A pH-sensitive delivery system based on N-succinyl chitosan-ZnO nanoparticles for improving antibacterial and anticancer activities of curcumin.

Inherent selective cytotoxicity, antibacterial activity and unique physicochemical properties of ZnO nanostructures and chitosan (CS) make them promising candidates for drug delivery. In this study, ZnO nanoparticles functionalized by N-succinyl chitosan as a pH-sensitive delivery system were synthesized to enhance the therapeutic potential of curcumin (CUR). CS coated-ZnO nanoparticles were synthesized by a co-precipitation method in the presence of CS. Chemical modification of CS-ZnO particles was performed by succinic anhydride for introducing -COOH functional groups which were then activated using 1,1'‑carbonyldiimidazole for CUR conjugation. The spherical-like CUR-conjugated system (CUR-CS-ZnO) with the average particle size of 40 nm presented significantly enhanced water dispersibility versus free CUR. The experimental study of CUR release from the system showed a pH-sensitive release profile, which enabled drug delivery to tumors and infection sites. MTT and Annexin-V FITC/PI assays revealed the superior anticancer activity of CUR-CS-ZnO compared to free CUR against breast cancer cells (MDA-MB-231) by inducing the apoptotic response with no cytotoxic effects on HEK293 normal cells. Moreover, CUR conjugation to the system notably dropped the MIC (25 to 50-fold) and MBC values (10 to 40-fold) against S. aureus and E. coli. The features qualify the formulation for anticancer and antimicrobial applications in the future.