Through The Identification Of Phage Library Transdermal Transport Protein Peptide

As the largest organ of the human body, skin provides a painless interface for ystemic drug delivery. However, the permeability of foreign molecules, especially large hydrophilic molecules, across the stratum corneum in the outer skin surface is extremely low. In the last 50 years a large number of chemical penetration enhancers (CPEs), belonging to several different classes such as surfactants, fatty acids, fatty esters and Azone-like compounds, have enabled limited skin permeation enhancement. CPEs have two major limitations: skin irritation and inability to deliver large molecules.Without physical enhancement, mediated by iontophoresis, ultrasound or microneedles, CPEs are generally unable to deliver therapeautic levels of relatively large drugs (molecular mass > 500 Da) through intact skin to the systemic circulation. Recent progress in high-throughput screening to identify enhancer combinations and application of CPE design principles may help overcome these two limitations, but transdermal delivery of large hydrophilic proteins remains a formidable task.Phage display peptide libraries are commonly used to obtain defined peptide sequences that interact with a particular molecule. We applied Ph.D.-C7C, a disulfide-constrained, phage-display, peptide library, onto the abdominal skin of BALB/cA nude mice and recovered phage particles from the blood circulation. Recovered phage were amplified and used for the next round of in vivo selection. Amplified phage from the first round exhibited a transdermal efficiency two orders of magnitude higher than that of the library phage. After the second round, twelve clones were randomly picked and sequenced. Eight of them contained an identical nucleotide sequence insert (termed PH-1), which coded for the displayed peptide CSSSPSKHC.Efficient transdermal drug delivery of large hydrophilic drugs is challenging. Here we report that the short synthetic peptide, ACSSSPSKHCG, identified by in vivo phage display, facilitated efficient transdermal protein drug delivery through intact skin. Coadministration of the peptide and insulin to the abdominal skin of diabetic rats resulted in elevated systemic levels of insulin and suppressed serum glucose levels for at least 11 h. Significant systemic bioavailability of human growth hormone was also achieved when topically coadministered with the peptide. The transdermal-enhancing activity of the peptide was sequence specific and dose dependent, did not involv direct interaction with insulin and enabled penetration of insulin into hair follicles beyond a depth of 600 μm. Time- lapse studies suggested that the peptide creates a transient opening in the skin barrier to enable macromolecular drugs to reach systemic circulation.