Structure-property effects of novel bioresorbable hybrid structures with controlled release of analgesic drugs for wound healing applications.

Over the last decades, wound dressings have developed from the traditional gauze dressing to tissue-engineered scaffolds. A wound dressing should ideally maintain a moist environment at the wound surface, allow gas exchange, act as a barrier to micro-organisms and remove excess exudates. In order to provide these characteristics, we developed and studied bioresorbable hybrid structures which combine a synthetic porous drug-loaded top layer with a spongy collagen sublayer. The top layer, prepared using the freeze-drying of inverted emulsions technique, was loaded with the analgesic drugs ibuprofen or bupivacaine, for controlled release to the wound site. Our investigation focused on the effects of the emulsion's parameters on the microstructure and on the resulting drug-release profile, as well as on the physical and mechanical properties. The structure of the semi-occlusive top layer enables control over vapor transmission, in addition to strongly affecting the drug release profile. Release of the analgesic drugs lasted from several days to more than 100 days. Higher organic:aqueous phase ratios and polymer contents reduced the burst release of both drugs and prolonged their release due to a lower porosity. The addition of reinforcing fibers to this layer improved the mechanical properties. Good binding of the two components, PDLGA and collagen, was achieved due to our special method of preparation, which enables a third interfacial layer in which both materials are mixed to create an "interphase". These new PDLGA/collagen structures demonstrated a promising potential for use in various wound healing applications.