Encapsulation of SOD in chitosan-coated gel particles of alginate or mixture of alginate and shellac for targeted intestinal delivery

The chitosan-coated alginate gel particles (CS/SA) and chitosan-coated alginate-shellac gel particles (CS/SA/Lac) were constructed to serve as a potential oral delivery system to enhance the stability and activity of superoxide dismutase (SOD) in this study. The encapsulation efficiency (EE), enzyme activity retention ratio (ER), particle structure, and SOD release behavior, as well as the effect of shellac, were evaluated. The best formula is determined by the percentage of total effective activity (PTEA).The results showed that CS/SA prepared by 0.30‰ chitosan, 1.00% CaCl2, 2.00% sodium alginate (M/G = 1:1, Mw: 38,857 kDa), and gelation solution pH 5.50 had the best chitosan shell, the strongest gel structure and the maximum PTEA which was 10.75 ± 1.45%. Based on the optimal formula, addition of shellac that formed shellac-Ca2+ microspheres in the gel network was averse to SOD encapsulation, but it significantly improved the stability of SOD in gastric conditions. By adding 15.00% shellac, the PTEA reached 16.30 ± 1.64%. At optimal formulation, SOD encapsulated in CS/SA was completely released in the stimulated intestinal fluid and accumulative release enzyme activity (EA) was 966.62 ± 103.75 (U) after 6 h. However, the CS/SA/Lac with a low swelling ratio only released SOD in stimulated colonic fluid and the EA value reached 1692.28 ± 101.82 (U) after 1 h. These findings demonstrated that CS/SA and CS/SA/Lac were excellent candidates for SOD oral administration, which was useful in the food and biomedical industries for developing functional products containing SOD.