Fabrication of Rubisco-curcumin nanoparticles: comprehensive characterization and photochemical, thermal, and gastrointestinal stability evaluation

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was utilized as a novel food-grade nanocarrier for curcumin delivery via a pH-triggered dissociation-reassembly strategy. At pH 10.0, the holoenzyme dissociated into subunits, exposing hydrophobic domains that facilitated curcumin loading upon neutral reassembly. Multi-spectroscopic, thermodynamic, and computational analyses verified deep insertion of curcumin into the large subunit hydrophobic pocket via cooperative hydrophobic interactions and hydrogen bonding. The complex exhibited a hydrodynamic diameter of approximately 120 nm, an entrapment efficiency of 88.2%, and an approximately 3000-fold in aqueous solubility. Encapsulated curcumin demonstrated superior photostability, thermal stability, and 30-day storage stability. In vitro gastrointestinal digestion revealed a 12.7-fold improvement in estimated in vitro bioavailability. Cell viability assessment on Caco-2 cells demonstrated that the nanocarrier significantly attenuated curcumin-induced cytotoxicity at concentrations ≥75 μg/mL, with empty Rubisco nanoparticles showing no intrinsic toxicity. These findings establish Rubisco as a structurally defined, biocompatible platform for oral delivery of hydrophobic nutraceuticals.