methods, biosynthesis may result in NPs with more clearly defined sizes and morphologies [121].

In the characterization context, FT-IR, TEM, UV–Vis, XRD, and EDAX were the most commonly employed characterization methods (Figure 4(a)). Zeta potential (ZP) was done only in four studies, while the thermal stability of NPs was analyzed in one study. ZP is critical for determining NP stability; a high zeta potential value indicates high stability attributed to a considerable electric charge on a surface [48].

(a)

(b)

Different types of Au NPs described in the table were promising in efficiency against a wide range of microbial pathogens. E. ribes (seeds) and Thyme Au NPs demonstrated potent efficacy against a wide range of bacterial pathogens with the highest zone of inhibition of 34 mm and MIC value of 1.95 μg/mL, respectively (Table 1). It is assumed that the constituents present in the seeds of E. ribes, like alkaloids, quinones, and saponins, may be responsible for the NPs’ antibacterial efficacy. Subsequently, the shape, size, solubility, and capability to generate free biocidal metal ions directly influence nanoparticle’s antimicrobial efficacy [122]. Smaller NPs generally have higher antibacterial activity than larger ones [123].

Similarly, Table 1 also demonstrated that NPs <10 nm seemed to have more substantial antimicrobial efficacy than particles with >10 nm size. Thus, the size of NPs holds excellent promise in biological applications. The biological potential of plant-mediated NPs depends significantly on the selection of plants and the plant part. The researchers mainly utilize the leaves of the plants (12 studies), followed by whole plants, seeds, and others (Figure 4(b)). Figure 4 provides a comprehensive overview of methods employed to characterize NPs and the plant parts used.

Subsequently, there are few toxicity investigations on Au NPs. Hamelian et al. [98] found no significant toxicity when evaluating the cytotoxicity effect (MTT assay) of Au NPs synthesized using Thyme on HeLa cell lines. The physicochemical characteristics of Au NPs, including their shape, size, surface charge, synthesis method, dose, the route of administration, can affect their toxicity. Several researchers have reported varied toxicity profiles of Au NPs by utilizing different models. To support the safe use of Au NPs in biomedicine, it is necessary to address the contradicting findings about their toxicity [124, 125].

5. Mechanism of Action of Green Synthesized NPs: Two-Way Attack

Despite the development of various technologies and formulations over time, the exact mechanism of action of metallic NPs and plant bioactive components against bacteria and fungi remains uncertain. However, several examples in the literature support the idea that the mechanisms of action of metallic NPs in bacteria and fungi are nearly identical. Figure 5 proposes a mechanism for the antimicrobial activity of plant-mediated nanoparticles based on a two-way attack comprising of NPs [126] and plant-bioactive constituents [90]. Recently, Balkrishna et al. [127] provided insights about the two-way attack that needs evidence-based validation in the future.

First, the antimicrobial action of metal NPs includes direct contact with the cell wall/cell membrane, biofilms inhibition, disruption of the cell membrane, alteration of its permeability and metal ion release, generation of ROS, and modulation of signal transduction pathways (Figure 5) [36, 45, 126, 128]. Sharmin et al. [126] reported that NPs may interact with DNA molecules after entering the cell, causing the helical structure to be disrupted by cross-linking inside the nucleic acid strands. Second, the bioactive compounds from the plants attached to the surface of NPs exhibit antimicrobial potential that can be mediated via suppressing efflux pump expression, DNA and protein synthesis, biofilm, and other processes, as demonstrated in Figure 5 [90, 129–131].

6. Commercialization of Au NPs

Drug resistance among bacterial strains is a significant problem that can be effectively solved by synthesizing antibacterial NPs. Because they are good drug carriers with outstanding biocompatibility and bactericidal capability, Au NPs can increase the antibacterial effects of loaded antibacterial medications. The green synthesized Au NPs are one of them and have been effectively tested against various pathogenic and drug-resistant bacterial strains. They have numerous biological and therapeutic applications. Additionally, their use as a means of drug delivery in managing tumors has been noted [132, 133]. The role of Au NPs in protecting nucleic acids from being degraded by nucleases was reported by Klębowski et al. [134]. By covering Au NPs with a biopolymer that can firmly adsorb insulin to its surface, Joshi et al. [135] employed Au NPs as protein carriers. They validated the increased effectiveness of insulin delivery. The coupled Au NPs with oligonucleotides and their special qualities, according to Hu et al. [136], have allowed them to be used as prospective gene carriers. In addition, the function of Au NPs in therapies such as photothermal therapy, photodynamic therapy, and radiation therapy has also been noted [136, 137]. The literature has also documented Au NPs’ antioxidant and photocatalytic activity. Commercial Au NPs can be used in diverse biomedical applications. More study on biosynthetic procedures with well-defined size and shape is needed before Au NPs are widely used in commercial applications.

7. Conclusion and Future Perspectives

In conclusion, different researchers have successfully achieved the green synthesis of Au NPs (3–100 nm) using diverse plant extracts. All plant parts have been utilized, leaves being the most commonly employed part. Most of the studies only revealed a zone of inhibition, which is a major gap in antimicrobial studies; MIC and MBC were performed in a few studies. The antimicrobial studies should be supplemented with toxicity studies to maximize the benefit of these studies as it is early to comment on the toxicity of NPs as most of the studies are in preliminary stages. Notably, the stability of NPs cannot be ignored. The process for NPs synthesis must be optimized as the biological activity of NPs is influenced by various factors, including size, shape, and reaction variables. Nanotechnology-based formulations could be used in the fight against drug-resistant pathogens and to prevent the never-ending resistance pandemic. Intriguingly, the ability to modify the properties of Au NPs by merely altering their size or form will be used in novel applications in the future. Docking programs for deducing the mechanisms of NPs and phytoactive components will aid in broadening the field of smart antimicrobials that could be utilized to combat drug resistance. Furthermore, drug design theoretical frameworks can be used to suggest the possibility of green synthesized NPs as novel drugs. As biosynthesis of NPs has developed as a prominent field of nanobiology, there are numerous potentials for investigating innovative green preparatory approaches.

