Boronate affinity-based surface molecularly imprinted polymer microspheres using polyethyleneimine/dopamine coating for efficient selective recognition and separation of Ginsenoside Rb1

Abstract

A novel approach combining boronate affinity with surface molecular imprinting was developed for the specific recognition and separation of ginsenoside Rb1. Firstly, the boronic acid-functionalized polymer microspheres were prepared as inner cores via suspension polymerization using methyl methacrylate, ethyleneglycol dimethacrylate, and 4-vinylphenyl boronic pinacol ester (4-VBPE) as polymerization monomers. Then, the Ginsenoside Rb1 (GRb1) template was covalently pre-anchored onto the surface of microspheres through boronate affinity binding after the hydrolysis of 4-VBPE. Finally, dopamine and polyethyleneimine were used as co-coating monomers to form a thickness-controllable imprinting layer onto the polymer microspheres via in-water self-copolymerization. The key factors affecting specific recognition, including the boronic acid content, adsorption media, and polymerization time were carefully optimized. The resulting molecularly imprinted microspheres (MIMs) exhibited strong surface hydrophilicity. In the aqueous media, the optimal adsorption capacity for the template reached 81.45 μmol g−1, and the imprinting factor was 5.32. The specific evaluation showed that the MIMs had a much higher selectivity for GRb1 than its analogues, and the selectivity coefficients were all higher than 2.4. In addition, the MIMs can be applied as adsorbents for solid-phase extraction to selectively separate ginsenosides from American ginseng extract. The eluting recovery ratios of GRb1, GRg2, and GRd reach 92.39%, 88.90%, and 92.49%, respectively.