Biogenic selenium nanoparticles from Bacillus mycoides SeITE01 and their potential as antimicrobial agents

Abstract

This study is focused on biosynthesis and characterization of Selenium nanoparticles (SeNPs) by Bacillus mycoides SelTE01 (biogenic SeNPs), evaluating their ability as antimicrobial agents. In so doing, a comparison between biogenically and chemically synthesized SeNPs was carried out, in order to stress differences and similarities. During my project, I worked in the Environmental Microbiology Laboratory at University of Verona and in Biofilm Research Group at University of Calgary (Canada). At University of Verona, I synthesized biogenic SeNPs by Bacillus mycoides SelTE01 grown with Na2SeO3 and chemical SeNPs using L-cysteine, ascorbic acid or a mix of SDS and Na2S2O3. I also characterized both SeNPs using Dynamic Light Scattering (DLS), Z potential measurement, Scanning Electron Microscopy (SEM) analysis and Energy Disperse Spectrometer (EDS) analysis. In Biofilm Research Group in Calgary, I evaluated SeNPs antimicrobial activity against pathogenic biofilms, normally resistant to conventional methods of disinfection. I investigated SeNPs ability to inhibit biofilm formation, exposing pathogenic biofilms to different concentrations of SeNPs and using Minimum Biofilm Eradication Concentration (MBEC) test and Calgary Biofilm Device (CBD). MBEC test is a high throughput screening assay used to determine the efficacy of antimicrobials against biofilms. It’s based on use of CBD: particular 96-well plate in which one batch culture apparatus allows multiple species biofilms to be tested against a lot of variables. In particular, I used CBDs coated of hydroxyapatite (HA), component of bones and teeth. In so doing, I was able to verify that biogenic SeNPs have stronger antimicrobial activity than those chemically synthetized.