Biological Synthesis of Reusable Silver Nanoparticle-Protein Antimicrobial Films

Silver nanoparticles (AgNPs) are used in electronics, medical and environmental applications. However, the toxicity of AgNPs in humans and the environment is a cause of concern. To address this, AgNPs are incorporated into nanocomposites to control their release and activity. As such, it is proposed to use curli fibers as a biological scaffold to integrate AgNPs. Curli fibers are amyloid proteins present in bacterial biofilms. Due to their adherence to many surfaces, they can facilitate their interaction with a range of nanomaterials. Curli films are manufactured by crosslinking them with glutaraldehyde and subsequently synthesizing AgNPs. By changing the precursor concentrations, the content of AgNPs synthesized is modulated. Curli-AgNP films are stable in pHs between 3–11 and in different solvents for 24 h. The release of AgNPs is greatest in alkaline pHs, with practically no release in acidic conditions. Additionally, curli-AgNP films display antimicrobial activity against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis), and the same film can be re-used multiple times against growing bacterial cultures. The ease of synthesis of curli-AgNP films coupled with their impressive stability, variable AgNPs release, and strong antimicrobial properties are suitable qualities that can be exploited to aid in wound healing or water treatment applications.