Photo-thermally enhanced antimicrobial efficacy of silver nanoplates against Gram-negative, Gram-positive bacterial and fungal pathogens

Aim: This paper aims to investigate the photo-thermally enhanced antimicrobial efficacy of triangular silver nanoplates for a broad range of harmful pathogens viz., Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and fungus (Candida albicans). Methods and Results: Triangular silver nanoplates were synthesized using the chemical method and were characterized for optical absorption, size and morphology, surface charge and concentration via UV-Vis spectroscopy, transmission electron microscopy, zeta potential analysis and inductively coupled plasma mass spectrometry, respectively. Furthermore, the photo-thermally enhanced antimicrobial efficacy of the triangular silver nanoplates (10 mu g/ml concentration) was evaluated on broadband near-infrared irradiation. The photothermal response shows that for the fixed concentration of silver nanoplates, the smaller-sized nanoplates (similar to 52nm) lead to higher temperature rise than larger-sized nanoplates (similar to 68nm). It is demonstrated that within a short exposure duration of 15 min, the photothermal activation of silver nanoplates led to similar to 5 log(10) CFU/ml reduction for E. coli and C. albicans, and similar to 7 log(10) CFU/ml reduction for S. aureus from a considerably high initial load of 5 x 10(8) CFU/ml. Conclusions: The present study demonstrates that photo-thermally enhanced triangular silver nanoplates possess much stronger antimicrobial efficacy over a short exposure duration of few minutes and exhibits the applicability for a broad range of pathogens. Significance and Impact of Study: The study is highly significant and explains the eradication of broad-spectrum of microbial pathogens by photo-thermally enhanced silver nanoplates in short exposure duration with low nanoparticle concentration, which is useful for diverse antibacterial and antifungal applications.