Interaction of nanoparticles and cell-penetrating peptides with skin for transdermal drug delivery.

Topical or transdermal drug delivery is challenging because the skin acts as a natural and protective barrier. Therefore, several methods have been examined to increase the permeation of therapeutic molecules into and through the skin. One approach is to use the nanoparticulate delivery system. Starting with liposomes and other vesicular systems, several other types of nanosized drug carriers have been developed such as solid lipid nanoparticles, nanostructured lipid carriers, polymer-based nanoparticles and magnetic nanoparticles for dermatological applications. This review article discusses how different particulate systems can interact and penetrate into the skin barrier. In this review, the effectiveness of nanoparticles, as well as possible mode of actions of nanoparticles, is presented. In addition to nanoparticles, cell-penetrating peptide (CPP)-mediated drug delivery into the skin and the possible mechanism of CPP-derived delivery into the skin is discussed. Lastly, the effectiveness and possible mechanism of CPP-modified nanocarriers into the skin are addressed.

Targeting of plasmid DNA-lipoplexes to cells with molecules anchored via a metal chelator lipid.

BACKGROUND: The ability to deliver plasmid DNA (pDNA) to specific cells in vivo is crucial for achieving efficient targeted transfection with nonviral vectors. We previously used stealth liposomes containing the chelator lipid 3(nitrilotriacetic acid)-ditetradecylamine (NTA(3)-DTDA) to target delivery of antigen and cytokines to immune cells in vivo. In the present study, we utilized liposomes containing NTA(3)-DTDA and the ionizable aminolipid 1,2-dioleoyl-3-dimethyl-ammonium-propane (DODAP) to incorporate pDNA into complexes for targeting to cells. METHODS: Liposomes containing DODAP, NTA(3)-DTDA and helper lipids were acidified (pH 5.5) and mixed with pDNA to form complexes. These lipoplexes were neutralized and engrafted with His-tagged molecules for targeting to extracellular receptors. Targeted transfection efficiency was assessed using the enhanced green fluorescent protein reporter gene. RESULTS: Initial transfections of HEK-293 cells using a His-tagged peptide (T2) related to the Arg-rich motif of HIV-1 TAT protein resulted in a low transfection efficiency (<2.5%). Optimization of the lipid formulation and use of an endosome-destabilizing peptide and inhibitor of DNase II, increased transfection approximately 20-fold. These lipoplexes are approximately 250 nm in diameter, and transfection efficiencies were: approximately 50% for HEK-293 cells targeted with lipoplexes containing pEGFP-N1 and engrafted with T2, and 30-40% for HepG2 cells targeted with lipoplexes engrafted with a peptide specific for the VEGF receptor Flt-1. CONCLUSIONS: The results show that DODAP-containing lipoplexes incorporating NTA(3)-DTDA enable the engraftment of targeting molecules and the effective targeting of pDNA to cells in serum-containing media, resulting in efficient transgene expression. The strategy may provide a convenient approach for targeting pDNA to cells in vivo in therapeutic applications.

(31)P solid-state NMR based monitoring of permeation of cell penetrating peptides into skin.

The main objective of the current study was to investigate penetration of cell penetrating peptides (CPPs: TAT, R8, R11, and YKA) through skin intercellular lipids using (31)P magic angle spinning (MAS) solid-state NMR. In vitro skin permeation studies were performed on rat skin, and sections (0-60, 61-120, and 121-180µm) were collected and analyzed for (31)P NMR signal. The concentration-dependent shift of 0, 25, 50, 100, and 200mg/ml of TAT on skin layers, diffusion of TAT, R8, R11, and YKA in the skin and time dependent permeation of R11 was measured on various skin sections using (31)P solid-state NMR. Further, CPPs and CPP-tagged fluorescent dye encapsulate liposomes (FLip) in skin layers were tagged using confocal microscopy. The change in (31)P NMR chemical shift was found to depend monotonically on the amount of CPP applied on skin, with saturation behavior above 100mg/ml CPP concentration. R11 and TAT caused more shift in solid-state NMR peaks compared to other peptides. Furthermore, NMR spectra showed R11 penetration up to 180µm within 30min. The results of the solid-state NMR study were in agreement with confocal microscopy studies. Thus, (31)P solid-state NMR can be used to track CPP penetration into different skin layers.

Translocation of cell penetrating peptide engrafted nanoparticles across skin layers.

The objective of the current study was to evaluate the ability of cell penetrating peptides (CPP) to translocate the lipid payload into the skin layers. Fluorescent dye (DID-oil) encapsulated nano lipid crystal nanoparticles (FNLCN) were prepared using Compritol, Miglyol and DOGS-NTA-Ni lipids by hot melt homogenization technique. The FNLCN surface was coated with TAT peptide (FNLCNT) or control YKA peptide (FNLCNY) and in vitro rat skin permeation studies were performed using Franz diffusion cells. Observation of lateral skin sections obtained using cryotome with a confocal microscope demonstrated that skin permeation of FNLCNT was time dependent and after 24h, fluorescence was observed upto a depth of 120 microm which was localized in the hair follicles and epidermis. In case of FNLCN and FNLCNY formulations fluorescence was mainly observed in the hair follicles. This observation was further supported by confocal Raman spectroscopy where higher fluorescence signal intensity was observed at 80 and 120 microm depth with FNLCNT treated skin and intensity of fluorescence peaks was in the ratio of 2:1:1 and 5:3:1 for FNLCNT, FNLCN, and FNLCNY treated skin sections, respectively. Furthermore, replacement of DID-oil with celecoxib (Cxb), a model lipophilic drug showed similar results and after 24h, the CXBNT formulation increased the Cxb concentration in SC by 3 and 6 fold and in epidermis by 2 and 3 fold as compared to CXBN and CXBNY formulations respectively. Our results strongly suggest that CPP can translocate nanoparticles with their payloads into deeper skin layers.