Spatiotemporal closure of fractional laser-ablated channels imaged by optical coherence tomography and reflectance confocal microscopy

Impact of skin hydration on patterns of microthermal injury produced by fractional CO2 laser

OBJECTIVES

The impact of skin hydration on patterns of thermal injury produced by ablative fractional lasers (AFLs) is insufficiently examined under standardized conditions. Using skin with three different hydration levels, this study assessed the effect of hydration status on microchannel dimensions generated by a fractional CO2 laser.

METHODS

A hydration model (hyperhydrated-, dehydrated- and control) was established in ex vivo porcine skin, validated by changes in surface conductance and sample mass. After, samples underwent AFL exposure using a CO2 laser (10,600 nm) at two examined pulse energies (10 and 30 mJ/mb, fixed 10% density, six repetitions per group). Histological assessment of distinct microchannels (n = 60) determined three standardized endpoints in H&E sections: (1) depth of microthermal treatment zones (MTZs), (2) depth of microscopic ablation zones (MAZs), and (3) coagulation zone (CZ) thickness. As a supplemental in vivo assessment, the same laser settings were applied to hyperhydrated- (7-h occlusion) and normohydrated forearm skin (no pretreatment) of a human volunteer. Blinded measurement of MAZ depth (n = 30) was performed using noninvasive optical coherence tomography (OCT).

RESULTS

Modest differences in microchannel dimensions were shown between hyperhydrated, dehydrated and control skin at both high and low pulse energy. Compared to controls, hyperhydration led to median reductions in MTZ and MAZ depth ranging from 5% to 8% (control vs. hyperhydrated at 30 mJ/mb; 848 vs. 797 µm (p < 0.003) (MAZ); 928 vs. 856 µm (p < 0.003) (MTZ)), while 14%-16% reductions were shown in dehydrated skin (control vs. dehydrated at 30 mJ/mb; MAZ: 848 vs. 727 µm (p < 0.003); MTZ: 928 vs. 782 µm (p < 0.003)). The impact of skin hydration on CZ thickness was in contrast limited. Corresponding with ex vivo findings, hyperhydration was similarly associated with lower ablative depth in vivo skin. Thus, median MAZ depth in hydrated skin was 10% and 14% lower than in control areas at 10 and 30 mJ/mb pulse energy, respectively (10 mJ: 210 vs. 180 µm (p < 0.001); 30 mJ: 335 vs. 300 µm (p < 0.001)).

CONCLUSION

Skin hydration status can exert a minimal impact on patterns of microthermal injury produced by fractional CO2 lasers, although the clinical implication in the context of laser therapy requires further study.

Treatment of hypertrophic scars with ablative fractional carbon dioxide laser assisted with different topical triamcinolone delivery ways

Objectives

Ablative fractional carbon dioxide laser has been used with triamcinolone to treat hypertrophic scars, resulting in promising success rates. However, there are different topical triamcinolone delivery methods used in scar treatment. To assess the efficacy among the different triamcinolone delivery methods, this study was designed to compare the efficacy and safety of ablative fractional carbon dioxide laser followed by penetration and injection of topical triamcinolone into thicker hypertrophic scars (height score of VSS ≥2).

Study design/materials and methods

We performed a retrospective study of 155 thicker hypertrophic scar patients (height score of VSS ≥2), including 88 patients in the triamcinolone external application group and 67 patients in the triamcinolone intralesional injection group. One month after the patients had 3 treatment sessions at 4-week intervals, the scars were assessed by photography, the Vancouver Scar Scale (VSS), durometry and spectrocolorimetry. Any adverse effects were also evaluated.

Results

The VSS scores and the hardness of the scars in both groups improved significantly compared to baseline. Moreover, the patients in the triamcinolone intralesional injection group had higher treatment efficacy (19.77 ± 21.25 %) based on their VSS scores than the patients in the triamcinolone external application group (5.94 ± 24.07 %), especially in the improvement of scar pliability, height and hardness. Meanwhile, in the triamcinolone injection group, more patients had mild and moderate improvement than in the triamcinolone application group. However, there were no differences in the distribution of the adverse effects in either group.

Conclusions

This study demonstrated that using the ablative fractional carbon dioxide laser followed by different topical triamcinolone delivery methods is effective and safe for thicker hypertrophic scar improvement. The method of using the ablative fractional carbon dioxide laser assisted with triamcinolone injection had a better therapeutic outcome in thicker hypertrophic scars, as compared with triamcinolone penetration.

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.

