Battling bacterial infection with hexamethylene diisocyanate cross-linked and Cefaclor-loaded collagen scaffolds

Implant infections remain a major healthcare problem due to the prolonged hospitalisation period required to disrupt and treat bacterial biofilm formation, and the need for additional surgery to remove/replace the infected implant, which if not removed in a timely manner may lead to sepsis. Although localised drug administration, via an implanted scaffold, has shown promise in a clinical setting, the ideal scaffold cross-linking (to initially withstand the aggressive infection environment) and drug (to be effective against infection) have yet to be identified. In this work, in the first instance, the biochemical, biophysical, and biological properties of collagen sponges as a function of various concentrations (0.625%, 1.0%, 2.5%, 5.0%, and 10.0%) of hexamethylene diisocyanate were assessed. Data presented illustrate that hexamethylene diisocyanate at 0.625% concentration was able to effectively stabilise collagen scaffolds, as judged by the reduction in free amines, adequate resistance to collagenase digestion, reduction in swelling, increase in denaturation temperature, suitable mechanical properties, and appropriate cytocompatibility. Subsequently, collagen scaffolds stabilised with 0.625% hexamethylene diisocyanate were loaded with variable concentrations (0, 10, 100, and 500 μg ml^-1) of Cefaclor and Ranalexin. Both drugs exhibited similar loading efficiency, release profile, and cytocompatibility. However, only collagen scaffolds loaded with 100 μg ml^-1 Cefaclor exhibited adequate antibacterial properties against both 10⁶ and 10⁸ colony-forming units per ml of both Escherichia coli and Staphylococcus epidermidis.