Heat: A Highly Efficient Skin Enhancer for Transdermal Drug Delivery

Wearable transdermal drug delivery system controlled by wirelessly powered acoustic waves

Transdermal drug administration offers an alternative route for drug delivery through the skin, and surface acoustic wave (SAW) technology has recently emerged as a promising approach to enhance this process. However, conventional cable-connected SAW control units face several challenges, including inconvenience, poor wearability, limited miniaturization and integration, and restricted reusability. This study introduces a wireless-powered transport strategy for the transdermal delivery of large drug molecules using a thin-film-based SAW platform. This approach leverages interfacial acoustic stimulation, localized acoustic heating, and streaming/micro-cavitation to enhance drug penetration. By eliminating the need for physical connections, the wireless power transfer system reduces potential heating effects and localized tissue damage. To evaluate its performance, synthetic skin-like agarose gel and pig skin tissue were used as models. Hyaluronate rhodamine (5000 Da) was successfully delivered transdermally into pig skin tissue, achieving approximately 77.89 % of the efficiency observed with a conventional cable-connected SAW platform. These findings highlight wireless SAW technology as a promising alternative for enhancing transdermal drug delivery, offering a safer, more effective, and user-friendly therapeutic solution for patients.

Emulgel Containing Metronidazole and Clindamycin for the Treatment of Rosacea

Rosacea is a common skin condition with quite a relevance. It currently affects at least 10% of the European population at some point after the age of 30. It is a chronic disorder that mainly affects the skin on the face and is characterized by outbreaks and remissions. Under normal circumstances, the skin face presents a wide range of commensal organisms, such as Staphylococcus epidermidis or Demodex folliculorum, but dysbiosis of the skin flora plays a relevant role in inflammatory processes and the development of the disease. Metronidazole (MD) is one of the main treatments indicated to reduce redness on the cheeks, nose, chin, or forehead and also to treat flushing, erythema, pimples, and other symptoms due in part to its anti-inflammatory action. On the other hand, clindamycin (CM) is another antibiotic used for rosacea, especially for its action against anaerobic and Gram-positive bacteria. Background/Objectives: This study aimed to develop an emulgel formulation that includes MD and CM, using excipients with non-comedogenic and non-irritating properties. Methods: The formulation was characterised physiochemically, rheological measurements were made, and short-term stability studies were carried out. In vitro release, permeation studies, toxicity an in vitro inflammation model were evaluated in a HaCaT cell model. To determine the interaction between the antibiotics, the minimum inhibitory concentration was determined separately and together using the broth microdilution method. To determine the formulation's antimicrobial activity, an agar diffusion method was used. Results: The MD-CM-gel droplet size was measured by laser diffraction and the diameter obtained was less than 2.68 ± 0.18 µm in 50% of the particles. Suitable results was observed for the short-term stability. Release and permeation data revealed sustained drug release and adequate permeation through human skin. Non-toxicity was detected and the MD showed an anti-inflammatory effect with non-interference of CM. Also, there is no antagonism between the two antibiotics and the MD-CM-gel shows better results when compared to the formulations with the antibiotics separately and to commercial formulations. Conclusions: It is suggested that, following detailed preclinical and clinical studies, MD-CM-gel could be considered as an alternative for treating rosacea.

Peptides: Emerging Candidates for the Prevention and Treatment of Skin Senescence: A Review

One class of cosmetic compounds that have raised interest of many experts is peptides. The search for ingredients with good biocompatibility and bioactivity has led to the use of peptides in cosmetic products. Peptides are novel active ingredients that improve collagen synthesis, enhance skin cell proliferation, or decrease inflammation. Based on their mechanism of action, they can be classified into signal peptides, carrier peptides, neurotransmitter inhibitor peptides, and enzyme inhibitor peptides. This review focuses on the main types of peptides and their application in the cosmetic field, underlining their main limitations. One of the most significant drawbacks of cosmetic peptides is their poor permeability through membranes, which limits their delivery and effectiveness. As a result, this review follows the methods used for improving permeability through the stratum corneum. Increasing peptide bioavailability and stability for enhanced delivery to the desired site of action and visible effects have become central points for the latest research due to their promising features. For this purpose, several methods have been identified and described. Physical techniques include thermal ablation (radiofrequency and laser), electrical methods (electroporation, iontophoresis), mechanical approach (microneedles), and ultrasounds. As an alternative, innovative formulations have been developed in nano-systems such as liposomes, niosomes, ethosomes, nanoemulsions, and other nanomaterials to reduce skin irritation and improve product effectiveness. The purpose of this review is to provide the latest information regarding these noteworthy molecules and the reasoning behind their use in cosmetic formulations.

Iontophoresis-Integrated Smart Microneedle Delivery Platform for Efficient Transdermal Delivery and On-Demand Insulin Release

Transdermal insulin delivery in a painless, convenient, and on-demand way remains a long-standing challenge. A variety of smart microneedles (MNs) fabricated by glucose-responsive phenylboronic acid hydrogels have been previously developed to provide painless and autonomous insulin release in response to a glucose level change. However, like the majority of MNs, their transdermal delivery efficiency was still relatively low compared to that with subcutaneous injection. Herein, we report an iontophoresis (ITP)-integrated smart MNs delivery platform with enhanced transdermal delivery efficiency and delivery depth. Carbon nanotubes (CNTs) were induced in the boronate-containing hydrogel to develop a semi-interpenetrating network hydrogel with enhanced stiffness and conductivity. Remarkably, ITP not only facilitated efficient and deeper transdermal delivery of insulin via electroosmosis and electrophoresis but also well-maintained glucose responsiveness. This ITP-combined smart MNs delivery platform, which could provide on-demand insulin delivery in a painless, convenient, and safe way, is promising to achieve persistent glycemic control. Furthermore, transdermal delivery of payloads with a wide size range was achieved by this delivery platform and thus shed light on the development of an efficient transdermal delivery platform with deep skin penetration in a minimally invasive way.

Skin Structure, Physiology, and Pathology in Topical and Transdermal Drug Delivery

Several industries are increasingly focused on enhancing the delivery of active ingredients through the skin to optimize therapeutic outcomes. By facilitating the penetration of active ingredients through the skin barrier, these enhancers can significantly improve the efficacy of various formulations, ranging from skincare products to therapeutic agents targeting systemic circulation. As the understanding of skin physiology and the mechanisms of drug absorption deepen, these industries are adopting permeation enhancers more widely, ultimately leading to better patient outcomes and expanded treatment options. However, the structure and physiological function of the skin can vary according to different factors, such as the area of the body and between individuals. These variations, along with external environmental exposures, aging and pathological conditions, introduce complexities that must be carefully considered when designing effective delivery systems. Considering the intricacies of skin structure and physiology, tailoring systems to account for regional differences, individual variability, and changes induced by environmental factors or disease is critical to optimizing therapeutic outcomes. This review discusses the features of skin structure, physiology, and pathologies, as well as the application of permeation enhancers in these contexts. Furthermore, it addresses the use of animal skin models in transdermal delivery and dermatological studies, along with the latest developments in this field.