Transdermal Delivery of Therapeutic Compounds With Nanotechnological Approaches in Psoriasis

Psoriasis is a chronic, immune-mediated skin disorder involving hyperproliferation of the keratinocytes in the epidermis. As complex as its pathophysiology, the optimal treatment for psoriasis remains unsatisfactorily addressed. Though systemic administration of biological agents has made an impressive stride in moderate-to-severe psoriasis, a considerable portion of psoriatic conditions were left unresolved, mainly due to adverse effects from systemic drug administration or insufficient drug delivery across a highly packed stratum corneum via topical therapies. Along with the advances in nanotechnologies, the incorporation of nanomaterials as topical drug carriers opens an obvious prospect for the development of antipsoriatic topicals. Hence, this review aims to distinguish the benefits and weaknesses of individual nanostructures when applied as topical antipsoriatics in preclinical psoriatic models. In view of specific features of each nanostructure, we propose that a proper combination of distinctive nanomaterials according to the physicochemical properties of loaded drugs and clinical features of psoriatic patients is becoming a promising option that potentially drives the translation of nanomaterials from bench to bedside with improved transdermal drug delivery and consequently therapeutic effects.

Update Dermatologische Lasertherapie II – Weiterentwicklung der photodynamischen Therapie durch Laser‐assistierte transkutane Applikation von Topika

Die technische Fortentwicklung der jüngeren Vergangenheit bietet dem Dermatologen Zugriff auf neue Laser, Strahlquellen und Behandlungskonzepte. Seit langem eingeführte Wellenlängen zur Ablation sind nunmehr fraktioniert applizierend verfügbar und stehen nunmehr für eine wirksamere und effizientere Behandlung von zahlreichen Hautveränderungen zur Verfügung. Das gezielte Einbringung von Topika (laser assisted drug delivery; LADD) ist das wichtigste Beispiel. Die LADD erfordert eine spezifische Weiterbildung, um sicher und wirksam zur Therapie (prä-)maligner nichtmelanozytärer Neoplasien der Haut wie der Feldkanzerisierung in Form der Laser-assistierten photodynamischen Therapie angewandt werden zu können. Bisher verfügbare Daten weisen auf eine höhere Effektivität im Vergleich zu konventionell verwendeten Topika hin, wobei anhaltend über Weiterentwicklungen berichtet wird. Unter anderem wurde die Kombination mit Tageslicht oder alternativen tageslichtähnlichen Strahlquellen bekannt. Dieses Update basiert wie zitiert gekürzt und aktualisiert auf "Paasch, U. 2019. Laser-assistierte photodynamische Therapie. p. 226-239. In G. Kautz (ed.) Energie für die Haut. Springer Nature, Springer Nature.".

Update on dermatologic laser therapy II - advances in photodynamic therapy using laser-assisted drug delivery

Technical advances in recent years have led to the development of new dermatologic laser systems, light sources, and treatment concepts. With the introduction of ablative fractional lasers (using common wavelengths) in the field of dermatology, it is now possible to more effectively and efficiently treat a variety of skin disorders. One important example of these advances is laser-assisted drug delivery (LADD). A type of LADD, laser-assisted photodynamic therapy has been successfully employed in the treatment of non-melanoma skin cancer including field cancerization. This treatment concept has been continually modified and today includes the use of daylight as well as artificial daylight systems. This update is based as cited, shortened and updated according to "Paasch,U. 2019. Laser-assistierte photodynamische Therapie. p. 226-239. In G.Kautz (ed.) Energie für die Haut. Springer Nature, Springer Nature".

Development of a Predictive Monte Carlo Radiative Transfer Model for Ablative Fractional Skin Lasers

It is possible to enhance topical drug delivery by pretreatment of the skin with ablative fractional lasers (AFLs). However, the parameters to use for a given AFL to achieve the desired depth of ablation or the desired therapeutic or cosmetic outcome are hard to predict. This leaves open the real possibility of overapplication or underapplication of laser energy to the skin. In this study, we developed a numerical model consisting of a Monte Carlo radiative transfer (MCRT) code coupled to a heat transfer and tissue damage algorithm. The simulation is designed to predict the depth effects of AFL on the skin, verified with in vitro experiments in porcine skin via optical coherence tomography (OCT) imaging. Ex vivo porcine skin is irradiated with increasing energies (50-400 mJ/pixel) from a CO₂ AFL. The depth of microscopic treatment zones is measured and compared with our numerical model. The data from the OCT images and MCRT model complement each other well. Nonablative thermal effects on surrounding tissue are also discussed. This model, therefore, provides an initial step toward a predictive determination of the effects of AFL on the skin. Lasers Surg. Med. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC.

