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

Dissolvable microneedles in the skin: Determination the impact of barrier disruption and dry skin on dissolution

Dissolvable microneedles (DMNs), fabricated from biocompatible materials that dissolve in both water and skin have gained popularity in dermatology. However, limited research exists on their application in compromised skin conditions. This study compares the hyaluronic acid-based DMNs penetration, formation of microchannels, dissolution, and diffusion kinetics in intact, barrier-disrupted (tape stripped), and dry (acetone-treated) porcine ear skin ex vivo. After DMNs application, comprehensive investigations including dermoscopy, stereomicroscope, skin hydration, transepidermal water loss (TEWL), optical coherence tomography (OCT), reflectance confocal laser scanning microscopy (RCLSM), confocal Raman micro-spectroscopy (CRM), two-photon tomography combined with fluorescence lifetime imaging (TPT-FLIM), histology, and scanning electron microscopy (SEM) were conducted. The 400 µm long DMNs successfully penetrated the skin to depths of ≈200 µm for dry skin and ≈200-290 µm for barrier-disrupted skin. Although DMNs fully inserted into all skin conditions, their dissolution rates were high in barrier-disrupted and low in dry skin, as observed through stereomicroscopy and TPT-FLIM. The dissolved polymer exhibited a more significant expansion in barrier-disrupted skin compared to intact skin, with the smallest increase observed in dry skin. Elevated TEWL and reduced skin hydration levels were evident in barrier-disrupted and dry skins compared to intact skin. OCT and RCLSM revealed noticeable skin indentation and pronounced microchannel areas, particularly in barrier-disrupted and dry skin. Additional confirmation of DMN effects on the skin and substance dissolution was obtained through histology, SEM, and CRM techniques. This study highlights the impact of skin condition on DMN effectiveness, emphasizing the importance of considering dissolvability and dissolution rates of needle materials, primarily composed of hyaluronic acid, for optimizing DMN-based drug delivery.

Histological Assessment of the Effectiveness of Microneedling Device-Assisted Filler Delivery

BACKGROUND

Microneedling is used to enhance transcutaneous drug delivery. However, the extent to which microneedling devices impact filler delivery and whether this varies by filler type, microneedling device type, and treatment sequence is not known.

OBJECTIVE

To histologically assess and quantify the delivery of commonly used fillers through microneedling, using both a microneedling pen and a microneedling roller. In addition, the authors investigated whether there is a variation in filler delivery based on the sequence of microneedling in relation to topical filler application.

METHODS

Ex vivo human abdominal skin samples were subjected to microneedling pen or microneedling roller treatment. Black tissue marking ink, hyaluronic acid, poly-l-lactic acid, or undiluted calcium hydroxyapatite was topically applied before or immediately after microneedling treatment.

RESULTS

Histological evaluation revealed a notable presence of black ink within channels formed by both microneedling treatments (15.5%-98.1%), whereas there was limited presence of the various filler types tested (0%-6.6%) in all settings. Topical application before microneedling treatment led to relatively higher filler/ink deposition within the channels formed by the microneedling treatments compared with topical application after microneedling.

CONCLUSION

Transcutaneous delivery of fillers was not significantly helped by microneedling treatment, whereas the microneedling devices demonstrated effective delivery of an aqueous solution.

Laser-Assisted and Device-Assisted Filler Delivery: A Histologic Evaluation

BACKGROUND

Lasers and devices are used to enhance transcutaneous delivery of fillers. However, little has been published on the histologic findings of this form of laser/device-assisted delivery to determine the optimal devices and fillers.

OBJECTIVE

To objectively evaluate the histological effects of laser-assisted and device-assisted filler delivery.

METHODS

Ex vivo human abdominoplasty skin samples were treated with fractional CO 2 laser (ECO 2 , 120 μm tip, 120 mJ), fractional radiofrequency microneedling (FRMN, Genius, 1.5 mm, 20 mJ/pin), and microneedling (2.0 mm). Immediately after poly- l -lactic acid (PLLA), hyaluronic acid gel, calcium hydroxylapatite, and black tissue marking dye were topically applied. After treatment, biopsies were collected for histologic evaluation.

RESULTS

Histology revealed that PLLA and black dye were found in greatest abundance, hyaluronic acid was found to a lesser extent, and calcium hydroxylapatite was least found within channels created by fractional CO 2 laser. Microneedling was effective only at delivering black dye, whereas FRMN failed to show significant channel formation or delivery of the studied products.

CONCLUSION

Among the devices and fillers studied, fractional CO 2 laser and PLLA proved to be the most effective combination for laser/device-assisted filler delivery. Neither microneedling nor FRMN was effective as devices to enhance filler delivery.

Enhancing Skin Uptake of Topical Antioxidants With 1,440-nm Nonablative Fractional Diode Laser Pretreatment

BACKGROUND

Energy-based devices, such as nonablative lasers, are a promising method to enhance the delivery and absorption of topically applied molecules.

OBJECTIVE

To characterize ex vivo uptake of common antioxidant topicals after pretreatment with a nonablative laser wavelength.

MATERIALS AND METHODS

Using donor human skin tissue, uptake of 3 topical antioxidants was analyzed (C E Ferulic with 15% l-ascorbic acid [15% vitamin C serum], Phloretin CF with ferulic acid [10% vitamin C serum], and Phyto+ [botanical serum]; SkinCeuticals, Dallas, TX; 2010 formulations) after pretreatment with a 1,440-nm nonablative fractional diode laser.

RESULTS

Pretreatment with the 1,440-nm laser enhanced uptake of 15% and 10% vitamin C serums by approximately 10 and 21 times, respectively, compared to controls. Laser pretreatment also enhanced uptake of botanical serum by approximately 6 times relative to controls. Permeation of vitamin C and botanical serums was also enhanced through laser pretreatment.

CONCLUSION

Nonablative laser pretreatment increased uptake and permeation of topical antioxidants. Optimizing treatment requires consideration of the device and treatment parameters as well as the properties of the topical formulation.

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.

Quantifying Skin Uptake of Topicals After 1,927-nm and 1,440-nm Nonablative Fractional Diode Laser Treatment

BACKGROUND

Although the stratum corneum limits transdermal absorption of topicals, laser devices can enhance topical uptake by disrupting the skin barrier. Nonablative lasers are commonly used, but their effects on topical uptake should be quantified to optimize outcomes.

OBJECTIVE

The objective of this study is to analyze transdermal uptake of 4 topicals after nonablative fractional diode laser pretreatment.

METHODS AND MATERIALS

Human donor tissue was pretreated ex vivo with a nonablative fractional diode laser (1,927 nm or 1,440 nm, at varying treatment densities, powers, and peak energies) followed by application of either 2% salicylic acid, 10% ascorbic acid, over-the-counter mineral eye serum, or 4% hydroquinone. Topical uptake was quantified over 24 hours.

RESULTS

Despite lower power settings, pretreatment with the 1,927 nm wavelength was associated with greater uptake of 10% ascorbic acid, mineral eye serum, and 4% hydroquinone than the 1,440 nm wavelength. In addition, 1,440-nm laser pretreatment with higher density (320 microscopic treatment zones [MTZ]/cm2) and peak power (3 W) was associated with similar uptake but greater retention of 2% salicylic acid and greater uptake of 10% ascorbic acid than that with lower density (80 MTZ/cm2) and peak power (1.2 W).

CONCLUSION

When using laser pretreatment, device settings should be adjusted to balance outcomes with potential side effects.