Novel intrinsically antimicrobial polymers to control biofilm formation on medical devices

Device coating with antimicrobial agents able to inhibit microbial colonisation and biofilm formation represents a pivotal approach in the prevention of medical device-associated infections. Existing antiseptic or antibiotic loaded devices mainly suffer from a relatively short persistence of antimicrobial action as consequence of an early and rapid drug release. On the other hand, the most frequently implicated microrganisms in device colonisation, such as Staphylococcus, Pseudomonas and Candida spp, are known to develop a largely increased antibiotic resistance due to their sessile mode of growth to form a biofilm. These issues are both critical for the management of patients in clinical settings and need the development of innovative and safer medical devices refractory to microbial adhesion and biofilm formation. To this aim, we developed and tested in vitro novel intrinsically antimicrobial polymers based on functionalized polyurethanes able to coordinate metal ions, including silver, zinc, copper, aluminium and iron. With the exception of the aluminium-containing polymer, all the other experimented polymers showed satisfactory antimicrobial properties. The best antibacterial effect was obtained by the polyurethane functionalized with silver ions which showed an ability to inhibit the S. epidermidis growth up to 16 days. The further adsorption of ciprofloxacin on this polymer allowed to obtain a long-lasting antibacterial synergistic activity against Gram-positives and Gram-negatives. In conclusion, the combined treatment of our functionalised polyurethanes with antibiotic/antifungal drugs and silver ions seems to offer promising perspectives in prevention of bacterial colonisation, biofilm formation and control of drug resistance.