Self-dissolving micropile array chip as percutaneous delivery system of protein drug

Erythropoietin (EPO) was successfully loaded on self-dissolving micropile array (SDMA) chip using chondroitin sulfate as the base polymer. "Drug glue" was prepared by adding EPO solution to chondroitin sulfate solution and SDMA was formed by micromolding fabrication technology. One SDMA chip, 1.0x1.0 cm, contained 100 micropile arrays. Two types of SDMA, partially-loaded SDMA (p-SDMA) and fully-loaded SDMA (f-SDMA), were prepared. The mean lengths of the SDMAs were 474.8+/-8.1 microm for p-SDMA and 473.4+/-5.2 microm for f-SDMA. The diameters of the array basements were 288.4+/-4.5 microm (p-SDMA) and 294.6+/-3.2 microm (f-SDMA). EPO content was 25.0+/-3.8 IU (p-SDMA) and 125.9+/-26.7 IU (f-SDMA). After percutaneous administration of each SDMA chip to rats, maximum serum EPO concentrations (C(max)) were 30.5+/-4.2 mIU/ml for p-SDMA and 32.4+/-5.0 mIU/ml for f-SDMA. The mean areas under the serum EPO concentration vs. time curves (AUC) were 534.0+/-102.4 mIU.h/ml (p-SDMA) and 523.1+/-50.4 mIU.h/ml (f-SDMA). Bioavailability (BA) values of EPO delivered from SDMAs were calculated to be 39.4% for p-SDMA and 7.7% for f-SDMA. Dose-dependency of the serum EPO concentration vs. time curve was studied using p-SDMA chip containing less EPO, 11.6+/-1.06 IU. Good dose-dependency was observed for C(max) and AUC. The p-SDMA chip was also evaluated in dogs. One or two p-SDMA chips, where 1 chip contained 22.4 IU of EPO, were percutaneously administered to dogs. BA of EPO delivered from p-SDMA was 65.9-69.0%. These results suggest the usefulness of p-SDMA as a percutaneous drug delivery system (DDS) for EPO.