Chitosan Oligosaccharide-Coated Carrier-Free Evodiamine–Curcumin Nanoassemblies Enhance Oral Delivery and Anti-Atherosclerotic Efficacy

Evo and Cur directly co-assembled into carrier-free nanoparticles • COS@EC NPs prolonged intestinal retention and increased systemic exposure • COS@EC NPs reduced ROS and VSMC proliferation with Nrf2/HO-1 upregulation • CETSA and DARTS supported HO-1 involvement in the cellular response • Oral COS@EC NPs reduced plaque burden in high-fat diet-fed ApoE −/− mice Oxidative stress and dysregulated vascular smooth muscle cell (VSMC) proliferation drive atherosclerotic (AS) progression and plaque development. Natural phytochemicals, including evodiamine (Evo) and curcumin (Cur), show anti-atherosclerotic potential, but poor aqueous solubility and insufficient intestinal absorption limit their oral use. Here, Evo and Cur were co-assembled into carrier-free Evo–Cur nanoparticles (EC NPs) and coated with chitosan oligosaccharide (COS) to obtain COS-coated EC nanoparticles (COS@EC NPs). Spectroscopic analyses and molecular dynamics simulations indicated that hydrophobic interactions, hydrogen bonding, and π–π stacking mediated Evo–Cur nanoassembly. Under simulated gastrointestinal conditions, COS@EC NPs reduced gastric Cur release and increased intestinal Cur release. After oral administration, COS@EC NPs prolonged intestinal residence and increased systemic exposure. In platelet-derived growth factor-BB (PDGF-BB)-stimulated VSMCs, COS@EC NPs suppressed excessive proliferation, reduced intracellular reactive oxygen species (ROS), elevated nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) expression, and restrained cell-cycle progression. This antiproliferative effect was partially reversed by the HO-1 inhibitor zinc protoporphyrin IX, suggesting HO-1 involvement. Cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) analyses showed treatment-associated increases in the apparent thermal and proteolytic stability of HO-1, further supporting its involvement. In high-fat diet-fed ApoE −/− mice, oral administration of COS@EC NPs reduced plaque burden, improved lipid profiles, and alleviated oxidative stress without detectable systemic toxicity. Overall, these findings support COS@EC NPs as a potential carrier-free oral nanomedicine strategy for AS therapy and suggest that HO-1-associated redox regulation contributes to their vascular protective effects.