Alleviating rheumatoid arthritis with a photo-pharmacotherapeutic glycan-integrated nanogel complex for advanced percutaneous delivery

The prospective of percutaneous drug delivery (PDD) mechanisms to address the limitations of oral and injectable treatment for rheumatoid arthritis (RA) is increasing. These limitations encompass inadequate compliance among patients and acute gastrointestinal side effects. However, the skin's intrinsic layer can frequently hinder the percutaneous dispersion of RA medications, thus mitigating the efficiency of drug delivery. To circumvent this constraint, we developed a strontium ranelate (SrR)-loaded alginate (ALG) phototherapeutic hydrogel to assess its effectiveness in combating RA. Our studies revealed that this SrR-loaded ALG hydrogel incorporating photoelectrically responsive molybdenum disulfide nanoflowers (MoS2 NFs) and photothermally responsive polypyrrole nanoparticles (Ppy NPs) to form ALG@SrR-MoS2 NFs-Ppy NPs demonstrated substantial mechanical strength, potentially enabling delivery of hydrophilic therapeutic agents into the skin and significantly impeding the progression of RA. Comprehensive biochemical, histological, behavioral, and radiographic analyses in an animal model of zymosan-induced RA demonstrated that the application of these phototherapeutic ALG@SrR-MoS2 NFs-Ppy NPs effectively reduced inflammation, increased the presence of heat shock proteins, regulatory cluster of differentiation M2 macrophages, and alleviated joint degeneration associated with RA. As demonstrated by our findings, treating RA and possibly other autoimmune disorders with this phototherapeutic hydrogel system offers a distinctive, highly compliant, and therapeutically efficient method.

Modulation of hair growth by topical drug delivery enhanced by STAR particles

Topical treatments to modulate hair growth are generally limited by low drug bioavailability due to poor skin permeability. Here, we studied the use of STAR particles, which are millimeter-sized ceramic particles with protruding microneedles, to form micropores in the skin to increase skin permeability to hair growth-modulating drugs. STAR particle design and fabrication were optimized, and the resulting STAR particles were shown to reduce lag time and increase skin permeability to minoxidil and acyclovir by more than three-fold compared to no treatment in pig skin ex vivo. In rats, STAR particles also improved topical delivery of minoxidil and acyclovir, which resulted in an increase or a decrease in the number, length and/or thickness of hairs and/or the number of anagen-phase hair follicles after minoxidil or acyclovir treatment, respectively. Clinical exam and histological evaluation showed no evidence of skin irritation or other adverse effects of the treatments. We conclude that STAR particles can increase topical delivery of minoxidil and acyclovir to improve modulation of hair growth promotion and inhibition, respectively.

Hyaluronic Acid-Extraction Methods, Sources and Applications

In this review, a compilation of articles in databases on the extraction methods and applications of hyaluronic acid (HA) was carried out. HA is a highly hydrated component of different tissues, including connective, epithelial, and neural. It is an anionic, linear glycosaminoglycan (GAG) primarily found in the native extracellular matrix (ECM) of soft connective tissues. Included in the review were studies on the extraction methods (chemical, enzymatical, combined) of HA, describing advantages and disadvantages as well as news methods of extraction. The applications of HA in food are addressed, including oral supplementation, biomaterials, medical research, and pharmaceutical and cosmetic industry applications. Subsequently, we included a section related to the structure and penetration routes of the skin, with emphasis on the benefits of systems for transdermal drug delivery nanocarriers as promoters of percutaneous absorption. Finally, the future trends on the applications of HA were included. This final section contains the effects before, during, and after the application of HA-based products.

Magneto-Responsive Textiles for Non-Invasive Heating

Magneto-responsive textiles have emerged lately as an important carrier in various fields, including biomedical engineering. To date, most research has been performed on single magnetic fibers and focused mainly on the physical characterization of magnetic textiles. Herein, from simple woven and non-woven textiles we engineered materials with magnetic properties that can become potential candidates for a smart magnetic platform for heating treatments. Experiments were performed on tissue-mimicking materials to test the textiles' heating efficiency in the site of interest. When the heat was induced with magneto-responsive textiles, the temperature increase in tissue-mimicking phantoms depended on several factors, such as the type of basic textile material, the concentration of magnetic nanoparticles deposited on the textile's surface, and the number of layers covering the phantom. The values of temperature elevation, achieved with the use of magnetic textiles, are sufficient for potential application in magnetic hyperthermia therapies and as heating patches or bandages.

From Plants to Wound Dressing and Transdermal Delivery of Bioactive Compounds

Transdermal delivery devices and wound dressing materials are constantly improved and upgraded with the aim of enhancing their beneficial effects, biocompatibility, biodegradability, and cost effectiveness. Therefore, researchers in the field have shown an increasing interest in using natural compounds as constituents for such systems. Plants, as an important source of so-called "natural products" with an enormous variety and structural diversity that still exceeds the capacity of present-day sciences to define or even discover them, have been part of medicine since ancient times. However, their benefits are just at the beginning of being fully exploited in modern dermal and transdermal delivery systems. Thus, plant-based primary compounds, with or without biological activity, contained in gums and mucilages, traditionally used as gelling and texturing agents in the food industry, are now being explored as valuable and cost-effective natural components in the biomedical field. Their biodegradability, biocompatibility, and non-toxicity compensate for local availability and compositional variations. Also, secondary metabolites, classified based on their chemical structure, are being intensively investigated for their wide pharmacological and toxicological effects. Their impact on medicine is highlighted in detail through the most recent reported studies. Innovative isolation and purification techniques, new drug delivery devices and systems, and advanced evaluation procedures are presented.

