Immunological effects of microneedle-mediated insulin delivery: preliminary rat studies

The objective of the present study is to compare the immunogenicity of insulin by microneedle-mediated intradermal delivery or subcutaneous injection. Female and male rats were treated with insulin by either microneedle-mediated intradermal delivery or subcutaneous injection twice a week for 4 weeks. A control group without insulin administration was also studied. Human anti-insulin antibody (AIA) levels were measured by radioimmunoassay (RIA) before starting insulin treatment and after that within 20 weeks. The male rats did not induce positive AIA levels, and there was no significant difference between all male groups. In contrast, in female rats the AIA levels were significantly higher in microneedle group compared with injection group, and lasted from 6 to 20 weeks after starting insulin treatment. The increased immunogenicity of insulin delivery by microneedle might be due to the large number of immune cells in skin.