Potential of combined ultrasound and microneedles for enhanced transdermal drug permeation: a review

A narrative review: Ultrasound-Assisted drug delivery: Improving treatments via multiple mechanisms

Safe and efficient drug delivery is as important as drug development. Biological barriers, such as cell membranes, present significant challenges in drug delivery, especially for newly developed protein-, nucleic acid-, and cell-based drugs. Ultrasound-mediated drug delivery systems offer a promising strategy to overcome these challenges. Ultrasound, a mechanical wave with energy, produces thermal effects, cavitation, acoustic radiation, and other biophysical effects. Used alone or in combination with microbubbles or sonosensitizers, it breaks biological barriers, enhances targeted drug delivery, reduces adverse reactions, controls drug release, switches on/off drug functions, and ultimately improves therapeutic efficiency. Various ultrasound-mediated drug delivery methods, including transdermal drug delivery, nebulization, targeted microbubble destruction, and sonodynamic therapy, are being actively explored for the treatment of various diseases. This review article introduces the principles, advantages, and applications of ultrasound-mediated drug delivery methods for improved therapeutic outcomes and discusses future prospects in this field.

Modified Phospholipid Vesicular Gel for Transdermal Drug Delivery: The Influence of Glycerin and/or Ethanol on Their Lipid Bilayer Fluidity and Penetration Characteristics

This review explores the enhanced transdermal therapy of several skin disorders with the application of carriers comprising phospholipid vesicular gel systems. Topical drug delivery has several advantages compared to other administration methods, including enhanced patient compliance, the avoidance of the first-pass impact associated with oral administration, and the elimination of the need for repeated doses. Nonetheless, the skin barrier obstructs the penetration of drugs, hence affecting its therapeutic efficacy. Carriers with phospholipid soft vesicles comprise a novel strategy used to augment drug delivery into the skin and boost therapeutic efficacy. These vesicles encompass chemicals that possess the ability to fluidize phospholipid bilayers, producing a pliable vesicle that facilitates penetration into the deeper layers of the skin. Phospholipid-based vesicular carriers have been extensively studied for improved drug delivery through dermal and transdermal pathways. Traditional liposomes are limited to the stratum corneum of the skin and do not penetrate the deeper layers. Ethosomes, glycerosomes, and glycethosomes are nanovesicular systems composed of ethanol, glycerol, or a combination of ethanol and glycerol, respectively. Their composition produce pliable vesicles by fluidizing the phospholipid bilayers, facilitating deeper penetration into the skin. This article examines the impact of ethanol and glycerol on phospholipid vesicles, and outlines their respective manufacturing techniques. Thus far, these discrepancies have not been analyzed comparatively. The review details several active compounds integrated into these nanovesicular gel systems and examined through in vitro, in vivo, or clinical human trials involving compositions with various active molecules for the treatment of various dermatological conditions.

Nanoparticle Skin Penetration: Depths and Routes Modeled In-Silico

Nanoparticles (NPs) are increasingly explored for targeted skin penetration, particularly for pharmaceutical and cosmetic applications. However, the complex system between NP properties, skin structure, and experimental conditions poses significant challenges in predicting their penetration depth and pathways. To what depth do NPs penetrate the skin, and which pathways do they follow? These are the questions which we tried to answer in this paper. A n in-silico human skin model based on 20 years of literature on NPs skin penetration is developed. The model incorporates 19 independent parameters, including a wide range of NP properties, skin across species, and test conditions. Using random forest analysis coupled with Kennard-Stone sorting, the model achieves a high predictive accuracy of 95%. The study identifies hair follicle diameter as the most critical factor influencing NP penetration across skin layers, surpassing other skin properties, NP properties, or experimental variables. Pig and rabbit skin are the most suitable models for simulating human skin in NP penetration studies. Additionally, the in-silico model reveals that NPs in emulsions and oil-based media predominantly follow the intercellular and transappendageal route. In contrast, those embedded in aqueous media favor the intracellular route. These findings offer insights for optimizing NP-based drug delivery systems.

Hyaluronic acid based approaches for wound healing: A comprehensive review

Wound healing is a natural, however complex, tissue repair and regeneration mechanism. Understanding the cascade of biological events associated with wound healing facilitates scientists in designing topical skin formulations with enhanced therapeutic outcomes. In recent years, several innovative approaches have been utilized to treat wounds. Hyaluronic acid (HA)-based formulations have shown promising results. The current manuscript provides a systematic review of various aspects of HA, including its structure, synthesis, mechanism involved in wound healing, and various formulations developed using HA to treat wounds. Covered are innovative treatment strategies explicitly emphasizing nanocarrier-based approaches. Various patents wherein HA has been used to treat wounds are also summarized with the help of a Google patent search. Diving deep, clinical perspectives, toxicity aspects, and application of computational chemistry in HA research are also discussed.

Development of a dual-frequency sonophoresis for enhanced skin permeability and efficient drug delivery

Effective transdermal drug delivery has long been a research focus, constrained by the skin's selective permeability, which limits the passage of drugs larger than 500 Daltons. Sonophoresis, employing low-frequency ultrasound waves, enhances skin permeability through transient cavitation, but its application faces two significant challenges: delivering large molecules and reducing prolonged treatment durations. This study introduces a novel dual-frequency sonophoresis designed to address these limitations. Through the integration of high-frequency ultrasound with low-frequency waves, a synergistic effect was generated, enhancing transient cavitation process. In few studies on dual-frequency systems, there has been challenges of large system size and long treatment duration. In our novel proposed system, the size was reduced by utilizing a piezoelectric disc operating at high frequency, and through a precise positioning relative to low-frequency ultrasonic horn, the synergistic effect was maximized, thus the treatment time was reduced. Initial tests employed single-frequency setup on aluminum foil, utilizing a two-level experimental design to maximize transient cavitation effects. The resulting optimal operating conditions were then applied to the dual-frequency system. Subsequent experiments were carried out on both aluminum foil and ex vivo guinea pig skin samples. It was observed that integration of high- and low- frequency ultrasound resulted in a remarkable 51-fold increase in skin permeation. Meanwhile, the penetration time was significantly reduced to four minutes in comparison with twenty minutes using single-frequency system. The obtained results highlighted the potential of our newly proposed dual-frequency sonophoresis to improve transdermal drug delivery efficiency by enhancing molecule transfer rates and minimizing treatment durations.