Efficacy and safety of needle-free jet injector-assisted intralesional treatments in dermatology-a systematic review

Needle-free jet injectors are used for the intralesional treatment of various dermatological indications. However, a systematic review that evaluates the efficacy and safety of these treatments has not been published. The objectives of this study are to evaluate the efficacy and safety of needle-free jet injections for dermatological indications and to provide evidence-based treatment recommendations. An electronic literature search was conducted in April 2022. Two reviewers independently selected studies based on predefined criteria and performed a methodological quality assessment using the Cochrane Collaborations risk-of-bias 2.0 assessment tool and Newcastle-Ottawa Scale. Thirty-seven articles were included, involving 1911 participants. Dermatological indications included scars, alopecia areata, hyperhidrosis, nail diseases, non-melanoma skin cancer, common warts, local anesthesia, and aesthetic indications. Keloids and other types of scars (hypertrophic, atrophic, and burn scars) were investigated most frequently (n = 7). The included studies reported favorable efficacy and safety outcomes for intralesional jet injector-assisted treatment with triamcinolone acetonide/hexacetonide, 5-fluorouracil, bleomycin, or hyaluronic acid. Two high-quality studies showed good efficacy and tolerability of intralesional jet injections with a combination of 5-fluorouracil and triamcinolone acetonide in hypertrophic scars and with saline in boxcar and rolling acne scars. No serious adverse reactions and good tolerability were reported in the included studies. Overall, the methodological quality of the included studies was low. Limited evidence suggests that needle-free jet injector-assisted intralesional treatment is efficacious and safe for hypertrophic and atrophic acne scars. More well-powered RCTs investigating the efficacy and safety of jet injector treatment in dermatology are warranted to make further evidence-based recommendations.

Antimicrobial releasing hydrogel forming microneedles

Hydrogel-forming microneedle arrays as a technique for transdermal drug delivery show promise as an alternative to traditional drug delivery methods. In this work, hydrogel-forming microneedles have been created with effective, controlled delivery of amoxicillin and vancomycin within comparable therapeutic ranges to that of oral delivered antibiotics. Fabrication using reusable 3D printed master templates enabled quick and low-cost hydrogel microneedle manufacturing through micro-molding. By 3D printing at a tilt angle of 45° the resolution of the microneedle tip was improved by double (from ca. 64 μm down to 23 μm). Amoxicillin and vancomycin were encapsulated within the hydrogel's polymeric network through a unique room temperature swell/deswell drug loading method within minutes, eliminating the need for an external drug reservoir. The hydrogel-forming microneedle mechanical strength was maintained, and successful penetration of porcine skin grafts observed with negligible damage to the needles or surrounding skin morphology. Hydrogel swell rate was tailored by altering the crosslinking density, resulting in controlled antimicrobial release for an applicable delivered dosage. The potent antimicrobial properties of the antibiotic-loaded hydrogel-forming microneedles against both Escherichia coli and Staphylococcus aureus, highlights the beneficial use of hydrogel-forming microneedles towards the minimally invasive transdermal drug delivery of antibiotics.

Recent Advances in Oral and Transdermal Protein Delivery Systems

Protein and peptide drugs are predominantly administered by injection to achieve high bioavailability, but this greatly compromises patient compliance. Oral and transdermal drug delivery with minimal invasiveness and high adherence represent attractive alternatives to injection administration. However, oral and transdermal administration of bioactive proteins must overcome biological barriers, namely the gastrointestinal and skin barriers, respectively. The rapid development of new materials and technologies promises to address these physiological obstacles. This review provides an overview of the latest advances in oral and transdermal protein delivery, including chemical strategies, synthetic nanoparticles, medical microdevices, and biomimetic systems for oral administration, as well as chemical enhancers, physical approaches, and microneedles in transdermal delivery. We also discuss challenges and future perspectives of the field with a focus on innovation and translation.

Aminodihydrophthalazinedione Sodium Transdermal Therapeutic System Specific Activity on an ExperimentalModel of Extensive Liver Resection

Previously, the authors showed that the application of the aminodihydrophthalazinedione sodium (ADPS) immunomodulator transdermal therapeutic system (TTS) to laboratory animals provides bioavailability analogous to the intramuscular administration of this drug at the same dose. At the same time, its maximum blood concentration is significantly reduced, and the retention time of the drug in the body is increased more than 10-fold, which can contribute to prolonging the drug effect. The aim of the work was to identify a possible positive effect of the transdermal administration of the ADPS immunomodulator on reparative liver regeneration on an experimental model of extensive liver resection (ELR). It has been shown that at a period of 48 h after ELR, the percutaneous administration of the immunomodulator has a pronounced stimulating effect on the mitotic activity of rat liver cells; by 72 h after ELR, an accelerated rate of recovery of hepatic homeostasis in the body was observed in laboratory animals in groups with the application of the ADPS TTS versus the control group.

Acoustic metamaterials-driven transdermal drug delivery for rapid and on-demand management of acute disease

Transdermal drug delivery provides convenient and pain-free self-administration for personalized therapy. However, challenges remain in treating acute diseases mainly due to their inability to timely administrate therapeutics and precisely regulate pharmacokinetics within a short time window. Here we report the development of active acoustic metamaterials-driven transdermal drug delivery for rapid and on-demand acute disease management. Through the integration of active acoustic metamaterials, a compact therapeutic patch is integrated for penetration of skin stratum corneum and active percutaneous transport of therapeutics with precise control of dose and rate over time. Moreover, the patch device quantitatively regulates the dosage and release kinetics of therapeutics and achieves better delivery performance in vivo than through subcutaneous injection. As a proof-of-concept application, we show our method can reverse life-threatening acute allergic reactions in a female mouse model of anaphylaxis via a multi-burst delivery of epinephrine, showing better efficacy than a fixed dosage injection of epinephrine, which is the current gold standard 'self-injectable epinephrine' strategy. This innovative method may provide a promising means to manage acute disease for personalized medicine.

Betamethasone-loaded dissolvable microneedle patch for oral ulcer treatment

Oral inflammatory disease (OID) is among the most common oral lesions, affecting people's quality of life and even leading to oral cancer. Oral ulcers are the most common OID. However, the pain and fear caused by the localized injection of hormones hinder the clinical treatment of oral ulcers. To address this problem, soluble hyaluronic acid (HA) microneedle patches (BSP-BDP@HAMN) containing betamethasone 21-phosphate sodium (BSP) and betamethasone 17,21-dipropionate (BDP) were fabricated for potential application in oral ulcers. BSP-BDP@HAMNs had the sufficient mechanical strength to penetrate the rat tongue abdomen mucosa with an insertion depth of approximately 207 ± 3 µm. The rapidly solubilized HA microneedle carrier released BSP and BDP into the ulcer base within 3 min of entering the mucosa. Cellular assays have shown that BDP@HAMNs have wound healing-promoting and anti-inflammatory effects. Compared with topical injections and creams, BSP-BDP@HAMNs not only penetrated the ulcer surface painlessly but also worked deep in the ulcer for a long time. In conclusion, the proposed BSP-BDP@HAMN patch can improve the comfort and efficacy of oral ulcer treatment, thus providing a new prospect for oral ulcer treatment.

