Biodistribution studies of radiolabelled ¹³¹I-BSA loaded gelatin microspheres were carried out on BALB/c mice after peroral administration. To two groups, the radiolabelled [¹³¹I]BSA gelatin microspheres with different particle size, 1.2 (+/- 1.1) mm and 7.0 (+/- 1.2) mm were administered orally. To the control group, a solution of [¹³¹I]BSA was also orally administered. Biodistribution was followed periodically within 15 days as a percent of total radioactivity present in stomach, small intestine with Peyer's patches and mesentery, colon with Peyer's patches, appendix and mesentery, liver, spleen, blood, kidney, lungs and heart. Preliminary in vitro biodegradation and drug release studies confirmed the potential of gelatin microspheres to protect the antigen of interest from enzymatic degradation in the gut, and to release it in a controlled manner. The biodistribution data confirmed that particle uptake into Peyer's patches and passage to the liver and spleen via the mesentery lymph supply and nodes, increased with decreasing particle size.

Keywords:gelatin microspheres, ¹³¹I, bovine serum albumin, particle size, peroral, biodistribution