Encapsulation of ciprofloxacin within modified xanthan gum- chitosan based hydrogel for drug delivery. 
The aim of the present work was to investigate the preparation of polyelectrolyte hydrogel as potential drug carrier for antibacterial Ciprofloxacin drug (CFX), intended for controlled release formulation.  Hydrogel of N-trimehtyl chitosan (TMC)/sodium carboxymethyl xanthan gum (CMXG) was prepared and ciprofloxacin was employed as a model drug to investigate the loading and release performance of the prepared hydrogel.  FTIR, DSC, TGA and SEM analysis were used to characterize the TMC/CMXG hydrogel and its CFX loaded hydrogel.  The results showed that the ciprofloxacin was successfully incorporated and released from the prepared hydrogel without the loss of structural integrity or the change in its functionality.  The encapsulation efficiency of CFX within the prepared hydrogel was found to be increased with increasing the concentration of drug reaching about 93.8 ± 2.1% with concentration of CFX 250 µg/ml.  It was shown also that the drug is entrapped within the gel without significant interaction as confirmed from FTIR spectra and DSC analysis.  In vitro release study in phosphate buffer saline (PBS), indicated the steady rise in cumulative drug release with the highest release amount, reaching about 96.1 ± 1.8% up to 150 min, whereby the gel with high drug loading efficiency (3.52 ± 0.07%) displayed faster and higher release rate than that of gel containing a smaller amount of drug (0.44 ± 0.01%).  The release kinetics of loaded drug followed zero-order kinetics.  CFX drug loaded hydrogel showed high activity against the gram positive and gram negative bacterial strains due to the successful released of CFX from the CFX loaded hydrogel into the tested bacterial strains with the highest diameter of inhibition zone against Escherichia coli (67.0 ± 1.0) as compared to reference antibiotic, Gentamicin (28 ± 0.5).  Cytotoxicity of the prepared hydrogel was examined in vitro using lung human normal cell lines and showed the highest cell viability (97 ± 0.5%) at concentration up to 50 µg/ml.  Consequently, TMC/CMXG hydrogel can be proposed as new controlled release drug delivery system.