Characterization of a polyurethane-based controlled release system for local delivery of chlorhexidine diacetate

Conventional formulations of chlorhexidine usually provide short-term efficiency, requiring repeated applications to maintain antibacterial activity. Therefore, appropriate release system of chlorhexidine controlling local drug delivery would reduce the number of applications and enhance patient compliance. The aim of this study was to develop a controlled release system based on medical polyurethane for the local delivery of chlorhexidine diacetate (CDA). CDA-loaded polyurethane films (CDA-Films) and CDAloaded polyurethane sandwiches (CDA-Sandwiches) were obtained by casting and solvent evaporation. The physico-chemical aspects of CDA-loaded polyurethane systems were investigated, and the crystalline state of CDA in the polymeric system was highlighted. CDA-Films exhibited appropriate mechanical properties for further applications. Drug release was measured in two different media: (i) distilled water and (ii) physiological saline solution to mimic in vivo conditions. Drug release studies were performed up to 11 days on CDA-Films and 29 days for CDA-Sandwiches. Release of CDA depended on drug loading and the structure of the system. In particular, release of CDA from the sandwich system followed zero-order kinetic. The release rate was significantly lower in physiological solution. Antibacterial studies were carried out on CDA-Films against Staphylococcus aureus and Staphylococcus epidermidis showing 35 days persisting antibacterial activity. In conclusion, the polyurethane-based system developed in this study is potentially useful as a local delivery system for CDA and could be used not only in surgery but also in dental and clinical applications.