Fractional thermolysis by bipolar radiofrequency facilitates cutaneous delivery of peptide and siRNA with minor loss of barrier function.

PURPOSE: In this study, we aimed to illustrate the utility of fractional radiofrequency (RF) that generated microchannels in the skin, allowing delivery of peptide and siRNA via the skin. The mechanisms involved in the correlation between macromolecule permeation and skin structure were also elucidated. METHODS: The morphology of the skin was examined by transmission electron microscopy (TEM), higher harmonic generation microscopy (HGM), and physiological factors. In vivo skin distribution of macromolecules was assessed by fluorescence and confocal microscopies. RESULTS: RF thermolysis selectively created an array of micropores deep into the epidermis without significant removal of the stratum corneum (SC). With energy of 30 mJ, a pore depth of 35 µm was achieved. The bipolar RF resulted in a 3-fold increase of transepidermal water loss (TEWL) compared with intact skin. The respective skin accumulation and flux of the peptide with a molecular weight (MW) of 2335 Da was 3- and 23-fold greater for the RF-treated group than for the non-treatment group. RF enhanced skin accumulation of siRNAs with MW of 10 and 15 kDa by 6.2- and 2.6-fold, respectively. Cutaneous penetration of the macromolecules with an MW of at least 40 kDa could be accomplished by RF. Confocal microscopy imaging revealed that RF could effectively deliver the peptide up to at least a 74-µm depth. The penetration depth of siRNA by RF irradiation was about 50 µm. CONCLUSIONS: The novel RF device efficiently delivered macromolecules into the skin while reserving SC layers to support some barrier functions. In this work, for the first time the assistance of fractional RF on peptide and siRNA transport was demonstrated.

Noninvasive delivery of siRNA and plasmid DNA into skin by fractional ablation: erbium:YAG laser versus CO2 laser.

The present study was conducted to evaluate the impacts of fractional erbium (Er):YAG and CO2 lasers on skin permeation of small interfering (si)RNA and plasmid (p)DNA vectors. In vitro skin delivery was determined with a Franz diffusion cell. In vivo absorption was investigated by observing fluorescence and confocal microscopic imaging. Fractional laser-mediated ablation of the skin resulted in significant enhancement of dextran and siRNA penetration. Respective fluxes of dextran (10 kDa) and siRNA, which had similar molecular size, with Er:YAG laser irradiation at 5 J/cm(2) were 56- and 11-fold superior to that of intact skin. The respective permeation extents of dextran and siRNA by the CO2 laser at 4 mJ/400 spots were 42- and 12-fold greater than that of untreated skin. Fluorescence and confocal images showed increased fluorescence intensities and penetration depths of siRNA and pDNA delivery. According to an examination of the follicular permeant amount and fluorescence microscopy, hair follicles were important deposition areas for fractional laser-assisted delivery, with the Er:YAG modality revealing higher follicular siRNA selectivity than the CO2 modality. This is the first report of siRNA and pDNA penetrating the skin with a sufficient amount and depth with the assistance of fractional lasers.