Stimulation of collagen and elastin production in-vivo using 1,540 nm Er:Glass laser: assessment of safety and efficacy

Introduction: Induction of collagen and elastin remodeling in the human skin can be achieved by non-ablative fractional laser (NAFXL) and ablative fractional laser (AFXL). Our objective was to compare the safety, efficacy, tolerability, and ability to induce collagen and elastin remodeling of NAFXL versus AFXL in a series of treatments over time.Materials and Methods: In this prospective, proof of principle, single-case study, the safety, tolerability and efficacy of the laser systems were assessed via histopathology and clinical evaluations including photographs. Optical biopsies by means of multiphoton tomography (MPT) were used to evaluate the induction of collagen and elastin remodeling.Results: Treatments by both NAFXL and AFXL were well tolerated. The NAFXL system was found to be less painful and resulted in a shorter down- and healing times. MPT findings showed the superior capability of the AFXL procedure to induce collagen; on the other hand, elastin induction was more pronounced after NAFXL treatments.Conclusions: While NAFXL is as effective and safe as the traditional AFXL, it is better tolerated and has a shorter downtime. Serial optical biopsies over time over time can be a useful tool to assess the induction of collagen and elastin remodeling in the human skin.

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.

A New Method for Percutaneous Drug Delivery by Thermo-Mechanical Fractional Injury

BACKGROUND AND OBJECTIVES

Percutaneous drug delivery (PDD) is a means of increasing the uptake of topically applied agents into the skin. Successful delivery of a photosensitizer into the skin is an important factor for effective photodynamic therapy. To evaluate the efficacy of pretreatment by thermomechanical fractional injury (TMFI) (Tixel®, Novoxel®, Israel) at low-energy settings in increasing the permeability of the skin to a known hydrophilic-photosensitizer medication, 5-amino-levulinic-acid hydrochloride (ALA) in compounded 20% ALA gel. To compare the effect of TMFI on ALA permeation into the skin in compounded gel to three commercial photosensitizing medications in different vehicles: ALA microemulsion gel, methyl-amino-levulinic-acid hydrochloride (MAL) cream, and ALA hydroalcoholic solution.

STUDY DESIGN/MATERIALS AND METHODS

Five healthy subjects were treated in two separate experiments and on a total of 136 test sites, with four topical photosensitizer preparations as follows: compounded 20% ALA gel prepared in a good manufacturing practice (GMP)-certified pharmacy (Super-Pharm Professional, Israel), 10% ALA microemulsion gel (Ameluz®, Biofrontera Bioscience GmbH, Leverkusen, Germany), 16.8% MAL cream (Metvix®, Galderma, Lausanne, Switzerland), and 20% ALA hydroalcoholic solution (Levulan Kerastick®, DUSA Pharmaceuticals, Inc., Wilmington, MA, USA). The dermal sites were pretreated by Tixel® (Novoxel® Ltd., Israel) prior to topical drug application. One site was untreated to serve as control. Protoporphyrin IX (PpIX) fluorescence intensity readouts were taken immediately and 1, 2, 3, 4, and 5 hours posttreatment.

RESULTS

The highest average PpIX fluorescence intensity measurements were obtained for the compounded 20% ALA gel following pre-treatment by TMFI at 6 milliseconds pulse duration. After 2 and 3 hours, TMFI-treated sites exhibited an increased hourly rate in readouts of FluoDerm units, which were 156-176% higher than the control rates (P ≤ 0.004). TMFI pre-treatment did not enhance the percutaneous permeation of either ALA or MAL following the microemulsion gel, hydroalcoholic solution, and cream applications.

CONCLUSIONS

Pretreatment with low-energy TMFI at a pulse duration of 6 milliseconds increased the percutaneous permeation of ALA linearly over the first 5 hours from application when the compounded 20% ALA gel was used. Formulation characteristics have substantial influence on the ability of TMFI pretreatment to significantly increase the percutaneous permeation of ALA and MAL. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Application of reflectance confocal microscopy to investigate the non-ablative, micro-ablative, and ablative effects of CO2 fractional laser irradiation on skin

