Bacterial colonization and biofilm formation on catheters are the primary causes of nosocomial infections and entails a limitation for their long-term use, often requiring catheter removal. Ca. 80% of the urinary tract infections contracted by patients in hospitals are catheter-associated, leading to substantial morbidity, mortality and higher costs. The increase of multi-drug resistant bacteria has created an urgent need for new strategies to prevent biofilm formation on catheters and antimicrobial photodynamic inactivation (aPDI) appears to be a promising approach. We have developed (patent pending) self-sterilizing silicone catheters with a covalently attached layer of photosensitizer (PS) that shows strong antibacterial effect in vitro against a panel of bacterial species commonly related to catheter-associated infections such as Pseudomonas aeruginosa and Staphylococcus epidermidis. Illumination with a 532 nm diode laser light of the PSderivatized catheter surfaces induced killing of 99-99.9% of the bacterial biofilm attached to it. The population survival decreased to a negligible level after 60 min of illumination and no significant decrease of the bacterial viability was observed in the absence of either light or PS. Time-resolved luminescence measurements with detection at 1265 nm confirmed generation of singlet molecular oxygen (1O2) only in PS-derivatized catheters upon illumination, paving the way for future applications to reduce the occurrence of catheter-associated urinary tract infections.
A novel therapeutic drug monitoring point of care testing (POCT) optical device for the detection of immunosuppressants in transplanted patients was designed and tested, with the body interface constituted by an intravascular microdialysis catheter (MicroEye®) which provides the dialysate as clinical sample. An optical biochip with 10 microchannels, based on total internal reflection fluorescence (TIRF), enables the frequent measurement of immunosuppressants. Heterogeneous competitive immunoassays for the detection of mycophenolic acid, tacrolimus and cyclosporine A are implemented on the different microchannels, with the derivative of the immunosuppressants immobilised on the bottom part of the micro-channels.