Optimization of microdermabrasion for controlled removal of stratum corneum

Breaking barriers: Innovative approaches for skin delivery of RNA therapeutics

RNA therapeutics represent a rapidly expanding platform with game-changing prospects in personalized medicine. The disruptive potential of this technology will overhaul the standard of care with reference to both primary and specialty care. To date, RNA therapeutics have mostly been delivered parenterally via injection, but topical administration followed by intradermal or transdermal delivery represents an attractive method that is convenient to patients and minimally invasive. The skin barrier, particularly the lipid-rich stratum corneum, presents a significant hurdle to the uptake of large, charged oligonucleotide drugs. Therapeutic oligonucleotides need to be engineered for stability and specificity and formulated with state-of-the-art delivery strategies for efficient uptake. This review will cover various passive and active strategies deployed to enhance permeation through the stratum corneum and achieve effective delivery of RNA therapeutics to treat both local skin disorders and systemic diseases. Some strategies to achieve selectivity between local and systemic administration will also be discussed.

Advancements in Skin-Mediated Drug Delivery: Mechanisms, Techniques, and Applications

Skin-mediated drug delivery methods currently are receiving significant attention as a promising approach for the enhanced delivery of drugs through the skin. Skin-mediated drug delivery offers the potential to overcome the limitations of traditional drug delivery methods, including oral administration and intravenous injection. The challenges associated with drug permeation through layers of skin, which act as a major barrier, are explored, and strategies to overcome these limitations are discussed in detail. This review categorizes skin-mediated drug delivery methods based on the means of increasing drug permeation, and it provides a comprehensive overview of the mechanisms and techniques associated with these methods. In addition, recent advancements in the application of skin-mediated drug delivery are presented. The review also outlines the limitations of ongoing research and suggests future perspectives of studies regarding the skin-mediated delivery of drugs.

Laser-assisted intradermal delivery of a microparticle vaccine for respiratory syncytial virus induces a robust immune response

Respiratory syncytial virus (RSV) is an infectious disease that poses a significant public health risk in young children. Vaccine studies conducted in the 1960s using an intramuscular injection of formalin-inactivated respiratory syncytial virus (Fi-RSV) resulted in an enhanced respiratory disease and led to the failure of the vaccine. Thus, the virus-like particles (VLP) of the RSV fusion (F) protein was used as the vaccine antigen in this study. The F-VLP was encapsulated in a microparticle (MP) matrix composed of cross-linked bovine serum albumin (BSA) to enhance the antigen presentation and uptake. Moreover, a painless vaccination method would be desirable for an infectious disease that mainly affects young children. Thus, an ablative laser device, Precise Laser Epidermal System (P.L.E.A.S.E), was utilized to create micropores on the skin for vaccine delivery. We observed enhanced antigen presentation of the vaccine microparticles (F-VLP MP) with and without the adjuvant monophosphoryl lipid A (MPL-A) MP in dendritic cells. Consequently, Swiss Webster mice were immunized with the adjuvanted vaccine microparticles using the P.L.E.A.S.E laser to study the in vivo immunogenicity. The immunized mice had high serum immunoglobulin (IgG, IgG2a) levels, indicating a Th1 response. Subsequent analysis of lung homogenates post- RSV challenge revealed high IgA, indicating generation of a mucosal immune response upon intradermal immunization. Flowcytometry analysis showed high CD8+, and CD4+ expression in the lymph node and spleen of the adjuvanted vaccine microparticle immunized mice. Increased expression of interferon gamma (IFN-γ) in the spleen cells further proved Th1 polarized immune response. Finally, an immune plaque assay indicated significantly low lung viral titer in the mice immunized with intradermal adjuvanted vaccine microparticles. Thus, ablative laser-assisted immunization with the F-VLP based adjuvanted vaccine microparticles could be a promising vaccine candidate for RSV.

