Biodistribution of 131I-BSA loaded gelatin microspheres after peroral application to BALB/c mice--particle size study.

Biodistribution studies of radiolabelled 131I-BSA loaded gelatin microspheres were carried out on BALB/c mice after peroral administration. To two groups, radiolabelled 131I-BSA gelatin microspheres of different particle size, 1.2 +/- 1.1 microm and 7.0 +/- 1.2 microm, were administered orally. To the control group, a solution of 131I-BSA was administered orally as well. Biodistribution was followed periodically within 15 days as the percent of total radioactivity present in the stomach and small intestine with Peyer's patches and mesentery, in colon with Peyer's patches, appendix and mesentery, in 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.