Laser-assisted topical drug delivery by using a low-fluence fractional laser: imiquimod and macromolecules

Safety and Efficacy of High-Dose Fractional Erbium: Yttrium Aluminium Garnet Laser in Stable Vitiligo

Objective: Evaluate the treatment outcome of vitiligo patients receiving a standard regimen of high-dose biweekly fractional 2940 nm erbium:yttrium aluminium garnet (YAG) laser applications as an add-on to various treatment modalities. Materials and methods: The authors extracted the study population's clinical images before treatment and 3rd-month control from their clinical archive and used the medical records. The primary outcome measure was 50% repigmentation at 3rd-month follow-up. Institutional ethical committee approved the study. Results: Of the evaluated 28 patients, 18 were eligible with 31 treatment regions. All patients received at least one topical agent [steroids, calcineurin inhibitors, or 5-fluorouracil (5-FU)] and 11 patients received either targeted ultraviolet B (UVB) or narrow-band UVB. Of the 31 study regions, 88.8% (8/9) of facial; 77.7% (7/9) of dorsal hand; 75% (3/4) of limb; and 25% (2/8) of finger lesions achieved 50% repigmentation at 3rd-month control. The facial and dorsal hand lesions' treatment responses were higher than finger lesions (p = 0.008 and 0.03, respectively). Upon evaluating adjuvant treatment modalities, all of the treatment regions receiving targeted UVB (n = 4) or topical 5-FU (n = 5) achieved the primary endpoint, whereas severe irritation limited the topical use of 5-FU. The most common adverse effects were mild oozing and crusting related to laser treatments. Conclusions: Even with high-energy settings, fractional erbium: YAG laser does not induce the Koebner phenomenon. Although controlled trials are required to make firm conclusions, fractional erbium: YAG laser was an effective and safe adjunctive option for stable vitiligo in a real-life setting.

Laser facilitated epicutaneous peptide immunization using dry patch technology

The skin has been intensely investigated as a target tissue for immunization because it is populated by multiple types of antigen presenting cells. Directly addressing dendritic cells or Langerhans cells in vivo represents an attractive strategy for inducing T cell responses in cancer immunotherapy. We and others have studied fractional laser ablation as a novel method combining efficient delivery of macromolecules to the skin with an inherent adjuvant effect of laser illumination. In this proof of concept study, we demonstrate the feasibility of peptide delivery to the skin using the P.L.E.A.S.E. professional Erb:YAG fractional infrared laser together with EPIMMUN patches. In an ovalbumin mouse model we demonstrate that a dry patch formulation of SIINFEKL peptide in combination with CpG-ODN1826, but not imiquimod or polyI:C, induces potent cytotoxic T cell responses, which can be further boosted by co-delivery of the pan-helper T cell epitope PADRE.

Asiaticoside-laden silk nanofiber hydrogels to regulate inflammation and angiogenesis for scarless skin regeneration

Scarless skin regeneration remains a challenge due to the complicated microenvironment involved in wound healing. Here, the hydrophobic drug, asiaticoside (AC), was loaded inside silk nanofiber hydrogels to achieve bioactive and injectable matrices for skin regeneration. AC was dispersed in aqueous silk nanofiber hydrogels with retention of biological functions that regulated inflammatory reactions and vascularization in vitro. After implantation in full-thickness wound defects, these AC-laden hydrogel matrices achieved scarless wound repair. Inflammatory reactions and angiogenesis were regulated during inflammation and remodeling, which was responsible for wound regeneration similar to normal skin. Both in vitro and in vivo studies demonstrated promising applications of these AC-laden silk hydrogels towards scarless tissue regeneration.

Laser irradiation of ocular tissues to enhance drug delivery

Scleral and corneal membranes represent substantial barriers against drug delivery to the eye. Conventional hypodermic needles-based intraocular injections are clinically employed to overcome these barriers. This study, for the first time, investigated a non-invasive alternative to intraocular injections by laser irradiation of ocular tissues. The P.L.E.A.S.E.® laser device was applied on excised porcine scleral and corneal tissues, which showed linear relationships between depths of laser-created micropores and laser fluences at range 8.9-444.4 J/cm². Deeper and wider micropores were observed in scleral relative to corneal tissues. The permeation of rhodamine B and fluorescein isothiocyanate (FITC)-dextran were investigated through ocular tissues at different laser parameters (laser fluences 0-44.4 J/cm² and micropore densities 7.5 and 15%). Both molecules showed enhanced permeation through ocular tissues on laser irradiation. Maximum transscleral permeation of the molecules was attained at laser fluence 8.9 J/cm² and micropore density 15%. Transcorneal permeation of rhodamine B increased with increasing either laser fluence or micropore density, while that of FITC-dextran was not affected by either parameter. The transscleral water loss increased significantly after laser irradiation then returned to the baseline values within 24 h, indicating healing of the laser-created micropores. Laser irradiation is a promising technique to enhance intraocular delivery of both small and large molecule drugs.

