Fabrication of Self-Assembled (−)-Epigallocatechin Gallate (EGCG) Ovalbumin–Dextran Conjugate Nanoparticles and Their Transport across Monolayers of Human Intestinal Epithelial Caco-2 Cells

Nanoparticles have the potential to increase bioavailability of nutraceutical compounds such as (−)-epigallocatechin gallate (EGCG). Ovalbumin was conjugated with dextran using the Maillard reaction. The resultant ovalbumin–dextran (O–D) conjugates were self-assembled with EGCG to form EGCG O–D conjugate nanoparticles at pH 5.2 after heating at 80 °C for 60 min. Ovalbumin in EGCG O–D conjugate nanoparticles was further cross-linked by glutaraldehyde for 24 h at room temperature. EGCG O–D conjugate nanoparticles and cross-linked EGCG O–D conjugate nanoparticles in aqueous suspension had particle sizes of 285 and 339 nm, respectively, and showed a spherical morphology. The loading efficiencies of EGCG in these two nanoparticles were 23.4 and 30.0%, whereas the loading capacities were 19.6 and 20.9%, respectively. These nanoparticles showed positive zeta-potentials in a pH range from 2.5 to 4.0 but had negative charges at pH ≥5.0. EGCG O–D conjugate nanoparticles maintained a particle size of 183–349 nm in simulated gastric fluid (SGF) and 188–291 nm in simulated intestinal fluid (SIF) at 37 °C for 2 h, whereas cross-linked nanoparticles had particle sizes of 294–527 nm in SGF and 206–300 nm in SIF. Limited release of EGCG was observed in both nanoparticle systems in simulated gastric and intestinal fluids without and with digestive enzymes. EGCG O–D conjugate nanoparticles significantly enhanced the apparent permeability coefficient (Papp) of EGCG on Caco-2 monolayers compared with EGCG solution, suggesting that these nanoparticles may improve the absorption of EGCG.