Portable Iontophoresis Device for Efficient Drug Delivery

The timely delivery of drugs to specific locations in the body is imperative to ensure the efficacy of treatment. This study introduces a portable facial device that can deliver drugs efficiently using iontophoresis. Two types of power supplies-direct current and pulse ionization supplies-were manufactured by injection molding. Electrical stimulation elements, which contained Ag metal wires, were woven into facial mask packs. The diffusion phenomenon in the skin and iontophoresis were numerically modeled. Injection molding was simulated before the device was manufactured. Analysis using rhodamine B demonstrated a remarkable increase in the moisture content of the skin and effective absorption of the drug under an applied electric field upon the application of iontophoresis. The proposed concept and design constitute a new method of achieving effective drug absorption with wearable devices.

Advances and Prospects of Prolamine Corn Protein Zein as Promising Multifunctional Drug Delivery System for Cancer Treatment

Zein is a type of prolamine protein that is derived from corn, and it has been recognized by the US FDA as one of the safest biological materials available. Zein possesses valuable characteristics that have made it a popular choice for the preparation of drug carriers, which can be administered through various routes to improve the therapeutic effect of antitumor drugs. Additionally, zein contains free hydroxyl and amino groups that offer numerous modification sites, enabling it to be hybridized with other materials to create functionalized drug delivery systems. However, despite its potential, the clinical translation of drug-loaded zein-based carriers remains challenging due to insufficient basic research and relatively strong hydrophobicity. In this paper, we aim to systematically introduce the main interactions between loaded drugs and zein, administration routes, and the functionalization of zein-based antitumor drug delivery systems, in order to demonstrate its development potential and promote their further application. We also provide perspectives and future directions for this promising area of research.

Enhanced transdermal insulin basal release from silk fibroin (SF) hydrogels via iontophoresis

Insulin is the peptide hormone used to treat the diabetes patient. The hormone is normally taken by injection. The transdermal drug delivery system (TDDS) is an alternative route. The silk fibroin (SF) hydrogels were fabricated via solution casting as the insulin matrix. The release and release-permeation experiments of the insulin loaded SF hydrogels were carried out using a modified Franz-diffusion cell at 37 °C for 36 h, under the effects of SF concentrations, pH, and electric field. The release-permeation mechanism through the pig skin was from the Case-II transport with the constant release rate. The diffusion coefficient (D) increased with decreasing SF concentration due to a larger mesh size, and with increasing electric field due to the electroreplusive forces between the insulin and the SF hydrogels against the negatively-charged electrode, and the induced SF hydrogel expansion. The rate and amount of insulin release-permeation became relatively lower as it required a longer time to generate aqueous pathways through the pig skin. The present SF hydrogels are demonstrated here deliver insulin with the required constant release rate, and the suitable amount within a prescribed duration.

Thermodynamic and kinetic analysis of human epidermal penetration of phenolic compounds: I. Stratum corneum solubility and partitioning

Warming of the skin is now an accepted means of promoting skin permeation. Accordingly, the usually quite onerous thermodynamic studies on solute transport through the skin have practical applications. Phenolic compounds permeate through the skin by partitioning into and diffusing through the stratum corneum (SC) intercellular lipids, with their size being the main determinant of their maximal solute flux through skin. This paper sought to characterise the enthalpic and entropic changes associated with the solubility and equilibrium partitioning into the human SC of a series of phenols similar in size but with differing log P from aqueous vehicles. The solubilities of 9 phenolic compounds, covering a range of polarities, were determined in water and SC following 72 h at 4, 24, 32 and 37 °C which allowed the estimation of the SC-water partition coefficients. Van't Hoff plots were then used to estimate the enthalpies and entropies for the SC solubility, water solubility and SC partitioning of phenols. In addition, partition coefficients of 3 of the 9 phenols from mineral oil into hydrated and dehydrated SC were measured at the same temperatures. Van't Hoff plots were then used to estimate the enthalpies and entropies for the SC solubility, water solubility and SC partitioning of phenols from the oil. The SC solubility for the polar phenols increased more with temperature than the non-polar phenols, with the SC-water partition coefficients increasing with temperature for the polar phenols but decreasing with temperature for the non-polar phenols. Thermodynamic analyses suggest that, while enthalpy and entropy effects are involved in the SC partitioning of the non-polar solutes, the SC partitioning of the polar phenols were almost entirely entropy driven. The resultant thermodynamic parameters are consistent with the polar phenols being mainly associated with the SC polar head groups whereas the nonpolar phenols were more likely to be located in the interior interface SC lipid region adjacent to the polar head groups. Further, hydrating the SC led to an increase in the enthalpy of partitioning for both the polar and non-polar phenols studied. The estimated entropy of the partitioning for solutes from dehydrated SC suggests this is not only a hydrophobic effect in water but that the partitioning arises from the nature of phenolic compound - SC intercellular lipid interactions and SC intercellular lipid entropy. This partitioning process is dominated more by the extent of interaction between the SC and solute than the hydrophobic effect in water and is likely to be even greater above the SC lipid phase transition at around 36 °C for hydrated epidermal membranes.

Heat-based transdermal delivery of a ramipril loaded cream for treating hypertension

Angiotensin-converting enzyme (ACE) inhibitors play an important role in the development of anti-hypertension approaches, with ramipril being one of the most widely used ACE inhibitor prodrugs orally administered once or twice a day. Due to its low bioavailability, large amounts have to be administered to obtain a therapeutic effect. In this work, we propose a ramipril loaded pharmaceutical formulation in contact with an electrothermal actuator based on a gold nanohole array as an efficient approach to increase the transdermal ramipril flux. Using rats as an in vivo model, the effect on the systolic and diastolic blood pressure is evaluated, showing that under optimized conditions the blood pressure could be regulated. Heat activation resulted in total drug delivery out of a bandage loaded with 1 mg ramipril, revealing a flux of 50.9 ± 2.8 μg cm-2 h-1. Importantly, heat-based transdermal dispensing allowed efficient and rapid delivery of ramipril in spontaneously hypertensive rats, with its active form (ramiprilat) detected in blood as early as 5 minutes after delivery onset, accompanied by significant decrease in blood pressure.

Nanoporous Gold Ring-Integrated Photothermal Intraocular Lens for Active Prevention of Posterior Capsular Opacification

Posterior capsular opacification (PCO) is the leading complication after cataract surgery, and is mainly induced by the proliferation and migration of residual lens epithelial cells (LECs). Although numerous attempts have been made to reduce the incidence of PCO, this complication remains a critical challenge in postoperative visual recovery. This study aims to report a functionalized intraocular lens (R-IOL) with a region-confined photothermal effect for the active prevention of PCO after implantation. The outer rim of R-IOL (non-optical area) is decorated with a nanoporous gold (NPG) ring, which can effectively eliminate the LECs around R-IOL, ultimately inhibiting the migration of LECs from the periphery to the visual axis center in the initial stage, and preventing the subsequent PCO. Furthermore, the mechanism of LECs elimination can be attributed to apoptosis induced by mild photothermal therapy. After in vivo implantation for 30 days, PCO is rarely observed in the R-IOL group, whereas the considerably higher incidence of PCO (75%) is found in the pristine IOL (P-IOL) group. The region-confined photothermal effect based on NPG not only provides an active strategy to effectively prevent PCO, but also introduces new opportunities for the treatment of undesirable hyperplasia.

