The Synthesis and Characterization of Bimetallic Nanoparticles Made By Bacteria for Biomedical Applications

Bimetallic nanoparticles show novel electronic, optical, catalytic or photocatalytic properties due to the synergy between two metals, compared to their monometallic counterparts. When controlling the proportions and the size of these nanoparticles, quantum dots can be synthesized, having applications in biomedicine, imaging or even as antibacterial agents. Traditional synthesis has been employed for the production of these bimetallic nanoparticles in an efficient way. However, physicochemical protocols are full of drawbacks, such as the production of toxic by-products and the need of further functionalization to make them suitable for biomedical applications. Therefore, green-synthetic approaches have been proposed as an alternative.

In this research, we present the environmentally-friendly and cost-effective synthesis of CdSe and ZnSe bimetallic nanoparticles using living bacteria, in an entirely green-synthetic approach. Bacteria are cultured in media that is inoculated with both sodium selenite (Na₂SeO₃) and cadmium chloride (CdCl₂)/zinc chloride (ZnCl₂) as metallic precursors for the nanoparticles. Using a detoxification process, bacteria can reduce metallic salt ions dissolved in elemental metallic nanoparticles with unique electronic properties.

Nanoparticles generated by bacteria, as other biogenic products, can be purified by disruption of the cell membranes and they can be used as antibacterial agents against both Gram-negative and Gram-positive bacteria, showing low cytotoxicity for human cells. Therefore, these metallic nanoparticles can be used for biomedical and imaging applications, indicating that green synthetic approaches can overcome the main limitations of traditional quantum dots synthesis methods.