Data Availability

All data are included in the manuscript.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Authors’ Contributions

A. B. supervised the manuscript. A. K. (Ashwani Kumar), A. R., N. T. (Nikesh Thakur), and V. A. wrote the first draft. S. M. and V. K. contributed in figures and in providing literature. N. T. (Naveen Thakur), A. K. (Amita Kumari), and N. K. critically reviewed the first draft. A. K. (Ashwani Kumar) and V. A. improved the first draft. The final submitted version of the manuscript has been seen and approved by all contributors.

Acknowledgments

The authors (A. B., A. K., S. M., A. R., V. A., and V. K.) are grateful to Revered Swami Ramdev for providing all the necessary facilities. Sunil Kumar and Ira Abel, designers at Patanjali Herbal Research Department, assisted authors in designing infographics. Further, the authors are thankful to the Ministry of AYUSH under Grant-in-Aid for the Establishment of the Centre of Excellence of Renovation and Upgradation of Patanjali Ayurveda Hospital, Haridwar.

References

L. Hall-Stoodley, J. W. Costerton, and P. Stoodley, “Bacterial biofilms: from the natural environment to infectious diseases,” Nature Reviews Microbiology, vol. 2, pp. 95–108, 2004.
View at: Publisher Site | Google Scholar
N. Beyth, Y. Houri-Haddad, A. Domb, W. Khan, and R. Hazan, “Alternative antimicrobial approach: nano-antimicrobial materials,” Evidence-Based Complementary and Alternative Medicine, vol. 2015, Article ID 246012, 16 pages, 2015.
View at: Publisher Site | Google Scholar
F. Prestinaci, P. Pezzotti, and A. Pantosti, “Antimicrobial resistance: a global multifaceted phenomenon,” Pathogens and Global Health, vol. 109, no. 7, pp. 309–318, 2015.
View at: Publisher Site | Google Scholar
M. J. Renwick, D. M. Brogan, and E. Mossialos, “A systematic review and critical assessment of incentive strategies for discovery and development of novel antibiotics,” The Journal of Antibiotics, vol. 69, pp. 73–88, 2016.
View at: Publisher Site | Google Scholar
M. L. Katz, L. V. Mueller, M. Polyakov, and S. F. Weinstock, “Where have all the antibiotic patents gone?” Nature Biotechnology, vol. 24, pp. 1529–1531, 2006.
View at: Publisher Site | Google Scholar
B. Aslam, W. Wang, M. I. Arshad et al., “Antibiotic resistance: a rundown of a global crisis,” Infection and Drug Resistance, vol. 11, pp. 1645–1658, 2018.
View at: Publisher Site | Google Scholar
J. S. Kim, E. Kuk, K. N. Yu et al., “Antimicrobial effects of silver nanoparticles,” Nanomedicine: Nanotechnology, Biology and Medicine, vol. 3, no. 1, pp. 95–101, 2007.
View at: Publisher Site | Google Scholar
A. Balkrishna, V. Arya, A. Rohela et al., “Nanotechnology interventions in the management of COVID-19: prevention, diagnosis and virus-like particle vaccines,” Vaccines, vol. 9, no. 10, Article ID 1129, 2021.
View at: Publisher Site | Google Scholar
S. Lal, R. Verma, A. Chauhan et al., “Antioxidant, antimicrobial, and photocatalytic activity of green synthesized ZnO-NPs from Myrica esculenta fruits extract,” Inorganic Chemistry Communications, vol. 141, Article ID 109518, 2022.
View at: Publisher Site | Google Scholar
H. N. Cuong, S. Pansambal, S. Ghotekar et al., “New frontiers in the plant extract mediated biosynthesis of copper oxide (CuO) nanoparticles and their potential applications: a review,” Environmental Research, vol. 203, Article ID 111858, 2022.
View at: Publisher Site | Google Scholar
Y. Kashid, S. Ghotekar, M. Bilal et al., “Bio-inspired sustainable synthesis of silver chloride nanoparticles and their prominent applications,” Journal of the Indian Chemical Society, vol. 99, no. 5, Article ID 100335, 2022.
View at: Publisher Site | Google Scholar
S. Pansambal, R. Oza, S. Borgave et al., “Bioengineered cerium oxide (CeO₂) nanoparticles and their diverse applications: a review,” Applied Nanoscience, 2022.
View at: Publisher Site | Google Scholar
S. Ghotekar, S. Pansambal, M. Bilal, S. S. Pingale, and R. Oza, “Environmentally friendly synthesis of Cr₂O₃ nanoparticles: characterization, applications and future perspective—a review,” Case Studies in Chemical and Environmental Engineering, vol. 3, Article ID 100089, 2021.
View at: Publisher Site | Google Scholar
V. R. Rai and A. J. Bai, “Nanoparticles and their potential application as antimicrobials,” in Science Against Microbial Pathogens: Communicating Current Research and Technological Advances, A. Méndez-Vilas, Ed., vol. 1 of Microbiology Series, pp. 197–209, Formatex, Spain, 2011.
View at: Google Scholar
A. Kumar, S. Singh, and D. Kumar, “Evaluation of antimicrobial potential of cadmium sulphide nanoparticles against bacterial pathogens,” International Journal of Pharmaceutical Sciences Review and Research, vol. 24, no. 2, pp. 202–207, 2014.
View at: Google Scholar
N. Thakur, Anu, K. Kumar, and A. Kumar, “Effect of (Ag, Zn) co-doping on structural, optical and bactericidal properties of CuO nanoparticles synthesized by a microwave-assisted method,” Dalton Transactions, vol. 50, no. 18, pp. 6188–6203, 2021.
View at: Publisher Site | Google Scholar
S. T. Yerpude, A. K. Potbhare, P. Bhilkar et al., “Biomedical,clinical and environmental applications of platinum-based nanohybrids: an updated review,” Environmental Research, vol. 231, Part 2, Article ID 116148, 2023.
View at: Publisher Site | Google Scholar
N.-Y. Lee, W.-C. Ko, and P.-R. Hsueh, “Nanoparticles in the treatment of infections caused by multidrug-resistant organisms,” Frontiers in Pharmacology, vol. 10, Article ID 1153, 2019.
