The impact of treatment density and molecular weight for fractional laser-assisted drug delivery

Principles and clinical applications of transcutaneous laser-assisted drug delivery: A narrative review

Introduction

Transcutaneous laser-assisted drug delivery (LADD) is recognized as a developing therapy for skin disorders.

Method

Current literature was reviewed to summarize current applications for LADD.

Discussion

12 clinical applications for this therapy are currently reported.

Conclusion

LADD has potential for wide application in skin disorder treatment.

Lay Summary

Laser assisted drug delivery improves drug bioavailability for treatment of skin disorders. This technique is being assessed clinically in disorders ranging from skin cancers to alopecia.

Laser microporation facilitates topical drug delivery: a comprehensive review about preclinical development and clinical application

INTRODUCTION

Topical drug delivery is highly attractive and yet faces tissue barrier challenges. Different physical and chemical methods have been explored to facilitate topical drug delivery.

AREAS COVERED

Ablative fractional laser (AFL) has been widely explored by the scientific community and dermatologists to facilitate topical drug delivery since its advent less than two decades ago. This review introduces the major efforts in exploration of AFL to facilitate transdermal, transungual, and transocular drug delivery in preclinical and clinical settings.

EXPERT OPINION

Most of the preclinical and clinical studies find AFL to be safe and highly effective to facilitate topical drug delivery with little restriction on physicochemical properties of drugs. Clinical studies support AFL to enhance drug efficacy, shorten treatment time, reduce pain, improve cosmetic outcomes, reduce systemic drug exposure, and improve safety. Considering most of the clinical trials so far involved a small sample size and were in early phase, future trials will benefit from enrolling a large group of patients for thorough evaluation of the safety and efficacy of AFL-assisted topical drug delivery. The manufacturing of small and less costly AFL devices will also facilitate the translation of AFL-assisted topical drug delivery.

Evidence-Based Clinical Practice Guidelines for Laser-Assisted Drug Delivery

Importance

Laser-assisted drug delivery (LADD) is used for various medical and cosmetic applications. However, there is insufficient evidence-based guidance to assist clinicians performing LADD.

Objective

To develop recommendations for the safe and effective use of LADD.

Evidence Review

A systematic literature review of Cochrane Central Register of Controlled Trials, Embase, and MEDLINE was conducted in December 2019 to identify publications reporting research on LADD. A multidisciplinary panel was convened to draft recommendations informed by the systematic review; they were refined through 2 rounds of Delphi survey, 2 consensus meetings, and iterative review by all panelists until unanimous consensus was achieved.

Findings

Of the 48 published studies of ablative fractional LADD that met inclusion criteria, 4 were cosmetic studies; 21, oncologic; and 23, medical (not cosmetic/oncologic), and 6 publications of nonablative fractional LADD were included at the request of the expert panel, producing a total of 54 studies. Thirty-four studies (63.0%) were deemed to have low risk of bias, 17 studies (31.5%) had moderate risk, and 3 (5.5%) had serious risk. The key findings that informed the guidelines developed by the expert panel were as follows: LADD is safe in adults and adolescents (≥12 years) with all Fitzpatrick skin types and in patients with immunosuppression; it is an effective treatment for actinic keratosis, cutaneous squamous cell carcinoma in situ, actinic cheilitis, hypertrophic scars, and keloids; it is useful for epidermal and dermal analgesia; drug delivery may be increased through the application of heat, pressure, or occlusion, or by using an aqueous drug solution; laser settings should be selected to ensure that channel diameter is greater than the delivered molecule; antibiotic prophylaxis is not recommended, except with impaired wound healing; antiviral prophylaxis is recommended when treating the face and genitalia; and antifungal prophylaxis is not recommended. The guideline's 15 recommendations address 5 areas of LADD use: (I) indications and contraindications; (II) parameters to report; (III) optimization of drug delivery; (IV) safety considerations; and (V) prophylaxis for bacterial, viral, and fungal infections.

Conclusions and Relevance

This systematic review and Delphi consensus approach culminated in an evidence-based clinical practice guideline for safe and effective use of LADD in a variety of applications. Future research will further improve our understanding of this novel treatment technique.

Optical Imaging Visualizes a Homogeneous and Horizontal Band-Like Biodistribution of Large- and Small-Size Hydrophilic Compounds Delivered by Ablative Fractional Laser

The skin barrier generally limits the topical delivery of hydrophilic molecules. Ablative fractional laser (AFL) facilitates cutaneous drug uptake of smaller hydrophilic compounds in several studies. In this imaging-based study, we aim to investigate the cutaneous biodistribution of two different-sized hydrophilic compounds delivered by an ablative fractional CO₂ laser at minimally invasive settings. Intact or CO₂ AFL-pretreated (2.5 mJ/mb and 5% density) ex vivo porcine skin was topically applied with a large or small hydrophilic compound (fluorescence labeled antibody nivolumab (150,000 g/mol, n = 4) or ATTO 647N (746 g/mol, n = 3)). Samples were incubated for 20 h in a Franz cell setup, whereafter optical coherence tomography (OCT) was used to assess laser channel depth, and ex vivo confocal microscopy (EVCM) was used to assess epidermal thickness and cutaneous biodistribution of nivolumab and ATTO 647N. With an EVCM-assessed median epidermal thickness of 70.3 µm and OCT-assessed ablation depth of 31.9 µm, minimally invasive settings enabled shallow penetration into the mid-epidermis. The AFL-assisted uptake of the antibody nivolumab and the smaller compound ATTO 647N showed a similar homogenous and horizontal band-like biodistribution pattern that reached mid-dermis. No uptake of nivolumab or ATTO 647N was observed in intact skin. In conclusion, AFL-induced mid-epidermal laser channels facilitates the cutaneous delivery of two hydrophilic compounds that are distributed in a similar homogeneous and horizontal band-like pattern, irrespective of their molecular size.

