Endophthalmitis therapy revolution: Proof of concept based on in vivo evaluation of maleic acid modified chitosan

The aim was to develop chitosan-maleic acid (CS-MA) based ocular inserts with enhanced mucoadhesiveness for prevention of endophthalmitis caused by Escherichia coli. Therefore, chitosan (CS) and maleic acid (MA) were conjugated via formation of amide bond. Characterization via proton nuclear magnetic resonance and infrared spectroscopy was carried out and attached maleic acid groups were quantified by free amino groups assay. Biocompatibility of the conjugate was assessed following resazurin assay on fibroblasts, membrane damage on human erythrocytes and Hen's Egg-Chorioallantoic membrane tests. Inserts were pressed and characterized in terms of swelling behavior, pH, hardness, in vitro drug release and disintegration. To test mucoadhesive properties of CS-MA inserts, rheometer, rotating cylinder, inclined plane, and texture analyzer were the instruments utilized. Furthermore, antibacterial efficacy of the conjugate was established by direct agar diffusion method and in vivo Draize test was carried out to determine tolerability of the inserts. Results exhibited successful synthesis of the biomaterial, maintaining the great biocompatibility of native chitosan even though a 68.81% of modification was achieved. Additionally, mucoadhesive studies showed improved properties of CS-MA compared to native polymer, with 2.42-fold, 4-fold, 3.42-fold and 4.05-fold increase in dynamic viscosity, retention time, overall attachment work and peak force of detachment, respectively. Finally, antibacterial activity was enhanced in 1.77-fold and in vivo experiments showed no irritation and good tolerability of CS-MA inserts. In conclusion, CS-MA ocular inserts effectively developed exhibiting promising features capable of revolutionizing the endophthalmitis therapy field.