View at: Publisher Site | Google Scholar
P. Dhandapani, A. S. Siddarth, S. Kamalasekaran, S. Maruthamuthu, and G. Rajagopal, “Bio-approach: ureolytic bacteria mediated synthesis of ZnO nanocrystals on cotton fabric and evaluation of their antibacterial properties,” Carbohydrate Polymers, vol. 103, pp. 448–455, 2014.
View at: Publisher Site | Google Scholar
K. S. Kavitha, S. Baker, D. Rakshith et al., “Plants as green source towards synthesis of nanoparticles.,” International Research Journal of Biological Sciences, vol. 2, no. 6, pp. 66–76, 2013.
View at: Google Scholar
M. S. Akhtar, J. Panwar, and Y.-S. Yun, “Biogenic synthesis of metallic nanoparticles by plant extracts,” ACS Sustainable Chemistry & Engineering, vol. 1, no. 6, pp. 591–602, 2013.
View at: Publisher Site | Google Scholar
M. Mehta, P. Sharma, S. Kaur et al., “Plant-based drug delivery systems in respiratory diseases,” in Targeting Chronic Inflammatory Lung Diseases Using Advanced Drug Delivery Systems, pp. 517–539, Academic Press, 2020.
View at: Publisher Site | Google Scholar
M. Can, “Green gold nanoparticles from plant-derived materials: an overview of the reaction synthesis types, conditions, and applications,” Reviews in Chemical Engineering, vol. 36, no. 7, pp. 859–877, 2020.
View at: Publisher Site | Google Scholar
S. Ying, Z. Guan, P. C. Ofoegbu et al., “Green synthesis of nanoparticles: current developments and limitations,” Environmental Technology & Innovation, vol. 26, Article ID 102336, 2022.
View at: Publisher Site | Google Scholar
D. Lahiri, M. Nag, H. I. Sheikh et al., “Microbiologically-synthesized nanoparticles and their role in silencing the biofilm signaling cascade,” Frontiers in Microbiology, vol. 12, Article ID 636588, 2021.
View at: Publisher Site | Google Scholar
P. B. Chouke, T. Shrirame, A. K. Potbhare et al., “Bioinspired metal/metal oxide nanoparticles: a road map to potential applications,” Materials Today Advances, vol. 16, Article ID 100314, 2022.
View at: Publisher Site | Google Scholar
R. K. Bachheti, A. Fikadu, A. Bachheti, and A. Husen, “Biogenic fabrication of nanomaterials from flower-based chemical compounds, characterization and their various applications: a review,” Saudi Journal of Biological Sciences, vol. 27, no. 10, pp. 2551–2562, 2020.
View at: Publisher Site | Google Scholar
H. Kumar, K. Bhardwaj, K. Kuča et al., “Flower-based green synthesis of metallic nanoparticles: applications beyond fragrance,” Nanomaterials, vol. 10, no. 4, Article ID 766, 2020.
View at: Publisher Site | Google Scholar
B. K. Thakur, A. Kumar, and D. Kumar, “Green synthesis of titanium dioxide nanoparticles using Azadirachta indica leaf extract and evaluation of their antibacterial activity,” South African Journal of Botany, vol. 124, pp. 223–227, 2019.
View at: Publisher Site | Google Scholar
S. Sharma, K. Kumar, N. Thakur, S. Chauhan, and M. S. Chauhan, “Eco-friendly Ocimum tenuiflorum green route synthesis of CuO nanoparticles: characterizations on photocatalytic and antibacterial activities,” Journal of Environmental Chemical Engineering, vol. 9, no. 4, Article ID 105395, 2021.
View at: Publisher Site | Google Scholar
C. Khatana, A. Kumar, M. W. Alruways et al., “Antibacterial potential of zinc oxide nanoparticles synthesized using Aloe vera (L.) Burm.f.: a green approach to combat drug resistance,” Journal of Pure and Applied Microbiology, vol. 15, no. 4, pp. 1907–1914, 2021.
View at: Publisher Site | Google Scholar
E. Sánchez-López, D. Gomes, G. Esteruelas et al., “Metal-based nanoparticles as antimicrobial agents: an overview,” Nanomaterials, vol. 10, no. 2, Article ID 292, 2020.
View at: Publisher Site | Google Scholar
A. M. Allahverdiyev, K. V. Kon, E. S. Abamor, M. Bagirova, and M. Rafailovich, “Coping with antibiotic resistance: combining nanoparticles with antibiotics and other antimicrobial agents,” Expert Review of Anti-infective Therapy, vol. 9, no. 11, pp. 1035–1052, 2011.
View at: Publisher Site | Google Scholar
F. Ghasemi and R. Jalal, “Antimicrobial action of zinc oxide nanoparticles in combination with ciprofloxacin and ceftazidime against multidrug-resistant Acinetobacter baumannii,” Journal of Global Antimicrobial Resistance, vol. 6, pp. 118–122, 2016.
View at: Publisher Site | Google Scholar
S. Prabhu and E. K. Poulose, “Silver nanoparticles: mechanism of antimicrobial action, synthesis, medical applications, and toxicity effects,” International Nano Letters, vol. 2, Article ID 32, 2012.
View at: Publisher Site | Google Scholar
T. C. Dakal, A. Kumar, R. S. Majumdar, and V. Yadav, “Mechanistic basis of antimicrobial actions of silver nanoparticles,” Frontiers in Microbiology, vol. 7, Article ID 1831, 2016.
View at: Publisher Site | Google Scholar
D. A. Giljohann, D. S. Seferos, W. L. Daniel, M. D. Massich, P. C. Patel, and C. A. Mirkin, “Gold nanoparticles for biology and medicine,” Angewandte Chemie International Edition, vol. 49, no. 19, pp. 3280–3294, 2010.
View at: Publisher Site | Google Scholar
D. B. Chithrani, M. Dunne, J. Stewart, C. Allen, and D. A. Jaffray, “Cellular uptake and transport of gold nanoparticles incorporated in a liposomal carrier,” Nanomedicine: Nanotechnology, Biology and Medicine, vol. 6, no. 1, pp. 161–169, 2010.
View at: Publisher Site | Google Scholar
P. Murawala, A. Tirmale, A. Shiras, and B. L. V. Prasad, “In situ synthesized BSA capped gold nanoparticles: effective carrier of anticancer drug methotrexate to MCF-7 breast cancer cells,” Materials Science and Engineering: C, vol. 34, pp. 158–167, 2014.
