New antiinfectious biomaterials. Ciprofloxacin containing polyurethanes as potential drug delivery systems to prevent foreign-body infections.

Device related infections are an increasing problem since foreign materials are used in modern medicine. Ciprofloxacin-HCl salt (CAS 86393-32-0) and lipophilic ciprofloxacin-betaine (Bay o 9867) incorporated into polyurethanes by solvent casting technique were studied in order to develop antiinfectious properties of this biomaterial. Drug release rates, bacterial colonization and morphological features of the polymerciprofloxacin combinations were studied and the physico-chemical mechanisms of the delivery were discussed. Ciprofloxacin salt showed a fast initial release rate, whereas ciprofloxacin-betaine was characterized by a more continuous release behaviour. A higher diffusity of the lipophilic ciprofloxacin-betaine in the polymer could be shown as compared to its salt incorporated into the polyurethane. The high initial burst effect of the hydrochloride antibiotic was caused by its high solubility in the elution medium. Bacterial colonization to the antibiotic-loaded polyurethanes was inhibited effectively only by preparations showing a slower but more sustained drug release. Scanning electron microscopy (SEM) demonstrated that the polyurethane-antibiotic combination was most homogenous for ciprofloxacin-betaine. Polyurethane material loaded with ciprofloxacin salt showed crystals at the surface and a granular structure of the polymeric matrix. Crystalline structure of the drug on polymeric surfaces varied with loading concentration and lipophilicity. Physico-chemical similarity of the polymeric material and the antibodies is important for the homogeneity of the polymer-antibiotic combinations. High homogeneity is required for a sustained and prolonged release and effective inhibition of bacterial colonization.