Efficacy and Safety of Using Noninsulated Microneedle Radiofrequency Alone versus in Combination with Polynucleotides for Treatment of Periorbital Wrinkles

Introduction

A few studies have evaluated the efficacy and safety of noninsulated radiofrequency microneedling (RFMN) to treat periorbital wrinkles in Asian patients. Recently, wound healing accelerators, polynucleotides (PNs), have received attention in wound management. However, their efficacy and safety have not been fully elucidated following RFNM. This study aimed to evaluate the efficacy and safety of noninsulated RFMN for periorbital wrinkles and the synergistic effect of PNs after RFMN.

Methods

Thirty subjects with Fitzpatrick skin types III to V and facial wrinkles (Fitzpatrick grades I and II) were enrolled. All volunteers were treated over the entire face with noninsulated RFMN for three sessions at 2-week intervals. The left and right sides of each patient’s face were randomly assigned to receive PNs (treatment group) or normal saline solution (control group). The indentation and maximum depth of wrinkles were objectively measured using Antera 3D. Subjective self-evaluations were obtained at baseline, 2 weeks after the third treatment, and at 1, 2, 3, and 6 months after the final treatment. In addition, pain scores, immediate reactions, and other adverse effects were evaluated.

Results

Twenty-nine subjects completed the treatment protocol. Most presented with grade II wrinkling (69%). At 2-month follow-up, Antera 3D image analysis revealed faster improvement for the treatment group. At 6-month follow-up, the majority of subjects reported an improvement of 25–75% in their periorbital wrinkles. The average pain score was 2.2 out of 10. No serious adverse events (infection, pigmentary alteration, persistent erythema, or scarring) were observed.

Conclusions

Noninsulated RFMN is safe and effective for treating periorbital wrinkles and can be used as a modality for transdermal drug delivery. Topical polynucleotides as an adjunctive treatment provide additional benefits for periorbital wrinkle treatment.

Trial Registration Number

TCTR20201105007.

A Review of Potential Use of Amazonian Oils in the Synthesis of Organogels for Cosmetic Application

New strategies for the delivery of bioactives in the deeper layers of the skin have been studied in recent years, using mainly natural ingredients. Among the strategies are organogels as a promising tool to load bioactives with different physicochemical characteristics, using vegetable oils. Studies have shown satisfactory skin permeation, good physicochemical stability mainly due to its three-dimensional structure, and controlled release using vegetable oils and low-molecular-weight organogelators. Within the universe of natural ingredients, vegetable oils, especially those from the Amazon, have a series of benefits and characteristics that make them unique compared to conventional oils. Several studies have shown that the use of Amazonian oils brings a series of benefits to the skin, among which are an emollient, moisturizing, and nourishing effect. This work shows a compilation of the main Amazonian oils and their nutraceutical and physicochemical characteristics together with the minority polar components, related to health benefits, and their possible effects on the synthesis of organogels for cosmetic purposes.

Fabrication of Laponite-Reinforced Dextran-Based Hydrogels for NIR-Responsive Controlled Drug Release

Natural polymer gels with sensitivity to near-infrared (NIR) light have attracted the attention of scientists working on intelligent drug delivery systems. Compared to ultraviolet or visible light, NIR light has the advantages of strong trigger levels, deep penetration through affected tissues, and fewer side effects. Herein, we present a topical photothermal hydrogel for NIR-controlled drug delivery. The proposed DexIEM-GM-Laponite hydrogel was prepared through free radical polymerization of vinyl-functionalized dextran (DexIEM), vinyl-modified graphene oxide (GM), and Laponite; thereafter, the hydrogel was loaded with ciprofloxacin (CIP, an antibacterial drug) as a model drug. With the Laponite content increased, the density of crosslinking in the hydrogel increased, and its mechanical properties improved noticeably. Under NIR irradiation, the DexIEM-GM-Laponite hydrogel exhibited a photothermal property, where the surface temperature increased from 26.8 to 55.5 °C. The simulation of subcutaneous drug delivery experiments ex vivo showed that under the specified pork tissue thickness (2, 4, and 6 mm), the CIP release remained NIR-controllable. Additionally, the results of the antibacterial performance tests indicated the excellent antibacterial effect of the hydrogel, and the blood hemolysis ratio of the hydrogel was less than 5%, signifying good blood compatibility. This work will provide an avenue for the application of NIR light-responsive materials in antimicrobial therapy.

Iontophoresis of Biological Macromolecular Drugs

Over the last few decades, biological macromolecular drugs (e.g., peptides, proteins, and nucleic acids) have become a significant therapeutic modality for the treatment of various diseases. These drugs are considered superior to small-molecule drugs because of their high specificity and favorable safety profiles. However, such drugs are limited by their low oral bioavailability and short half-lives. Biological macromolecular drugs are typically administrated via invasive methods, e.g., intravenous or subcutaneous injections, which can be painful and induce needle phobia. Noninvasive transdermal delivery is an alternative administration route for the local and systemic delivery of biological macromolecular drugs. However, a challenge with the noninvasive transdermal delivery of biological macromolecular drugs is the outermost layer of the skin, known as the stratum corneum, which is a physical barrier that restricts the entry of extraneous macromolecules. Iontophoresis (IP) relies on the application of a low level of electricity for transdermal drug delivery, in order to facilitate the skin permeation of hydrophilic and charged molecules. The IP of several biological macromolecular drugs has recently been investigated. Herein, we review the IP-mediated noninvasive transdermal delivery of biological macromolecular drugs, their routes of skin permeation, their underlying mechanisms, and their advance applications.