Ultrasonic Hollow Microneedle Array (USHM) for Androgenetic Alopecia Treatment through Modulating the Expression of Hair-Growth-Associated Genes

The application of finasteride through the skin to treat androgenetic alopecia shows promise, as it avoids side effects on the prostate and sexual function. However, the effectiveness has been limited due to the structure of the skin. In this study, we developed a drug delivery system called an ultrasound hollow microneedle array (USHM) to enhance the transdermal delivery of finasteride for the treatment of androgenetic alopecia. This technique successfully used ultrasonic cavitation effects in the skin to improve the delivery and therapeutic effects of finasteride. Hair regeneration experiments in mice showed that USHM accelerated hair regrowth by one to two treatment cycles compared to microneedle delivery and by three cycles compared to topical application. Analysis based on RNA sequencing showed that USHM-mediated finasteride delivery upregulated genes related to keratin filaments, intermediate filaments, and the intermediate filament cytoskeleton, enhancing hair regeneration. This study expands the potential of finasteride treatment for androgenetic alopecia and offers an effective strategy for transdermal drug delivery.

Flexible surface acoustic wave technology for enhancing transdermal drug delivery

Transdermal drug delivery provides therapeutic benefits over enteric or injection delivery because its transdermal routes provide more consistent concentrations of drug and avoid issues of drugs affecting kidneys and liver functions. Many technologies have been evaluated to enhance drug delivery through the relatively impervious epidermal layer of the skin. However, precise delivery of large hydrophilic molecules is still a great challenge even though microneedles or other energized (such as electrical, thermal, or ultrasonic) patches have been used, which are often difficult to be integrated into small wearable devices. This study developed a flexible surface acoustic wave (SAW) patch platform to facilitate transdermal delivery of macromolecules with fluorescein isothiocyanates up to 2000 kDa. Two surrogates of human skin were used to evaluate SAW based energized devices, i.e., delivering dextran through agarose gels and across stratum corneum of pig skin into the epidermis. Results showed that the 2000 kDa fluorescent molecules have been delivered up to 1.1 mm in agarose gel, and the fluorescent molecules from 4 to 2000 kDa have been delivered up to 100 µm and 25 µm in porcine skin tissue, respectively. Mechanical agitation, localised streaming, and acousto-thermal effect generated on the skin surface were identified as the main mechanisms for promoting drug transdermal transportation, although micro/nanoscale acoustic cavitation induced by SAWs could also have its contribution. SAW enhanced transdermal drug delivery is dependent on the combined effects of wave frequency and intensity, duration of applied acoustic waves, temperature, and drug molecules molecular weights.

Pharmacological Behavior of Propylene Glycol/Polyvinyl Alcohol Hydrogel Incorporating Indomethacin Nanocrystals in the Skin

BACKGROUND

We previously reported that carbopol hydrogels incorporating indomethacin nanoparticles (IMC NPs) improved the low permeability and bioavailability of skin formulations in transdermal drug delivery systems. However, the combination of NPs with other types of hydrogels has not been sufficiently explored to date. Therefore, this study investigated propylene glycol (PG)/polyvinyl alcohol (PVA) hydrogel as an alternative base to carbopol hydrogel for incorporating IMC NPs.

METHODS

IMC NPs were prepared using bead milling treatment, and these NPs were incorporated into PG/PVA hydrogel (IMC-NP@PG/PVA hydrogel). The IMC concentration was measured using the HPLC method, and seven-week-old Wistar rats were used to evaluate skin absorption.

RESULTS

Bead milling reduced the IMC particle size in the PG/PVA hydrogels to the nanoscale (30-200 nm) without altering its crystalline form. The IMC-NP@PG/PVA hydrogel exhibited enhanced uniformity, solubility, and drug release compared to the IMC microparticle-loaded PG/PVA hydrogel (IMC-MP@PG/PVA hydrogel), with a 1.44-fold greater area under the concentration-time curve. Transdermal permeability studies revealed that IMC-NP@PG/PVA had 2.36-fold higher absorption than the IMC-MP@PG/PVA hydrogel, with dissolved IMC permeating the skin. Pharmacokinetics in the rats showed significantly increased plasma levels, absorption rates, and bioavailability for IMC-NP@PG/PVA, demonstrating its superior delivery efficiency. Moreover, the skin absorption of IMC-NP@PG/PVA was higher than that of carbopol hydrogel.

CONCLUSIONS

These findings highlight the potential of PG/PVA hydrogels as an effective base for transdermal drug delivery systems based on NPs.