View at: Publisher Site | Google Scholar
Q. Guo, Q. Guo, J. Yuan, and J. Zeng, “Biosynthesis of gold nanoparticles using a kind of flavonol: dihydromyricetin,” Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 441, pp. 127–132, 2014.
View at: Publisher Site | Google Scholar
N. M. Suchak, P. H. Desai, M. P. Deshpande et al., “Study on the concentration of gold nanoparticles for antibacterial activity,” Advances in Natural Sciences: Nanoscience and Nanotechnology, vol. 12, no. 3, Article ID 035003, 2021.
View at: Publisher Site | Google Scholar
A. U. E. Pei, P. C. Huai, M. A. A. Masimen, W. I. W. Ismail, I. Idris, and N. A. Harun, “Biosynthesis of gold nanoparticles (AuNPs) by marine baitworm Marphysa moribidii idris, hutchings and arshad 2014 (annelida: polychaeta) and its antibacterial activity,” Advances in Natural Sciences: Nanoscience and Nanotechnology, vol. 11, no. 1, Article ID 015001, 2020.
View at: Publisher Site | Google Scholar
Y. Mikhlin, A. Karacharov, M. Likhatski et al., “Submicrometer intermediates in the citrate synthesis of gold nanoparticles: new insights into the nucleation and crystal growth mechanisms,” Journal of Colloid and Interface Science, vol. 362, no. 2, pp. 330–336, 2011.
View at: Publisher Site | Google Scholar
U. Shedbalkar, R. Singh, S. Wadhwani, S. Gaidhani, and B. A. Chopade, “Microbial synthesis of gold nanoparticles: current status and future prospects,” Advances in Colloid and Interface Science, vol. 209, pp. 40–48, 2014.
View at: Publisher Site | Google Scholar
K. Bhardwaj, D. S. Dhanjal, A. Sharma et al., “Conifer-derived metallic nanoparticles: green synthesis and biological applications,” International Journal of Molecular Sciences, vol. 21, no. 23, Article ID 9028, 2020.
View at: Publisher Site | Google Scholar
C. Pandit, A. Roy, S. Ghotekar et al., “Biological agents for synthesis of nanoparticles and their applications,” Journal of King Saud University-Science, vol. 34, no. 3, Article ID 101869, 2022.
View at: Publisher Site | Google Scholar
K. S. Mukunthan and S. Balaji, “Cashew apple juice (Anacardium occidentale L.) speeds up the synthesis of silver nanoparticles,” International Journal of Green Nanotechnology, vol. 4, no. 2, pp. 71–79, 2012.
View at: Publisher Site | Google Scholar
A. Balkrishna, A. Kumar, V. Arya et al., “Phytoantioxidant functionalized nanoparticles: a green approach to combat nanoparticle-induced oxidative stress,” Oxidative Medicine and Cellular Longevity, vol. 2021, Article ID 3155962, 20 pages, 2021.
View at: Publisher Site | Google Scholar
K. B. Narayanan and N. Sakthivel, “Green synthesis of biogenic metal nanoparticles by terrestrial and aquatic phototrophic and heterotrophic eukaryotes and biocompatible agents,” Advances in Colloid and Interface Science, vol. 169, no. 2, pp. 59–79, 2011.
View at: Publisher Site | Google Scholar
M. A. Ali, T. Ahmed, W. Wu et al., “Advancements in plant and microbe-based synthesis of metallic nanoparticles and their antimicrobial activity against plant pathogens,” Nanomaterials, vol. 10, no. 6, Article ID 1146, 2020.
View at: Publisher Site | Google Scholar
B. Baruwati and R. S. Varma, “High value products from waste: grape pomace extract—a three-in-one package for the synthesis of metal nanoparticles,” ChemSusChem, vol. 2, no. 11, pp. 1041–1044, 2009.
View at: Publisher Site | Google Scholar
A. Gupta, S. Pandey, and J. S. Yadav, “A review on recent trends in green synthesis of gold nanoparticles for tuberculosis,” Advanced Pharmaceutical Bulletin, vol. 11, no. 1, pp. 10–27, 2021.
View at: Publisher Site | Google Scholar
B. D. Lade and A. S. Shanware, “Phytonanofabrication: methodology and factors affecting biosynthesis of nanoparticles,” in Smart Nanosystems for Biomedicine, Optoelectronics and Catalysis, T. Shabatina and V. Bochenkov, Eds., pp. 1–18, IntechOpen, Rijeka, 2020.
View at: Publisher Site | Google Scholar
G. Mountrichas, S. Pispas, and E. I. Kamitsos, “Effect of temperature on the direct synthesis of gold nanoparticles mediated by poly(dimethylaminoethyl methacrylate) homopolymer,” The Journal of Physical Chemistry C, vol. 118, no. 39, pp. 22754–22759, 2014.
View at: Publisher Site | Google Scholar
L. A. P. Gontijo, E. Raphael, D. P. S. Ferrari, J. L. Ferrari, J. P. Lyon, and M. A. Schiavon, “pH effect on the synthesis of different size silver nanoparticles evaluated by DLS and their size-dependent antimicrobial activity. Matéria (Rio de Janeiro),” Matéria (Rio de Janeiro), vol. 25, no. 4, pp. 1–10, 2020.
View at: Publisher Site | Google Scholar
P. Traiwatcharanon, K. Timsorn, and C. Wongchoosuk, “Effect of pH on the green synthesis of silver nanoparticles through reduction with Pistiastratiotes L. extract,” Advanced Materials Research, vol. 1131, pp. 223–226, 2015.
View at: Publisher Site | Google Scholar
T. Ahmad, M. Irfan, and S. Bhattacharjee, “Parametric study on gold nanoparticle synthesis using aqueous Elaise guineensis (oil palm) leaf extract: effect of precursor concentration,” Procedia Engineering, vol. 148, pp. 1396–1401, 2016.
View at: Publisher Site | Google Scholar
R. Veerasamy, T. Z. Xin, S. Gunasagaran et al., “Biosynthesis of silver nanoparticles using mangosteen leaf extract and evaluation of their antimicrobial activities,” Journal of Saudi Chemical Society, vol. 15, no. 2, pp. 113–120, 2011.
View at: Publisher Site | Google Scholar