Innovative transdermal delivery of insulin using gelatin methacrylate-based microneedle patches in mice and mini-pigs

Painless and controlled on-demand drug delivery is the ultimate goal for the management of various chronic diseases, including diabetes. To achieve this purpose, microneedle patches are gaining increased attention. While degradable microneedle (MN) arrays are widely employed, the use of non-dissolving MN patches remains a challenge to overcome. In this study, we demonstrate that crosslinking gelatin methacrylate with polyethylene glycol diacrylate (PEGDA) is potent for engineering non-dissolving MN arrays. Incorporation of MoS2 nanosheets as a photothermal component into MN hydrogels results in MNs featuring on-demand release properties. An optimized MoS2-MN array patch formed using a hydrogel solution containing 500 μg mL-1 of MoS2 and photochemically crosslinked for 5 min shows required mechanical behavior under a normal compressive load to penetrate the stratum corneum of mice or pig skin and allows the delivery of macromolecular therapeutics such as insulin upon swelling. Using ex vivo and in vivo models, we show that the MoS2-MN patches can be used for loading and releasing insulin for therapeutic purposes. Indeed, transdermal administration of insulin loaded into MoS2-MN patches reduces blood glucose levels in C57BL/6 mice and mini-pigs comparably to subcutaneously injected insulin. We believe that this on-demand delivery system might alter the current insulin therapies and might be a potential approach for delivery of other proteins.

A novel dermal delivery system using natural spicules for cosmetics and therapeutics

BACKGROUND

Dermal delivery is versatile in therapeutics as well as cosmetics in pursuit of enhancing safety/efficacy and alleviating pain/fear to alternate oral/injective administrations. Natural siliceous spicules offer a potential approach via simple topical medications to circumvent poor penetrations through the skin barrier by loading, carrying and releasing the active ingredients in a highly efficient and controlled manner.

AIMS

The delivery of ingredients loaded on spicules is assessed to improve the dermal efficacy compared to simple topical treatments.

METHODS

First, needle-like spicules were isolated from natural freshwater sponges. Then, the active ingredient was loaded via liposome formations. Finally, the dermal efficiency was evaluated.

RESULTS

Natural siliceous spicules were purified, sorted, and fully characterized to appear 250 μm of length and 12 μm of diameter on average. A model ingredient, pectolinarin, was efficiently loaded onto the internal space of spicules via lecithin-based liposome formations. The penetration was visualized using a porcine skin sample with a fluorescent dye and assessed quantitatively by a Franz diffusion cell system. Dermal absorption rate was measured 73.4%, while the percutaneous penetration rate was 2.2%. The release pattern turned out a simple diffusion analyzed by Fick's law and Higuchi model. The liposomes loaded onto spicules were further stabilized by a hydrophobic capsulation, which may benefit the overall efficacy of the ingredient.

CONCLUSION

A novel dermal delivery system is beneficial to improve the topical efficacy of biologically active ingredients. The outcomes shed a light upon developing skin-protective/improving cosmetics and therapeutics with enhanced performance.

Toward closed-loop drug delivery: Integrating wearable technologies with transdermal drug delivery systems

The recent advancement and prevalence of wearable technologies and their ability to make digital measurements of vital signs and wellness parameters have triggered a new paradigm in the management of diseases. Drug delivery as a function of stimuli or response from wearable, closed-loop systems can offer real-time on-demand or preprogrammed drug delivery capability and offer total management of disease states. Here we review the key opportunities in this space for development of closed-loop systems, given the advent of digital wearable technologies. Particular considerations and focus are given to closed-loop systems combined with transdermal drug delivery technologies.

Devices for drug delivery in the gastrointestinal tract: A review of systems physically interacting with the mucosa for enhanced delivery

The delivery of macromolecules via the gastrointestinal (GI) tract remains a significant challenge. A variety of technologies using physical modes of drug delivery have been developed and investigated to overcome the epithelial cell layer of the GI tract for local and systemic delivery. These technologies include direct injection, jetting, ultrasound, and iontophoresis, which have been largely adapted from transdermal drug delivery. Direct injection of agents using needles through endoscopy has been used clinically for over a century. Jetting, a needle-less method of drug delivery where a high-speed stream of fluid medication penetrates tissue, has been evaluated pre-clinically for delivery of agents into the buccal mucosa. Ultrasound has been shown to be beneficial in enhancing delivery of macromolecules, including nucleic acids, in pre-clinical animal models. The application of an electric field gradient to drive drugs into tissues through the technique of iontophoresis has been shown to deliver highly toxic chemotherapies into GI tissues. Here in, we provide an in-depth overview of these physical modes of drug delivery in the GI tract and their clinical and preclinical uses.

Transdermal Delivery of Macromolecules Using Nano Lipid Carriers

Skin being the largest external organ, offers an appealing procedure for transdermal drug delivery, so the drug needs to reach above the outermost layer of the skin, i.e., stratum corneum. Small molecular drug entities obeying the Lipinski rule, i.e., drugs having a molecular weight less than 500 Da, high lipophilicity, and optimum polarity, are favored enough to be used on the skin as therapeutics. Skin's barrier properties prevent the transport of macromolecules at pre-determined therapeutic rates. Notable advancements in macromolecules' transdermal delivery have occurred in recent years. Scientists have opted for liposomes, the use of electroporation, low-frequency ultrasound techniques, etc. Some of these have shown better delivery of macromolecules at clinically beneficial rates. These physical technologies involve complex mechanisms, which may irreversibly incur skin damage. Majorly, two types of lipid-based formulations, including Solid Lipid Nanoparticles (SLNs) and Nanostructured Lipid Carriers (NLCs), are widely investigated as transdermal delivery systems. In this review, the concepts, mechanisms, and applications of nanostructured lipid carriers used to transport macromolecules via transdermal routes are thoroughly reviewed and presented along with their clinical perspective.

Comprehensive review on ultrasound-responsive theranostic nanomaterials: mechanisms, structures and medical applications

The field of theranostics has been rapidly growing in recent years and nanotechnology has played a major role in this growth. Nanomaterials can be constructed to respond to a variety of different stimuli which can be internal (enzyme activity, redox potential, pH changes, temperature changes) or external (light, heat, magnetic fields, ultrasound). Theranostic nanomaterials can respond by producing an imaging signal and/or a therapeutic effect, which frequently involves cell death. Since ultrasound (US) is already well established as a clinical imaging modality, it is attractive to combine it with rationally designed nanoparticles for theranostics. The mechanisms of US interactions include cavitation microbubbles (MBs), acoustic droplet vaporization, acoustic radiation force, localized thermal effects, reactive oxygen species generation, sonoluminescence, and sonoporation. These effects can result in the release of encapsulated drugs or genes at the site of interest as well as cell death and considerable image enhancement. The present review discusses US-responsive theranostic nanomaterials under the following categories: MBs, micelles, liposomes (conventional and echogenic), niosomes, nanoemulsions, polymeric nanoparticles, chitosan nanocapsules, dendrimers, hydrogels, nanogels, gold nanoparticles, titania nanostructures, carbon nanostructures, mesoporous silica nanoparticles, fuel-free nano/micromotors.