The Synergistic Potential of Hydrogel Microneedles and Nanomaterials: Breaking Barriers in Transdermal Therapy

The stratum corneum, which acts as a strong barrier against external agents, presents a significant challenge to transdermal drug delivery. In this regard, microneedle (MN) patches, designed as modern systems for drug delivery via permeation through the skin with the ability to pass through the stratum corneum, are known to be convenient, painless, and effective. In fact, MN have shown significant breakthroughs in transdermal drug delivery, and among the various types, hydrogel MN (HMNs) have demonstrated desirable inherent properties. Despite advancements, issues such as limited loading capacity, uncontrolled drug release rates, and non-uniform therapeutic approaches persist. Conversely, nanomaterials (NMs) have shown significant promise in medical applications, however, their efficacy and applicability are constrained by challenges including poor stability, low bioavailability, limited payload capacity, and rapid clearance by the immune system. Incorporation of NMs within HMNs offers new prospects to address the challenges associated with HMNs and NMs. This combination can provide a promising field of research for improved and effective delivery of therapeutic agents and mitigate certain adverse effects, addressing current clinical concerns. The current review highlights the use of NMs in HMNs for various therapeutic and diagnostic applications.

Advancements in microneedle technology: current status and next-generation innovations

Microneedle technology is a pivotal component of third-generation transdermal drug delivery systems featuring tiny needles that create temporary microscopic channels in the stratum corneum which facilitate drug penetration in the dermis. This review offers a detailed examination of the current types of microneedles, including solid, coated, dissolving, hollow, and swelling microneedles, along with their preparation techniques as well as their benefits and challenges. Use of 3D printing technology is especially gaining significant attention due to its ability to achieve the high dimensional accuracy required for precise fabrication. Additionally, its customisability presents significant potential for exploring new designs and creating personalised microneedles products. Furthermore, this review explores next generation microneedles, especially stimuli-responsive microneedle, bioinspired microneedle and microneedles combined with other transdermal technology like sonophoresis, electroporation and iontophoresis. Regulatory aspects, characterisation techniques, safety considerations, and cost factors have also been addressed which are crucial for translation from lab to the market.

Transdermal Drug Delivery Systems: Different Generations and Dermatokinetic Assessment of Drug Concentration in Skin

Transdermal drug delivery systems (TDDS) are a highly appealing and innovative method of administering drugs through the skin, as it enables the drugs to achieve systemic effects. A TDDS offers patient convenience, avoids first-pass hepatic metabolism, enables local targeting, and reduces the toxic effect of drug. This review details several generations of TDDS and the advancements made in their development to address the constraints associated with skin delivery systems. Transdermal delivery methods of the first generation have been consistently growing in their clinical application for administering small, lipophilic, low-dose drugs. Second-generation TDDS, utilizing chemical enhancers and iontophoresis, have led to the development of clinical products. Third-generation delivery systems employ microneedles, thermal ablation, and electroporation to specifically target the stratum corneum, which is the skin's barrier layer. Dermatokinetics is the study of the movement of drugs and formulations applied to the skin over a period of time. It provides important information regarding the rate and extent to which drugs penetrate skin layers. Several dermatokinetic techniques, including tape stripping, microdialysis, and laser scanning microscopy, have been used to study the intricate barrier properties and clearance mechanisms of the skin. This understanding is essential for developing and improving effective TDDS.

A Perspective on the Permeability of Cocrystals/Organic Salts of Oral Drugs

According to the BCS classification system, the differentiation of drugs is based on two essential parameters of solubility and permeability, meaning the latter is as pivotal as the former in creating marketable pharmaceutical products. Nevertheless, the indispensable role of permeability in pharmaceutical cocrystal profiles has not been sufficiently cherished, which can be most probably attributed to two principal reasons. First, responsibility may be on more user-friendly in vitro measurement procedures for solubility compared to permeability, implying the permeability measurement process seems unexpectedly difficult for researchers, whereas they have a complete understanding of solubility concepts and experiments. Besides, it may be ascribed to the undeniable attraction of introducing new crystal-based structures which mostly leaves the importance of improving the function of existing multicomponents behind. Bringing in new crystalline entities, to rephrase it, researchers have a fairly better chance of achieving high-class publications. Although the Food and Drug Administration (FDA) has provided a golden opportunity for pharmaceutical cocrystals to straightforwardly enter the market by simply considering them as derivatives of the existing active pharmaceutical ingredients, inattention to assessing and scaling up permeability which is intimately linked with solubility has resulted in limited numbers of them in the global pharmaceutical market. Casting a glance at the future, it is apprehended that further development in the field of permeability of pharmaceutical cocrystals and organic salts requires a meticulous perception of achievements to date and potentials to come. Thence, this perspective scrutinizes the pathway of permeation assessment making researchers confront their fear upfront through mapping the simplest way of permeability measurement for multicomponents of oral drugs.

3D printing redefines microneedle fabrication for transdermal drug delivery

Microneedles (MNs) have emerged as an innovative, virtually painless technique for intradermal drug delivery. However, the complex and costly fabrication process has limited their widespread accessibility, especially for individuals requiring frequent drug administration. This study introduces a groundbreaking and cost-effective method for producing MNs utilizing fused deposition modeling (FDM) 3D printing technology to enhance transdermal drug delivery. The proposed fabrication process involves the elongation of molten polylactic acid (PLA) filaments to create meticulously designed conoid and neiloid MNs with smooth surfaces. This study underscores the critical role of printing parameters, particularly extrusion length and printing speed, in determining the shape of the MNs. Notably, the conoid-shaped MNs exhibit exceptional skin-penetrating capabilities. In order to evaluate their effectiveness, the MNs were tested on a polydimethylsiloxane (PDMS) skin model for skin penetration. The results highlight the high potential of 3D-printed MNs for transdermal drug administration. This novel approach capitalizes on the benefits of 3D printing technology to fabricate MNs that hold the promise of transforming painless drug administration for a variety of medical applications.

