Antipyrine cationic surfactants capping silver nanoparticles as potent antimicrobial agents against pathogenic bacteria and fungi

Development of effective anti-microbial agents has been hindered by the emergence of bacterial strains with multi-drug resistance. In this article, we report an efficient synthesis of silver nanoparticle (AgNP) by capping with a synthetic cationic surfactants-based antipyrine. The synthesized antipyrine cationic surfactants were characterized by FT-IR and 1H NMR and their AgNPs were also delineated by TEM, DLS and UV-vis techniques. These AgNPs-capped cationic surfactants have average particle size of ~ 15-30 nm. These surfactants could self-assemble to form micelles in an aqueous medium and the critical micelle concentration (CMC) values as well as the surface parameters were determined at 20, 40 and 60 °C. The synthesized antipyrine cationic surfactants and their AgNPs were tested against growth of both Gram positive (Bacillus subtilis and Staphyl. aureus) and Gram negative (Pseudomonas aeruginosa and E. coli.) bacterial strains as well as fungi (Candida albicans and Aspergillus niger). It was found that the AgNPs significantly enhanced the antimicrobial activities of the synthesized antipyrine cationic surfactants. A strong structure-activity relationship was observed as a function of AgNPs functionality; providing guidance to activity prediction and rational design of effective antimicrobial nanoparticles. We propose that the antipyrine cationic surfactants-capped AgNPs can have potential bio-medical application against pathogenic bacteria.