There is a strong and growing need to monitor stress biomarkers in human beings and animals for real-time wellness assessment, which is a key indicator of health. Toward this, we report an optical fiber immunosensor based on laser-induced graphene (LIG) for the potential quantification and monitoring of cortisol hormone. The developed sensors were created using the Fabry-Pérot cavity principle. The cavities were filled with polyimide (PI) and, in some cases, PI mixed with gold nanoparticles. The interferometers were tested for temperature and refractive index, and an increase of two times in the sensitivity to the refractive index was observed due to the addition of the gold nanoparticles. In addition, the PI cavity was partially transformed into LIG using a CO₂ 20 kHz pulsed laser. The resulting LIG morphology was quite porous and presented a leafy texture. The presence of LIG creates a second cavity within the interferometer, and as a consequence, the spectral response of the interferometers resembled the Vernier effect. The refractive index behavior of the LIG-modified interferometers shows improvements in sensitivity up to 15.3 times due to the creation of the LIG cavity. The interferometers were then functionalized with anti-cortisol to promote an affinity for cortisol. Excellent sensitivities of up to -34.7 ± 0.7 nm/log(ng/mL) were achieved within few ng/mL concentration ranges (within the 0.5 to 3 ng/mL). The results obtained show an increase of up to 50 times in sensitivity when compared with other cortisol sensors. The achieved limit of detection was 0.1 ng/mL for the proposed sensors. The sensors’ responses were also shown to be immune to the interference from substances such as glucose, sucrose, fructose, and ascorbic acid. This study lays the foundation for new cortisol biosensors demonstrating a great potential for detection in a simple and highly sensitive way, opening its path for relevant biomedical and environmental monitoring applications in real samples. As a future outline, selectivity studies employing the detection of cortisol in the presence of interfering agents, both using synthetic and real samples, will be accomplished in order to fully investigate the potential of these sensing tools in real-life scenarios.

人们迫切需要监测人类和动物的压力生物标志物，以进行实时健康评估，这是健康的关键指标。为此，我们报告了一种基于激光诱导石墨烯（LIG）的光纤免疫传感器，用于皮质醇激素的潜在定量和监测。开发的传感器是利用法布里-珀罗腔原理创建的。空腔中填充有聚酰亚胺 (PI)，在某些情况下，PI 与金纳米颗粒混合。对干涉仪进行了温度和折射率测试，发现由于金纳米颗粒的添加，对折射率的灵敏度增加了两倍。此外，使用CO ₂ 20 kHz脉冲激光将PI腔部分转化为LIG。由此产生的 LIG 形态非常多孔，并呈现出叶状纹理。LIG 的存在在干涉仪内创建了第二个空腔，因此，干涉仪的光谱响应类似于游标效应。由于 LIG 腔的创建，LIG 改进干涉仪的折射率行为显示灵敏度提高了 15.3 倍。然后用抗皮质醇功能化干涉仪以促进对皮质醇的亲和力。在几个 ng/mL 浓度范围内（0.5 至 3 ng/mL 内）即可实现高达 -34.7 ± 0.7 nm/log(ng/mL) 的出色灵敏度。获得的结果显示，与其他皮质醇传感器相比，灵敏度提高了 50 倍。所提出的传感器达到的检测限为 0.1 ng/mL。传感器的响应也被证明不受葡萄糖、蔗糖、果糖和抗坏血酸等物质的干扰。这项研究为新型皮质醇生物传感器奠定了基础，展示了以简单且高灵敏度的方式检测的巨大潜力，为实际样品中的相关生物医学和环境监测应用开辟了道路。作为未来的纲要，将完成在存在干扰剂的情况下使用合成样品和真实样品检测皮质醇的选择性研究，以便充分研究这些传感工具在现实生活场景中的潜力。