CO₂ fractional laser, as an ablative fractional laser, is commonly used in cosmetic treatment. We applied CO₂ fractional laser irradiation to skin in vitro and used reflectance confocal microscopy (RCM) to image and detect the presence of any non-ablative, micro-ablative and ablative effects, in order to better understand the features of a CO₂ fractional laser. In vitro irradiation of foreskin was performed using a CO₂ fractional laser. Foreskin specimens were divided into 4 groups that received different amounts of irradiation energy, based on the number of irradiation passes they received: 5, 10, 15, and 20 passes, respectively. This corresponds to fluence energy of 16.3, 32.6, 48.9, 65.3 J/cm². Immediately after irradiation, digital microscopy (DM), RCM, and histopathology were performed to observe whether the non-ablative, micro-ablative, and ablative phenomenon occurred, and the injury features of MTZs. Immediately after CO₂ fractional laser irradiation, RCM and DM showed that when the numbers of passes were 5 and 10, a micro-ablative column (MAC) could not be observed or was very small. We mainly observed a thicker thermal coagulation zone (TCZ), representing non-ablative or micro-ablative effects. When the number of passes were increased to 15 and 20, the MAC was significantly enlarged and surrounded by a TCZ of medium thickness, representing ablative effects. For the first time, this study used RCM and DM to demonstrate that a CO₂ fractional laser could achieve non-ablative, micro-ablative, and ablative effects on irradiated skin via different energy levels.

Dynamic Optical Coherence Tomography Is a New Technique for Imaging Skin Around Lower Extremity Wounds

Chronic wounds such as venous leg ulcers invariably heal slowly and recur. In the case of venous leg ulcers, poor healing of chronic wounds is variously attributed to ambulatory hypertension, impaired perfusion and diffusion, presence of chronic inflammation at wound sites, lipodermatosclerosis, and senescence. The aim of this study was to investigate whether a new technique, optical coherence tomography (OCT), which permits imaging of blood capillaries in the peri-wound skin, can provide new insights into the pathology. OCT and its recent variant, dynamic OCT, permit rapid noninvasive depth-resolved imaging of the capillaries in the superficial dermis via a handheld probe, showing the morphology and density of vessels down to 20 µm in diameter. We used dynamic OCT to investigate 15 chronic wounds and assess characteristics of the vessels at the 4 poles around the wounds, the wound bed, adjacent dermatosclerosis, and unaffected skin. The results of the study show that both vessel morphology and density in the wound edges are dramatically different from that in healthy skin, showing clusters of glomuleri-like vessels (knot-like forms or clumps) and an absence of linear branching vessels, and also greater blood perfusion. Such vessel shapes are reported to be associated with tissue growth. The OCT imaging procedure was rapid and well tolerated by patients and provided new information not available from other devices. Thus, OCT appears to have great promise as a tool for the evaluation and study of chronic ulcers.

Experimental Study of 5-fluorouracil Encapsulated Ethosomes Combined with CO2 Fractional Laser to Treat Hypertrophic Scar

OBJECTIVE

This study is designed to explore permeability of ethosomes encapsulated with 5-florouracil (5-FU) mediated by CO₂ fractional laser on hypertrophic scar tissues. Moreover, therapeutic and duration effect of CO₂ fractional laser combined with 5-FU encapsulated ethosomes in rabbit ear hypertrophic scar model will be evaluated.

METHODS

The permeated amount of 5-FU and retention contents of 5-FU were both determined by high-performance liquid chromatography (HPLC). Fluorescence intensities of ethosomes encapsulated with 5-FU (5E) labeled with Rodanmin 6GO (Rho) were measured by confocal laser scanning microscopy (CLSM). The permeability promotion of 5E labeled with Rho in rabbit ear hypertrophic scar mediated by CO₂ fractional laser was evaluated at 0 h, 6 h, 12 h, 24 h, 3 days and 7 days after the irradiation. The opening rates of the micro-channels were calculated according to CLSM. The therapeutic effect of 5EL was evaluated on rabbit ear hypertrophic scar in vivo. Relative thickness of rabbit ear hypertrophic scar before and after the treatment was measured by caliper method. Scar elevation index (SEI) of rabbit ear hypertrophic scar was measured using H&E staining.

RESULTS

The data showed that the penetration amount of 5EL group was higher than 5E group (4.15 ± 2.22 vs. 0.73 ± 0.33; p < 0.05) after 1-h treatment. Additionally, the penetration amount of 5EL was higher than that of the 5E group (107.61 ± 13.27 vs. 20.73 ± 3.77; p < 0.05) after 24-h treatment. The retention contents of the 5EL group also showed higher level than 5E group (24.42 ± 4.37 vs.12.25 ± 1.64; p < 0.05). The fluorescence intensity of Rho in hypertrophic scar tissues of the 5EL group was higher than that of the 5E group at different time points (1, 6, and 24 h). The opening rates of the micro-channels were decreased gradually within 24 h, and micro-channels were closed completely 3 days after the irradiation by CO₂ fractional laser. The relative thickness and SEI of rabbit ear hypertrophic scar after 7 days of treatment in the 5EL group were significantly lower than the 5E group.