Potential Lipolytic Effect of Panduratin A Loaded Microspicule Serum as a Transdermal Delivery Approach for Subcutaneous Fat Reduction

Boesenbergia rotunda (L.) Mansf contained a potent anti-obesity agent. The objectives of this study were to investigate the anti-adipogenesis and lipolysis effects of panduratin A from B. rotunda extract and develop extract-loaded lipolytic body microspicule (MS) serum. Panduratin A that was separated from the ethanolic extract of B. rotunda in fraction 3 (BP-3) were studied the bioactivity of 3T3-L1 preadipocyte cells. The extract-loaded MS serum was formulated and evaluated for safety and efficacy. The BP-3 extract containing panduratin A at 0.29 g per g of the extract was not toxic to the cells at concentrations lower than 10 µg/mL, and the antiadipogenesis and lipolysis effects of the BP-3 extract were strong at 10 µg/mL. To deliver bioactive panduratin A into and through the skin, MS serum was successfully formulated. Application of BP-3 extract-loaded MS serum to the human thigh for 14 d reduced the thigh circumference and increased skin hydration and firmness. Although the skin erythema was increased, no severe redness or pain was found. In conclusion, BP-3 extract acts as a potent bioactive compound to inhibit adipocyte cells, and the antiadipogenesis and lipolysis effects of BP-3 extract in MS serum might play an important role as a potential lipolytic body product for reducing human subcutaneous fat mass.

A Comprehensive Review of Non-Energy-Based Treatments for Atrophic Acne Scarring

Scarring is a dire consequence of acne vulgaris. Particularly, atrophic acne scarring is highly prevalent among young adults, and its physical and psychological effects can persist throughout their lives if left untreated. This literature review will analyze various non-energy-based approaches to treating atrophic acne scarring, emphasizing recent advances within the last 5 to 10 years. To accomplish this, we performed a PubMed search for various acne scar treatments such as chemical peels, dermabrasion, microdermabrasion, subcision, microneedling, punch techniques, dermal fillers, and thread lifting. Our findings and analysis show that there is no panacean solution to treating atrophic acne scars, which explains the evolving trend towards developing unique combinatorial treatments. Although a fair comparison of each treatment approach is difficult to achieve due to the studies’ varying sample sizes, strength of evidence, treatment execution, etc, there still remains a level of consensus on what treatments are well suited for particular scar types.

Neoteric direct physical approaches in tdds: a boon for permeation enhancement

Abstract:

Human skin has been tremendously explored for decades as a potential route for the delivery of various substances. It has shown great applications to deliver drugs to systemic circulation as well as has provided adequate advantages to treat local manifestations over the skin. However, the rigid stratum corneum layer has served as the biggest barrier in transdermal drug delivery; various methods have been designed to overcome the stratum corneum layer and make the molecule pass through this. These methods were then broadly classified into chemical and physical approaches. The below study is an overall review of the physical approaches being used in transdermal drug delivery for overcoming the stratum corneum layer. Physical approaches also include direct and indirect methods; we will be physically considering the direct approaches herein.

Hair growth promoting effect of bioactive extract from deer antler velvet-loaded niosomes and microspicules serum

Deer antler velvet (DAV) extract is important in stimulating the growth of skin and hair cells. The aim of this study was to develop DAV extract-loaded niosomes (NIs) and microspicules (MS) serum for effective hair growth. Bioactivities of DAV extract on human dermal papilla cells were studied. To develop protein delivery, NIs were prepared to entrap DAV extract and then loaded into MS serum (NI serum MS). Physicochemical properties and in vitro skin permeations were evaluated. The formulations were applied on human scalp and relative efficacies were evaluated. DAV extract at 2,000 µg/ml significantly enhanced cell proliferation and aggregation. DAV extract-loaded NI exhibited nanovesicle, narrow size distribution and negative surface charge. The vesicles were able to load into MS serum and showed significantly highest macromolecular protein permeation through the skin, with deposition into the deepest skin layer compared with other formulations. Applying the serum on human scalp for 14 and 30 days significantly enhanced hair elongation and melanin content, with increased skin hydration and decreased the erythema index, thereby promoting hair growth without skin irritation. NI serum MS containing DAV extract played an important role to deliver biomacromolecular protein through the skin and hair follicles, leading to effective hair growth.

