This work describes fabrication of gold electrodes modified with peptide conjugate DAL-PEG-DK5-PEG-OH that enables ultra-sensitive detection of lipopolysaccharide (LPS) isolated from the reference strain of O26:B6. The initial step of the established procedure implies immobilization of the fully protected DAL-PEG-DK5-PEG-OH peptide on the surface of the gold electrode previously modified by cysteamine. Then side chain- and Fmoc-deprotection was performed on the electrode surface, followed by its incubation in 1 % of BSA solution to block non-specific bindings sites before LPS detection. The efficiency of the modification was confirmed by X-ray Photoelectron Spectroscopy (XPS) measurements. Additionally, the cyclic voltammetry (CV) and electrochemical impendance spectroscopy (EIS) were employed to monitor the effectiveness of each step of the modification. The obtained results confirmed that the presence of the surface-attached covalently bound peptide DAL-PEG-DK5-PEG-OH enables LPS detection by means of CV technique within the range from 5 × 10 to 5 × 10 g/mL in PBS solution. The established limit of detection (LOD) for EIS measurements was 4.93 × 10 g/mL with wide linear detection range from 5 × 10 to 5 × 10 g/mL in PBS solution. Furthermore, we confirmed the ability of the electrode to detect LPS in a complex biological samples, like mouse urine and human serum. The effectiveness of the electrodes in identifying LPS in both urine and serum matrices was confirmed for samples containing LPS at both 2.5 × 10 g/mL and 2.5 × 10 g/mL.

中文翻译：

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DAL-PEG-DK5-PEG-OH-抗菌肽缀合物修饰金电极电化学检测细菌内毒素脂多糖 (LPS)

这项工作描述了用肽缀合物 DAL-PEG-DK5-PEG-OH 修饰的金电极的制造，该电极能够超灵敏地检测从 O26:B6 参考菌株中分离出的脂多糖 (LPS)。所建立程序的第一步意味着将完全受保护的 DAL-PEG-DK5-PEG-OH 肽固定在先前由半胱胺修饰的金电极的表面上。然后在电极表面进行侧链和 Fmoc 去保护，然后在 1% BSA 溶液中孵育，以在 LPS 检测之前封闭非特异性结合位点。 X 射线光电子能谱 (XPS) 测量证实了修饰的效率。此外，还采用循环伏安法（CV）和电化学阻抗谱（EIS）来监测修饰的每个步骤的有效性。所得结果证实，表面附着的共价结合肽 DAL-PEG-DK5-PEG-OH 的存在使得能够通过 CV 技术在 PBS 溶液中检测 5 × 10 至 5 × 10 g/mL 范围内的 LPS。 EIS 测量的既定检测限 (LOD) 为 4.93 × 10 g/mL，PBS 溶液中的线性检测范围为 5 × 10 g/mL 至 5 × 10 g/mL。此外，我们还证实了该电极能够检测复杂生物样品（如小鼠尿液和人血清）中的 LPS。对于含有 2.5 × 10 g/mL 和 2.5 × 10 g/mL LPS 的样品，电极可有效识别尿液和血清基质中的 LPS。