Nanoparticles composed of the tea polysaccharide-complexed cationic vitamin B₁₂-conjugated glycogen derivative

Tea polysaccharides exhibit multiple important bioactivities, but very few of them can be absorbed through the small intestine. To enhance the absorption efficacy of tea polysaccharides, a cationic vitamin B₁₂-conjugated glycogen derivative bearing the diethylenetriamine residues (VB₁₂-DETA-Gly) was synthesized and characterized using FTIR, ¹H NMR, and UV-vis spectroscopy. An acidic tea polysaccharide (TPSA) was isolated from green tea. The TPSA/VB₁₂-DETA-Gly complexed nanoparticles were prepared, which showed positive zeta potentials and were irregular spherical nanoparticles in the sizes of 50-100 nm. To enable the fluorescence and UV-vis absorption properties of TPSA, a Congo red residue-conjugated TPSA derivative (CR-TPSA) was synthesized. The interactions and complexation mechanism between the CR-TPSA and the VB₁₂-DETA-Gly derivatives were investigated using fluorescence spectroscopy, resonance light scattering spectroscopy, and UV-vis spectroscopy. The results indicated that the electrostatic interaction could play a major role during the CR-TPSA and VB₁₂-DETA-Gly-II complexation processes. The TPSA/VB₁₂-DETA-Gly nanoparticles were nontoxic and exhibited targeted endocytosis for the Caco-2 cells, and showed high permeation through intestinal enterocytes using the Caco-2 cell model. Therefore, they exhibit potential for enhancing the absorption efficacy of tea polysaccharides through the small intestinal mucosa.