Glass - Back to the Future!

Presenting Author:

article posted 04 April 2016

Farah Raja

The antimicrobial efficacy of cobalt and zinc doped phosphate based glasses on Gram positive and negative bacteria

Farah Raja*, Tony Worthington and Richard A. Martin
Aston Research centre for Healthy Ageing, Aston University. Birmingham

The growth and attachment of microorganisms on devices, such as catheters, dental and orthopaedic implants, is the major cause of biofilm formation and thus lead to infections. Prevention of microbial adhesion and colonisation is therefore the preeminent strategy to combat device related infections. The aim of the given study was to evaluate the antimicrobial efficacy of increasing cobalt and zinc content in phosphate based glasses. 1%, 3%, 5% and 10% cobalt and zinc doped glasses were prepared via the melt-quench technique and cut into discs. A decrease in the dissolution rates of cobalt glasses was seen with increasing Co content, however an increase in dissolution rate was observed with higher zinc content (5% and 10%). The antimicrobial activity was studied using the shaking flask and film contact method against both Gram negative (Escherichia coli NCTC 10538) and Gram positive (Staphylococcus aureus ATCO 6538) bacteria. Initial experiments using shaking flask method failed to demonstrate any significant decrease in bacterial density over a 5 day time period except for 5% and 10% zinc doped glasses which showed ~ 1 log reduction within 48 hours. However promising results were exhibited by both cobalt and zinc in the film contact method. Significant log reduction in S. aureus load was observed within 6 hours compared to the untreated glass as well as originally seeded bacteria. Complete kill was seen between 24 to 48 hours. E. coli on the other hand showed higher susceptibility to cobalt and zinc since the viability decreased to zero within 4 hours. Even though no significant results were obtained within the glass composition tested for each glass however strain specificity was observed, with Gram negative more susceptible than Gram positive bacteria. The study has shown that cobalt and zinc doped phosphate based glasses could potentially be used to coat or deliver antimicrobial ions to help combat device related infections.