Enhancement of skin permeability with thermal ablation techniques: concept to commercial products

Traditionally, the skin is considered as a protective barrier which acts as a highly impermeable region of the human body. But in recent times, it is recognized as a specialized organ that aids in the delivery of a wide range of drug molecules into the skin (intradermal drug delivery) and across the skin into systemic circulation (transdermal drug delivery, TDD). The bioavailability of a drug administered transdermally can be improved by several penetration enhancement techniques, which are broadly classified into chemical and physical techniques. Application of mentioned techniques together with efforts of various scientific and innovative companies had made TDD a multibillion dollar market and an average of 2.6 new transdermal drugs are being approved each year. Out of various techniques, the thermal ablation techniques involving chemicals, heating elements, lasers, and radiofrequency (RF) are proved to be more effective in terms of delivering the drug across the skin by disrupting the stratum corneum (SC). The reason behind it is that the thermal ablation technique resulted in improved bioavailability, quick treatment and fast recovery of the SC, and more importantly it does not cause any damage to underlying dermis layer. This review article mainly discussed about various thermal ablation techniques with commercial products and patents in each classes, and their safety aspects. This review also briefly presented anatomy of the skin, penetration pathways across the skin, and different generations of TDD.

Factors Affecting Depth of Penetration in Microneedling- and Laser-Assisted Drug Delivery: The Importance of Timing of Topical Application

BACKGROUND

Microneedling- and laser-assisted drug delivery are emerging techniques used to treat various conditions. However, key parameters affecting drug penetration remain unknown.

OBJECTIVE

This study aims to investigate the importance of timing of topical application, needle length, and device type for drug delivery.

MATERIALS AND METHODS

Skin harvested from cosmetic surgeries was treated with black ink applied before or after treatment with a microneedling pen (MP), roller, or fractional ablative CO2 laser, and incubated for different time intervals. Ink penetration was additionally tested using different needle lengths. Sandwich estimator was used for statistical analysis.

RESULTS

Ink applied before MP penetrated deeper compared to ink applied afterward at 1 and 3 hours, and roller microneedling in both the ink-before and -after scenarios at 1, 3, and 6 hours (p < .05). Microneedling demonstrated lateral extension of ink beyond microchannels with increased ink penetration over time. CO2 laser demonstrated ink localization within microthermal zones without time-dependent increases in depth after 30 minutes. Ink penetration increases by 0.06 mm per 1 mm increase in needle length.

CONCLUSION

Ink applied before MP results in the deepest penetration of ink. Microneedling offers unique advantages in transdermal delivery as its channels exhibit increasing penetration over time and lateral extension of product.

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.

Laser facilitates week-long sustained transdermal drug delivery at high doses

Traditional patches are most successful in transdermal delivery of low-dose hydrophobic drugs. Week-long transdermal delivery of high-dose hydrophilic drugs remains a big challenge. This study explored ablative fractional laser (AFL) to assist 3-day to week-long sustained transdermal delivery of powder hydrophilic drugs in murine models. Bulk drug powder was coated into reservoir patches followed by topical application onto AFL-treated skin. Water evaporated from AFL-generated skin microchannels (MCs) gradually dissolve topical drug powder to elicit multi-day sustained drug delivery. Using sulforhodamine b, zidovudine, and bovine serum albumin as model hydrophilic drugs, we found tapped coating could coat 10-20 mg drug per 0.5 cm² reservoir patch to elicit 3-day sustained delivery, while compression coating could coat ~35-70 mg drug per 0.5 cm² reservoir patch to elicit week-long sustained delivery. Besides sustained drug delivery, AFL-assisted powder reservoir patch delivery showed a good safety. AFL-generated skin MCs resealed in 1-2 days and completely recovered in 3 days after the week-long sustained delivery. AFL-assisted powder reservoir patch delivery involves no complex powder formulation and only requires incorporation of highly water-soluble mannitol or a similar excipient to elicit the high-efficient delivery. Enlarging reservoir patch size to 10 cm² can conveniently expand the delivery capacity to gram scale. To our knowledge, this is the first time that high-dose week-long sustained transdermal delivery of hydrophilic drugs was achieved via a simple laser-based powder delivery platform.

