To prepare the assembly, the team used protein-coated graphene oxide as a template to guide the arrangement of Au@Ag core-shell nanoparticles into a two-dimensional (2D) array. In the case of such a nano-hybrid, the researchers observed significantly increased bacteria-killing ability compared with individual nanoparticles and silver ions.

The group believes that this activity enhancement could be related to a "group-attacking" effect of the assembled nanoparticles. Mechanistic studies revealed strong adhesion of the 2D Au@Ag nano-assembly on the cell surface, which caused an aggregation and cellular lysis of the bacteria. During this process, the increased local concentration of silver around a bacterium and the "polyvalent" nanoparticle-bacterium interaction were both critical.

Next, the scientists plan to study the composition-, size-, and shape-related antibacterial behaviors of self-assembled materials, and to evaluate the antibacterial activity of samples against more bacterial species, including gram-positive ones.

Additional details can be found in the journal Nanotechnology 24 205102

Further reading

Photothermal effect of gold nanorod cluster disinfects biofilm (Jul 2013)
Antibacterial coatings: taking lessons from nature (Dec 2012)