Recent advances in transdermal drug delivery systems: a review

Various non-invasive administrations have recently emerged as an alternative to conventional needle injections. A transdermal drug delivery system (TDDS) represents the most attractive method among these because of its low rejection rate, excellent ease of administration, and superb convenience and persistence among patients. TDDS could be applicable in not only pharmaceuticals but also in the skin care industry, including cosmetics. Because this method mainly involves local administration, it can prevent local buildup in drug concentration and nonspecific delivery to tissues not targeted by the drug. However, the physicochemical properties of the skin translate to multiple obstacles and restrictions in transdermal delivery, with numerous investigations conducted to overcome these bottlenecks. In this review, we describe the different types of available TDDS methods, along with a critical discussion of the specific advantages and disadvantages, characterization methods, and potential of each method. Progress in research on these alternative methods has established the high efficiency inherent to TDDS, which is expected to find applications in a wide range of fields.

Enhancing Permeation of Drug Molecules Across the Skin via Delivery in Nanocarriers: Novel Strategies for Effective Transdermal Applications

The transdermal route of administration provides numerous advantages over conventional routes i.e., oral or injectable for the treatment of different diseases and cosmetics applications. The skin also works as a reservoir, thus deliver the penetrated drug for more extended periods in a sustained manner. It reduces toxicity and local irritation due to multiple sites for absorption and owes the option of avoiding systemic side effects. However, the transdermal route of delivery for many drugs is limited since very few drugs can be delivered at a viable rate using this route. The stratum corneum of skin works as an effective barrier, limiting most drugs' penetration posing difficulty to cross through the skin. Fortunately, some non-invasive methods can significantly enhance the penetration of drugs through this barrier. The use of nanocarriers for increasing the range of available drugs for the transdermal delivery has emerged as a valuable and exciting alternative. Both the lipophilic and hydrophilic drugs can be delivered via a range of nanocarriers through the stratum corneum with the possibility of having local or systemic effects to treat various diseases. In this review, the skin structure and major obstacle for transdermal drug delivery, different nanocarriers used for transdermal delivery, i.e., nanoparticles, ethosomes, dendrimers, liposomes, etc., have been discussed. Some recent examples of the combination of nanocarrier and physical methods, including iontophoresis, ultrasound, laser, and microneedles, have also been discussed for improving the therapeutic efficacy of transdermal drugs. Limitations and future perspectives of nanocarriers for transdermal drug delivery have been summarized at the end of this manuscript.

Hollow microneedles: A perspective in biomedical applications

Microneedles (MN) have the potential to become a highly progressive device for both drug delivery and monitoring purposes as they penetrate the skin and pierce the stratum corneum barrier, allowing the delivery of drugs in the viable skin layers and the extraction of body fluids. Despite the many years of research and the different types of MN developed, only hollow MN have reached the pharmaceutical market under the path of medical devices. Therefore, this review focuses on hollow MN, materials and methods for their fabrication as well as their application in drug delivery, vaccine delivery and monitoring purposes. Furthermore, novel approaches for the fabrication of hollow MN are included as well as prospects of microneedle-based products on the market.

STAR particles in context: a novel contender in the search for optimized drug-delivery systems

Targeted delivery, maximized bioavailability, minimal invasiveness, minimal side effects and cost-effectiveness are all markers of a successful drug delivery method. Although topical therapy, where diseased skin is targeted, remains a method of limited use, transdermal drug delivery systems seek to utilize skin as a vehicle for deeper systemic effects. Recently, Tadros et al. outlined an innovation to maximize the potential of topical delivery as a minimally invasive, user-friendly and safe medium. STAR particles seek to improve transdermal delivery by creating micropores in the stratum corneum. Several investigations have been conducted with promising results, including in vitro and in vivo animal and human studies. Despite a number of limitations and further considerations, the potential implications of STAR particles in the clinical disease setting are monumental.

Microneedle Arrays Combined with Nanomedicine Approaches for Transdermal Delivery of Therapeutics

Organic and inorganic nanoparticles (NPs) have shown promising outcomes in transdermal drug delivery. NPs can not only enhance the skin penetration of small/biomacromolecule therapeutic agents but can also impart control over drug release or target impaired tissue. Thanks to their unique optical, photothermal, and superparamagnetic features, NPs have been also utilized for the treatment of skin disorders, imaging, and biosensing applications. Despite the widespread transdermal applications of NPs, their delivery across the stratum corneum, which is the main skin barrier, has remained challenging. Microneedle array (MN) technology has recently revealed promising outcomes in the delivery of various formulations, especially NPs to deliver both hydrophilic and hydrophobic therapeutic agents. The present work reviews the advancements in the application of MNs and NPs for an effective transdermal delivery of a wide range of therapeutics in cancer chemotherapy and immunotherapy, photothermal and photodynamic therapy, peptide/protein vaccination, and the gene therapy of various diseases. In addition, this paper provides an overall insight on MNs' challenges and summarizes the recent achievements in clinical trials with future outlooks on the transdermal delivery of a wide range of nanomedicines.

Challenges and opportunities for small volumes delivery into the skin

Each individual's skin has its own features, such as strength, elasticity, or permeability to drugs, which limits the effectiveness of one-size-fits-all approaches typically found in medical treatments. Therefore, understanding the transport mechanisms of substances across the skin is instrumental for the development of novel minimal invasive transdermal therapies. However, the large difference between transport timescales and length scales of disparate molecules needed for medical therapies makes it difficult to address fundamental questions. Thus, this lack of fundamental knowledge has limited the efficacy of bioengineering equipment and medical treatments. In this article, we provide an overview of the most important microfluidics-related transport phenomena through the skin and versatile tools to study them. Moreover, we provide a summary of challenges and opportunities faced by advanced transdermal delivery methods, such as needle-free jet injectors, microneedles, and tattooing, which could pave the way to the implementation of better therapies and new methods.

Characterisation of Drug Delivery Efficacy Using Microstructure-Assisted Application of a Range of APIs

Polymer-based solid microstructures (MSts) have the potential to significantly increase the quantity and range of drugs that can be administered across the skin. MSt arrays are used to demonstrate their capacity to bypass the skin barrier and enhance permeability by creating microchannels through the stratum corneum, in a minimally invasive manner. This study is designed to demonstrate the ability of MSts to exceed the current boundaries for transdermal delivery of compounds with different molecular weights, partition coefficients, acid dissociation constants, melting points, and water solubilities. In vitro permeation of a range of selected molecules, including acetyl salicylic acid (aspirin), galantamine, selegiline hydrochloride (Sel-HCl), insulin, caffeine, hydrocortisone (HC), hydrocortisone 21-hemisuccinate sodium salt (HC-HS) and bovine serum albumin (BSA) has been studied across excised porcine skin with and without poke and patch application of MSts. Permeation of the molecules was monitored using Franz diffusion cells over 24 h. MSts significantly increased the permeation of all selected molecules up to 40 times, compared to topical applications of the molecules without MSts. The greatest increase in permeation was observed for caffeine with 70 ± 8% permeation and the lowest enhancement was observed for HC with a 2.4 ± 1.3% increase in permeation. The highest obtained flux was BSA (8133 ± 1365 μg/cm2/h) and the lowest flux observed for HC (11 ± 4 μg/cm2/h). BSA and HC also showed the highest (16,275 ± 3078 μg) and the lowest (73 ± 47 μg) permeation amount after 24 h respectively. MSt-treated skin exhibits greatly increased permeation. The molecule parameters (size, acid dissociation constant, partition coefficient and solubility)-traditional hurdles associated with passive diffusion through intact skin-are overcome using MSt skin treatment.