Lasers for cutaneous lesions: An update

There are several types of medical settings which use lasers. Dermatologists use lasers as it is non-invasive with preferential cosmetic outcomes and finer wound healing. The types of lasers are relying on their wavelengths and delivery systems. Over time, by using several distinct devices and strategies, new lasers have been generated; as a consequence, they are manipulated in a wide range of dermatological settings. In this review, laser applications in various vascular, infectious, and hyperpigmented cutaneous lesions were framed. We aimed to represent the fitness of phototherapy for each condition as well as the overall challenges that face laser. In addition, low-level laser therapy, and laser resurfacing were noted as the marketable line of lasers in the current time for cosmetic purposes.

Evaluation of Device-Based Cutaneous Channels Using Optical Coherence Tomography: Impact for Topical Drug Delivery

BACKGROUND

Topical medications play a large role in the management of cutaneous diseases, but penetration is limited. Device-assisted drug delivery using mechanical destruction, lasers, and other energy-based modalities can increase penetration and absorption through creation of transcutaneous channels.

OBJECTIVE

To examine real-time, in vivo cutaneous changes in response to various devices used to improve topical drug delivery through optical coherence tomography (OCT) imaging.

METHODS AND MATERIALS

Treatment was performed with 8 medical devices, including mechanical destruction, lasers, and other energy-based modalities. Optical coherence tomography was used for real-time, noninvasive, in vivo imaging.

RESULTS

Using OCT, microneedling and radiofrequency microneedling demonstrated no cutaneous channels. Both low-energy, low-density, fractional nonablative lasers produced transient channels, which closed within hours. The fractional nonablative 1,927-nm thulium fiber and 1,550-nm erbium fiber lasers created channels with epidermal debris within, which were still closing at 24 hours. The fractional thermomechanical ablative device and the fractional ablative CO2 laser produced channels that were still open at 24 hours. CO2 laser channels had thick rims of coagulated tissue and remained open for longer.

CONCLUSION

Demonstrable differences among the devices were seen, and only some can produce observable channels, the characteristics of which vary with each technology.

Topical delivery of PD-1 inhibitors with laser-assisted passive diffusion and active intradermal injection: Investigation of cutaneous pharmacokinetics and biodistribution patterns

BACKGROUND AND OBJECTIVES

Current cancer immunotherapeutic treatment with PD-1 inhibitors is administered systemically. However, a local treatment strategy may be advantageous as it could provide targeted drug delivery as well as attenuate side effects seen with systemic treatments. For keratinocyte cancers, where surgical excision is not always applicable, an alternate local treatment approach would be beneficial. This study aims to examine cutaneous pharmacokinetics and biodistribution of the PD-1 inhibitor nivolumab, locally delivered either by ablative fractional laser (AFL)-assisted passive diffusion or active intradermal injection, in vivo.

MATERIALS AND METHODS

In vivo pig skin was either exposed to CO₂ AFL (80 mJ/mb by two stacked pulses of 40 mJ/mb) at 5% or 15% density followed by topical application of nivolumab (1 mg/ml, 100 µl/10 × 10 mm) or intradermally injected with nivolumab (1 mg/ml, 100 µl). Cutaneous nivolumab delivery was evaluated at different timepoints (0, 1, 2, 4 hours and 2 days) at two tissue depths (100-800 and 900-1600 µm) by ELISA. Visualization of cutaneous biodistribution was shown in vertical tissue sections using HiLyte Fluor^TM 488 SE labeled nivolumab for fluorescence microscopy whereas nivolumab was DOTA-tagged with Dysprosium before the laser ablation-inductively coupled plasma-mass spectrometry analysis (LA-ICP-MS).

RESULTS

Our in vivo study revealed different pharmacokinetic and biodistribution patterns for the AFL- and injection techniques. A superficial horizontal band-like uptake of nivolumab was provided with AFL-assisted passive diffusion whereas a deep focal deposition was seen with active intradermal injection, compared with controls showing remnant deposition on the skin surface. AFL-assisted nivolumab uptake in upper dermis peaked after 4 hours (p < 0.01). The cutaneous concentration of nivolumab achieved by intradermal injection was markedly higher than with AFL, the highest deposition with intradermal injection was detected at time 0 hours in both upper and deep dermis (p < 0.01) and decreased throughout the study period, although the concentration remained higher compared with saline control injections at all time points (0 hours -2 d) (p < 0.01).