Ablative fractional laser-assisted treatments for keratinocyte carcinomas and its precursors-Clinical review and future perspectives

Keratinocyte carcinomas (KC) are the most common malignant human neoplasms. Although surgery and destructive approaches are first-line treatments, topical therapies are commonly used. Due to limited uptake of topical agents across the skin barrier, clearance rates are often sub-optimal. In pre-clinical investigations, ablative fractional laser (AFL)-assisted drug delivery has demonstrated improved uptake of topical drugs commonly used to treat KC. In 22 clinical trials, the effect of AFL-assisted treatments has been investigated for actinic keratosis (AK; n = 14), Bowen's disease (BD; n = 5), squamous cell carcinoma (n = 1), and basal cell carcinoma (n = 7). The most substantial evidence currently exists for AFL-assisted photodynamic therapy for the treatment of AK and BD. AFL improved 12-months follow-up clearance rates of photodynamic therapy from 45.0-51.0% to 78.5-84.8% for AK and from 50.0-55.3% to 87.0-87.5% for BD. AFL-assisted pharmacological therapy is a promising tool for optimizing topical treatments of KC and its precursor lesions. Future developments include AFL-assisted immune activation, changing drug administration route of systemic therapies, and utilizing drug chemo-combinations.

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.

Active Er-laser drug delivery using drug-impregnated gel for treatment of nail diseases

Active Er-laser drug delivery under the nail plate using a drug-impregnated gel containing liquid methylene blue clusters is demonstrated for the first time. The effect of the agar-agar concentration in the gel and the gel plate thickness on the number of Er:YLF-laser pulses required for formation of a through microhole in the gel and in the nail plate with subsequent active drug delivery is discussed. The influence of the laser pulse energy, the gel plate thickness, and the external pressure applied to the gel on the rate of delivery of methylene blue under the nail plate through a single microhole in it is investigated. It is shown that with a laser pulse energy of 4.0 ± 0.1 mJ, the delivery rate can reach 0.024 ± 0.004 mg/pulse.

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.

Transdermal delivery of human growth hormone via laser-generated micropores

The epidermal skin barrier plays an important role in protecting underlying structures. It allows the passage of low molecular weight lipophilic molecules, but restricts the passage of hydrophilic molecules and macromolecules. The objective of this study was to investigate the feasibility of transdermal delivery of human growth hormone (hGH) through laser-microporated dermatomed porcine ear skin. The permeation of hGH was evaluated at different laser fluences and micropore densities. In vitro permeation studies were performed on vertical Franz diffusion cells using dermatomed porcine ear skin treated with ablative laser (2940 nm; P.L.E.A.S.E®, Pantec Biosolutions AG). The effect of different fluences (34.1, 45.4, and 68.1 J/cm²) at 10% pore density as well as different densities of micropores (5, 10, and 15%) at fluence of 34.1 J/cm², on the permeation of hGH was evaluated. After 48 h, 77.12 ± 10.77 μg/cm² hGH was delivered into the receptor with the application of fluence of 45.4 J/cm², which was significantly higher than that observed from 34.1 J/cm² group (53.13 ± 1.75 μg/cm², p < 0.05). Application of fluence of 68.1 J/cm² showed permeation of 90.94 ± 3.93 μg/cm² that was significantly higher than that from 34.1 J/cm² group (p < 0.05), but not as compared to the 45.4 J/cm² group (p > 0.05). With the increase in density of micropores from 5 to 15%, permeation of hGH increased significantly from 7.1 ± 2.63 μg/cm² to 95.89 ± 13.43 μg/cm² after 48 h (p < 0.05). Thus, overall, the variations in the fluence as well as micropore density of the laser were observed to influence hGH permeation, through laser-microporated dermatomed porcine skin.