Exploring Microsponges in Dermatology: Opportunities and Hurdles Ahead

Abstract:

Microsponges are porous, polymeric particles that have been extensively explored in the field of dermatology. They offer numerous advantages as a topical delivery system, including controlled release of active ingredients, enhanced bioavailability, and improved stability. Microsponges have been used for a wide range of dermatological applications, including the treatment of acne, psoriasis, and other skin disorders. This review article provides an overview of the various applications of microsponges in dermatology, along with the challenges associated with their development and use. The article begins with a brief introduction to microsponges, the benefits of microsponges, and their properties. It then discusses the different methods of microsponge preparation, such as emulsion solvent evaporation and spray drying, along with their mechanism of drug release and also applications of microsponges in dermatology, including their use in the treatment of acne, psoriasis, and other skin disorders, are discussed in detail. Overall, microsponges have shown great promise as a topical delivery system in dermatology, and their continued development and use will likely lead to significant advances in the field.

Recent progress on the development of bioinspired surfaces with high aspect ratio microarray structures: From fabrication to applications

Surfaces with high aspect ratio microarray structures can implement sophisticated assignment in typical fields including microfluidics, sensor, biomedicine, et al. via regulating their deformation or the material properties. Inspired by natural materials and systems, for example sea cockroaches, water spiders, cacti, lotus leaves, rice leaves, and cedar leaves, many researchers have focused on microneedle functional surface studies. When the surface with high aspect ratio microarray structures is stimulated by the external fields, such as optical, electric, thermal, magnetic, the high aspect ratio microarray structures can undergo hydrophilic and hydrophobic switching or shape change, which may be gifted the surfaces with the ability to perform complex task, including directional liquid/air transport, targeted drug delivery, microfluidic chip sensing. In this review, the fabrication principles of various surfaces with high aspect ratio microarray structures are classified and summarized. Mechanisms of liquid manipulation on hydrophilic/hydrophobic surfaces with high aspect ratio microarray structures are clarified based on Wenzel model, Cassie model, Laplace pressure theories and so on. Then the intelligent control strategies have been demonstrated. The applications in microfluidic, drug delivery, patch sensors have been discussed. Finally, current challenges and new insights of future prospects for dynamic manipulation of liquid/air based on biomimetic surface with high aspect ratio microarray structures are also addressed.

Drug Delivery Systems based on Microneedles for Dermatological Diseases and Aesthetic Enhancement

Microneedle (MN) devices comprise of micron-sized structures that circumvent biological barriers in a minimally invasive manner. MN research continues to grow and evolve; the technology was recently identified as one of the top ten overall emerging technologies of 2020. There is a growing interest in using such devices in cosmetology and dermatological conditions where the MNs mechanically disrupt the outer skin barrier layer, creating transient pathways that allow the passage of materials to underlying skin layers. This review aims to appraise the application of microneedle technologies in skin science, provide information on potential clinical benefits, as well as indicate possible dermatological conditions that can benefit from this technology, including autoimmunemediated inflammatory skin diseases, skin aging, hyperpigmentation, and skin tumors. A literature review was carried out to select studies that evaluated the use of microneedles to enhance drug delivery for dermatologic purposes. MN patches create temporary pathways that allow the passage of therapeutic material to deeper layers of the skin. Given their demonstrable promise in therapeutic applications it will be essential for healthcare professionals to engage with these new delivery systems as they transition to the clinic.

Revolutionizing Brain Drug Delivery: Buccal Transferosomes on the Verge of a Breakthrough

The buccal cavity, also known as the oral cavity, is a complex anatomical structure that plays a crucial role in various physiological processes. It serves as a gateway to the digestive system and facilitates the initial stages of food digestion and absorption. However, its significance extends beyond mere digestion as it presents a promising route for drug delivery, particularly to the brain. Transferosomes are lipid-based vesicles that have gained significant attention in the field of drug delivery due to their unique structure and properties. These vesicles are composed of phospholipids that form bilayer structures capable of encapsulating both hydrophilic and lipophilic drugs. Strategies for the development of buccal transferosomes for brain delivery have emerged as promising avenues for pharmaceutical research. This review aims to explore the various approaches and challenges associated with harnessing the potential of buccal transferosomes as a means of enhancing drug delivery to the brain. By understanding the structure and function of both buccal tissue and transferosomes, researchers can develop effective formulation methods and characterization techniques to optimize drug delivery. Furthermore, strategic approaches and success stories in buccal transferosome development are highlighted, showcasing inspiring examples that demonstrate their potential to revolutionize brain delivery.

Advances in Formulations of Microneedle System for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic joint inflammation, eventually leading to severe disability and premature death. At present, the treatment of RA is mainly to reduce inflammation, swelling, and pain. Commonly used drugs are non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, and disease-modifying anti-rheumatic drugs (DMARDs). These drugs lack specificity and require long-term, high-dose administration, which can cause serious adverse effects. In addition, the oral, intravenous, and intra-articular injections will reduce patient compliance, resulting in high cost and low bioavailability. Due to these limitations, microneedles (MNs) have emerged as a new strategy to efficiently localize the drugs in inflamed joints for the treatment of RA. MNs can overcome the cuticle barrier of the skin without stimulating nerves and blood vessels. Which can increase patient compliance, improve bioavailability, and avoid systemic circulation. This review summarizes and evaluates the application of MNs in RA, especially dissolving MNs (DMNs). We encourage the use of MNs to treat RA, by describing the general properties of MNs, materials, preparation technology, drug release mechanism, and advantages. Furthermore, we discussed the biological safety, development prospects, and future challenges of MNs, hoping to provide a new strategy for the treatment of RA.

