Hydrogen-producing hyperthermophilic bacteria synthesized size-controllable fine gold nanoparticles with excellence for eradicating biofilm and antibacterial applications

Herein, we employed the hydrogen-producing hyperthermophilic bacterial strain Caldicellulosiruptor changbaiensis for preparing uniform and size-tunable gold nanoparticles (AuNPs). Compared with the commonly used chemically synthesized nanoparticles, the biological synthesis of nanoparticles appears to be a suitable process since it has a low manufacturing cost of scalability, good biocompatibility, and better nanoparticles stabilization. The produced AuNPs possessed a unique property, whereby the smallest AuNPs exhibited the highest peroxidase activity over a broad pH range, even at neutral pH, which was quite different from the commonly chemical-synthesized ones. Also, when the size of AuNPs increased, the peroxidase activity of B-AuNPs at neutral pH decreased. Owing to the excellent antibacterial capability of ROS, the AuNPs exhibited striking antibacterial properties against both Gram-positive and Gram-negative bacteria, and moreover, the AuNPs showed excellent ability to disperse bacterial biofilms both in vitro and in vivo. Our studies indicate that living bacterial cells, as a biosynthesizer, can synthesize size-controllable AuNPs with improved bioactivity. This work may promote the design and synthesis of other types of metal nanoparticles with defined properties for future applications.