CONCLUSION

Local cutaneous delivery of nivolumab with either AFL or intradermal injection revealed two different pharmacokinetic and biodistribution patterns. Passive AFL-assisted diffusion of nivolumab resulted in enhanced uptake after 4 hours, while intradermal actively injected nivolumab showed immediate enhanced cutaneous deposition with retention up to 2 days after injection. The two local delivery techniques show potential for development of individualized treatment strategies depending on the clinical tumor appearance.

Treatment of Scars with Laser-Assisted Delivery of Growth Factors and Vitamin C: A Comparative, Randomised, Double-blind, Early Clinical Trial

BACKGROUND

Scarring can jeopardize the final result of plastic surgeries. Deep dermal injuries activate dermal fibroblasts that produce excessive amount of collagen and inflammatory cytokines and growth factors, which contributes to increased fibrous tissue and scarring tissue formation.

OBJECTIVES

The aim of this early study, double-blind, prospective, randomised clinical trial was to investigate the use of laser-assisted drug delivery (LADD) for scar improvement to support the establishment of LADD as standard therapy modality and to indicate suitable drugs for dermal administration.

MATERIAL AND METHODS

In total, 132 patients seeking scar treatment were consented and randomised. The control group (64 patients) received laser resurfacing immediately followed by skin surface application of Vitamin C and 68 patients received laser treatment followed by skin surface application of a cosmeceutical containing growth factors (GFs) and Vitamin C. Photographs were obtained before and three months after the procedure and submitted to three-dimensional reconstruction by the software Dermapix^®. Objective measurements provided by the software were statistically analysed and established the differences in the treatment result between the two groups.

RESULTS

There was a significant reduction in scar roughness and volume in both groups (p < 0.01). Mann-Whitney test confirmed that the group treated vitamin C and GFs presented significantly better results than the group treated with vitamin C alone (p < 0.01).

CONCLUSION

LADD has proven efficient as scars were reduced in both study groups. Furthermore, the addition of growth factors provided statistically significant better outcomes and resulted in more inconspicuous scars. No adverse reactions were observed.

CLINICAL TRIAL REGISTRATION

Plataforma Brasil under the number CAAE: 63710716.2.0000.5664.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article. For a full description of these evidence-based medicine ratings, please refer to the Table of Contents or the online Instructions to Authors   www.springer.com/00266 .

Treatment of atrophic acne scars: Topical or intralesional plasma gel?

BACKGROUND

Atrophic post-acne scarring is considered to be a therapeutic challenge.

OBJECTIVES

The aim was to compare the safety and efficacy of (A) FCL combined with intradermal injection of plasma gel, (B) FCL combined with topical application of plasma gel, and (C) FCL monotherapy in the treatment of atrophic post-acne scars.

METHODS

Thirty patients with facial atrophic post-acne scars were enrolled in this study and randomly assigned into one of three groups. All of them underwent four treatment sessions at 4-weeks intervals. They were assessed objectively by the quantitative global scarring grading system (GSGS). This system was applied at baseline, and after 1- and 6-month follow-up (FU). Subjective assessments were performed through the global esthetic improvement scale (GAIS) and level of patient satisfaction. The DLQI questionnaire was employed at the baseline and 6-month FU.

RESULTS

According to the quantitative GSGS scores, the reductions in group A (68.4%) and group B (63%) scores were comparable, and both were significantly higher than that in group C (41.2%) in all steps of evaluation. At 6-month FU, both groups A and B showed further significant improvement, while group C did not. Based on the GAIS and patients' satisfaction, there were no significant differences between all groups. The reductions in DLQI scores in groups A and B were comparable; however, both were significantly higher than group C (P < .001).

CONCLUSIONS

The combination of plasma gel and FCL resurfacing was noticeably outstanding in their efficacy and impact on the patients' quality of life.

Comparative Study on the Outcome of Periorbital Wrinkles Treated with Laser-Assisted Delivery of Vitamin C or Vitamin C Plus Growth Factors: A Randomized, Double-blind, Clinical Trial

Background

Despite promising results, laser-assisted drug delivery (LADD) is not yet considered as standard therapies and published data rely mainly on laboratory tests, animal experiments or cadaver skin.

Objectives

This double-blind, prospective, randomized clinical trial investigates the impact in topical application of vitamin C and a cosmeceutical containing growth factors (GFs) on periorbital wrinkles primarily treated with laser skin resurfacing.

Material and Methods

In total, 149 female patients with periorbital wrinkles were consented and randomized into two study groups, R-C (receiving vitamin C only) and R-CGF (receiving vitamin C and a cosmeceutical containing growth factors). The statistical analysis evaluated the efficacy of each treatment regimen using software readouts provided by a three-dimensional stereophotogrammetry system prior to treatment and three months after the procedure. Results were compared to confirm if there was a significant change in the skin roughness and the average depth of the wrinkles between the two groups after treatment.

Results

There was a significant reduction in both skin roughness and average depth of the wrinkles in the group treated with vitamin C and growth factors (p <0.01) than those treated with LADD followed by topical application of vitamin C alone. There were no cutaneous reactions or adverse systemic reactions observed in this study related to LADD with vitamin C and GFs.

Conclusion

Controlled laser application might have a great potential to facilitate the absorption of exogenous macromolecules by the skin. Periorbital wrinkles were reduced in both groups, but LADD using vitamin C and GFs provided significantly better results.

