Development and characterisation of novel antimicrobial phosphate glasses for urinary tract infections

Abstract

Urinary tract infections (UTIs) affect significant proportions of the population, particularly prevalent in elderly patients. Up to 40 % of healthcare associated infections are UTIs and 80% of those are associated with catheter use. CA-UTIs significantly effect patient’s health and are frequently associated with substantial morbidity and mortality. Furthermore, the financial implications are enormous as the high complication rate arising from catheterisation requires significant time and cost. In the UK, more than a million cases are reported each year accounting for annual economic burden of approximately £125 million. The aim of this study was to develop novel antimicrobial bioactive glasses that can be used to prevent and treat catheter associated urinary tract infections. This was achieved by assessing the antimicrobial efficacy of increasing cobalt or zinc content (1, 3, 5 and 10 mol %) in phosphate based glass system (P2O5-Na2O-CaO). Glass compositions with two metal oxides (cobalt, copper or zinc) were also studied to determine synergistic combinations against a panel of clinically relevant microorganisms. A decrease in the dissolution rates of cobalt glasses was seen with increasing cobalt content, however an increase in dissolution rate was observed with higher zinc content (5% and 10%). A strong antimicrobial activity was exhibited by 5 and 10 mol % cobalt or zinc doped glasses which was not only time dependent but also strain specific. Moreover, combinations such as Co/Cu, Co/Zn and Cu/Zn showed synergism against E. coli and S. aureus. Whilst a strong antimicrobial activity was seen, the cytotoxic studies demonstrated decrease in cell viability of mammalian cells when exposed to glasses directly and their dissolution products. Nevertheless, cobalt and/or zinc doped phosphate based glasses could potentially be used as a cartridge in drainage bags or to coat catheters with a decreasing amount to prevent cytotoxic effects.