Fractional Thermolysis by Bipolar Radiofrequency Facilitates Cutaneous Delivery of Peptide and siRNA with Minor Loss of Barrier Function

Enhancing Permeation of Drug Molecules Across the Skin via Delivery in Nanocarriers: Novel Strategies for Effective Transdermal Applications

The transdermal route of administration provides numerous advantages over conventional routes i.e., oral or injectable for the treatment of different diseases and cosmetics applications. The skin also works as a reservoir, thus deliver the penetrated drug for more extended periods in a sustained manner. It reduces toxicity and local irritation due to multiple sites for absorption and owes the option of avoiding systemic side effects. However, the transdermal route of delivery for many drugs is limited since very few drugs can be delivered at a viable rate using this route. The stratum corneum of skin works as an effective barrier, limiting most drugs' penetration posing difficulty to cross through the skin. Fortunately, some non-invasive methods can significantly enhance the penetration of drugs through this barrier. The use of nanocarriers for increasing the range of available drugs for the transdermal delivery has emerged as a valuable and exciting alternative. Both the lipophilic and hydrophilic drugs can be delivered via a range of nanocarriers through the stratum corneum with the possibility of having local or systemic effects to treat various diseases. In this review, the skin structure and major obstacle for transdermal drug delivery, different nanocarriers used for transdermal delivery, i.e., nanoparticles, ethosomes, dendrimers, liposomes, etc., have been discussed. Some recent examples of the combination of nanocarrier and physical methods, including iontophoresis, ultrasound, laser, and microneedles, have also been discussed for improving the therapeutic efficacy of transdermal drugs. Limitations and future perspectives of nanocarriers for transdermal drug delivery have been summarized at the end of this manuscript.

Transdermal delivery of FITC-Dextrans with different molecular weights using radiofrequency microporation

Background

Transdermal delivery is of great importance for the effective delivery of bioactive or therapeutic agents into a body. The microporation device based on radiofrequency can be used to enhance delivery efficiency by removing the epidermis layer.

Methods

The micropores were developed on pig skin and human cadaver skin with dermal and epidermal layers by the microporation device. The regeneration of micropores in the human cadaver skin caused by microporation was confirmed using an optical microscope and haematoxylin/eosin (H&E) staining. The permeability of fluorescein isothiocyanate-dextrans (FITC-dextrans) with different molecular weights through the pig and human cadaver skins were measured using Franz diffusion cell.

Results

The optical image and histological analysis confirmed that the micropores on the skin were recovered over time. The enhanced permeability through micropores was confirmed by Franz diffusion cell. The lower molecular weight of FITC-dextran permeated more on both human and pig skin. In addition, the permeation rate was higher in pig skin than in human skin.

Conclusions

We believe that the microporation device can be used as a potential technique for effective transdermal drug delivery.

Prospective Nanotechnology-Based Strategies for Enhanced Intra- and Transdermal Delivery of Antifungal Drugs

Topical therapy of superficial fungal infections allows the prevention of systemic side effects and provides drug targeting at the site of disease. However, an appropriate drug concentration in these sites should be provided to ensure the efficacy of such local treatment. The enhancement of intra- and transdermal penetration and accumulation of antifungal drugs is an important aspect here. The present overview is focused on novel nano-based formulations served to improve antimycotic penetration through the skin. Furthermore, it summarizes various approaches towards the stimulation of drug penetration through and into the stratum corneum and hair follicles, which are considered to be promising for the future improvement of superficial antifungal therapy as providing the drug localization and prolonged storage property at the targeted area.

Enhanced topical cutaneous delivery of indocyanine green after various pretreatment regimens: comparison of fractional CO2 laser, fractional Er:YAG laser, microneedling, and radiofrequency

Different devices have been used to enhance topical drug delivery. Aim of this study was to compare the efficacy of different skin pretreatment regimens in topical drug delivery. In six ex vivo human abdominal skin samples, test regions were pretreated with fractional CO₂ and Er:YAG laser (both 70 and 300 μm ablation depth, density of 5%), microneedling (500 μm needle length), fractional radiofrequency (ablation depth of ± 80–90 μm), and no pretreatment. The fluorescent agent indocyanine green (ICG) was applied. After 3 h, fluorescence intensity was measured at several depths using fluorescence photography. Significantly higher surface fluorescence intensities were found for pretreatment with fractional Er:YAG and CO₂ laser and for microneedling vs. no pretreatment (p < 0.05), but not for radiofrequency vs. no pretreatment (p = 0.173). Fluorescence intensity was highest for the Er:YAG laser with 300 μm ablation depth (mean 38.89 arbitrary units; AU), followed by microneedling (33.02 AU) and CO₂ laser with 300 μm ablation depth (26.25 AU). Pretreatment with both lasers with 300 μm ablation depth gave higher fluorescence intensity than with 70 μm ablation depth (Er:YAG laser, 21.65; CO₂ laser, 18.50 AU). Mean fluorescence intensity for radiofrequency was 15.27 AU. Results were comparable at 200 and 400 μm depth in the skin. Pretreatment of the skin with fractional CO₂ laser, fractional Er:YAG laser, and microneedling is effective for topical ICG delivery, while fractional radiofrequency is not. Deeper laser ablation results in improved ICG delivery. These findings may be relevant for the delivery of other drugs with comparable molecular properties.

