The aim of this research was to describe a facile protocol to obtain biocompatible gold nanoparticles (AuNPs) suitable for microbial optical sensing. For this purpose, polycationic poly-L-lysine (PLL) was employed as both reducing and stabilizing agent in order to obtain an optically active microbial nanotag based on the electrostatic interaction with negatively charged cell envelopes. A one-pot procedure was developed to produce homogeneous, positively charged AuNPs. The as-synthesized particles, named PLL@AuNPs, exhibited maximal surface plasmon resonance (SPR) at 532 nm, a FCC crystalline nature, and sizes ranging from 20 to 25 nm, according to spectroscopy, X-ray diffractometry (XRD), transmission electron microscopy (TEM), and dynamic light scattering (DLS) analyses. The reduction of gold ions by PLL was featured by Fourier-transform infrared (FTIR) absorption bands of various functional groups. Zeta potential analysis confirmed the high cationic feature with a value of + 57 mV. The applicability of the particles to tag bacterial cell surfaces was exemplified by their adherence to Escherichia coli, a bacterial species commonly used to monitor fecal pollution in water sources. Finally, the potential of this tagging approach for microbial sensing through surface-enhanced Raman scattering (SERS) was explored.

中文翻译：

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聚阳离子金纳米粒子的新合成及其微生物光学传感的潜力

本研究的目的是描述一种简便的方案，以获得适用于微生物光学传感的生物相容性金纳米粒子 (AuNPs)。为此，聚阳离子聚-L-赖氨酸（PLL）被用作还原剂和稳定剂，以获得基于与带负电荷的细胞包膜的静电相互作用的光学活性微生物纳米标签。开发了一种一锅法来生产均匀的、带正电的 AuNP。根据光谱学、X 射线衍射 (XRD)、透射分析，合成的粒子称为 PLL@AuNPs，在 532 nm 处表现出最大表面等离子体共振 (SPR)，FCC 结晶性质，尺寸范围为 20 至 25 nm。电子显微镜 (TEM) 和动态光散射 (DLS) 分析。PLL 还原金离子的特点是各种官能团的傅里叶变换红外 (FTIR) 吸收带。Zeta 电位分析证实了具有 + 57 mV 值的高阳离子特征。颗粒对标记细菌细胞表面的适用性通过它们对大肠杆菌的粘附来举例说明，大肠杆菌是一种常用于监测水源中粪便污染的细菌种类。最后，探索了这种通过表面增强拉曼散射 (SERS) 进行微生物传感的标记方法的潜力。一种常用于监测水源粪便污染的细菌。最后，探索了这种通过表面增强拉曼散射 (SERS) 进行微生物传感的标记方法的潜力。一种常用于监测水源粪便污染的细菌。最后，探索了这种通过表面增强拉曼散射 (SERS) 进行微生物传感的标记方法的潜力。