Enhanced Drug Permeation into Human Keloid Tissues by Sonophoresis-Assisted Microneedling

Recent advances in transdermal insulin delivery technology: A review

Transdermal drug delivery refers to the administration of drugs through the skin, after which the drugs can directly act on or circulate through the body to the target organs or cells and avoid the first-pass metabolism in the liver and kidneys experienced by oral drugs, reducing the risk of drug poisoning. From the initial singular approach to transdermal drug delivery, there has been a shift toward combining multiple methods to enhance drug permeation efficiency and address the limitations of individual approaches. Technological advancements have also improved the accuracy of drug delivery. Optimizing insulin itself also enables its long-term release via needle-free injectors. In this review, the diverse transdermal delivery methods employed in insulin therapy and their respective advantages and limitations are discussed. By considering factors such as the principles of transdermal penetration, drug delivery efficiency, research progress, synergistic innovations among different methods, patient compliance, skin damage, and posttreatment skin recovery, a comprehensive evaluation is presented, along with prospects for potential novel combinatorial approaches. Furthermore, as insulin is a macromolecular drug, insights gained from its transdermal delivery may also serve as a valuable reference for the use of other macromolecular drugs for treatment.

Targeting Diverse Wounds and Scars: Recent Innovative Bio-design of Microneedle Patch for Comprehensive Management

Wounds and the subsequent formation of scars constitute a unified and complex phased process. Effective treatment is crucial; however, the diverse therapeutic approaches for different wounds and scars, as well as varying treatment needs at different stages, present significant challenges in selecting appropriate interventions. Microneedle patch (MNP), as a novel minimally invasive transdermal drug delivery system, has the potential for integrated and programmed treatment of various diseases and has shown promising applications in different types of wounds and scars. In this comprehensive review, the latest applications and biotechnological innovations of MNPs in these fields are thoroughly explored, summarizing their powerful abilities to accelerate healing, inhibit scar formation, and manage related symptoms. Moreover, potential applications in various scenarios are discussed. Additionally, the side effects, manufacturing processes, and material selection to explore the clinical translational potential are investigated. This groundwork can provide a theoretical basis and serve as a catalyst for future innovations in the pursuit of favorable therapeutic options for skin tissue regeneration.

The Pathophysiology and Management of Pathologic Scarring-a Contemporary Review

Significance: Pathologic scarring occurs secondary to imbalances in the cellular mechanisms of wound healing and affects millions of people annually. This review article aims to provide a concise overview of the pathophysiology and management of pathologic scarring for clinicians and scientists alike. Recent Advances: Contemporary research in the field has identified aberrations in transforming growth factor-β/small mothers against decapentaplegic (TGF-β/SMAD) signaling pathways as key drivers of pathologic scar formation; indeed, this pathway is targeted by many treatment modalities and translational investigations currently underway. Although intralesional injection of corticosteroids has been the gold standard in the treatment of pathologic scarring, studies show greater treatment efficacy with the use of combination injections such as triamcinolone/5-fluorouracil and triamcinolone/botulinum toxin. Adjunctive therapies including ablative fractional carbon dioxide/erbium-doped yttrium aluminum garnet and non-ablative pulsed-dye lasers, microneedling, and carboxytherapy have shown encouraging results in small cohort studies. Translational investigations involving the use of nanogels, RNA interference, and small molecules targeting TGF-β/SMAD pathways are also currently underway and hold promise for the future. Critical Issues: The heterogeneous nature of hypertrophic scars and keloids poses significant challenges in formulating standardized treatment and assessment protocols, thereby limiting the conclusions that can be drawn. Future Directions: Rigorous clinical trials into the individual and synergistic effects of these therapies would be ideal before any definitive conclusions or evidence-based treatment recommendations can be made. Owing to the heterogeneity of the pathology and patient population, well-conducted cohort studies may be the next best option.

Comparative study of permeation effects between vibrating microneedle and low-frequency sonophoresis systems

Microneedle transdermal administration and low-frequency ultrasound represent two important physical penetration-promoting methods for enhancing drug penetration. This article aims to investigate and compare the effects of drug penetration enhancement through transdermal administration using vibrating microneedles versus low-frequency sonophoresis. In Vitro permeation studies were conducted using Valia-Chien double chamber diffusion cells to evaluate the transdermal delivery of tetramethylpyrazine hydrochloride (TMPH). The TMPH concentration in the receiving compartment was determined using high-performance liquid chromatography (HPLC). Several combinations of microneedles and ultrasound settings were investigated, including different needle heights, vibration frequencies, exposure times, and assorted distances of ultrasound horn and skin. The results revealed the vibrating microneedle system as the most efficacious treatment to increase the TMPH permeability into the rat skin. The combination of a larger needle, higher frequency, and a 3-min exposure led to a 41.92-fold increase in cumulative permeability compared to the control group. The ultrasound treatment exhibited a moderate enhancement effect on TMPH skin penetration. Using a horn-to-skin distance of 3 mm and a 3-min exposure resulted in a 4.34-fold increase in TMPH cumulative permeation compared to the control group. It could be concluded that while both the vibrating microneedle and the low-frequency ultrasound systems act as penetration enhancers for promoting the TMPH permeation through the skin, the vibrating microneedle system notably demonstrates a more effective penetration-promoting effect.