U. Riaz, W. Anum, G. H. Jatoi et al., “Synthesis of bionanomaterials for biomedical applications,” Synthesis of Bionanomaterials for Biomedical Applications, pp. 151–163, 2023.
View at: Publisher Site | Google Scholar
A. A. Zahir, I. S. Chauhan, A. Bagavan et al., “Synthesis of nanoparticles using Euphorbia prostrata extract reveals a shift from apoptosis to G0/G1 arrest in Leishmania donovani,” Journal of Nanomedicine & Nanotechnology, vol. 05, no. 4, Article ID 1000213, 2014.
View at: Publisher Site | Google Scholar
V. V. Makarov, A. J. Love, O. V. Sinitsyna et al., ““Green” nanotechnologies: synthesis of metal nanoparticles using plants,” Acta Naturae, vol. 6, no. 1, pp. 35–44, 2014.
View at: Google Scholar
G. Sathishkumar, P. K. Jha, V. Vignesh et al., “Cannonball fruit (Couroupita guianensis Aubl.) extract mediated synthesis of gold nanoparticles and evaluation of its antioxidant activity,” Journal of Molecular Liquids, vol. 215, pp. 229–236, 2016.
View at: Publisher Site | Google Scholar
P. Khanna, A. Kaur, and D. Goyal, “Algae-based metallic nanoparticles: synthesis, characterization and applications,” Journal of Microbiological Methods, vol. 163, Article ID 105656, 2019.
View at: Publisher Site | Google Scholar
R. K. Das, V. L. Pachapur, L. Lonappan et al., “Biological synthesis of metallic nanoparticles: plants, animals and microbial aspects,” Nanotechnology for Environmental Engineering, vol. 2, Article ID 18, 2017.
View at: Publisher Site | Google Scholar
G. Gahlawat and A. R. Choudhury, “A review on the biosynthesis of metal and metal salt nanoparticles by microbes,” RSC Advances, vol. 9, no. 23, pp. 12944–12967, 2019.
View at: Publisher Site | Google Scholar
J. Polte, T. T. Ahner, F. Delissen et al., “Mechanism of gold nanoparticle formation in the classical citrate synthesis method derived from coupled in situ XANES and SAXS evaluation,” Journal of the American Chemical Society, vol. 132, no. 4, pp. 1296–1301, 2010.
View at: Publisher Site | Google Scholar
J. Polte, R. Erler, A. F. Thünemann et al., “Nucleation and growth of gold nanoparticles studied viain situ small angle x-ray scattering at millisecond time resolution,” ACS Nano, vol. 4, no. 2, pp. 1076–1082, 2010.
View at: Publisher Site | Google Scholar
J. Polte, X. Tuaev, M. Wuithschick et al., “Formation mechanism of colloidal silver nanoparticles: analogies and differences to the growth of gold nanoparticles,” ACS Nano, vol. 6, no. 7, pp. 5791–5802, 2012.
View at: Publisher Site | Google Scholar
L. Minati, F. Benetti, A. Chiappini, and G. Speranza, “One-step synthesis of star-shaped gold nanoparticles,” Colloids and Surfaces A: Physicochemical and Engineering Aspects, vol. 441, pp. 623–628, 2014.
View at: Publisher Site | Google Scholar
J. H. Bang and K. S. Suslick, “Applications of ultrasound to the synthesis of nanostructured materials,” Advanced Materials, vol. 22, no. 10, pp. 1039–1059, 2010.
View at: Publisher Site | Google Scholar
A. Lähde, I. Koshevoy, T. Karhunen, T. Torvela, T. A. Pakkanen, and J. Jokiniemi, “Aerosol-assisted synthesis of gold nanoparticles,” Journal of Nanoparticle Research, vol. 16, Article ID 2716, 2014.
View at: Publisher Site | Google Scholar
Y. Shang, C. Min, J. Hu, T. Wang, H. Liu, and Y. Hu, “Synthesis of gold nanoparticles by reduction of HAuCl₄ under UV irradiation,” Solid State Sciences, vol. 15, pp. 17–23, 2013.
View at: Publisher Site | Google Scholar
A. K. Khan, R. Rashid, G. Murtaza, and A. Zahra, “Gold nanoparticles: synthesis and applications in drug delivery,” Tropical Journal of Pharmaceutical Research, vol. 13, no. 7, pp. 1169–1177, 2014.
View at: Publisher Site | Google Scholar
M. Rakhi and B. B. Gopal, “Terminalia arjuna bark extract mediated size controlled synthesis of polyshaped gold nanoparticles and its application in catalysis,” International Journal of Research in Chemistry and Environment, vol. 2, no. 4, pp. 338–344, 2012.
View at: Google Scholar
S. Raj, S. C. Mali, and R. Trivedi, “Green synthesis and characterization of silver nanoparticles using Enicostemma axillare (Lam.) leaf extract,” Biochemical and Biophysical Research Communications, vol. 503, no. 4, pp. 2814–2819, 2018.
View at: Publisher Site | Google Scholar
T. Ahmad, M. A. Bustam, M. Irfan, M. Moniruzzaman, H. M. A. Asghar, and S. Bhattacharjee, “Mechanistic investigation of phytochemicals involved in green synthesis of gold nanoparticles using aqueous Elaeis guineensis leaves extract: role of phenolic compounds and flavonoids,” Biotechnology and Applied Biochemistry, vol. 66, no. 4, pp. 698–708, 2019.
View at: Publisher Site | Google Scholar
Y.-S. Liu, Y.-C. Chang, and H.-H. Chen, “Silver nanoparticle biosynthesis by using phenolic acids in rice husk extract as reducing agents and dispersants,” Journal of Food and Drug Analysis, vol. 26, no. 2, pp. 649–656, 2018.
View at: Publisher Site | Google Scholar
S. M. Ghoreishi, M. Behpour, and M. Khayatkashani, “Green synthesis of silver and gold nanoparticles using Rosa damascena and its primary application in electrochemistry,” Physica E: Low-dimensional Systems and Nanostructures, vol. 44, no. 1, pp. 97–104, 2011.
View at: Publisher Site | Google Scholar
S. J. Amina and B. Guo, “A review on the synthesis and functionalization of gold nanoparticles as a drug delivery vehicle,” International Journal of Nanomedicine, vol. 15, pp. 9823–9857, 2020.
View at: Publisher Site | Google Scholar
J. Dong, P. L. Carpinone, G. Pyrgiotakis, P. Demokritou, and B. M. Moudgil, “Synthesis of precision gold nanoparticles using Turkevich method,” KONA Powder and Particle Journal, vol. 37, pp. 224–232, 2020.
