Silver and Gold-Silver Nanoparticles Can Serve as Potential Protease Inhibitors for Staphylococcus aureus and Serratia marcescens Hydrolytic Enzymes

Staphylococcus aureus and Serratia marcescens are bacterial opportunistic pathogens. Their infections can range from mild and local to systemic and life-threatening. It is imperative to identify ways of reducing the virulence potential of these pathogens. Proteases of S. aureus and S. marcescens can destroy host tissues and evade host immune defenses. Reducing the function of the toxins and/or proteolytic enzymes of these pathogens may be a potential strategy of reducing pathogenicity. Silver and other ions have been used as an antimicrobial agent for years, but its effect on S. aureus and S. marcescens proteolytic enzyme function has not been evaluated. The hypothesis of this study is that silver-based monometallic and/or bimetallic silver-gold nanoparticles can inhibit the proteolytic enzyme function of S. aureus and S. marcescens through interference with enzymatic structure. To test the hypothesis, experimental procedures were used including synthesis of silver nanoparticles (AgNP) and gold-silver nanoparticles (Ag- AuNP), bacterial culture fractionation, spectrometry, and protease/peptidase assays. Results show that both monometallic AgNP and bimetallic Ag-AuNP can reduce bacterial proteolytic activities in S. aureus and S. marcescens. In conclusion, the findings of this study support the hypothesis that monometallic AgNP and bimetallic nanoparticles Au-AgNP can inhibit bacterial enzyme function. Silver and silver-gold nanoparticles may be a potential protease inhibitor treatment option that can help treat and prevent complications caused by these pathogens.

Keywords: S. aureus; S. marcescens; Virulence factors; Proteases; Bacterial pathogenesis; Nanoparticles