Transdermal drug delivery via microneedles for musculoskeletal systems

As the population is ageing and lifestyle is changing, the prevalence of musculoskeletal (MSK) disorders is gradually increasing with each passing year, posing a serious threat to the health and quality of the public, especially the elderly. However, currently prevalent treatments for MSK disorders, mainly administered orally and by injection, are not targeted to the specific lesion, resulting in low efficacy along with a series of local and systemic adverse effects. Microneedle (MN) patches loaded with micron-sized needle array, combining the advantages of oral administration and local injection, have become a potentially novel strategy for the administration and treatment of MSK diseases. In this review, we briefly introduce the basics of MNs and focus on the main characteristics of the MSK systems and various types of MN-based transdermal drug delivery (TDD) systems. We emphasize the progress and broad applications of MN-based transdermal drug delivery (TDD) for MSK systems, including osteoporosis, nutritional rickets and some other typical types of arthritis and muscular damage, and in closing summarize the future prospects and challenges of MNs application.

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

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

Development of dissolving microneedles for intradermal delivery of the long-acting antiretroviral drug bictegravir

Oral administration and intramuscular (IM) injection are commonly recommended options for human immunodeficiency virus (HIV) treatment. However, poor patient compliance due to daily oral dosing, pain at injection sites and the demand for trained healthcare staff for injections limit the success of these administration routes, especially in low-resource settings. To overcome these limitations, for the first time, we propose novel bilayer dissolving microneedles (MNs) for the intradermal delivery of long-acting nanosuspensions of the antiretroviral (ARV) drug bictegravir (BIC) for potential HIV treatment and prevention. The BIC nanosuspensions were prepared using a wet media milling technique on a laboratory scale with a particle size of 358.99 ± 18.53 nm. The drug loading of nanosuspension-loaded MNs and BIC powder-loaded MNs were 1.87 mg/0.5 cm² and 2.16 mg/0.5 cm², respectively. Both dissolving MNs exhibited favorable mechanical and insertion ability in the human skin simulant Parafilm® M and excised neonatal porcine skin. Importantly, the pharmacokinetic profiles of Sprague Dawley rats demonstrated that dissolving MNs were able to intradermally deliver 31% of drug loading from nanosuspension-loaded MNs in the form of drug depots. After a single application, both coarse BIC and BIC nanosuspensions achieved sustained release, maintaining plasma concentrations above human therapeutic levels (162 ng/mL) in rats for 4 weeks. These minimally invasive and potentially self-administered MNs could improve patient compliance, providing a promising platform for the delivery of nanoformulated ARVs and resulting in prolonged drug release, particularly for patients in low-resource settings.

Skin absorption of felbinac solid nanoparticles in gel formulation containing l-menthol and carboxypolymethylene

BACKGROUND

It is important to design an effective formulation to enhance the skin penetration, and nanotechnologies have been used in dermal and transdermal drug delivery. In this study, we prepared formulations (gels) containing l-menthol and felbinac (FEL) solid nanoparticles (FEL-NP gel) for topical application, and investigated the local and systemic absorption of the prepared FEL-NP gel.

METHODS

FEL solid nanoparticles were obtained by bead milling of FEL powder (microparticles), and a topical formulation (FEL-NP gel) consisting of 1.5% FEL solid nanoparticles), 2% carboxypolymethylene, 2% l-menthol, 0.5% methylcellulose, and 5% 2-hydroxypropyl-β-cyclodextrin (w/w %) were prepared.

RESULTS

The particle size of FEL nanoparticles was 20-200 nm. The released FEL concentration from FEL-NP gel was significantly higher than that from FEL gel without bead mill treatment (carboxypolymethylene gel in which FEL microparticles (MPs) instead of FEL nanoparticles were incorporated, FEL-MP gel), and FEL was released as nanoparticles from the gel. Moreover, both transdermal penetration and percutaneous absorption of FEL-NP gel were significantly increased compared with those of FEL-MP gel, and the area under the FEL concentration-time curve (AUC) of FEL-NP gels was 1.52- and 1.38-fold of commercially available FEL ointment and FEL-MP gel, respectively. In addition, after 24 h of treatment, the FEL content in rat skin treated with FEL-NP gels was 1.38- and 2.54-fold higher than that when treated with commercially available FEL ointment and FEL-MP gel, respectively. Moreover, the enhanced skin penetration of FEL-NP gels was significantly attenuated by inhibition of energy-dependent endocytosis, such as clathrin-mediated endocytosis.

CONCLUSIONS

We successfully prepared a topically applied carboxypolymethylene gel containing FEL nanoparticles. In addition, we observed that the endocytosis pathway was mainly related to the high skin penetration of FEL nanoparticles, and FEL-NP gel application resulted in high local tissue concentration and systemic absorption of FEL. These findings provide useful information for the design of topically applied nanoformulations against inflammation by providing local and systemic effects.

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.

Emulsion-Based Gel Loaded with Ibuprofen and Its Derivatives

The aim of this study was to evaluate the effect of vehicle and chemical modifications of the structure of active compounds on the skin permeation and accumulation of ibuprofen (IBU). As a result, semi-solid formulations in the form of an emulsion-based gel loaded with ibuprofen and its derivatives, such as sodium ibuprofenate (IBUNa) and L-phenylalanine ethyl ester ibuprofenate ([PheOEt][IBU]), were developed. The properties of the obtained formulations were examined, including density, refractive index, viscosity, and particle size distribution. The parameters of release and permeability through the pig skin of the active substances contained in the obtained semi-solid formulations were determined. The results indicate that an emulsion-based gel enhanced the skin penetration of IBU and its derivatives compared to two commercial preparations in the form of a gel and a cream. The average cumulative mass of IBU after a 24 h permeation test from an emulsion-based gel formulation through human skin was 1.6-4.0 times higher than for the commercial products. Ibuprofen derivatives were evaluated as chemical penetration enhancers. After 24 h of penetration, the cumulative mass was 1086.6 ± 245.8 for IBUNa and 948.6 ± 87.5 µg IBU/cm2 for [PheOEt][IBU], respectively. This study demonstrates the perspective of the transdermal emulsion-based gel vehicle in conjunction with the modification of the drug as a potentially faster drug delivery system.