View at: Publisher Site | Google Scholar
R. Herizchi, E. Abbasi, M. Milani, and A. Akbarzadeh, “Current methods for synthesis of gold nanoparticles,” Artificial Cells, Nanomedicine, and Biotechnology, vol. 44, no. 2, pp. 596–602, 2016.
View at: Publisher Site | Google Scholar
K. Bloch, K. Pardesi, C. Satriano, and S. Ghosh, “Bacteriogenic platinum nanoparticles for application in nanomedicine,” Frontiers in Chemistry, vol. 9, Article ID 624344, 2021.
View at: Publisher Site | Google Scholar
K. D. Lee, P. C. Nagajyothi, T. V. M. Sreekanth, and S. Park, “Eco-friendly synthesis of gold nanoparticles (AuNPs) using Inonotus obliquus and their antibacterial, antioxidant and cytotoxic activities,” Journal of Industrial and Engineering Chemistry, vol. 26, pp. 67–72, 2015.
View at: Publisher Site | Google Scholar
Y. Qu, X. Pei, W. Shen et al., “Biosynthesis of gold nanoparticles by Aspergillum sp. WL-Au for degradation of aromatic pollutants,” Physica E: Low-Dimensional Systems and Nanostructures, vol. 88, pp. 133–141, 2017.
View at: Publisher Site | Google Scholar
H. M. Manjunath, C. G. Joshi, and N. G. Raju, “Biofabrication of gold nanoparticles using marine endophytic fungus—Penicillium citrinum,” IET Nanobiotechnology, vol. 11, no. 1, pp. 40–44, 2017.
View at: Publisher Site | Google Scholar
R. Teimuri-mofrad, R. Hadi, B. Tahmasebi, S. Farhoudian, M. Mehravar, and R. Nasiri, “Green synthesis of gold nanoparticles using plant extract: mini-review,” Nanochemistry Research, vol. 2, no. 1, pp. 8–19, 2017.
View at: Publisher Site | Google Scholar
K. S. Siddiqi and A. Husen, “Recent advances in plant-mediated engineered gold nanoparticles and their application in biological system,” Journal of Trace Elements in Medicine and Biology, vol. 40, pp. 10–23, 2017.
View at: Publisher Site | Google Scholar
N. K. R. Bogireddy, U. Pal, L. M. Gomez, and V. Agarwal, “Size controlled green synthesis of gold nanoparticles using Coffea arabica seed extract and their catalytic performance in 4-nitrophenol reduction,” RSC Advances, vol. 8, no. 44, pp. 24819–24826, 2018.
View at: Publisher Site | Google Scholar
B. Hammer and J. K. Norskov, “Why gold is the noblest of all the metals,” Nature, vol. 376, pp. 238–240, 1995.
View at: Publisher Site | Google Scholar
A. Balkrishna, A. Rohela, A. Kumar et al., “Mechanistic insight into antimicrobial and antioxidant potential of Jasminum species: a herbal approach for disease management,” Plants, vol. 10, no. 6, Article ID 1089, 2021.
View at: Publisher Site | Google Scholar
S. Naraginti and Y. Li, “Preliminary investigation of catalytic, antioxidant, anticancer and bactericidal activity of green synthesized silver and gold nanoparticles using Actinidia deliciosa,” Journal of Photochemistry and Photobiology B: Biology, vol. 170, pp. 225–234, 2017.
View at: Publisher Site | Google Scholar
R. Emmanuel, M. Saravanan, M. Ovais, S. Padmavathy, Z. K. Shinwari, and P. Prakash, “Antimicrobial efficacy of drug blended biosynthesized colloidal gold nanoparticles from Justicia glauca against oral pathogens: a nanoantibiotic approach,” Microbial Pathogenesis, vol. 113, pp. 295–302, 2017.
View at: Publisher Site | Google Scholar
A. Ahmad, Y. Wei, S. Ullah et al., “Synthesis of phytochemicals-stabilized gold nanoparticles and their biological activities against bacteria and Leishmania,” Microbial Pathogenesis, vol. 110, pp. 304–312, 2017.
View at: Publisher Site | Google Scholar
M. Dhayalan, M. I. J. Denison, L. A. Jegadeeshwari, K. Krishnan, and N. N. Gandhi, “In vitro antioxidant, antimicrobial, cytotoxic potential of gold and silver nanoparticles prepared using Embelia ribes,” Natural Product Research, vol. 31, no. 4, pp. 465–468, 2017.
View at: Publisher Site | Google Scholar
R. Vijayan, S. Joseph, and B. Mathew, “Indigofera tinctoria leaf extract mediated green synthesis of silver and gold nanoparticles and assessment of their anticancer, antimicrobial, antioxidant and catalytic properties,” Artificial Cells, Nanomedicine, and Biotechnology, vol. 46, no. 4, pp. 861–871, 2018.
View at: Publisher Site | Google Scholar
S. Francis, E. P. Koshy, and B. Mathew, “Green synthesis of Stereospermum suaveolens capped silver and gold nanoparticles and assessment of their innate antioxidant, antimicrobial and antiproliferative activities,” Bioprocess and Biosystems Engineering, vol. 41, pp. 939–951, 2018.
View at: Publisher Site | Google Scholar
D. Benedec, I. Oniga, F. Cuibus et al., “Origanum vulgare mediated green synthesis of biocompatible gold nanoparticles simultaneously possessing plasmonic, antioxidant and antimicrobial properties,” International Journal of Nanomedicine, vol. 13, pp. 1041–1058, 2018.
View at: Publisher Site | Google Scholar
M. Hamelian, K. Varmira, and H. Veisi, “Green synthesis and characterizations of gold nanoparticles using Thyme and survey cytotoxic effect, antibacterial and antioxidant potential,” Journal of Photochemistry and Photobiology B: Biology, vol. 184, pp. 71–79, 2018.
View at: Publisher Site | Google Scholar
D. Baruah, M. Goswami, R. N. S. Yadav, A. Yadav, and A. M. Das, “Biogenic synthesis of gold nanoparticles and their application in photocatalytic degradation of toxic dyes,” Journal of Photochemistry and Photobiology B: Biology, vol. 186, pp. 51–58, 2018.
View at: Publisher Site | Google Scholar
