Preparation and in vitro evaluation of a novel chitosan-based hydrogel for injectable delivery of enrofloxacin

The development of injectable sustained-release products are of great interest to veterinary pharmaceuticals and animal health business. Recently, great attention has been paid to in situ gel-forming chitosan/beta-glycerophosphate (chitosan/β-GP) solutions due to their good biodegradability and thermosensitivity.
The general aim of this study was to prepare a novel in situ gel-forming drug delivery system with a sustained release profile for enrofloxacin.
Chitosan, β-GP and enrofloxacin were used in different concentrations and six formulations of chitosan/β-GP were prepared. The properties of the hydrogels including the pattern of drug release, gelation time, syringeability, morphology, FTIR spectra, and in vitro antimicrobial activity were evaluated.
The release rate of enrofloxacin from the hydrogels and syringeability of the final solutions were decreased by increasing in β-GP and chitosan concentrations. All formulations could release the drug up to 120 hours but formulation 1 (chitosan-2%, β-GP-5% and enrofloxacin-1%) gave the best results based on its optimal drug release profile and viscosity. The FTIR studies showed that there were no interactions between enrofloxacin and hydrogel excipients. Scanning electron microscopy showed that the formed gel had a continuous texture, while the swelled gel in phosphate buffer had a porous structure. Microbiological tests revealed high bactericidal activities for this enrofloxacin- loaded hydrogel which were comparable to those of positive control (enrofloxacin suspension) in terms of inhibition zone, MIC and MBC values.
Because of simple preparation and sustained release profile of the drug, this hydrogel could be a promising delivery system for enrofloxacin in animals.