Prospective Nanotechnology-Based Strategies for Enhanced Intra- and Transdermal Delivery of Antifungal Drugs

Topical therapy of superficial fungal infections allows the prevention of systemic side effects and provides drug targeting at the site of disease. However, an appropriate drug concentration in these sites should be provided to ensure the efficacy of such local treatment. The enhancement of intra- and transdermal penetration and accumulation of antifungal drugs is an important aspect here. The present overview is focused on novel nano-based formulations served to improve antimycotic penetration through the skin. Furthermore, it summarizes various approaches towards the stimulation of drug penetration through and into the stratum corneum and hair follicles, which are considered to be promising for the future improvement of superficial antifungal therapy as providing the drug localization and prolonged storage property at the targeted area.

Motion Capture Quantification of User Variation in Topical Microparticle Application

Motion capture has the potential to shed light on topical drug delivery application. This approach holds promise both as a training tool, and for the development of skin technology, but first, this approach requires validation. Elongated microparticles (EMP) are a physical delivery enhancement technology that relies on a user working in the microparticles using a textured applicator. We used this approach to test the hypothesis that motion capture data can be used to characterize the topical application process. Motion capture was used to record participants while applying a mixture of EMP and sodium fluorescein to ex-vivo porcine skin samples. Treated skin was assessed using reflectance confocal and fluorescence microscopy. Image analysis was used to quantify the microparticle density and the presence of a fluorescent drug surrogate, sodium fluorescein. A strong correlation was present between applicator motion and microparticle and drug delivery profiles. There were quantitative and qualitative differences in the intra- and inter- user application methods that went beyond the level of training. Frequency and velocity of the applicator motion were key factors that correlated with EMP density. Our quantitative analysis of an experimental dermatological device supports the hypothesis that self-application may benefit from some form of digital monitoring or training with feedback. Our conclusion is that the integration of motion capture into experimental dermatological research offers an improved and quantifiable perspective that could be broadly useful with respect to topical applications, and with respect to the instruction provided to patients and clinicians.

Recent Advances in Micro-Electro-Mechanical Devices for Controlled Drug Release Applications

In recent years, controlled release of drugs has posed numerous challenges with the aim of optimizing parameters such as the release of the suitable quantity of drugs in the right site at the right time with the least invasiveness and the greatest possible automation. Some of the factors that challenge conventional drug release include long-term treatments, narrow therapeutic windows, complex dosing schedules, combined therapies, individual dosing regimens, and labile active substance administration. In this sense, the emergence of micro-devices that combine mechanical and electrical components, so called micro-electro-mechanical systems (MEMS) can offer solutions to these drawbacks. These devices can be fabricated using biocompatible materials, with great uniformity and reproducibility, similar to integrated circuits. They can be aseptically manufactured and hermetically sealed, while having mobile components that enable physical or analytical functions together with electrical components. In this review we present recent advances in the generation of MEMS drug delivery devices, in which various micro and nanometric structures such as contacts, connections, channels, reservoirs, pumps, valves, needles, and/or membranes can be included in their design and manufacture. Implantable single and multiple reservoir-based and transdermal-based MEMS devices are discussed in terms of fundamental mechanisms, fabrication, performance, and drug release applications.

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.

Near-infrared stimulated hydrogel patch for photothermal therapeutics and thermoresponsive drug delivery

Nanotechnology driven cancer theranostics hold potential as promising future clinical modalities. Currently, there is a strong emphasis on the development of combinational modalities, especially for cancer treatment. In this study, we present a topical hydrogel patch for nanomaterial-assisted photothermal therapeutics as well as for on-demand drug delivery application. The patch was derived from interpenetrating networks (IPNs) of alginate (Alg) and polyacrylamide (PAAm) in weight ratio 8:1 by free radical polymerization. The patch interiors were composed of hybrid nanostructures derived from gold nanorods (AuNRs) anchored onto polyvinylpyrrolidone (PVP) functionalized graphene oxide (PVP-nGO) to form PVP-nGO@AuNRs hybrids. Field emission scanning electron microscopy (FE-SEM) images revealed the porous nature of the hybrid hydrogel patch with an average pore size of ~28.60 ± 3.10 μm. Besides, functional characteristics of the hybrid patch, such as mechanical strength, viscoelastic and swelling behavior, were investigated. Under near-infrared (NIR) radiation exposure, the hybrid patch exhibited photothermal properties such as surface temperature rise to 75.16 ± 0.32 °C, sufficient to ablate cancer cells thermally. Besides, the heat generated in the hybrid patch could be transmitted to an underlying hydrogel (mimicking skin tissue) when stacked together without much loss. Under cyclic photothermal heating, the patch could retain its photothermal stability for four cycles. Furthermore, the hybrid patch demonstrated NIR stimulated drug release, which was evaluated using methotrexate (MTX, water-insoluble anticancer drug) and rhodamine B (RhB, water-soluble dye). Taken together, this work provides a new dimension towards the development of externally placed hydrogel patches for thermal destruction of localized solid tumors and tunable delivery of chemotherapeutic drugs at the target site.

Noninvasive transdermal delivery of liposomes by weak electric current

Noninvasive transdermal drug delivery (NTDD) offers an exciting new method of administration relative to conventional routes, but is associated with some challenges. Liposomes are capable of encapsulating transdermally-unfavorable drugs. However, the horny layer of skin is a significant barrier that limits efficient transdermal delivery of liposomes. Iontophoresis using weak electric current (WEC) represents a NTDD technology. WEC treatment of liposomes applied to the skin surface improves transdermal penetration of encapsulated drugs by cooperative effects. In this review, we provide an overview of the application of WEC/liposomes for transdermal delivery of macromolecules and low molecular weight drugs. We compare the transdermal delivery and therapeutic efficiency of the combined system with conventional routes of administration and their individual use. We discuss a novel perspective on the mechanism of WEC-mediated transdermal delivery of liposomes, which suggests that WEC activates the intracellular signaling pathway for transdermal permeation and induces unique endocytosis in skin cells.