Numerical Investigation of Analytical Models of Drug Flux Through Microporated Skin

In this study, drug flux through microporated skin was modeled using detailed numerical solution of the diffusion equation. The results of the modeling were compared to previously published simplified and easy to use analytical equations. Limitations and accuracy of these equations were investigated. Appropriate modifications of the equations were identified to expand them to wider practical applications when pore shape is not circular. Numerical simulations have shown a good accuracy of the new simple equations when these are used within their limits of application.

Is the Fractional Laser Still Effective in Assisting Cutaneous Macromolecule Delivery in Barrier-Deficient Skin? Psoriasis and Atopic Dermatitis as the Disease Models

PURPOSE

Most of the investigations into laser-assisted skin permeation have used the intact skin as the permeation barrier. Whether the laser is effective in improving cutaneous delivery via barrier-defective skin is still unclear.

METHODS

In this study, ablative (Er:YAG) and non-ablative (Er:glass) lasers were examined for the penetration of peptide and siRNA upon topical application on in vitro skin with a healthy or disrupted barrier.

RESULTS

An enhanced peptide flux (6.9 fold) was detected after tape stripping of the pig stratum corneum (SC). A further increase of flux to 11.7 fold was obtained after Er:YAG laser irradiation of the SC-stripped skin. However, the application of Er:glass modality did not further raise the flux via the SC-stripped skin. A similar trend was observed in the case of psoriasiform skin. Conversely, the flux was enhanced 3.7 and 2.6 fold after treatment with the Er:YAG and the Er:glass laser on the atopic dermatitis (AD)-like skin. The 3-D skin structure captured by confocal microscopy proved the distribution of peptide and siRNA through the microchannels and into the surrounding tissue.

CONCLUSIONS

The fractional laser was valid for ameliorating macromolecule permeation into barrier-disrupted skin although the enhancement level was lower than that of normal skin.

Anti-MRSA malleable liposomes carrying chloramphenicol for ameliorating hair follicle targeting

Pathogens usually invade hair follicles when skin infection occurs. The accumulated bacteria in follicles are difficult to eradicate. The present study aimed to assess the cutaneous and follicular delivery of chloramphenicol (Cm)-loaded liposomes and the antibacterial activity of these liposomes against methicillin-resistant Staphylococcus aureus (MRSA). Skin permeation was conducted by in vitro Franz diffusion cell. The anti-MRSA potential was checked using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), a well diffusion test, and intracellular MRSA killing. The classic, dimyristoylphosphatidylcholine (DMPC), and deoxycholic acid (DA) liposomes had a vesicle size of 98, 132, and 239 nm, respectively. The incorporation of DMPC or DA into the liposomes increased the bilayer fluidity. The malleable vesicles containing DMPC and DA showed increased follicular Cm uptake over the control solution by 1.5- and 2-fold, respectively. The MIC and MBC of DA liposomes loaded with Cm were 62.5 and 62.5–125 μg/mL, comparable to free Cm. An inhibition zone about 2-fold higher was achieved by DA liposomes as compared to the free control at a Cm dose of 0.5 mg/mL. DA liposomes also augmented antibacterial activity on keratinocyte-infected MRSA. The deformable liposomes had good biocompatibility against keratinocytes and neutrophils (viability >80%). In vivo administration demonstrated that DA liposomes caused negligible toxicity on the skin, based on physiological examination and histology. These data suggest the potential application of malleable liposomes for follicular targeting and the treatment of MRSA-infected dermatologic conditions.

Topically applied virus-like particles containing HIV-1 Pr55gag protein reach skin antigen-presenting cells after mild skin barrier disruption

Loading of antigen on particles as well as the choice of skin as target organ for vaccination were independently described as effective dose-sparing strategies for vaccination. Combining these two strategies, sufficient antigen recognition may be achievable via the transcutaneous route even with minimal-invasive tools. Here, we investigated the skin penetration and cellular uptake of topically administered virus-like particles (VLPs), composed of the HIV-1 precursor protein Pr55^gag, as well as the migratory activity of skin antigen-presenting cells (APCs). We compared VLP administration on ex vivo human skin pre-treated with cyanoacrylate tape stripping (CSSS, minimal-invasive) to administration by skin pricking and intradermal injection (invasive). CSSS as well as pricking treatments resulted in penetration of VLPs in the viable skin layers. Electron microscopy confirmed that at least part of VLPs remained intact during the penetration process. Flow cytometry of epidermal, dermal, and HLA-DR⁺ APCs harvested from culture media of skin explants cultivated at air-liquid interface revealed that a number of cells had taken-up VLPs. Similar results were found between invasive and minimal-invasive VLP application methods. CSSS pre-treatment was associated with significantly increased levels of IL-1α levels in cell culture media as compared to untreated and pricked skin. Our findings provide first evidence for effective cellular uptake of VLPs after dermal application and indicate that even mild physical barrier disruption, as induced by CSSS, provides stimulatory signals that enable the activation of APCs and uptake of large antigenic material.