Antimicrobial Silver Nanoclusters Bearing Biocompatible Phosphorylcholine-Based Zwitterionic Protection

Infection is one of the most serious issues in medical treatments leading to the development of several antimicrobial agents. In particular, silver ions released from silver substrates is well-known as a reliable antimicrobial agent that either kills the microorganisms or inhibits their growth. Unfortunately, many reports have shown that silver-based antimicrobial agents are toxic for human cells as well. To improve the biocompatibility of silver antimicrobial agents, we have synthesized thiol-terminated phosphorylcholine (PC-SH)-protected silver nanoclusters (PC-AgNCs) via strong thiol-metal coordination with controlled ultrasmall size of the clusters. A change in plasmon-like optical absorption was studied to affirm the successful synthesis of small thiolated AgNCs through the absorption spectra that become molecular-like for the AgNCs. We observed that PC-AgNCs were spherical with an average diameter of <2 nm. The ultrasmall size clusters were exceedingly immobilized by the PC-SH on the surface, resulting in excellent biocompatibility and antibacterial activity simultaneously. The biocompatible, antimicrobial PC-AgNCs exhibit interesting advantages compared with other silver antimicrobial agents for medical applications.