Vaccination into the Dermal Compartment: Techniques, Challenges, and Prospects

In 2019, an 'influenza pandemic' and 'vaccine hesitancy' were listed as two of the top 10 challenges to global health by the WHO. The skin is a unique vaccination site, due to its immune-rich milieu, which is evolutionarily primed to respond to challenge, and its ability to induce both humoral and cellular immunity. Vaccination into this dermal compartment offers a way of addressing both of the challenges presented by the WHO, as well as opening up avenues for novel vaccine formulation and dose-sparing strategies to enter the clinic. This review will provide an overview of the diverse range of vaccination techniques available to target the dermal compartment, as well as their current state, challenges, and prospects, and touch upon the formulations that have been developed to maximally benefit from these new techniques. These include needle and syringe techniques, microneedles, DNA tattooing, jet and ballistic delivery, and skin permeabilization techniques, including thermal ablation, chemical enhancers, ablation, electroporation, iontophoresis, and sonophoresis.

Development of Sponge Microspicule Cream as a Transdermal Delivery System for Protein and Growth Factors from Deer Antler Velvet Extract

Sponge spicules are needle-like structures and used for dermabrasive treatment of the skin. This research aimed to develop an effective delivery system by using sponge spicules for enhancing skin permeation of bioactive proteins and growth factors from deer antler velvet (DAV). DAV was extracted by sonication and bioactivity studies were evaluated. The size of microspicules (MSs) was reduced and mixed with DAV extract cream. In vitro skin permeation was analyzed by using bovine serum albumin-fluorescein isothiocyanate conjugate (BSA-FITC) as a model macromolecular compound. For in vivo study, DAV extract formulations were applied on the skin of healthy humans, and effects were evaluated. Results showed that DAV extract containing proteins and growth factors increased the proliferation and migration of skin fibroblast cells. This extract was homogeneously mixed with spicule cream. Without blending, MS was 11.89 µm wide and 176.77 µm long; blending time exhibited short and broken MSs (MBs) for short blending (30 s) and fine powder (MF) for long blending (10 min). MS cream showed the highest permeation of BSA-FITC through the skin (2.26-fold enhancement), but it resulted in skin irritation. Therefore, MB cream that increased the permeation of BSA-FITC by 1.94-fold was not significantly different from MS formulations chosen for in vivo study. Applying DAV-containing MB cream on the skin for 14 d decreased the melanin content and erythema value but increased elasticity and hydration. Therefore, the MB-containing cream can enhance the macromolecule delivery through the skin, improve the skin properties, and avoid skin irritation.

Topical and Transdermal Drug Delivery: From Simple Potions to Smart Technologies

This overview on skin delivery considers the evolution of the principles of percutaneous ab-sorption and skin products from ancient times to today. Over the ages, it has been recognised that products may be applied to the skin for either local or systemic effects. As our understanding of the anatomy and physiology of the skin has improved, this has facilitated the development of technologies to effectively and quantitatively deliver solutes across this barrier to specific target sites in the skin and beyond. We focus on these technologies and their role in skin delivery today and in the future.

3D printing applications for transdermal drug delivery

The role of two and three-dimensional printing as a fabrication technology for sophisticated transdermal drug delivery systems is explored in literature. 3D printing encompasses a family of distinct technologies that employ a virtual model to produce a physical object through numerically controlled apparatuses. The applicability of several printing technologies has been researched for the direct or indirect printing of microneedle arrays or for the modification of their surface through drug-containing coatings. The findings of the respective studies are presented. The range of printable materials that are currently used or potentially can be employed for 3D printing of transdermal drug delivery (TDD) systems is also reviewed. Moreover, the expected impact and challenges of the adoption of 3D printing as a manufacturing technique for transdermal drug delivery systems, are assessed. Finally, this paper outlines the current regulatory framework associated with 3D printed transdermal drug delivery systems.

