Abstract
The persistence of multidrug resistance among microorganisms has directed a mandate towards a hunt for the development of alternative therapeutic modalities. In this context, antimicrobial photodynamic therapy (aPDT) is sprouted as a novel strategy to mitigate biofilms and planktonic cells of pathogens. Nanoparticles (NPs) are reported with unique intrinsic and antimicrobial properties. Therefore, silver NPs (AgNPs) were investigated in this study to determine their ability to potentiate the aPDT of photosensitizer against Staphylococcus aureus and Pseudomonas aeruginosa. Biologically synthesized AgNPs were surface coated with methylene blue (MB) and studied for their aPDT against planktonic cells and biofilms of bacteria. The nano-conjugates (MB-AgNPs) were characterized for their size, shape and coated materials. MB-AgNPs showed significant phototoxicity against both forms of test bacteria and no toxicity was observed in the dark. Moreover, activity of MB-AgNPs was comparatively higher than that of the free MB, which concludes that MB-AgNPs could be an excellent alternative to combat antibiotic resistant bacteria.
Highlights
The emergence of several new diseases and multidrug resistant (MDR) bacterial strains has accelerated the drug discovery program for the search of novel drugs
Some reports on the effect of PS-coated nanometal conjugates against several bacterial strains are available [14,40], for the first time, the present study demonstrates the extracellular biosynthesis of AgNPs using culture supernatants of bacterial isolate B. subtilis RY3 surface coated with methylene blue (MB) for the antimicrobial and antibiofilm photodynamic treatment
The present study demonstrated that silver nanoparticles surface coated with MB enhanced the antimicrobial photodynamic therapy (aPDT) of MB against planktonic cells and biofilms of Gram-negative and Gram-positive bacteria
Summary
The emergence of several new diseases and multidrug resistant (MDR) bacterial strains has accelerated the drug discovery program for the search of novel drugs. The ESKAPE group of pathogens including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. are major causes of bacterial and nosocomial infections and often “escape” from antimicrobial treatment by developing resistance mechanisms against current antimicrobial agents [3]. This is a serious concern associated with the increasing global rate of mortality and morbidity [4]. Bacteria-mediated synthesis of AgNPs is considered a beneficial biological route of synthesis owing to the simple synthesis process, lower production costs, and non-toxic nature [8]
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