Nanobiomaterials and Bioprocessing Laboratory (NABLAB), Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, TX 77710, USA.
School of Biological Sciences and Engineering, Yachay Tech University, Hacienda San José s/n, San Miguel de Urcuquí 100119, Ecuador.
Molecules. 2019 Sep 27;24(19):3506. doi: 10.3390/molecules24193506.
In the current study, extracellular polymeric substances (EPS) of and photon energy biosynthetically converted Ag to silver nanoparticles (AgNPs). The reaction mechanism began with the non-photon-dependent adsorption of Ag to EPS biomolecules. An electron from the EPS biomolecules was then donated to reduce Ag to Ag, while a simultaneous release of H acidified the reaction mixture. The acidification of the media and production rate of AgNPs increased with increasing light intensity, indicating the light-dependent nature of the AgNP synthesis process. In addition, the extent of Ag disappearance from the aqueous phase and the AgNP production rate were both dependent on the quantity of EPS in the reaction mixture, indicating Ag adsorption to EPS as an important step in AgNP production. Following the reaction, stabilization of the NPs took place as a function of EPS concentration. The shifts in the intensities and positions of the functional groups, detected by Fourier-transform infrared spectroscopy (FTIR), indicated the potential functional groups in the EPS that reduced Ag, capped Ag, and produced stable AgNPs. Based on these findings, a hypothetic three-step, EPS-mediated biosynthesis mechanism, which includes a light-independent adsorption of Ag, a light-dependent reduction of Ag to Ag, and an EPS concentration-dependent stabilization of Ag to AgNPs, has been proposed.
在本研究中，细胞外聚合物质 (EPS) 生物合成地将银转化为银纳米粒子 (AgNPs)。反应机制始于 Ag 非光子依赖性地吸附到 EPS 生物分子上。然后，EPS 生物分子中的一个电子被捐献出来将 Ag 还原为 Ag，同时 H 的释放使反应混合物酸化。随着光强度的增加，介质的酸化和 AgNPs 的产率增加，表明 AgNP 合成过程依赖于光。此外，从水相消失的 Ag 量和 AgNP 的产率都取决于反应混合物中 EPS 的数量，表明 Ag 吸附到 EPS 是 AgNP 生产的重要步骤。反应后，作为 EPS 浓度的函数，纳米粒子的稳定化发生。傅里叶变换红外光谱 (FTIR) 检测到的官能团强度和位置的变化表明，EPS 中可能存在还原 Ag、封端 Ag 和产生稳定 AgNPs 的官能团。基于这些发现，提出了一个假设的三步 EPS 介导的生物合成机制，包括 Ag 的非光子依赖性吸附、Ag 到 Ag 的光依赖性还原以及 EPS 浓度依赖性的 Ag 到 AgNPs 的稳定化。