Objective measurements of skin surface roughness after microdermabrasion treatment

BACKGROUND

The aim of this article is to present a new methodology for assessment of skin topology using a three-dimensional image (3D).

METHODS

The measurement of the skin surface roughness is based on 3D scanning of silicone replicas by chromatic aberration length technique in a contactless manner, i.e. by a polychromatic light beam. Analysis of the skin surface reprints was performed using Talymap, Gold version. Results were analysed by fractal geometry, which allows to evaluate changes of the skin surface before and after application of cosmetics and instrumental cosmetological techniques. The methodology was applied for objective assessment of the effects of diamond microdermabrasion on the skin surface roughness. Measurements were performed on 23 volunteers in the age group of 31-67 years.

RESULTS

Based on the results of skin surface scanning after the treatment with diamond microdermabrasion it may be concluded that inequalities of the skin surface are reduced immediately after exfoliation. However, this effect mostly diminishes within 14 days after treatment. The entire study ultimately suggests that the instrumental method used only leads to improvement of the skin surface immediately after its application. Thermo vision images of the skin surface temperature were obtained during the application of the abrasive method. The experimental results showed that the skin is rather cooled than heated by the treatment.

CONCLUSION

This study is focused on the development of a methodology for objective measurement of changes in treated skin relief using 3D scanning. The results are evaluated using fractal dimension. The output may also include also an enlarged model of the skin surface made by 3D printer, which can serve for illustrative communication with the client.

Effect of liposomal fluidity on skin permeation of sodium fluorescein entrapped in liposomes

The purpose of this study was to investigate the effect of ultradeformable liposome components, Tween 20 and terpenes, on vesicle fluidity. The fluidity was evaluated by electron spin resonance spectroscopy using 5-doxyl stearic acid and 16-doxyl stearic acid as spin labels for phospholipid bilayer fluidity at the C5 atom of the acyl chain near the polar head group (hydrophilic region) and the C16 atom of the acyl chain (lipophilic region), respectively. The electron spin resonance study revealed that Tween 20 increased the fluidity at the C5 atom of the acyl chain, whereas terpenes increased the fluidity at the C16 atom of the acyl chain of the phospholipid bilayer. The increase in liposomal fluidity resulted in the increased skin penetration of sodium fluorescein. Confocal laser scanning microscopy showed that ultradeformable liposomes with terpenes increase the skin penetration of sodium fluorescein by enhancing hair follicle penetration.

Effective transcutaneous immunization against hepatitis B virus by a combined approach of hydrogel patch formulation and microneedle arrays

Transcutaneous immunization (TCI) has many advantages compared with needle-based administrations. But the conventional TCI shows poor permeation of antigens across the skin barrier. In this study, Functional MicroArray (FMA) system was used to poke the skin and increase the permeability, and the hydrogel patch formulation was used as the carrier for transdermal delivery of hepatitis B surface antigen (HBsAg) and cholera toxin B (CTB) as an adjuvant. In vitro permeation of antigen was studied using porcine ear skin and rat abdominal skin. The results showed that FMA system could significantly increase the permeation of HBsAg across skin compared with conventional TCI. HBsAg loaded hydrogel formulation exhibited better antigenic thermostability than the liquid formulation. In vivo immunization studies were performed in mice, and the serum IgG titer, IgG2a/IgG1 ratio were measured. The results showed that TCI with FMA induced more potent immune responses than the groups without FMA pretreatment. CTB adjuvanted TCI group could induce higher IgG titers compared with the group without CTB. Furthermore, TCI group can maintain a longer duration of stable IgG titers compared with the intramuscular injection (IM) group. In conclusion, the FMA/hydrogel system was proved to be a potential vaccination strategy against hepatitis B virus.

