Abstract
Chitosan-based nanogels are promising colloidal carriers for hydrophilic drugs de too their biocompatibility, adjustable physicochemical properties, and mild preparation conditions. In this study, cefazolin-loaded chitosan nanogels were prepared by ionic gelation using sodium tripolyphosphate (TPP) as a crosslinker. The effect of drug incorporation on the colloidal characteristics and interfacial behavior of the system was systematically evaluated. Freshly prepared blank and cefazolin-loaded nanogels showed hydrodynamic diameters of about 210 nm and 285 nm, respectively. Both systems exhibited positive zeta potential values above +25mV, indicating good electrostatic stability under acidic conditions. The encapsulation efficiency of cefazolin, determined by an indirect UV-Vis method, was 48 ± 6%, confirming effective drug entrapment within the crosslinked polymer network. After dialysis to remove low-weight impurities, purified dispersions were analyzed by dynamic surface tension measurements using the pendant drop method. Blank nanogels gradually adsorbed at the air-water interface, reducing surface tension from 71.8 to 67.4 mN/m ver time. In contrast, cefazoli-loaded nanogels exhibited slower adsorption kinetics and a smaller decrease in surface tension, reahing equilibrium values around 68.9mN/m.These differences are attributed to increased hydration and reduced mobility of chitosan chains after drug incorporation. Overall, cefazolin encapsulation significantly modified the interfacial adsorption behavior of chitosan nanogels while maintaining their colloidal stability. The results provide insight into structure-property relationships relevant to aqueous and topical drug delivery applications.