Hyaluronic Acid-Based Nanosystems for CD44 Mediated Anti-Inflammatory and Antinociceptive Activity

The nervous and immune systems go hand in hand in causing inflammation and pain. However, the two are not mutually exclusive. While some diseases cause inflammation, others are caused by it. Macrophages play an important role in modulating inflammation to trigger neuropathic pain. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan that has a well-known ability to bind with the cluster of differentiation 44 (CD44) receptor on classically activated M1 macrophages. Resolving inflammation by varying the molecular weight of HA is a debated concept. HA-based drug delivery nanosystems such as nanohydrogels and nanoemulsions, targeting macrophages can be used to relieve pain and inflammation by loading antinociceptive drugs and enhancing the effect of anti-inflammatory drugs. This review will discuss the ongoing research on HA-based drug delivery nanosystems regarding their antinociceptive and anti-inflammatory effects.

Transdermal drug delivery system of lidocaine hydrochloride based on dissolving gelatin/sodium carboxymethylcellulose microneedles

In this study, it was aimed to introduce a transdermal drug delivery system with dissolving microneedles (DMNs) based on gelatin (GEL) and sodium carboxymethyl cellulose (NaCMC) for lidocaine hydrochloride (LidoHCl) delivery. Different ratios of GEL and NaCMC were mixed, loaded with an active agent of LidoHCl, and treated with glutaraldehyde (GTA) as a crosslinker agent. Prepared hydrogels were cast into a silicon mold. Hereby, microneedles (MNs) with 500 µm height, 35° needle angle, 40-µm tip radius, and 960-µm tip-to-tip distance were fabricated. Samples containing LidoHCl 40%, GEL/NaCMC 5:1 (wt/wt), and polymer/GTA ratio 3.1 (wt/wt) showed the highest drug release ability (t < 10 min) with proper mechanical properties in comparison with other samples. Due to the drug release in a short time (fewer than 10 min), this drug delivery system can be used for rapid local anesthesia for pain relief as well as before minor skin surgeries.

Graphical Abstract

State of the Art in Constructing Gas-Propelled Dissolving Microneedles for Significantly Enhanced Drug-Loading and Delivery Efficiency

Dissolving microneedles (MNs) have emerged as a promising transdermal delivery system, as they integrate the advantages of both injection and transdermal preparations. However, the low drug-loading and limited transdermal delivery efficiency of MNs severely hinder their clinical applications. Microparticle-embedded gas-propelled MNs were developed to simultaneously improve drug-loading and transdermal delivery efficiency. The effects of mold production technologies, micromolding technologies, and formulation parameters on the quality of gas-propelled MNs were systematically studied. Three-dimensional printing technology was found to prepare male mold with the highest accuracy, while female mold made from the silica gel with smaller Shore hardness could obtain a higher demolding needle percentage (DNP). Vacuum micromolding with optimized pressure was superior to centrifugation micromolding in preparing gas-propelled MNs with significantly improved DNP and morphology. Moreover, the gas-propelled MNs could achieve the highest DNP and intact needles by selecting polyvinylpyrrolidone K30 (PVP K30), polyvinyl alcohol (PVA), and potassium carbonate (K2CO3): citric acid (CA) = 0.15:0.15 (w/w) as the needle skeleton material, drug particle carrier, and pneumatic initiators, respectively. Moreover, the gas-propelled MNs showed a 1.35-fold drug loading of the free drug-loaded MNs and 1.19-fold cumulative transdermal permeability of the passive MNs. Therefore, this study provides detailed guidance for preparing MNs with high productivity, drug loading, and delivery efficiency.

Polymeric and Composite Carriers of Protein and Non-Protein Biomolecules for Application in Bone Tissue Engineering

Conventional intake of drugs and active substances is most often based on oral intake of an appropriate dose to achieve the desired effect in the affected area or source of pain. In this case, controlling their distribution in the body is difficult, as the substance also reaches other tissues. This phenomenon results in the occurrence of side effects and the need to increase the concentration of the therapeutic substance to ensure it has the desired effect. The scientific field of tissue engineering proposes a solution to this problem, which creates the possibility of designing intelligent systems for delivering active substances precisely to the site of disease conversion. The following review discusses significant current research strategies as well as examples of polymeric and composite carriers for protein and non-protein biomolecules designed for bone tissue regeneration.

Advances in Antiviral Delivery Systems and Chitosan-Based Polymeric and Nanoparticulate Antivirals and Antiviral Carriers

Current antiviral therapy research is focused on developing dosage forms that enable highly effective drug delivery, providing a selective effect in the organism, lower risk of adverse effects, a lower dose of active pharmaceutical ingredients, and minimal toxicity. In this article, antiviral drugs and the mechanisms of their action are summarized at the beginning as a prerequisite background to develop relevant drug delivery/carrier systems for them, classified and briefly discussed subsequently. Many of the recent studies aim at different types of synthetic, semisynthetic, and natural polymers serving as a favorable matrix for the antiviral drug carrier. Besides a wider view of different antiviral delivery systems, this review focuses on advances in antiviral drug delivery systems based on chitosan (CS) and derivatized CS carriers. CS and its derivatives are evaluated concerning methods of their preparation, their basic characteristics and properties, approaches to the incorporation of an antiviral drug in the CS polymer as well as CS nanoparticulate systems, and their recent biomedical applications in the context of actual antiviral therapy. The degree of development (i.e., research study, in vitro/ex vivo/in vivo preclinical testing), as well as benefits and limitations of CS polymer and CS nanoparticulate drug delivery systems, are reported for particular viral diseases and corresponding antivirotics.