In vivo evaluation of antitumoral and antiangiogenic effect of imiquimod-loaded polymeric nanoparticles

The chemotherapeutic agent imiquimod (Imq) is used to treat skin cancers, the most common type of human cancer. However, the high incidence of local and systemic side effects associated with its use as well as its low skin permeation impair patient compliance and therapeutic effectiveness To overcome these limitations, nanostructured systems such as nanoparticles can be a promising alternative. Nanoparticles are submicron particles (size less than 1000 nm) with high surface area that facilitates the interaction and cellular uptake by biological membranes. Therefore, the aim of the present work is to evaluate antiangiogenic effect and antitumoral activity of imiquimod-loaded nanoparticles compared to market Imq formulation. Polymeric nanoparticles containing Imq were obtained by the technique of precipitation of preformed polymer. Antiangiogenic activity of the formulations was determined in chicken embryo chorioallantoic membrane (CAM) and its chemopreventive potential was evaluate during multistage DMBA and croton oil model of skin carcinogenesis in mice. Nanoparticles containing Imq presented antiangiogenic activity superior than negative control, placebo dispersion and market Imq (p < 0.05) in the CAM model and also significantly reduced the number and size of papillomas compared to all other groups. These results suggest, therefore, that the obtained delivery system can be an alternative to treat diseases related to vessels formation and also potentially increase cutaneous permeation and efficacy of poor soluble drugs normally used to treat cutaneous diseases.

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.

Heat: A Highly Efficient Skin Enhancer for Transdermal Drug Delivery

Advances in materials science and bionanotechnology have allowed the refinements of current drug delivery systems, expected to facilitate the development of personalized medicine. While dermatological topical pharmaceutical formulations such as foams, creams, lotions, gels, etc., have been proposed for decades, these systems target mainly skin-based diseases. To treat systemic medical conditions as well as localized problems such as joint or muscle concerns, transdermal delivery systems (TDDSs), which use the skin as the main route of drug delivery, are very appealing. Over the years, these systems have shown to offer important advantages over oral as well as intravenous drug delivery routes. Besides being non-invasive and painless, TDDSs are able to deliver drugs with a short-half-life time more easily and are well adapted to eliminate frequent administrations to maintain constant drug delivery. The possibility of self-administration of a predetermined drug dose at defined time intervals makes it also the most convenient personalized point-of-care approach. The transdermal market still remains limited to a narrow range of drugs. While small and lipophilic drugs have been successfully delivered using TDDSs, this approach fails to deliver therapeutic macromolecules due to size-limited transport across the stratum corneum, the outermost layer of the epidermis. The low permeability of the stratum corneum to water-soluble drugs as well as macromolecules poses important challenges to transdermal administration. To widen the scope of drugs for transdermal delivery, new procedures to enhance skin permeation to hydrophilic drugs and macromolecules are under development. Next to iontophoresis and microneedle-based concepts, thermal-based approaches have shown great promise to enhance transdermal drug delivery of different therapeutics. In this inaugural article for the section "Frontiers in Bioengineering and Biotechnology," the advances in this field and the handful of examples of thermal technologies for local and systemic transdermal drug delivery will be discussed and put into perspective.

Fractional erbium-doped yttrium aluminum garnet laser-assisted drug delivery of hydroquinone in the treatment of melasma

Background

Melasma is a difficult-to-treat hyperpigmentary disorder. Ablative fractional laser (AFL)-assisted delivery of topically applied drugs to varied targets in the skin has been an area of ongoing study and research.

Objective

The objective of this study was to evaluate the efficacy and safety of fractional erbium-doped yttrium aluminum garnet (Er:YAG) laser as an assisted drug delivery for enhancing topical hydroquinone (HQ) permeation into the skin of melasma patients.

Patients and methods

Thirty female patients with bilateral melasma were randomly treated in a split-face controlled manner with a fractional Er:YAG laser followed by 4% HQ cream on one side and 4% HQ cream alone on the other side. All patients received six laser sessions with a 2-week interval. The efficacy of treatments was determined through photographs, dermoscopic photomicrographs and Melasma Area Severity Index (MASI) score, all performed at baseline and at 12 weeks of starting therapy. The patient’s level of satisfaction was also recorded.

Results

Er:YAG laser + HQ showed significantly better results (p<0.005) with regard to decrease in the degree of pigmentation as assessed on the 4-point scale than HQ alone. There was a significant decrease in MASI scores on Er:YAG laser + HQ side vs HQ side. Minor reversible side effects were observed on both sides.

Conclusion

AFL-assisted delivery of HQ is a safe and effective method for the treatment of melasma.