Peptide-containing nanoformulations: Skin barrier penetration and activity contribution

Transdermal drug delivery presents a less invasive pathway, circumventing the need to pass through the gastrointestinal tract and liver, thereby reducing drug breakdown, initial metabolism, and gastrointestinal discomfort. Nevertheless, the unique composition and dense structure of the stratum corneum present a significant barrier to transdermal delivery. This article presents an overview of the current developments in peptides and nanotechnology to address this challenge. Initially, we sum up peptide-containing nanoformulations for transdermal drug delivery, examining them through the lenses of both inorganic and organic materials. Particular emphasis is placed on the diverse roles that peptides play within these nanoformulations, including conferring functionality upon nanocarriers and enhancing the biological efficacy of drugs. Subsequently, we summarize innovative strategies for enhancing skin penetration, categorizing them into passive and active approaches. Lastly, we discuss the therapeutic potential of peptide-containing nanoformulations in addressing a range of diseases, drawing insights from the biological activities and functions of peptides. Furthermore, the challenges hindering clinical translation are also discussed, providing valuable insights for future advancements in transdermal drug delivery.

Microneedle-mediated drug delivery for scar prevention and treatment

Scars are an inevitable natural outcome of most wound healing processes and affect skin functions, leading to cosmetic, psychological and social problems. Several strategies, including surgery, radiation, cryotherapy, laser therapy, pressure therapy and corticosteroids, can be used to either prevent or treat scars. However, these strategies are ineffective, have side effects and are typically expensive. Microneedle (MN) technology is a powerful, minimally invasive platform for transdermal drug delivery. This review discusses the most recent progress in MN-mediated drug delivery to prevent and treat pathological scars (hypertrophic and keloids). A comprehensive overview of existing challenges and future perspectives is also provided.

Highly stable and fast-dissolving ascorbic acid-loaded microneedles

OBJECTIVES

Ascorbic acid has many benefits to the skin. Numerous attempts to promote its topical delivery show great challenges since its chemical instability and poor skin impermeability. Microneedle delivery is a simple, safe, painless and effective means to deliver therapeutic or nourishing molecules into the skin. The purpose of this study was twofold: (a) to develop a new formulation of ascorbic acid-loaded microneedles to enhance ascorbic acid stability by investigating an optimal amount of polyethyleneimine as an additive to the dextran-based microneedle formulation and (b) to assess microneedle properties in terms of dissolving rate, skin penetration ability, biocompatibility and antimicrobial activity.

METHODS

The microneedles formulated with ascorbic acid and varied polyethyleneimine concentrations were fabricated and subsequently tested for ascorbic acid stability using 2,2-diphenyl-1-picrylhydrazyl assay. The dissolution rate and skin penetration depth were investigated in porcine skin and the reconstructed human full-thickness skin model respectively. The skin irritation tests were done according to the Organisation for Economic Co-operation and Development Test Guideline No. 439. An antimicrobial disc susceptibility test was performed against Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis.

RESULTS

Among varied amounts of 0%, 1.5%, 3.0% and 4.5% (w/v), the 3.0% polyethyleneimine showed the most desirable characteristics, including well-preserved shape integrity after demoulding, significantly improved stability of ascorbic acid (p < 0.001) from 33% to 96% antioxidant activity after 8 weeks of storage at 40°C, increased dissolving rate (p < 0.001) by being completely dissolved within 2 min after the skin insertion, passing skin penetration and biocompatibility tests as well as having a broad spectrum of antimicrobial property.

CONCLUSION

With a safety profile and enhanced properties, the new formulation of ascorbic acid-loaded microneedles shows outstanding potential as commercially available cosmetics and healthcare products.