Cutaneous immunization: an evolving paradigm in influenza vaccines

INTRODUCTION

Most vaccines are administered by intramuscular injection using a hypodermic needle and syringe. Some limitations of this procedure include reluctance to be immunized because of fear of needlesticks, and concerns associated with the safe disposal of needles after their use. Skin delivery is an alternate route of vaccination that has potential to be painless and could even lead to dose reduction of vaccines. Recently, microneedles have emerged as a novel painless approach for delivery of influenza vaccines via the skin.

AREAS COVERED

In this review, we briefly summarize the approaches and devices used for skin vaccination, and then focus on studies of skin immunization with influenza vaccines using microneedles. We discuss both the functional immune response and the nature of this immune response following vaccination with microneedles.

EXPERT OPINION

The cutaneous administration of influenza vaccines using microneedles offers several advantages: it is painless, elicits stronger immune responses in preclinical studies and could improve responses in high-risk populations. These dry formulations of vaccines provide enhanced stability, a property of high importance in enabling their rapid global distribution in response to possible outbreaks of pandemic influenza and newly emerging infectious diseases.

Strengthening the skin with topical delivery of keratinocyte growth factor-1 using a novel DNA plasmid

Fragile skin, susceptible to decubitus ulcers and incidental trauma, is a problem particularly for the elderly and for those with spinal cord injury. Here, we present a simple approach to strengthen the skin by the topical delivery of keratinocyte growth factor-1 (KGF-1) DNA. In initial feasibility studies with the novel minimalized, antibiotic-free DNA expression vector, NTC8385-VA1, the reporter genes luciferase and enhanced green fluorescent protein were delivered. Transfection was documented when luciferase expression significantly increased after transfection. Microscopic imaging of enhanced green fluorescent protein-transfected skin showed green fluorescence in hair follicles, hair shafts, and dermal and superficial epithelial cells. With KGF-1 transfection, KGF-1 mRNA level and protein production were documented with quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry, respectively. Epithelial thickness of the transfected skin in the KGF group was significantly increased compared with the control vector group (26 ± 2 versus 16 ± 4 µm) at 48 hours (P = 0.045). Dermal thickness tended to be increased in the KGF group (255 ± 36 versus 162 ± 16 µm) at 120 hours (P = 0.057). Biomechanical assessment showed that the KGF-1-treated skin was significantly stronger than control vector-transfected skin. These findings indicate that topically delivered KGF-1 DNA plasmid can increase epithelial thickness and strength, demonstrating the potential of this approach to restore compromised skin.

Engineering approaches to transdermal drug delivery: a tribute to contributions of prof. Robert Langer

Transdermal drug delivery continues to provide an advantageous route of drug administration over injections. While the number of drugs delivered by passive transdermal patches has increased over the years, no macromolecule is currently delivered by the transdermal route. Substantial research efforts have been dedicated by a large number of researchers representing varied disciplines including biology, chemistry, pharmaceutics and engineering to understand, model and overcome the skin's barrier properties. This article focuses on engineering contributions to the field of transdermal drug delivery. The article pays tribute to Prof. Robert Langer, who pioneered the engineering approach towards transdermal drug delivery. Over a period spanning nearly 25 years since his first publication in the field of transdermal drug delivery, Bob Langer has deeply impacted the field by quantitative analysis and innovative engineering. At the same time, he has inspired several generations of engineers by collaborations and mentorship. His scientific insights, innovative technologies, translational efforts and dedicated mentorship have transformed the field.