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.

Laser-Assisted Delivery to Treat Facial Scars

Treatment of facial scars is a multispecialty endeavor for optimal patient recovery. One new innovation helping in facial scar treatments are lasers. Fractional laser predictably (tunable) disrupts the barrier of the skin creating deep channels that allow the delivery of drug and cellular materials; this is called laser-assisted drug delivery (LAD). Without exception thus far, LAD has been found to enhance the local uptake of any drug or substance applied to the skin. These zones may be used postoperatively to deliver drugs and other substances to create an enhanced scar therapeutic response to drug or substance applied to the skin.

Fractional laser-assisted percutaneous drug delivery via temperature-responsive liposomes

Liposomes are used for transdermal delivery of drugs and vaccines. Our objective was to develop temperature-responsive (TR) liposomes to achieve temperature-dependent, controlled release of an encapsulated drug, and use fractional laser irradiation to enhance transdermal permeability of these liposomes. TR-liposomes prepared using a thermosensitive polymer derived from poly-N-isopropylacrylamide, N,N-dimethylacrylamide, egg phosphatidylcholine, and dioleoylphosphatidylethanolamine, delivered fluorescein isothiocyanate-conjugated ovalbumin (OVA-FITC) as a model drug. Effect of temperature on liposome size and drug release rate was estimated at two temperatures. Transdermal permeation through hairless mouse skin, with and without CO₂ fractional laser irradiation, and penetration into Yucatan micro-pig skin were investigated using Franz cell and fluorescence microscopy. Dynamic light scattering showed that mean liposome diameter nearly doubled from 190 to 325 nm between 37 and 50 °C. The rate and amount of OVA-FITC released from TR-liposomes were higher at 45 °C that those at 37 °C. Transdermal permeation of OVA-FITC across non-irradiated skin from both TR- and unmodified liposomes was minimal at 37 °C, but increased at 45 °C. Laser irradiation significantly increased transdermal permeation of both liposome groups at both temperatures. Fluorescence microscopy of frozen biopsy specimens showed deeper penetration of FITC from unmodified liposomes compared to that from polymer-modified liposomes. Rhodamine accumulation was not observed with polymer-modified liposomes at either temperature. Temperature-dependent controlled release of an encapsulated drug was achieved using the TR-liposomes. However, TR-liposomes showed lower skin permeability despite higher hydrophobicity. Fractional laser irradiation significantly increased the transdermal permeation. Additional studies are required to control liposome size and optimize transdermal permeation properties.

Sustained epidermal powder drug delivery via skin microchannels

Transdermal delivery of hydrophilic drugs is challenging. This study presents a novel sustained epidermal powder delivery technology (sEPD) for safe, efficient, and sustained delivery of hydrophilic drugs across the skin. sEPD is based on coating powder drugs into high-aspect-ratio, micro-coating channels (MCCs) followed by topical application of powder drug-coated array patches onto ablative fractional laser-generated skin MCs to deliver drugs into the skin. We found sEPD could efficiently deliver chemical drugs without excipients and biologics drugs in the presence of sugar excipients into the skin with a duration of ~12h. Interestingly the sEPD significantly improved zidovudine bioavailability by ~100% as compared to oral gavage delivery. sEPD of insulin was found to maintain blood glucose levels in normal range for at least 6h in chemical-induced diabetes mice, while subcutaneous injection failed to maintain blood glucose levels in normal range. sEPD of anti-programmed death-1 antibody showed more potent anti-tumor efficacy than intraperitoneal injection in B16F10 melanoma models. Tiny skin MCs and 'bulk' drug powder inside relatively deep MCCs are crucial to induce the sustained drug release. The improved bioavailability and functionality warrants further development of the novel sEPD for clinical use.

Evaluation of Laser-Assisted Trans-Nail Drug Delivery with Optical Coherence Tomography

The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. The nail plate consists of three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. In this study, we investigate the application of fractional CO₂ laser that produces arrays of microthermal ablation zones (MAZs) to facilitate drug delivery in the nails. We utilized optical coherence tomography (OCT) for real-time monitoring of the laser-skin tissue interaction, sparing the patient from an invasive surgical sampling procedure. The time-dependent OCT intensity variance was used to observe drug diffusion through an induced MAZ array. Subsequently, nails were treated with cream and liquid topical drugs to investigate the feasibility and diffusion efficacy of laser-assisted drug delivery. Our results show that fractional CO₂ laser improves the effectiveness of topical drug delivery in the nail plate and that OCT could potentially be used for in vivo monitoring of the depth of laser penetration as well as real-time observations of drug delivery.

