Integrating a Drug Release System into Textile Long Bone Implants by Dip Coating from Drug Suspension - Influence of Grain Size and Grain Size Distribution on the Releasing Profile

To reduce the risk of infection in the treatment of long bone defects, implant materials can be provided with an antibiotic drug delivery system. A novel bone implant for the tissue engineering of critical long bone defects was developed by stacking embroidered scaffolds, seeded with mesenchymal human stem cells. Controlled drug release is to be integrated in this implant by coating the thread material with antibiotics incorporated in a resorbable polymer matrix. A predictable release with defined and steady-going dosages must be guaranteed. Scaffolds, embroidered from a degradable surgical poly(caprolactone-co-lactide)-thread, were provided with an antibiotic depot by dip-coating them in a poly(lactide-co-glycolide) (RESOMER RG 756) solution with the antibiotic gentamicin sulfate distributed as suspended grains. Influence on the releasing profile is taken by varying grain size and grain size distribution. Antibiotic load in a required range could be achieved and an influence of the grain size on the releasing profile could be verified. The required initial and daily dosages could be realized and were exceeded in most of the cases. As optimum an approximated zeroorder kinetic in a time interval from 1 to 24 hours could be attained.