| The goal of this research was to investigate the transdermal delivery of recombinant human insulin via thermally created micropores either alone or in combination with iontophoresis.; Micropores (80 pores/cm2) were created in stratum corneum of freshly excised mouse/rat skin, using prototype porator system. Each of these micropores was approximately 100mum in diameter and 40mum deep. Microporated or intact skin was mounted on Franz diffusion cells and insulin formulation was added to the donor compartment. Permeation of insulin through intact skin was very negligible while significant amounts were delivered through microporated skin at the end of 24 hours. A linear increase in cumulative amounts was observed with increasing insulin concentration, except at the lowest concentration. A concentration dependent loss of insulin was observed in the receptor compartment; at highest concentration percent loss was low and vice versa. Passive and iontophoretic delivery resulted in very low amounts of insulin permeating through intact skin. Iontophoresis did not enhance transdermal delivery over passive diffusion across microporated skin.; For in vivo studies, hairless rats were anesthetized by an intraperitoneal dose of ketamine and xylazine. Micropore array was created on rat abdomen using thermal microporation device and patch was placed over it. Factors affecting insulin delivery such as insulin concentration in formulation, micropore density and micropore area were investigated. A glucometer was used to analyze serum samples for glucose concentration while a validated ELISA was used to determine insulin concentrations.; Steady state levels were maintained during 4 hour patch application period and they returned to baseline values upon patch removal. A linear increase in these levels was seen with increasing insulin concentration (0.227 +/- 0.004, 0.782 +/- 0.04, 1.1 +/- 0.05, 1.81 +/- 0.01 ng/mL respectively for 10, 25, 50 and 100 IU/mL insulin concentrations) as well as with increasing micropore area. Greatest increase in delivery (3.7 +/- 0.2 ng/mL for 3cm2) was achieved with increasing microporation area. Repeated patch application was able to maintain steady state levels during each 4 hours patch application for a total of 12 hours. The insulin formulation used was shown to be stable over during the study period by CD analysis, light scattering, gel electrophoresis and RP-HPLC. |