CONCLUSION

CO₂ fractional laser combined with topical 5E can be effective in the treatment of hypertrophic scar in vivo and supply a novel therapy method for human hypertrophic scar.

Investigation of optical attenuation imaging using optical coherence tomography for monitoring of scars undergoing fractional laser treatment

We demonstrate the use of the near-infrared attenuation coefficient, measured using optical coherence tomography (OCT), in longitudinal assessment of hypertrophic burn scars undergoing fractional laser treatment. The measurement method incorporates blood vessel detection by speckle decorrelation and masking, and a robust regression estimator to produce 2D en face parametric images of the attenuation coefficient of the dermis. Through reliable co-location of the field of view across pre- and post-treatment imaging sessions, the study was able to quantify changes in the attenuation coefficient of the dermis over a period of ∼20 weeks in seven patients. Minimal variation was observed in the mean attenuation coefficient of normal skin and control (untreated) mature scars, as expected. However, a significant decrease (13 ± 5%, mean ± standard deviation) was observed in the treated mature scars, resulting in a greater distinction from normal skin in response to localized damage from the laser treatment. By contrast, we observed an increase in the mean attenuation coefficient of treated (31 ± 27%) and control (27 ± 20%) immature scars, with numerical values incrementally approaching normal skin as the healing progressed. This pilot study supports conducting a more extensive investigation of OCT attenuation imaging for quantitative longitudinal monitoring of scars. En face 2D OCT attenuation coefficient map of a treated immature scar derived from the pre-treatment (top) and the post-treatment (bottom) scans. (Vasculature (black) is masked out.) The scale bars are 0.5 mm.

Application of reflectance confocal microscopy to evaluate skin damage after irradiation with an yttrium-scandium-gallium-garnet (YSGG) laser

The objective of this study was to observe the characteristics of the skin after irradiation with a 2790-nm yttrium-scandium-gallium-garnet (YSGG) laser using reflectance confocal microscopy (RCM). A 2790-nm YSGG laser was used to irradiate fresh foreskin (four doses, at spot density 3) in vitro. The characteristics of microscopic ablative columns (MAC), thermal coagulation zone (TCZ), and microscopic treatment zones (MTZ) were observed immediately after irradiation using digital microscope and RCM. The characteristics of MAC, TCZ, and MTZ with variations in pulse energy were comparatively analyzed. After irradiation, MAC, TCZ, and MTZ characteristics and undamaged skin between MTZs can be observed by RCM. The depth and width of MTZ obviously increased with the increase in pulse energy. At 80, 120, and 160 mJ/microbeam (MB), the MTZ actual area and proportion were about two times that of the theoretical value and three times at 200 mJ/MB. With increases in depth, the single MAC gradually decreased in a fingertip-shaped model, with TCZ slowly increasing, and MTZ slightly decreasing in a columnar shape. RCM was able to determine the characteristics of thermal injury on the skin after the 2790-nm YSGG laser irradiation with different pulse energies. Pulse energy higher than 200 mJ/MB may have much larger thermal injury and side effect. RCM could be used in the clinic in future.

Quantitative monitoring of laser-treated engineered skin using optical coherence tomography

Nowadays, laser therapy is a common method for treating various dermatological troubles such as acne and wrinkles because of its efficient and immediate skin enhancement. Although laser treatment has become a routine procedure in medical and cosmetic fields, the prevention of side-effects, such as hyperpigmentation, redness and burning, still remains a critical issue that needs to be addressed. In order to reduce the side-effects while attaining efficient therapeutic outcomes, it is essential to understand the light-skin interaction through evaluation of physiological changes before and after laser therapy. In this study, we introduce a quantitative tissue monitoring method based on optical coherence tomography (OCT) for the evaluation of tissue regeneration after laser irradiation. To create a skin injury model, we applied a fractional CO2 laser on a customized engineered skin model, which is analogous to human skin in terms of its basic biological function and morphology. The irradiated region in the skin was then imaged by a high-speed OCT system, and its morphologic changes were analyzed by automatic segmentation software. Volumetric OCT images in the laser treated area clearly visualized the wound healing progress at different time points and provided comprehensive information which cannot be acquired through conventional monitoring methods. The results showed that the laser wound in engineered skins was mostly recovered from within 1~2 days with a fast recovery time in the vertical direction. However, the entire recovery period varied widely depending on laser doses and skin type. Our results also indicated that OCT-guided laser therapy would be a very promising protocol for optimizing laser treatment for skin therapy.