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Nanoscience has practical applications in antimicrobial materials and surfaces with a focus on preventing the formation of biofilms on implanted medical devices. Health risks associated with silver and gold nanoparticles are undesirable. Silica is a very safe, biocompatible material that is easier and cheaper to synthesise. My own previous experiments found that, at certain concentrations and size ranges, silica nanoparticles demonstrate very promising antimicrobial activity so this project set out to find a material which could be coated with fewer risks and better sustainability prospects.
This project investigated coating four different materials, brass, aluminium, acrylic and PDMS. These materials were cut into 10 mm squares and submerged into 15ml of a silica nanoparticle-deionized water suspension of 59.5 µg/mL and left for two days. The coated materials were placed on lawn plates of bacteria grown on standard nutrient agar plates and the visible zone of inhibition around the coated materials was measured after a 48-hour incubation period.
Silica-coated brass was the only effective material against any of the bacteria. It was effective against gram negative Klebsiella pneumoniae and Escherichia coli. I deduced that the silica nanoparticles on the brass surface showed statistically significant growth inhibition against gram negative Klebsiella pneumoniae and Escherichia coli by puncturing small holes in the membrane of the bacterial cell allowing the copper (and possible zinc) ions access, causing the visible discolouration and resulting in cell lysis.
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