Insulin therapies: Current and future trends at dawn

Insulin is a key player in the control of hyperglycemia for type 1 diabetes patients and selective individuals in patients of type 2 diabetes. Insulin delivery systems that are currently available for the administration of insulin include insulin syringes, insulin infusion pumps, jet injectors and pens. The traditional and most predictable method for the administration of insulin is by subcutaneous injections. The major drawback of current forms of insulin therapy is their invasive nature. To decrease the suffering, the use of supersonic injectors, infusion pumps, sharp needles and pens has been adopted. Such invasive and intensive techniques have spurred the search for alternative, more acceptable methods for administering insulin. Several non-invasive approaches for insulin delivery are being pursued. The newer methods explored include the artificial pancreas with closed-loop system, transdermal insulin, and buccal, oral and pulmonary routes. This review focuses on the new concepts that are being explored for use in future.

Transdermal delivery of molecules is limited by full epidermis, not just stratum corneum

PURPOSE

Most methods to increase transdermal drug delivery focus on increasing stratum corneum permeability, without addressing the need to increase permeability of viable epidermis. Here, we assess the hypothesis that viable epidermis offers a significant permeability barrier that becomes rate limiting upon sufficient permeabilization of stratum corneum.

METHODS

We tested this hypothesis by using calibrated microdermabrasion to selectively remove stratum corneum or full epidermis in pig and human skin, and then measuring skin permeability to a small molecule (sulforhodamine) and macromolecules (bovine serum albumin, insulin, inactivated influenza vaccine) in vitro.

RESULTS

We found that removal of stratum corneum dramatically increased skin permeability to all compounds tested. However, removal of full epidermis increased skin permeability by another 1-2 orders of magnitude. We also studied the effects of removing skin tissue only from localized spots on the skin surface by covering skin with a mask containing 125-μm holes during tissue removal. Skin permeabilized in this less-invasive way showed similar results. This suggests that microdermabrasion of skin using a mask may provide an effective way to increase skin permeability.

CONCLUSIONS

We conclude that viable epidermis offers a significant permeability barrier that becomes rate limiting upon removal of stratum corneum.

Transdermal drug delivery: from micro to nano

Delivery across skin offers many advantages compared to oral or intravenous routes of drug administration. Skin however is highly impermeable to most molecules on the basis of size, hydrophilicity, lipophilicity and charge. For this reason it is often necessary to temporarily alter the barrier properties of skin for effective administration. This can be done by applying chemical enhancers, which alter the lipid structure of the top layer of skin (the stratum corneum, SC), by applying external forces such as electric currents and ultrasounds, by bypassing the stratum corneum via minimally invasive microneedles or by using nano-delivery vehicles that can cross and deliver their payload to the deeper layers of skin. Here we present a critical summary of the latest technologies used to increase transdermal delivery.

Novel methods and devices to enhance transdermal drug delivery: the importance of laser radiation in transdermal drug delivery

Skin permeation-enhancement technology is a rapidly developing field, which could significantly increase the number of drugs suitable for transdermal delivery. In this review, we highlight recent advances in both ‘passive’ and ‘active’ transdermal drug-delivery technologies, as well as in the laser ablation method. This paper concludes with a brief forward-looking perspective discussing what can be expected as laser technology continues to develop in the coming years.

Recovery of skin barrier after stratum corneum removal by microdermabrasion

Microdermabrasion is widely used as a non-invasive cosmetic technique that has recently been adapted to selectively remove stratum corneum to increase skin permeability for transdermal drug delivery. This study measured the kinetics of skin barrier recovery after stratum corneum removal using microdermabrasion in hairless guinea pigs. The skin was abraded at two sites on each animal, one of which was allowed to recover under occlusion while the other remained non-occluded. Histological measurements showed that skin barrier properties to sulforhodamine B largely recovered within 12 h, and the stratum corneum appeared largely reformed within 24 h for both occluded and non-occluded skin. Skin electrical resistance measurements showed significant recovery of the skin barrier within 24 h. We conclude that transdermal drug delivery may occur for up to 12 h after microdermabrasion in guinea pigs; however, humans will probably have a longer recovery time due to expected slower skin healing rates.