Optimal scaling analysis of polymeric microneedle length and its effect on transdermal insulin delivery

Polymeric microneedle is a highly effective, painless and safe method for transdermal drug delivery with broad market prospect and high application potential. In this paper, a novel method for the preparation of microneedle array with flexible substrate using the method of micro-injection compression molding was proposed. The influence of microneedle length on transdermal insulin delivery was investigated basing on the testing results of drug diffusion experiments. The results showed that the polymeric microneedles prepared by micro-injection compression molding had enough mechanical strength to pierce the skin without breaking. The correlations between dimensionless permeation amount of insulin and the ratio of surface area to microneedle length as well as the ratio of skin thickness to microneedle length were both obtained through optimal scaling analysis. The insulin penetration efficiency presented a 2.29 times improvement after treated with 337 mu m microneedle compared with that of untreated skin. The modification of polymeric microneedles could enhance the transdermal penetration efficiency of insulin, and also provide technical basis for the study of transdermal penetration.