A. Chahardoli, N. Karimi, F. Sadeghi, and A. Fattahi, “Green approach for synthesis of gold nanoparticles from Nigella arvensis leaf extract and evaluation of their antibacterial, antioxidant, cytotoxicity and catalytic activities,” Artificial Cells, Nanomedicine, and Biotechnology, vol. 46, no. 3, pp. 579–588, 2018.
View at: Publisher Site | Google Scholar
M. Dhayalan, M. I. J. Denison, M. Ayyar, N. N. Gandhi, K. Krishnan, and B. Abdulhadi, “Biogenic synthesis, characterization of gold and silver nanoparticles from Coleus forskohlii and their clinical importance,” Journal of Photochemistry and Photobiology B: Biology, vol. 183, pp. 251–257, 2018.
View at: Publisher Site | Google Scholar
V. Soshnikova, Y. J. Kim, P. Singh et al., “Cardamom fruits as a green resource for facile synthesis of gold and silver nanoparticles and their biological applications,” Artificial Cells, Nanomedicine, and Biotechnology, vol. 46, no. 1, pp. 108–117, 2018.
View at: Publisher Site | Google Scholar
R. Vijayan, S. Joseph, and B. Mathew, “Anticancer, antimicrobial, antioxidant, and catalytic activities of green-synthesized silver and gold nanoparticles using Bauhinia purpurea leaf extract,” Bioprocess and Biosystems Engineering, vol. 42, pp. 305–319, 2019.
View at: Publisher Site | Google Scholar
R. Nishanthi, S. Malathi, S. J. Paul, and P. Palani, “Green synthesis and characterization of bioinspired silver, gold and platinum nanoparticles and evaluation of their synergistic antibacterial activity after combining with different classes of antibiotics,” Materials Science and Engineering: C, vol. 96, pp. 693–707, 2019.
View at: Publisher Site | Google Scholar
N. E. Moustafa and A. A. Alomari, “Green synthesis and bactericidal activities of isotropic and anisotropic spherical gold nanoparticles produced using Peganum harmala L. leaf and seed extracts,” Biotechnology and Applied Biochemistry, vol. 66, no. 4, pp. 664–672, 2019.
View at: Publisher Site | Google Scholar
M.-N. Chen, C.-F. Chan, S.-L. Huang, and Y.-S. Lin, “Green biosynthesis of gold nanoparticles using Chenopodium formosanum shell extract and analysis of the particles’ antibacterial properties,” Journal of the Science of Food and Agriculture, vol. 99, no. 7, pp. 3693–3702, 2019.
View at: Publisher Site | Google Scholar
Q. Huang, A. Luo, L. Jiang et al., “Disinfection efficacy of green synthesized gold nanoparticles for medical disinfection applications,” African Health Sciences, vol. 19, no. 1, pp. 1441–1448, 2019.
View at: Publisher Site | Google Scholar
S. Valsalam, P. Agastian, G. A. Esmail, A.-K. M. Ghilan, N. A. Al-Dhabi, and M. V. Arasu, “Biosynthesis of silver and gold nanoparticles using Musa acuminata colla flower and its pharmaceutical activity against bacteria and anticancer efficacy,” Journal of Photochemistry and Photobiology B: Biology, vol. 201, Article ID 111670, 2019.
View at: Publisher Site | Google Scholar
P. Boomi, R. M. Ganesan, G. Poorani, H. G. Prabu, S. Ravikumar, and J. Jeyakanthan, “Biological synergy of greener gold nanoparticles by using Coleus aromaticus leaf extract,” Materials Science and Engineering: C, vol. 99, pp. 202–210, 2019.
View at: Publisher Site | Google Scholar
S. A. Khan, S. Shahid, and C.-S. Lee, “Green synthesis of gold and silver nanoparticles using leaf extract of Clerodendrum inerme; characterization, antimicrobial, and antioxidant activities,” Biomolecules, vol. 10, no. 6, Article ID 835, 2020.
View at: Publisher Site | Google Scholar
S. Donga, G. R. Bhadu, and S. Chanda, “Antimicrobial, antioxidant and anticancer activities of gold nanoparticles green synthesized using Mangifera indica seed aqueous extract,” Artificial Cells, Nanomedicine, and Biotechnology, vol. 48, no. 1, pp. 1315–1325, 2020.
View at: Publisher Site | Google Scholar
C. Vijilvani, M. R. Bindhu, F. C. Frincy et al., “Antimicrobial and catalytic activities of biosynthesized gold, silver and palladium nanoparticles from Solanum nigurum leaves,” Journal of Photochemistry and Photobiology B: Biology, vol. 202, Article ID 111713, 2020.
View at: Publisher Site | Google Scholar
P. Boomi, R. Ganesan, G. P. Poorani et al., “Phyto-engineered gold nanoparticles (AuNPs) with potential antibacterial, antioxidant, and wound healing activities under in vitro and in vivo conditions,” International Journal of Nanomedicine, vol. 15, pp. 7553–7568, 2020.
View at: Publisher Site | Google Scholar
R. Vinayagam, M. Santhoshkumar, K. E. Lee, E. David, and S. G. Kang, “Bioengineered gold nanoparticles using Cynodon dactylon extract and its cytotoxicity and antibacterial activities,” Bioprocess and Biosystems Engineering, vol. 44, pp. 1253–1262, 2021.
View at: Publisher Site | Google Scholar
T. U. Rahman, H. Khan, W. Liaqat, and M. A. Zeb, “Phytochemical screening, green synthesis of gold nanoparticles, and antibacterial activity using seeds extract of Ricinus communis L,” Microscopy Research and Technique, vol. 85, pp. 202–208, 2022.
View at: Publisher Site | Google Scholar
G. Suriyakala, S. Sathiyaraj, R. Babujanarthanam et al., “Green synthesis of gold nanoparticles using Jatropha integerrima Jacq. flower extract and their antibacterial activity,” Journal of King Saud University-Science, vol. 34, no. 3, Article ID 101830, 2022.
View at: Publisher Site | Google Scholar
A. Ahmed, A. Rauf, H. A. Hemeg et al., “Green synthesis of gold and silver nanoparticles using Opuntia dillenii aqueous extracts: characterization and their antimicrobial assessment,” Journal of Nanomaterials, vol. 2022, Article ID 4804116, 17 pages, 2022.
View at: Publisher Site | Google Scholar