Level of Evidence II

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Laser-Assisted Hyaluronic Acid Delivery by Fractional Carbon Dioxide Laser in Facial Skin Remodeling: A Prospective Randomized Split-Face Study in France

BACKGROUND AND OBJECTIVES

Combining the efficacy of ablative fractional carbon dioxide lasers (AFXL) to laser-assisted hyaluronic acid delivery (LAHAD) has not yet been studied. The objective of our study was to evaluate the safety and the efficacy of laser-assisted hyaluronic acid (HA) delivery with AFXL in facial skin remodeling.

STUDY DESIGN/MATERIALS AND METHODS

We conducted a prospective, double-blinded, randomized split-face study on 20 patients from 30 to 70 years old, with a skin phototype from I to IV. Each patient received full-face treatment with AFXL, immediately followed by the application in droplets into the fractional ablative tunnels of 1 ml of HA gel on one hemiface and 1 ml of physiological saline on the other hemiface. To evaluate postlaser aftermath, the intensity of erythema, edema, and crusts was graded. To assess facial skin remodeling, we scored the improvement of skin texture, firmness, fine lines, and skin radiance from baseline. Patients were evaluated on the 3rd and 7th day, 1st and 3rd month using clinical evaluations, photographs, and patient questionnaires.

RESULTS

We showed equivalence in postlaser aftermath between HA-treated and nontreated hemiface. Trend data analyses at the 3rd month suggested that immediate application of HA after AFXL resulted in a greater improvement in facial skin remodeling, especially for skin texture (mean score of 2.60 vs. 2.45) and skin firmness (mean score of 2.55 vs. 2.40). Skin radiance showed the best improvement, reaching almost a score of 5/10.

CONCLUSIONS

LAHAD with AFXL is a safe treatment showing promising results in facial skin remodeling. These findings need to be confirmed by a larger study to evaluate the value of LAHAD in daily clinical practice. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Fundamentals of fractional laser-assisted drug delivery: An in-depth guide to experimental methodology and data interpretation

In the decade since their advent, ablative fractional lasers have emerged as powerful tools to enhance drug delivery to and through the skin. Effective and highly customizable, laser-assisted drug delivery (LADD) has led to improved therapeutic outcomes for several medical indications. However, for LADD to reach maturity as a standard treatment technique, a greater appreciation of its underlying science is needed. This work aims to provide an in-depth guide to the technology's fundamental principles, experimental methodology and unique aspects of LADD data interpretation. We show that drug's physicochemical properties including solubility, molecular weight and tissue binding behavior, are crucial determinants of how laser channel morphology influences topical delivery. Furthermore, we identify strengths and limitations of experimental models and drug detection techniques, interrogating the usefulness of in vitro data in predicting LADD in vivo. By compiling insights from over 75 studies, we ultimately devise an approach for intelligent application of LADD, supporting its implementation in the clinical setting.

Drug penetration enhancement techniques in ablative fractional laser assisted cutaneous delivery of indocyanine green

Background and Objectives

Topical drug delivery can be increased by pretreatment of the skin with ablative fractional laser (AFXL). Several physical penetration enhancement techniques have been investigated to further improve AFXL‐assisted drug delivery. This study investigated the influence of three of these techniques, namely massage, acoustic pressure wave treatment, and pressure vacuum alterations (PVP) on the distribution of the fluorescent drug indocyanine green (ICG) at different depths in the skin after topical application on AFXL pretreated skin.

Materials and Methods

In ex vivo human skin, test regions were pretreated with AFXL (10,600 nm, channel depth 300 μm, channel width 120 μm, density 15%). Subsequently, ICG was applied, followed by massage, acoustic pressure wave treatment or PVP. ICG fluorescence intensity (FI) was assessed after 1, 3, and 24 hours at several depths using fluorescence photography.

Results

FI was higher when using enhancement techniques compared to control (AFXL‐only) up to 3 hours application time (P < 0.05). After 3 hours, mean surface FI was highest after acoustic pressure wave treatment (61.5 arbitrary units; AU), followed by massage (57.5AU) and PVP (46.9AU), respectively (for comparison: AFXL‐only 31.6AU, no pretreatment 14.9AU). Comparable or higher FI was achieved already after 1 hour with enhancement techniques compared to 3–24 hours application time without. After 24 hours, no significant differences between enhancement techniques and AFXL‐only were observed (P = 0.31).

Conclusion

Penetration enhancement techniques, especially acoustic pressure wave treatment and massage, result in improved drug accumulation in AFXL‐pretreated skin and reduce the application time needed. Lasers Surg. Med. © 2019 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Laser-assisted drug delivery: mode of action and use in daily clinical practice

Topical application of pharmaceutical agents is a basic principle of dermatological therapy. However, the effective barrier function of the skin significantly impairs the bioavailability of most topical drugs. Fractional ablative lasers represent an innovative strategy to overcome the epidermal barrier in a standardized, contact-free manner. The bioavailability of topical agents can be significantly enhanced using laser-assisted drug delivery (LADD). In recent years, the principle of LADD has become well established for various dermatological indications. Herein, we review the current literature on LADD and present potential future applications.