Microneedles: One-Plane Bevel-Tipped Fabrication by 3D-Printing Processes

This article presents microneedles analyses where the design parameters studied included length and inner and outer diameter ranges. A mathematical model was also used to generalize outer and inner diameter ratios in the obtained ranges. Following this, the range of inner and outer diameters was completed by mechanical simulations, ranging from 30 μm to 134 μm as the inner diameter range and 208 μm to 250 μm as the outer diameter range. With these ranges, a mathematical model was made using fourth-order polynomial regressions with a correlation of 0.9993, ensuring a safety factor of four in which von Misses forces of the microneedle are around 17.931 MPa; the ANSYS software was used to analyze the mechanical behavior of the microneedles. In addition, the microneedle concept was made by 3D printing using a bio-compatible resin of class 1. The features presented by the microneedle designed in this study make it a promising option for implementation in a transdermal drug-delivery device.

Overcoming skin barriers through advanced transdermal drug delivery approaches

Upon exhaustive research, the transdermal drug delivery system (TDDS) has appeared as a potential, well-accepted, and popular approach to a novel drug delivery system. Ease of administration, easy handling, minimum systemic exposure, least discomfort, broad flexibility and tunability, controlled release, prolonged therapeutic effect, and many more perks make it a promising approach for effective drug delivery. Although, the primary challenge associated is poor skin permeability. Skin is an intact barrier that serves as a primary defense mechanism to preclude any foreign particle's entry into the body. Owing to the unique anatomical framework, i.e., compact packing of stratum corneum with tight junction and fast anti-inflammatory responses, etc., emerged as a critical physiological barrier for TDDS. Fusion with other novel approaches like nanocarriers, specially designed transdermal delivery devices, permeation enhancers, etc., can overcome the limitations. Utilizing such strategies, some of the products are under clinical trials, and many are under investigation. This review explores all dimensions that overcome poor permeability and allows the drug to attain maximum potential. The article initially compiles fundamental features, components, and design of TDDS, followed by critical aspects and various methods, including in vitro, ex vivo, and in vivo methods of assessing skin permeability. The work primarily aimed to highlight the recent advancement in novel strategies for effective transdermal drug delivery utilizing active methods like iontophoresis, electroporation, sonophoresis, microneedle, needleless jet injection, etc., and passive methods such as the use of liposomes, SLN, NLC, micro/nanoemulsions, dendrimers, transferosomes, and many more nanocarriers. In all, this compilation will provide a recent insight on the novel updates along with basic concepts, the current status of clinical development, and challenges for the clinical translation of TDDS.

3D-Printed Integrated Ultrasonic Microneedle Array for Rapid Transdermal Drug Delivery

Transdermal drug delivery (TDD) is an attractive alternative to oral and hypodermic injection drug administration, and is poised to increase its impact on medicine and pharmaceutical design. Microneedles (MNs) are a new minimally invasive TDD method widely used in medicine and cosmetology. MNs create a microscale channel from the stratum corneum to the dermis and enable drug delivery of hydrophilic and macromolecular into the skin. Although MNs allow different drugs to penetrate the stratum corneum, they cannot provide an extra driving force for drug transport in tissue. To overcome this limitation and achieve fast, controllable drug delivery, an integrated 3D-printed ultrasonic MN array (USMA) device consisting of hollow MNs and an ultrasonic transducer is proposed. The hollow MNs enable drug to penetrate the stratum corneum, and the ultrasound transmitted through the MNs provides the driving force for drug transportation in tissue. Using methylene blue and bovine serum albumin as model drugs, we tested the drug delivery performance of USMA on porcine skin; the results show that USMA significantly enhanced the delivery efficiency of model drugs. Besides, USMA obviously reduced MNs insertion force and tissue damage, which were well-tolerated and gentle. This study suggests that the integrated ultrasonic MN array has great potential for clinical drug delivery with high efficiency and lessening the suffering of patients.

Recent Progress in Microneedles-Mediated Diagnosis, Therapy, and Theranostic Systems

Theranostic system combined diagnostic and therapeutic modalities is critical for the real-time monitoring of disease-related biomarkers and personalized therapy. Microneedles, as a multifunctional platform, are promising for transdermal diagnostics and drug delivery. They have shown attractive properties including painless skin penetration, easy self-administration, prominent therapeutic effects, and good biosafety. Herein, an overview of the microneedles-based diagnosis, therapies, and theranostic systems is given. Four microneedles-based detection methods are concluded based on the sensing mechanism: i) electrochemistry, ii) fluorometric, iii) colorimetric, and iv) Raman methods. Additionally, robust microneedles are suitable for implantable drug delivery. Microneedles-assisted transdermal drug delivery can be primarily classified as passive, active, and responsive drug release, based on the release mechanisms. Microneedles-assisted oral and implantable drug delivery mechanisms are also presented in this review. Furthermore, the key frontier developments in microneedles-mediated theranostic systems as the major selling points are emphasized in this review. These systems are classified into open-loop and closed-loop theranostic systems based on the indirectness and directness of feedback between the transdermal diagnosis and therapy, respectively. Finally, conclusions and future perspectives for next-generation microneedles-mediated theranostic systems are also discussed. Taken together, microneedle-based systems are promising as the new avenue for diagnosis, therapy, and disease-specific closed-loop theranostic applications.

