title: Peptides as skin penetration enhancers: mechanisms of action.
abstract: Skin penetrating peptides (SPPs) have garnered wide attention in recent years and emerged as a simple and effective noninvasive strategy for macromolecule delivery into the skin. Although SPPs have demonstrated their potential in enhancing skin delivery, they are still evolving as a new class of skin penetration enhancers. Detailed studies elucidating their mechanisms of action are still lacking. Using five SPPs (SPACE peptide, TD-1, polyarginine, a dermis-localizing peptide and a skin penetrating linear peptide) and a model hydrophobic macromolecule (Cyclosporine A, CsA), herein we provide a mechanistic understanding of SPPs. To evaluate the mechanism and safety of SPPs, their effects on skin lipids, proteins and keratinocyte cells were evaluated. Three SPPs (SPACE, Polyarginine and TD-1) significantly enhanced CsA penetration into the skin. SPPs did not alter the skin lipid barrier as measured by skin resistance, transepidermal water loss (TEWL) and Fourier transform infrared (FTIR) spectroscopic analysis. In contrast, SPPs interacted with skin proteins and induced changes in skin protein secondary structures (α-helices, β-sheet, random coils and turns), as evaluated by FTIR analysis and confirmed by in-silico docking. SPPs enhanced CsA skin penetration, via a transcellular pathway, enhancing its partitioning into keratin-rich corneocytes through concurrent binding of SPP with keratin and CsA. Interaction between SPP and keratin best correlated with measured CsA skin transport. Many SPPs appeared to be safe as shown by negligible effect on skin integrity, nominal skin irritation potential and cytotoxicity. Among the peptides tested, SPACE peptide was found to be least toxic to keratinocytes, and among the most effective at delivering CsA into the skin.
authors.affiliation: Center for Bioengineering, University of California, Santa Barbara, CA, United States; Department of Chemical Engineering, University of California, Santa Barbara, CA, United States.
authors.forename: Sunny
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Center for Bioengineering, University of California, Santa Barbara, CA, United States; Department of Chemical Engineering, University of California, Santa Barbara, CA, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Zakrewsky
authors.affiliation: Center for Bioengineering, University of California, Santa Barbara, CA, United States; Department of Chemical Engineering, University of California, Santa Barbara, CA, United States.
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.affiliation: Center for Bioengineering, University of California, Santa Barbara, CA, United States; Department of Chemical Engineering, University of California, Santa Barbara, CA, United States.
authors.forename: Stefano
authors.initials: S
authors.lastname: Menegatti
authors.affiliation: Convoy Therapeutics, 405 W Cool Drive, Suite 107, Oro Valley, AZ 85704, United States. Electronic address: jmuraski@convoytx.com.
authors.forename: John A
authors.initials: JA
authors.lastname: Muraski
authors.affiliation: Center for Bioengineering, University of California, Santa Barbara, CA, United States; Department of Chemical Engineering, University of California, Santa Barbara, CA, United States. Electronic address: samir@engineering.ucsb.edu.
authors.forename: Samir
authors.initials: S
authors.lastname: Mitragotri
mesh_terms: D002478:Cells, Cultured; D003198:Computer Simulation; D016572:Cyclosporine / Q000008:administration & dosage / Q000493:pharmacokinetics; D004337:Drug Carriers / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects; D007633:Keratins / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D010455:Peptides / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D012867:Skin / Q000737:chemistry / Q000187:drug effects; D012869:Skin Absorption / Q000187:drug effects*; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D014870:Water Loss, Insensible / Q000187:drug effects
chemical_list: D004337:Drug Carriers; D008055:Lipids; D010455:Peptides; C015462:polyarginine; D007633:Keratins; D016572:Cyclosporine
keywords: Cell penetrating peptide; Cyclosporine; Keratin; Topical; Transcellular; Transporter