Update of Ablative Fractionated Lasers to Enhance Cutaneous Topical Drug Delivery

Ablative fractional lasers (AFXL) enhance uptake of therapeutics and this newly emerging field is called laser-assisted drug delivery (LAD). This new science has emerged over the past decade and is finding its way into clinical practice. LAD is poised to change how medicine delivers drugs. Topical and systemic application of pharmaceutical agents for therapeutic effect is an integral part of medicine. With topical therapy, the stratum corneum barrier of the skin impairs the ability of drugs to enter the body. The purpose of LAD is to alter the stratum corneum, epidermis, and dermis to facilitate increased penetration of a drug, device, or cell to its respected target. AFXL represents an innovative, non-invasive strategy to overcome the epidermal barrier. LAD employs three steps: (1) breakdown of the skin barrier with a laser, (2) optional use a laser for a therapeutic effect, (3) delivery of the medicine through laser channels to further enhance the therapeutic effect. The advantages of using lasers for drug delivery include the ease of accessibility, the non-invasive aspect, and its effectiveness. By changing the laser settings, one may use LAD to have a drug remain locally within the skin or to have systemic delivery. Many drugs are not intended for use in the dermis and so it has yet to be determined which drugs are appropriate for this technique. It appears this developing technology has the ability to be a new delivery system for both localized and systemic delivery of drugs, cells, and other molecules. With responsible development AFXL-assisted drug delivery may become a new important part of medicine.

Skin vaccination via fractional infrared laser ablation - Optimization of laser-parameters and adjuvantation

BACKGROUND

Methods to deliver an antigen into the skin in a painless, defined, and reproducible manner are essential for transcutaneous immunization (TCI). Here, we employed an ablative fractional infrared laser (P.L.E.A.S.E. Professional) to introduce clinically relevant vaccines into the skin. To elicit the highest possible antibody titers with this system, we optimized different laser parameters, such as fluence and pore number per area, and tested various adjuvants.

METHODS

BALB/c mice were immunized with Hepatitis B surface antigen (HBsAg) by laser-microporation. Adjuvants used were alum, CRM₁₉₇, monophosphoryl lipid A, heat-labile enterotoxin subunit B of E. coli (LT-B), and CpG ODN1826. The influence of different fluences (2.1 to 16.8J/cm²) and pore densities (5-15%) was investigated. Furthermore, immunogenicity of HBsAg and the commercially available conjugate vaccines ActHIB® and Menveo® applied via TCI was compared to standard i.m. injection. Antigen-specific antibody titers were assessed by luminometric ELISA.

RESULTS

Antibody titers against HBsAg were dependent on pore depth and peaked at a fluence of 8.4J/cm². Immunogenicity was independent of pore density. Adjuvantation with alum significantly reduced antibody titers after TCI, whereas other adjuvants only induced marginal changes in total IgG titers. LT-B and CpG shifted the polarization of the immune response as indicated by decreased IgG1/IgG2a ratios. HBsAg/LT-B applied via TCI induced similar antibody titers compared to i.m. injection of HBsAg/alum. In contrast to i.m. injection, we observed a dose response from 5 to 20μg after TCI. Both, ActHIB® and Menveo® induced high antibody titers after TCI, which were comparable to i.m. injection.

CONCLUSIONS

Alum, the most commonly used adjuvant, is contraindicated for transcutaneous vaccination via laser-generated micropores. TCI with optimized laser parameters induces high antibody titers, which cannot be significantly increased by the tested adjuvants. Commercially available vaccines formulated without alum have the potential for successful TCI via laser-generated micropores, without the need for reformulation.

Fractional laser-assisted topical delivery leads to enhanced, accelerated and deeper cutaneous 5-fluorouracil uptake

BACKGROUND

Topical 5-Fluorouracil (5-FU) exhibits suboptimal efficacy for non-melanoma skin cancer, attributed to insufficient intracutaneous penetration. This study investigates the impact of ablative fractional laser (AFXL) at different laser-channel depths on cutaneous 5-FU pharmacokinetics and biodistribution.

METHODS

In vitro porcine skin underwent AFXL-exposure using a fractional 10,600 nm CO₂-laser, generating microscopic ablation zones (MAZ) reaching the dermoepidermal junction (MAZ-ED), superficial-(MAZ-DS), or mid-dermis(MAZ-DM). 5-FU in AFXL-exposed and control skin was measured in Franz diffusion cells at 4 and 24 hours (n = 55). HPLC quantified 5-FU in full-thickness skin, specific skin depths of 100μm-1500μm, and transcutaneous receiver-compartments. Qualitative matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) visualized 5-FU in selected samples.

RESULTS

Overall, AFXL enhanced and accelerated 5-FU uptake versus unexposed controls, with increased accumulation in deep skin layers (p < 0.01). While total, 24-hour 5-FU uptake in control skin was 0.096 mg/cm³ (0.19% of applied concentration), AFXL delivered up to 4.707 mg/cm³ (MAZ-DM; 9.41% uptake, 49-fold enhancement) (p = 0.002; 24 hours). Indicating accelerated delivery, 5-FU in laser-exposed samples at 4 hours was at least 10-fold that of 24-hour controls (p = 0.002). Deeper laser-channels increased delivery throughout the skin (MAZ-ED vs. MAZ-DM; p<0.01). MALDI-MSI confirmed enhanced, accelerated, deeper and more uniform 5-FU distribution after AFXL versus controls.

