Encapsulating GSH/NQO1-responsive SN38 prodrug micelles with Timosaponin AIII-based multifunctional liposomes for tumor-targeted chemotherapy

Colorectal cancer chemotherapy faces challenges with low intratumoral drug accumulation and off-target toxicity. Micellar liposome complex carriers are a promising anti-cancer platform due to their high encapsulation efficiency, responsive release, and multi-targeting capabilities. This study explores a novel tumor-targeted chemotherapy approach by encapsulating GSH/NQO1-responsive SN38 prodrug micelles into cholesterol-replacement multifunctional liposomes. Timosaponin AIII (TAIII), a steroid saponin with anticancer activity, substitutes cholesterol to stabilize liposomes, benefiting from its steroidal aglycone structure. Additionally, TAIII mimics PEGylation via its glucose moiety, enhancing tumor targeting via the overexpression of glucose transporter 1 (GLUT1) on cancer cells. Molecular docking studies with AutoDock revealed that GLUT1 residues stabilize TAIII in the binding pocket through hydrogen bonding, hydrophobic, and polar interactions, promoting its transmembrane transport. A specific amphiphilic SN38 prodrug, PEG-SS-SN38-QPA (PSSQ), was synthesized and self-assembled into micelles via a solvent injection-dialysis method for GSH/NQO1-responsive controlled drug release in the tumor microenvironment. PSSQ micelles were integrated into the hydrophilic cavity of TAIII-based liposomes (TLP, prepared by the thin-film hydration method) through passive encapsulation to form PSSQ@TLP. In vitro release study exhibiting GSH/NQO1-triggered release under simulated tumor microenvironment. In vitro cytotoxicity evaluation was performed using the MTT assay on HCT116, LOVO, CT26.WT cell lines. Following in vivo evaluations of biodistribution, anti-tumor efficacy, and biosafety in CT26.WT xenograft tumor-bearing mice, PSSQ@TLP demonstrated enhanced intratumoral accumulation, robust tumor suppression, and minimized systemic toxicity, underscoring its promise as a targeted therapeutic strategy for colorectal cancer.