Poly(2-Hydroxyethyl Methacrylate) Hydrogel-Based Microneedles for Metformin Release

The release of metformin, a drug used in the treatment of cancer and diabetes, from poly(2-hydroxyethyl methacrylate), pHEMA, hydrogel-based microneedle patches is demonstrated in vitro. Tuning the composition of the pHEMA hydrogels enables preparation of robust microneedle patches with mechanical properties such that they would penetrate skin (insertion force of a single microneedle to be ≈40 N). Swelling experiments conducted at 20, 35, and 60 °C show temperature-dependent degrees of swelling and diffusion kinetics. Drug release from the pHEMA hydrogel-based microneedles is fitted to various models (e.g., zero order, first order, second order). Such pHEMA microneedles have potential application for transdermal delivery of metformin for the treatment of aging, cancer, diabetes, etc.

Comparison of the efficacy of seven types of microneedles for treating a rabbit hypertrophic scar model

Microneedle technology can effectively suppress the formation of hypertrophic scarring in both animals and humans. Our previous research has revealed that this is due to the physical contact inhibition effect by using microneedles made of liquid-crystal polymers as the model device. One important factor we didn't study is the influence of the fabrication materials of microneedles. Therefore, this article examines this key point on a rabbit ear hypertrophic scar model. We monitor the thickness of the scars, and the expression of α-SMA and Ki-67 protein, and TGF-β1 mRNA in a period of 42 days. Among microneedles made of 6 polymeric materials and stainless steel, polymethylmethacrylate microneedles present superiority in all aspects including the reduction of tissue fibrosis, and the expression of α-SMA, Ki-67 protein and TGF-β1 mRNA. On the other hand, polycarbonates, polyurethane, and polylactic-co-glycolic acid microneedles could suppress three biomarker expressions.

Efficacy of a triamcinolone acetonide-loaded dissolving microneedle patch for the treatment of hypertrophic scars and keloids: a randomized, double-blinded, placebo-controlled split-scar study

The treatment of hypertrophic scars (HTSs) and keloids remains a challenge. Intralesional triamcinolone acetonide (TAC) is the mainstay treatment for these conditions. Despite its efficacy, TAC has several adverse side effects, including telangiectasias, skin atrophy, pigmentary changes, and skin necrosis. Dissolving microneedles (DMN) use the poke-and-release method to create microchannels that enhance drug delivery to the target tissue in the dermis, without causing pain and with a decreased risk of transmission of blood-borne diseases. To evaluate and compare the efficacy of a TAC-DMN versus a drug-free DMN patch for the treatment of HTSs and keloids, 20 patients (10 with HTSs and 10 with keloids) received a split-scar treatment: one half of the scar length was treated with TAC-DMNs and the other half was treated with drug-free DMN for three sessions at 14-day intervals. Efficacy was assessed by measuring the scar volume through a multispectral imaging system and using the Patient and Observer Scar Assessment Scale (POSAS). The HTSs treated with TAC-DMNs showed a significant reduction in the mean scar volume 2 weeks after the second treatment and 1 month after the third treatment (p = 0.028 and 0.020, respectively), while the HTSs treated with drug-free DMNs showed no significant reduction in the scar volume. Both sides of the keloids showed no significant reduction in mean scar volume. Using the POSAS, significant improvement in the appearance of both halves of the HTSs was observed 1 month after the treatments. A significant improvement (evaluated by POSAS) was also observed in the keloids treated with TAC-DMNs 2 weeks after the second treatment and 1 month after the third treatment. No significant improvement was observed from the patients' perspective as evaluated by POSAS in the keloids treated with drug-free DMNs. However, no significant difference was observed between the treatment and control halves. TAC-DMN is an effective treatment for HTSs. Increasing the dosage and duration of keloid scar treatment is required in future studies to determine whether it would result in a significant therapeutic outcome. This trial is registered in the Thai Clinical Trials Registry (TCTR20220318004; date of registration, March 17, 2022).

Layer-by-Layer Assembly of Lipid Nanobubbles on Microneedles for Ultrasound-Assisted Transdermal Drug Delivery

Microneedles as a typical device for transdermal drug delivery provide an alternative route for drug administration with minimal digestion by organs and better patient compliance. However, diffusion of passively released drug molecules within the skin tissue mainly depends on the interstitial fluid, which may be affected by different physiological conditions of individuals. Herein, we propose a nanobubble-modified microneedle patch for ultrasound-assisted drug delivery, which provides additional driving force for penetration and diffusion of the drug molecules. Layer-by-layer self-assembled drug-containing nanobubbles on the surfaces of microneedles trigger active drug release upon application of ultrasound. The concomitant microstreaming caused by cavitation effects facilitates the penetration and diffusion of drug molecules in the gelatin gel model and the ex vivo porcine skin model. The proposed drug delivery strategy holds great promise for rapid transdermal drug delivery with enhanced penetration and diffusion of the released drugs.