Antimicrobial properties of spray-dried silver–zinc nanozeolite particles and their application in formulating antimicrobial electrospun polymeric fibers

Abstract

Silver-based antimicrobials are used in the consumer, medical and agricultural industries. Silver salts, silver nanoparticles, and silver ions trapped in hosts are being used. In this study, we investigate nanometer sized zeolites as hosts for silver ions. However, zeolite nanoparticles are colloidal in nature and their use as solid substrates requires processing of the colloidal solutions. The most common method is drying, resulting in aggregates of varying dimensions. In this paper, we use spray drying to generate more uniform micron-sized particles from colloidal solutions of silver–zinc exchanged zeolite nanoparticles (SDZNPs). The morphologies of SDZNPs are spheres and doughnut shaped particles. The antimicrobial properties of SDZNPs are examined using E. coli and methicillin resistant S. aureus (MRSA). The results of the minimum inhibitory concentration (MIC), morphological changes in bacteria upon SDZNP treatment, development of antimicrobial resistance, biofilm inhibition and ability to kill bacteria within RAW 264.7 macrophages are presented. Cytotoxicity and hemolysis assays suggest a dosage dependent effect on toxicity. To demonstrate the practical applications of SDZNPs, we incorporated these particles into electrospun fibers of polymers, namely polyvinylidene fluoride (PVDF) and poly(methyl methacrylate) (PMMA). The mechanical properties of the SDZNP fibers as well as the antimicrobial activity and cytotoxicity of the fibers are examined. The PMMA fibers performed significantly better than the PVDF fibers in antimicrobial tests, while both fibers were not cytotoxic at the dosages examined. We hypothesize that the difference in the antimicrobial properties is related to the zeolite particles being located more on the surface of the PMMA fibers and being more accessible.