Gelatin microspheres cross-linked with EDC as a drug delivery system for doxycyline: development and characterization

Chronic wounds express elevated levels of proteases, in particular matrix metalloproteinases (MMPs), which degrades de novo granulation tissue and endogenous biologically active proteins. An effective therapeutic approach for chronic wounds would be to modify this hostile environment and reduce the proteolytic imbalance. Doxycycline has been proved recently to inhibit MMPs and used topically for chronic wound ulcers, beyond their antimicrobial profile. To this end, a carrier system for controlled release of doxycycline, suitable for incorporation into various wound dressings like membranes and sponges was developed. In the present study gelatin microspheres, cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) was proposed. The cross-linking was carried out with different concentrations of EDC (10 mM, 50 mM and 100 mM) and for different time periods (3-24 h). The cross-linked microspheres were characterized by evaluating the extent of cross-linking, the morphology, swelling behaviour and drug loading and in vitro studies of drug release, enzymatic degradation and biocompatibility. The extent of cross-linking increased as a function of both EDC concentration and the cross-linking time periods. It is found that the extent of cross-linking greatly influences the swelling and drug release behaviour of the microspheres. The cross-linked microspheres were found to be biocompatible to NIH 3T3 mouse embryonic fibroblast. The overall study indicates that the zero length cross-linker EDC can be considered as a potential alternative for cross-linking the gelatin microspheres.