Abstract
Bioreduction of gold ions by the thiol-modified M13 bacteriophage (M13-SH) has been exploited as the potential alternative to conventional methods based on toxic chemicals, due to the gold affinity of the thiol groups, inherent gold reduction, and high specific surface area of the filamentous virus. Such efforts have been hindered by harsh conditions involving strong reducing agents and extreme pH that are harmful to the virus. Herein, a virus-friendly and greener method of bioreduction of AuCl4 - at neutral pH based on M13-SH is demonstrated. M13-SH was prepared by coupling the virus with N-succinimidyl S-acetylthioacetate, followed by deacylation in the presence of hydroxylamine·HCl to expose the thiol groups. The key finding is that without time-consuming purification, the mixture after deacylation consisting of M13-SH, residual hydroxylamine, and so forth can directly turn ionic gold species into gold, leading to macroscopic precipitated products with interconnected linear structures consisting of fused gold nanoparticles. Besides working as the virus-friendly reducing agent with a unique autocatalytic style, hydroxylamine diminishes disulfide bonding-induced intervirus bundling of M13-SH so as to maintain its efficient biosorption of ionic gold precursors. This work demonstrates a general and green strategy of bioreduction of gold via combination of the gold-affinity proteins or organisms and the unique autocatalytic reduction of hydroxylamine.