CONCLUSIONS

AFXL offers laser-channel depth-dependent, enhanced and accelerated 5-FU uptake, with increased deposition in deep skin layers.

Ablative fractional laser improves treatment of actinic keratoses with Ingenol Mebutate

Actinic keratoses (AK) are pre-neoplastic lesions related to an excessive ultraviolet exposure that represent an emerging issue in the area of skin diseases which undergo high risk for developing squamous cell carcinoma (SCC). In this open study, we tested the safety efficacy profile of sequential ablative laser and Ingenol Mebutate gel (IngMeb). Thirteen patients with a total of 99 lesions were selected for this open study. When multiple lesions on the same area were found, the treatment area was split in half. In one group, fractional CO2 laser microablative treatment was performed the day before three daily applications of IngMeb 150 lg/g; the other group received IngMeb without previous laser ablation. Fifty-six lesions were treated with laser and IngMeb and a total of 43 lesions in the second group were treated with IngMeb alone. Results at the 12-week follow-up visit showed that a clearance rate of 50/56 (89.2%) had been achieved. On the side that was not pre-treated with laser, 31 out of 43 lesions were cleared (72.1%). In our opinion, ablative fractional laser treatment could improve topical treatment of AKs, or provide a further therapeutic option for resistant patients.

Fractional laser-assisted drug delivery: Laser channel depth influences biodistribution and skin deposition of methotrexate

BACKGROUND AND OBJECTIVE

Ablative fractional laser (AFXL) facilitates delivery of topical methotrexate (MTX). This study investigates impact of laser-channel depth on topical MTX-delivery.

MATERIALS AND METHODS

MTX (1% [w/v]) diffused for 21 hours through AFXL-exposed porcine skin in in vitro Franz Cells (n = 120). A 2,940 nm AFXL generated microscopic ablation zones (MAZs) into epidermis (11 mJ/channel, MAZ-E), superficial-dermis (26 mJ/channel, MAZ-DS), and mid-dermis (256 mJ/channel, MAZ-DM). High performance liquid chromatography (HPLC) was used to quantify MTX deposition in full-thickness skin, biodistribution profiles at specific skin levels, and transdermal permeation. Fluorescence microscopy was used to visualize UVC-activated MTX-fluorescence (254 nm) and semi-quantify MTX distribution in skin.

RESULTS

AFXL increased topical MTX-delivery (P < 0.001). Without laser exposure, MTX-concentration in full-thickness skin was 0.07 mg/cm(2) , increasing sixfold (MAZ-E), ninefold (MAZ-DS), and 11-fold (MAZ-DM) after AFXL (P < 0.001). Deeper MAZs increased MTX-concentrations in all skin layers (P < 0.038) and favored maximum accumulation in deeper skin layers (MAZ-E: 1.85 mg/cm(3) at 500 μm skin-level vs.

MAZ-DM

3.75 mg/cm(3) at 800 μm, P = 0.002). Ratio of skin deposition versus transdermal permeation remained constant, regardless of MAZ depth (P = 0.172). Fluorescence intensities confirmed MTX biodistribution through coagulation zones and into surrounding skin, regardless of thickness of coagulation zones (6-47 μm, P ≥ 0.438).

CONCLUSION

AFXL greatly increases topical MTX-delivery. Deeper MAZs deliver higher MTX-concentrations than superficial MAZs, which indicates that laser channel depth may be important for topical delivery of hydrophilic molecules. Lasers Surg. Med. 48:519-529, 2016. © 2016 Wiley Periodicals, Inc.

Topically applied methotrexate is rapidly delivered into skin by fractional laser ablation

OBJECTIVES

Methotrexate (MTX) is a chemotherapeutic and anti-inflammatory drug that may cause systemic adverse effects. This study investigated kinetics and biodistribution of MTX delivered topically by ablative fractional laser (AFXL).

METHODS

In vitro passive diffusion of 10 mg/ml MTX (1 w/v%) was measured from 0.25 to 24 h through AFXL-processed and intact porcine skin in Franz Cells (n = 46). A 2,940 nm fractional Erbium Yttrium Aluminium Garnet laser generated mid-dermal microchannels at 2.4% density, and 256 mJ/microchannel. HPLC quantified MTX-concentrations in extracts from mid-dermal skin sections, donor and receiver compartments. Fluorescence microscopy of UVC-activated MTX-fluorescence and desorption electro-spray ionization mass spectrometry imaging (DESI-MSI) evaluated MTX biodistribution.

RESULTS

AFXL-processed skin facilitated rapid MTX delivery through cone-shaped microchannels of 690 µm ablation depth, lined by the 47 µm thermal coagulation zone (CZ). Quantitatively, MTX was detectable by HPLC in mid-dermis after 15 min, significantly exceeded deposition in intact skin after 1.5 h, and saturated skin after 7 h at a 10-fold increased MTX-deposition versus intact skin (3.08 vs 0.30 mg/cm(3), p = 0.002). Transdermal permeation was < 1.5% of applied MTX before skin saturation, and increased up to 8.0% after 24 h. Qualitatively, MTX distributed into CZ within 15 min (p = 0.015) and further into surrounding dermal tissue after 1.5 h (p = 0.004). After skin saturation at 7 h, MTX fluorescence intensities in CZ and tissue were similar and DESI-MSI confirmed MTX biodistribution throughout the mid-dermal skin section.

