Engineering Selenium–Chitosan Nanoparticles for Enhanced Hepatic Delivery of Sunitinib and Improved In Vitro Anticancer Activity in Hepatocellular Carcinoma Models

Background/Objectives: Hepatocellular carcinoma (HCC) remains difficult to treat because systemic therapy is constrained by limited selectivity, resistance, and toxicity. This study aimed to engineer selenium–chitosan nanoparticles loaded with sunitinib (SeNPs-Ch-SUN) to enhance hepatic delivery and improve anticancer activity against HCC. Methods: The developed system was characterized for particle size (PS), zeta potential (ZP), loading efficiency (LE%), in vitro release, and storage stability. Their cytotoxicity was evaluated in parental HepG2 and Huh-7 cells, multidrug-resistant HepG2 cells, SUN-resistant Huh-7 cells, and THLE-2 normal hepatocytes. In vivo hepatic distribution after intravenous administration was also assessed in rats. Results: SeNPs-Ch-SUN exhibited a mean PS of 93.62 ± 1.06 nm, positive ZP of +24.47 ± 1.31 mV, and LE of 83.8 ± 2.16%. FTIR supported drug association with the chitosan-stabilized selenium system. Compared with free sunitinib, SeNPs-Ch-SUN exhibited sustained drug release, with 51.17 ± 1.26% released at 24 h, whereas the free drug was almost completely released within 3 h. This controlled-release behavior translated in vivo into prolonged hepatic retention and superior liver exposure after intravenous administration. SeNPs-Ch-SUN significantly increased liver AUC0–24 to 77.23 ± 10.56 µg/g·h, compared with 36.39 ± 9.66 µg/g·h for free SUN, corresponding to an approximately 2.1-fold increase in hepatic exposure. SeNPs-Ch-SUN enhanced cytotoxicity in parental and resistant HCC models, lowered IC50 values, improved selectivity toward malignant cells, and reduced resistance index (RI) in MDR-HepG2 cells, while maintaining reduced toxicity toward normal hepatocytes relative to the free SUN. Conclusions: SeNPs-Ch-SUN represents a promising liver-directed nanoplatform for sunitinib delivery.