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.

Skin permeation and retention of topical bead formulation containing tranexamic acid

The objective of this study is to develop a topical bead formulation of tranexamic acid (TA) which can be used concomitantly with laser treatment. The bead formulation of TA (TAB) was successfully prepared by fluidized bed drying method. Physicochemical properties of the TAB were evaluated in terms of chemical stability of TA and differential scanning calorimetry. TA in the bead was stable up to six months at 25°C and existed as amorphous state. In vitro skin permeation and in vivo skin retention of TA in the beads were significantly higher compared to a commercial product. When the bead was dissolved into distilled water and applied concomitantly with laser treatment, the amount of TA retained in the skin in the in vivo study was inversely proportional to the energy levels of laser treatment, indicating absorption into subcutaneous tissue and drainage to systemic circulation. Therefore, when laser treatment is used concomitantly with TAB, energy level should be very carefully monitored to avoid possible adverse events associated with systemic side effects of TA.

Fractional CO₂ Laser Pretreatment Facilitates Transdermal Delivery of Two Vitamin C Derivatives

BACKGROUND

Topical vitamin C derivatives have been used to treat melasma and used as a skin whitener. The aim of this study was to compare skin histology and permeation of l-ascorbic acid 2-phosphate sesquimagnesium salt (MAP-1) and magnesium l-ascorbic acid-2-phosphate (MAP-2) after fractional CO₂ laser pretreatment.

METHODS

The effect of fractional laser treatment on porcine skin was examined by scanning electron microscopy and confocal laser scanning electron microscopy. The effect of fractional CO₂ laser treatment of different fluencies and pass numbers on transdermal flux of the two vitamin C derivatives through porcine skin was examined in vitro using a Franz diffusion chamber.

RESULTS

Fluxes of MAP-1 and MAP-2 across fractional CO₂ laser-treated (5 W) skin were eight- to 13-fold, and 20- to 22-fold higher, respectively, than the fluxes of these compounds across intact skin. Fluxes of MAP-1 and MAP-2 across fractional CO₂ laser-treated (9 W) skin were 14- to 19-fold, and 30- to 42-fold higher, respectively, than their fluxes across intact skin.

CONCLUSION

Fractional CO₂ laser treatment is an effective way of delivering vitamin C derivatives into the skin.

Skin pre-ablation and laser assisted microjet injection for deep tissue penetration

BACKGROUND AND AIMS

For conventional needless injection, there still remain many unresolved issues such as the potential for cross-contamination, poor reliability of targeted delivery dose, and significantly painstaking procedures. As an alternative, the use of microjets generated with Er:YAG laser for delivering small doses with controlled penetration depths has been reported. In this study, a new system with two stages is evaluated for effective transdermal drug delivery. First, the skin is pre-ablated to eliminate the hard outer layer and second, laser-driven microjet penetrates the relatively weaker and freshly exposed epidermis. Each stage of operation shares a single Er:YAG laser that is suitable for skin ablation as well as for the generation of a microjet.

METHODS

In this study, pig skin is selected for quantification of the injection depth based on the two-stage procedure, namely pre-ablation and microjet injection. The three types of pre-ablation devised here consists of bulk ablation, fractional ablation, and fractional-rotational ablation. The number of laser pulses are 12, 18, and 24 for each ablation type. For fractional-rotational ablation, the fractional beams are rotated by 11.25° at each pulse. The drug permeation in the skin is evaluated using tissue marking dyes. The depth of penetration is quantified by a cross sectional view of the single spot injections. Multi-spot injections are also carried out to control the dose and spread of the drug.