CONCLUSIONS

MTX absorbs rapidly into mid-dermis of AFXL-processed skin with minimal transdermal permeation until skin saturation, suggesting a possible alternative to systemic MTX for some skin disorders.

α, ω-Cholesterol-functionalized low molecular weight polyethylene glycol as a novel modifier of cationic liposomes for gene delivery

Here, three novel cholesterol (Ch)/low molecular weight polyethylene glycol (PEG) conjugates, termed α, ω-cholesterol-functionalized PEG (Ch₂-PEG_n), were successfully synthesized using three kinds of PEG with different average molecular weight (PEG₆₀₀, PEG₁₀₀₀ and PEG₂₀₀₀). The purpose of the study was to investigate the potential application of novel cationic liposomes (Ch₂-PEG_n-CLs) containing Ch₂-PEG_n in gene delivery. The introduction of Ch₂-PEG_n affected both the particle size and zeta potential of cationic liposomes. Ch₂-PEG₂₀₀₀ effectively compressed liposomal particles and Ch₂-PEG₂₀₀₀-CLs were of the smallest size. Ch₂-PEG₁₀₀₀ and Ch₂-PEG₂₀₀₀ significantly decreased zeta potentials of Ch₂-PEG_n-CLs, while Ch₂-PEG₆₀₀ did not alter the zeta potential due to the short PEG chain. Moreover, the in vitro gene transfection efficiencies mediated by different Ch₂-PEG_n-CLs also differed, in which Ch₂-PEG₆₀₀-CLs achieved the strongest GFP expression than Ch₂-PEG₁₀₀₀-CLs and Ch₂-PEG₂₀₀₀-CLs in SKOV-3 cells. The gene delivery efficacy of Ch₂-PEG_n-CLs was further examined by addition of a targeting moiety (folate ligand) in both folate-receptor (FR) overexpressing SKOV-3 cells and A549 cells with low expression of FR. For Ch₂-PEG₁₀₀₀-CLs and Ch₂-PEG₂₀₀₀-CLs, higher molar ratios of folate ligand resulted in enhanced transfection efficacies, but Ch₂-PEG₆₀₀-CLs had no similar in contrast. Additionally, MTT assay proved the reduced cytotoxicities of cationic liposomes after modification by Ch₂-PEG_n. These findings provide important insights into the effects of Ch₂-PEG_n on cationic liposomes for delivering genes, which would be beneficial for the development of Ch₂-PEG_n-CLs-based gene delivery system.

Impact of different vehicles for laser-assisted drug permeation via skin: full-surface versus fractional ablation

PURPOSE

This study aimed to assess impact of different vehicles for laser-assisted skin drug delivery. We also tried to uncover the mechanisms by which different vehicles affect laser-aided skin permeation.

METHODS

Full-surface ablative (conventional) and fractional lasers were used to irradiate nude mouse skin. Imiquimod and 5-aminolevulinic acid (ALA) were used as lipophilic and hydrophilic permeants. Vehicles employed included water with 40% polyethylene glycol 400 (PEG 400), propylene glycol (PG), and ethanol. Lipid nanoparticles were also utilized as carriers.

RESULTS

In vitro permeation profiles showed improvement in imiquimod flux with conventional laser (2.5 J/cm2) producing a 12-, 9-, and 5-fold increase when loading imiquimod in 40% PEG400, PG, and ethanol, respectively, as compared with intact skin. Nanoparticulate delivery by laser produced a 6-fold enhancement in permeation. Fractional laser produced less enhancement of imiquimod delivery than conventional laser. Laser exposure increased follicular imiquimod accumulation from 0.80 to 5.81 μg/cm2. ALA permeation from aqueous buffer, PEG 400, and PG with conventional laser treatment was 641-, 445-, and 104-fold superior to passive control. In vivo skin deposition of topically applied ALA examined by confocal microscopy indicated the same trend as the in vitro experiment, with aqueous buffer showing the greatest proporphyllin IX signaling. Diffusion of cosolvent molecules into ablated skin and drug partitioning from vehicle to skin are two predominant factors controlling laser-assisted delivery. In contrast to conventional laser, lateral drug diffusion was anticipated for fractional laser.

CONCLUSIONS

Our results suggest that different drug delivery vehicles substantially influence drug penetration enhanced by lasers.

