Effect Of Microneedle Arrary Transdermal Delivering Nerve Growth Factor On Promoting The Rehabilitation Of Transplanted Skin Sensation

Objective To investigate a minimally invasive administration method of NGF for promoting the rehabilitation of transplanted skin sensation. Methods In vitro: Following treatment of microneedle arrays(250μm group, 500μm group and 1000μm group) in full thickness skin of rabbit, the distribution and the depth of microporous were visualized using methylene blue staining of the skin and HE staining of cryostat sections. In vivo: Three different methods: direct coating, Microneedles mediated delivery and intradermal injection were applicated in this research. After 6 hours, concentrations of NGF in the skin homogenate of rabbit graft mode were examined using sandwich ELISA. And NGF concentrations of the plasma of rabbit graft mode were examined using sandwich ELISA.for hours. Distribution of NGF was confirmed by immunohistochemical study. After 30 days, regeneration of nerve fiber was confirmed by immunohistochemical study of autograft of skin for S100. Results The microporous are uniform distribution in skin. the microchannels of 1000μm group extend through the epidermis and just up to superficial dermal layer of section, The average depth, average diameter and average amount of microchannels was 174±81μm,69±14μm and 32±1 by treatment of microneedles (length 1000μm). Compared with microneedles (length 1000μm), the average depth, average diameter and average amount of microchannels was low than by treatment of microneedles (length 1000μm). The skin homogenate of graft skin in vivo studies showed that, a 6.46-fold and 5.50-fold increase in concentration of NGFof intradermal injection group (22.74%) and the microneedle mediated delivery group(19.36%) compared with the direct coating group(3.52%)(P<0.05), microneedle mediated delivery group and intradermal injection group showed no significant difference (P>0.05), The plasma of microneedle mediated delivery group and intradermal injection group in vivo studies showed that, the maximal concentration of NGF in plasma are 84.13±10.61 pg/ml and 41.69±10.7 pg/ml, showed significant difference (P<0.05),direct coating group(10.91±2.35 pg/ml)is very low. But, the higher concentration of NGF in plasma of microneedle mediated delivery group keeped a long time than intradermal injection group. Immunohistochemical staining of skin showed that a large number of NGF and arranged equality in dermal tissue of the microneedle mediated delivery group. The nerve fibers were confirmed by immunohistochemical staining of skin for S100 in dermal tissue of the microneedle mediated delivery group.Conclusions The microneedle array used in this study are able to overcome the barrier of the skin, are painless and effective. NGF could successfully reach to dermis through microchannel by formed the microneedle arrary so as to promote the rehabilitation of transplanted skin sensation.