RESULTS

The benefits of a pre-ablation procedure prior to the actual microjet injection to the penetration is verified. The four possible combinations of injection are (a) microjet only; (b) bulk ablation and microjet injection; (c) fractional ablation and microjet injection; and (d) fractional-rotational ablation and microjet injection. Accordingly, the total depth increases with injection time for all cases. In particular, the total depth of penetration attained via fractional pre-ablation increased by 8 ∼ 11% and that of fractional-rotational pre-ablation increased by 13 ∼ 33%, when compared with the no pre-ablation or microjet only cases. A noticeable point is that the fraction-rotational pre-ablation and microjet result is comparable to the bulk ablation and microjet result of 11 ∼ 42%. The penetration depth underneath ablated stratum corneum (SC) is also measured in order to verify the pre-ablation effect. The penetration depths for each case are (a) 443 ± 104 µm; (b) 625 ± 98 µm; (c) 523 ± 95 µm; and (d) 595 ± 141 µm for microjet only, bulk ablation and microjet, fractional ablation and microjet, and fractional-rotational ablation and microjet, respectively. This is quite beneficial since any healing time associated with ablation is significantly reduced by avoiding hard-core bulk ablation. Thus the bulk pre-ablation and microjet may well be superseded by the less invasive fractiona-rotational ablation followed by the microjet injection. The density of micro-holes is 1.27 number/mm² for fractional ablation and 4.84 number/mm² for fractional-rotational ablation. The penetration depths measured underneath the ablated SC are 581 µm (fractional ablation and microjet) and 691 µm (fractional-rotational ablation and microjet).

CONCLUSIONS

Fractional-rotational ablation increases number of micro-holes in a unit area, enabling fast reepithelialization and high drug delivery efficiency. Optimization of system parameters such as ablation time, number of ablations, and injection time will eventually ensure a macromolecule delivery technique with the potential to include vaccines, insulins, and growth hormones, all of which require deeper penetration into the skin. Lasers Surg. Med. 49:387-394, 2017. © 2016 Wiley Periodicals, Inc.

Fractional Laser-Assisted Topical Imiquimod 5% Cream Treatment for Recalcitrant Common Warts in Children: A Pilot Study

BACKGROUND

Conventional treatments for warts like cryotherapy are limited by the pain during procedures, especially in pediatric patients. Imiquimod is a topical immune response modifier, but the thick stratum corneum of common warts prevents drug permeation through skin.

OBJECTIVE

To evaluate the efficacy and safety of fractional laser/topical 5% imiquimod cream for the treatment of warts in children.

METHODS

Eleven pediatric patients with multiple recalcitrant common warts were included. Lesions were treated using an ablative fractional 2,940-nm Er:YAG laser at 1- or 2-week interval. After each laser treatment session, imiquimod 5% cream was self-applied once daily 5 days a week. Response and adverse effects were assessed 2 weekly until complete clearance or up to maximum of 48 weeks. Pain during fractional laser was assessed using a visual analogue scale (0-10).

RESULTS

Eight of the 11 (72.7%) children experienced complete clearance. Mean duration was 29.7 (16-48) weeks, and the mean number of fractional laser was 17.5 (8-37). No significant adverse effect was observed. Pain visual analogue scale during fractional laser was 2.4 (1-4) compared to 6.2 (5-8) during cryotherapy.

CONCLUSION

This pilot study indicates that fractional laser-assisted topical imiquimod may provide benefit for recalcitrant warts in children.

Skin Pretreatment With Conventional Non-Fractional Ablative Lasers Promote the Transdermal Delivery of Tranexamic Acid

BACKGROUND

Laser pretreatment of skin can be used to enable drugs used in dermatology to penetrate the skin to the depth necessary for their effect to take place.

OBJECTIVE

To compare the permeation of tranexamic acid after conventional non-fractionated ablative Er:YAG and CO2 laser pretreatment in a laser-aided transdermal delivery system.

MATERIALS AND METHODS

An erbium-doped yttrium aluminium garnet (Er:YAG) and a CO2 laser were used to pretreat dorsal porcine skin. Scanning electron microscopy was used to examine disruption of the skin surface. Confocal laser scanning microscopy was used to determine the depth of penetration of a reporter molecule (fluorescein isothiocyanate) into the skin. A Franz diffusion assembly was used to examine fluency-related increases in transdermal delivery of transexamic acid.

RESULTS

Transdermal delivery of tranexamic acid increased as Er:YAG laser fluency increased. Transdermal delivery was higher when CO2 laser pretreatment was used than when Er:YAG laser pretreatment was used, but a "ceiling effect" was present and increasing the wattage did not cause a further increase in delivery. CO2 laser pretreatment also caused more extensive and deeper skin disruption than Er:YAG laser pretreatment.

CONCLUSION

For conventional, non-fractionated ablative laser pretreatment, the Er:YAG laser would be an optimal choice to enhance transdermal penetration of transexamic acid.

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.