Ablative laser assisted topical delivery of antifibrotics in the management of cicatricial ectropion

A variety of surgical techniques have traditionally been used to manage cicatricial ectropion. These techniques primarily aim at vertical lengthening of the anterior lamella and include a variety of skin flaps and grafts. Alternative techniques such as dermal filler injection to support the eyelid margin may also be used in the management of select patients with cicatricial ectropion. The application of different types of laser for scar revision throughout the body has rapidly evolved; similar mechanisms, principles and treatment rationale can be applied to the use of lasers in the management of cicatricial ectropion. Additionally, ablative lasers, such as Carbon Dioxide and Erbium:yttrium-aluminum-garnet lasers, may be used in the transdermal delivery of antifibrotic agents, such as interferon gamma, interferon alpha, vitamin D, triamcinolone and 5-fluorouracil, resulting in efficient target tissue penetration, limitation of systemic drug toxicity and decreased degradation. Although the combination of ablative fractional resurfacing and topical antifibrotic agents is a new treatment modality, there is a great potential for its efficient utility in the management of periocular scarring and cicatricial ectropion. The introduction of these innovative therapeutic modalities offers ophthalmologists a greater range of possible effective treatments to address periocular scar tissue and the resultant cicatricial ectropion.

Percutaneous bone marrow transplantation using fractional ablative Erbium:YAG laser

Topical application of therapeutic agents has been a mainstay in Dermatology for the treatment of skin disorders but is not commonly used for systemic delivery. For a topically applied agent to reach distant body sites it must first overcome the barrier function of the skin and then penetrate into deeper structures before reaching the systemic circulation. This has limited the use of topically applied agents to those having specific charge, solubility and size restrictions. Pretreatment of the skin with ablative fractional laser appears to enhance the uptake of some topically applied drugs but the ability to effectively deliver agents to distant sites is largely unproven. In this report we used a fractional ablative Erb:YAG (Erbium/Yttrium Aluminum Garnet) laser to facilitate the transfer of bone marrow stem cells through the skin in a murine bone marrow transplant model. Chimerism could be detected in the peripheral blood of recipient C57BL/6 mice that were pretreated with ablative fractional laser and had topically applied enhanced green fluorescent protein (GFP) labeled bone marrow cells from syngeneic donor transgenic mice. This study indicates that fractional laser can be used to deliver stem cells through the skin and remain functionally intact.

Lasers as an approach for promoting drug delivery via skin

INTRODUCTION

Using lasers can be an effective drug permeation-enhancement approach for facilitating drug delivery into or across the skin. The controlled disruption and ablation of the stratum corneum (SC), the predominant barrier for drug delivery, is achieved by the use of lasers. The possible mechanisms of laser-assisted drug permeation are the direct ablation of the skin barrier, optical breakdown by a photomechanical wave and a photothermal effect. It has been demonstrated that ablative approaches for enhancing drug transport provide some advantages, including increased bioavailability, fast treatment time, quick recovery of SC integrity and the fact that skin surface contact is not needed. In recent years, the concept of using laser techniques to treat the skin has attracted increasing attention.

AREAS COVERED

This review describes recent developments in using nonablative and ablative lasers for drug absorption enhancement. This review systematically introduces the concepts and enhancement mechanisms of lasers, highlighting the potential of this technique for greatly increasing drug absorption via the skin. Lasers with different wavelengths and types are employed to increase drug permeation. These include the ruby laser, the erbium:yttrium-gallium-garnet laser, the neodymium-doped yttrium-aluminum-garnet laser and the CO2 laser. Fractional modality is a novel concept for promoting topical/transdermal drug delivery. The laser is useful in enhancing the permeation of a wide variety of permeants, such as small-molecule drugs, macromolecules and nanoparticles.

EXPERT OPINION

This potential use of the laser affords a new treatment for topical/transdermal application with significant efficacy. Further studies using a large group of humans or patients are needed to confirm and clarify the findings in animal studies. Although the laser fluence or output energy used for enhancing drug absorption is much lower than for treatment of skin disorders and rejuvenation, the safety of using lasers is still an issue. Caution should be used in optimizing the feasible conditions of the lasers in balancing the effectiveness of permeation enhancement and skin damage.

Laser microporation of the skin: prospects for painless application of protective and therapeutic vaccines

Introduction:

In contrast to muscle and subcutaneous tissue, the skin is easily accessible and provides unique immunological properties. Increasing knowledge about the complex interplay of skin-associated cell types in the development of cutaneous immune responses has fueled efforts to target the skin for vaccination as well as for immunotherapy.

Areas covered:

This review provides an overview on skin layers and their resident immunocompetent cell types. Advantages and shortcomings of standard methods and innovative technologies to circumvent the outermost skin barrier are addressed. Studies employing fractional skin ablation by infrared lasers for cutaneous delivery of drugs, as well as high molecular weight molecules such as protein antigens or antibodies, are reviewed, and laserporation is introduced as a versatile transcutaneous vaccination platform. Specific targeting of the epidermis or the dermis by different laser settings, the resulting kinetics of uptake and transport and the immune response types elicited are discussed, and the potential of this transcutaneous delivery platform for allergen-specific immunotherapy is demonstrated.

Expert opinion:

Needle-free and painless vaccination approaches have the potential to replace standard methods due to their improved safety and optimal patient compliance. The use of fractional laser devices for stepwise ablation of skin layers might be advantageous for both vaccination against microbial pathogens, as well as immunotherapeutic approaches, such as allergen-specific immunotherapy. Thorough investigation of the underlying immunological mechanisms will help to provide the knowledge for a rational design of transcutaneous protective/therapeutic vaccines.