D. A. Lomelí-Rosales, A. Zamudio-Ojeda, O. K. Reyes-Maldonado et al., “Green synthesis of gold and silver nanoparticles using leaf extract of Capsicum chinense plant,” Molecules, vol. 27, no. 5, 2022, 1692.
View at: Publisher Site | Google Scholar
J. Kasthuri, S. Veerapandian, and N. Rajendiran, “Biological synthesis of silver and gold nanoparticles using apiin as reducing agent,” Colloids and Surfaces B: Biointerfaces, vol. 68, no. 1, pp. 55–60, 2009.
View at: Publisher Site | Google Scholar
M. H. Hussain, N. F. A. Bakar, A. N. Mustapa, K.-F. Low, N. H. Othman, and F. Adam, “Synthesis of various size gold nanoparticles by chemical reduction method with different solvent polarity,” Nanoscale Research Letters, vol. 15, no. 1, Article ID 140, 2020.
View at: Publisher Site | Google Scholar
S. Azizi, M. Ahmad, M. Mahdavi, and S. Abdolmohammadi, “Preparation, characterization, and antimicrobial activities of ZnO nanoparticles/cellulose nanocrystal nanocomposites,” BioResources, vol. 8, no. 2, pp. 1841–1851, 2013.
View at: Publisher Site | Google Scholar
S. T. Khan, J. Musarrat, and A. A. Al-Khedhairy, “Countering drug resistance, infectious diseases, and sepsis using metal and metal oxides nanoparticles: current status,” Colloids and Surfaces B: Biointerfaces, vol. 146, pp. 70–83, 2016.
View at: Publisher Site | Google Scholar
Z. Lu, K. Rong, J. Li, H. Yang, and R. Chen, “Size-dependent antibacterial activities of silver nanoparticles against oral anaerobic pathogenic bacteria,” Journal of Materials Science: Materials in Medicine, vol. 24, pp. 1465–1471, 2013.
View at: Publisher Site | Google Scholar
O. B. Adewale, H. Davids, L. Cairncross, and S. Roux, “Toxicological behavior of gold nanoparticles on various models: influence of physicochemical properties and other factors,” International Journal of Toxicology, vol. 38, no. 5, pp. 357–384, 2019.
View at: Publisher Site | Google Scholar
A. Sani, C. Cao, and D. Cui, “Toxicity of gold nanoparticles (AuNPs): a review,” Biochemistry and Biophysics Reports, vol. 26, Article ID 100991, 2021.
View at: Publisher Site | Google Scholar
S. Sharmin, M. M. Rahaman, C. Sarkar, O. Atolani, M. T. Islam, and O. S. Adeyemi, “Nanoparticles as antimicrobial and antiviral agents: a literature-based perspective study,” Heliyon, vol. 7, no. 3, Article ID e06456, 2021.
View at: Publisher Site | Google Scholar
A. Balkrishna, N. Thakur, B. Patial et al., “Synthesis, characterization and antibacterial efficacy of Catharanthus roseus and Ocimum tenuiflorum-mediated silver nanoparticles: phytonanotechnology in disease management,” Processes, vol. 11, no. 5, Article ID 1479, 2023.
View at: Publisher Site | Google Scholar
P. Jamdagni, P. K. Sidhu, P. Khatri, K. Nehra, and J. S. Rana, “Metallic nanoparticles: potential antimicrobial and therapeutic agents,” in Advances in Animal Biotechnology and its Applications, S. Gahlawat, J. Duhan, R. Salar, P. Siwach, S. Kumar, and P. Kaur, Eds., pp. 143–160, Springer, Singapore, 2018.
View at: Publisher Site | Google Scholar
B. Khameneh, R. Diab, K. Ghazvini, and B. S. F. Bazzaz, “Breakthroughs in bacterial resistance mechanisms and the potential ways to combat them,” Microbial Pathogenesis, vol. 95, pp. 32–42, 2016.
View at: Publisher Site | Google Scholar
J. O. Sekyere, U. Govinden, L. A. Bester, and S. Y. Essack, “Colistin and tigecycline resistance in carbapenemase-producing Gram-negative bacteria: emerging resistance mechanisms and detection methods,” Journal of Applied Microbiology, vol. 121, no. 3, pp. 601–617, 2016.
View at: Publisher Site | Google Scholar
B. Kongkham, D. Prabakaran, and H. Puttaswamy, “Opportunities and challenges in managing antibiotic resistance in bacteria using plant secondary metabolites,” Fitoterapia, vol. 147, Article ID 104762, 2020.
View at: Publisher Site | Google Scholar
M. Wójcik, W. Lewandowski, M. Król et al., “Enhancing anti-tumor efficacy of doxorubicin by non-covalent conjugation to gold nanoparticles—in vitro studies on feline fibrosarcoma cell lines,” PLOS ONE, vol. 10, no. 4, Article ID e0124955, 2015.
View at: Publisher Site | Google Scholar
M. Yafout, A. Ousaid, Y. Khayati, and I. S. El Otmani, “Gold nanoparticles as a drug delivery system for standard chemotherapeutics: a new lead for targeted pharmacological cancer treatments,” Scientific African, vol. 11, Article ID e00685, 2021.
View at: Publisher Site | Google Scholar
B. Klębowski, J. Depciuch, M. Parlińska-Wojtan, and J. Baran, “Applications of noble metal-based nanoparticles in medicine,” International Journal of Molecular Sciences, vol. 19, no. 12, Article ID 4031, 2018.
View at: Publisher Site | Google Scholar
H. M. Joshi, D. R. Bhumkar, K. Joshi, V. Pokharkar, and M. Sastry, “Gold nanoparticles as carriers for efficient transmucosal insulin delivery,” Langmuir, vol. 22, no. 1, pp. 300–305, 2006.
View at: Publisher Site | Google Scholar
X. Hu, Y. Zhang, T. Ding, J. Liu, and H. Zhao, “Multifunctional gold nanoparticles: a novel nanomaterial for various medical applications and biological activities,” Frontiers in Bioengineering and Biotechnology, vol. 8, Article ID 990, 2020.
View at: Publisher Site | Google Scholar
H. Jing, Q. Zhang, N. Large et al., “Tunable plasmonic nanoparticles with catalytically active high-index facets,” Nano Letters, vol. 14, no. 6, pp. 3674–3682, 2014.
View at: Publisher Site | Google Scholar

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Copyright © 2023 Acharya Balkrishna et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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