Novel light-activated antimicrobial biomaterials for medical device infections

These infections arise from bacterial colonisation and biofilm formation on biomaterial surfaces, driving antimicrobial resistance (AMR). Current antimicrobial coatings, which rely on antibiotics or surface modifications, are increasingly ineffective due to resistance and limited durability.

Therefore, there is an urgent need for alternative, resistance-free infection control strategies. This thesis developed light-activated antimicrobial coatings using the photosensitiser toluidine blue O (TBO) for antimicrobial photodynamic therapy (aPDT). Upon red-light irradiation, TBO adopts a catalytic approach, generating reactive oxygen species that damage a plethora of biological targets through oxidative mechanisms, causing bacterial death without promoting resistance. ‘First-generation’ polymeric coatings incorporating TBO reduced bacterial counts below the detection limit within four hours; however, regrowth occurred after 24 hours, indicating limited sustained activity under high-flow conditions due to rapid burst release of TBO. ‘Second-generation’ coatings combined TBO with hydrophobically capped silver nanoparticles (Ag-NPs) to enhance photodynamic efficacy and prolong protection.