A robust method to coat allograft bone with a drug-releasing polymer shell - biomed 2010

Bone allograft material used for osseous void filling and structural support in skeletal reconstructive surgeries can also be used in combination as a drug carrier. Previous coating methods to load drugs, such as antibiotics and anti-inflammatories, provided an initial burst release, which may not be optimal for combating persistent local implant-associated bacterial infections. Theoretical drug release kinetics can be optimized not only with a clinically relevant drug-to-polymer ratio but also with a robust, effective rate-limiting release coating method. Three coating methods were evaluated in which degradable polycaprolactone (PCL) polymer retains and controls the release of antibiotic tobramycin from commercial, clinically common allograft bone fragments. Methods are based on a common dip-coating of the allograft fragment, with each coating method distinguished by subsequent drying and processing steps. Using a combination of classic polymer coating techniques, dipping and rapid drying, a method has been developed to apply the drug-releasing polymer coating while concurrently maintaining the high surface area, cancellous pore allograft structure. This provides increased local drug loading and controlled release over the clinically relevant six-to-eight week time period. This method offers potential for industrial scale-up as multiple cancellous allograft fragments can be processed batch-wise. Multiple drugs and combination therapies can also be applied in laminate coating designs.