Recent advances in polymer microneedles for drug transdermal delivery: Design strategies and applications

In recent years, the transdermal drug delivery based on microneedles (MNs) technology has received extensive attention, which offers a safer and painless alternative to hypodermic needle injection. They can pierce the stratum corneum and deliver drugs to the epidermis and dermis-structures of skin, showing prominent properties such as minimally invasive, bypassing first-pass metabolism, and self-administered. A range of materials have been used to fabricate MNs, such as silicon, metal, glass, and polymers. Among them, polymer MNs have gained increasing attention from pharmaceutical and cosmetic companies as one of the promising drug delivery methods. Microneedle products have recently become available on the market, and some of them are under evaluation for efficacy and safety. This paper focuses on current state of polymer MNs in the drug transdermal delivery. The materials and methods for the fabrication of polymer MNs and their drug administration are described. The recent progresses of polymer MNs for treatment of cancer, vaccine delivery, blood glucose regulation, androgenetic alopecia, obesity, tissue healing, myocardial infarction and gout are reviewed. The challenges of MNs technology are summarized and the future development trend of MNs is also prospected. This article is protected by copyright. All rights reserved.

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.

Oleic acid-reinforced PEGylated polymethacrylate transdermal film with enhanced antidyslipidemic activity and bioavailability of atorvastatin: A mechanistic ex-vivo/in-vivo analysis

To enhance the poor bioavailability and extensive liver metabolism of atorvastatin calcium (ATC), we have developed an oleic acid-reinforced PEGylated polymethacrylate (OLA-PEG-E-RLPO) transdermal film as a convenient and alternative delivery system. The effect of varying levels of Eudragit RLPO, PEG 400, and oleic acid on the target product profile was optimized through Quality by Design (QbD) approach. The ATC-loaded OLA-PEG-E-RLPO transdermal films were evaluated in ex-vivo experiments using full thickness skin, utilizing Franz cell studies, and undergone in-vivo pharmacokinetics/pharmacodynamics (PK/PD) assessment, using poloxamer-induced dyslipidemic Sprague-Dawley rats. At 2 and 12 h, the optimized ATC films with a thickness of 0.79 mm showed permeation of 37.34% and 97.23% into the receptor compartment, respectively. Steady-state flux was 0.172 mg/cm²h, with 7.01 × 10^-4 cm/h permeability coefficient, and 0.713 × 10^-3 cm²/h diffusion coefficient. In-vivo PK results indicated that the absorption profiles (AUC_0-∞) of the optimized film in pre-treated group of animals were 8.6-fold and 2.8-fold greater than controls pre-treated with non-PEGylated non-oleic acid film and orally administered ATC, respectively. PD assessment of the lipid panel indicated that the lipid profile of the optimized film pre-treated group reached normal levels after 12 h, along with the significant enhancement over the non-PEGylated non-oleic acid film and the oral marketed tablet groups. The histopathological findings revealed near-normal hepatocyte structure for the optimized film pre-treated animal group. Our results further indicate that transdermal delivery films based on an optimized ATC-loaded OLA-PEG-E-RLPO were successfully developed and their assessment in both ex-vivo and in-vivo suggests enhanced permeability and improvement in bioavailability and antidyslipidemic activity of ATC. This approach can provide several advantages, especially during chronic administration of ATC, including improvement in patient compliance, therapeutic benefits, bioavailability, and feasibility for commercialization and as a platform for other drug classes.

Recent advances in microneedles-based drug delivery device in the diagnosis and treatment of cancer

Microneedles are unique, novel and an effective approach designed to deliver therapeutic agents and immunobiologicals in several diseases. These tiny needle patches are designed to load vaccine, small or large drug molecule, heavy molecular weighted proteins, genes, antibodies, nanoparticles and many more. These nanoparticles loaded microneedles deliver drugs deep within the skin near underlying neutrophils, langerhans and dendritic cells and induces required immunological response. With the drawbacks associated with conventional methods of cancer chemotherapy, the focus was shifted towards use of microneedles in not just anti-cancer vaccine/drug delivery but also for their early diagnosis. This delivery device is also suited for synergistic approaches such as chemotherapy or gene therapy combined with photothermal or photodynamic therapy. The painless self-administrative device offers an alternative over traditional routes of drug delivery including systemic administration via hypodermic needles. Additionally, these microneedles can be fabricated and altered in shape, size and geometry and the material polymer can be chosen depending on use and release mechanism. This review consolidates positive results obtained from studies done for different type of microneedle array in several tumor cell lines and animal models. It further highlights the use of biodegradable polymers such as hydrogel or any dissolving polymer that can be utilized for sustained codelivery of drug/vaccine to shun the need of multiple dosing. It covers the existing limitations that still needs to be resolved and further highlights on the future aspects of their use in cancer therapy.

Chitosan-Coated 5-Fluorouracil Incorporated Emulsions as Transdermal Drug Delivery Matrices

The purpose of the present study was to develop emulsions encapsulated by chitosan on the outer surface of a nano droplet containing 5-fluorouracil (5-FU) as a model drug. The emulsions were characterized in terms of size, pH and viscosity and were evaluated for their physicochemical properties such as drug release and skin permeation in vitro. The emulsions containing tween 80 (T80), sodium lauryl sulfate, span 20, and a combination of polyethylene glycol (PEG) and T20 exhibited a release of 88%, 86%, 90% and 92%, respectively. Chitosan-modified emulsions considerably controlled the release of 5-FU compared to a 5-FU solution (p < 0.05). All the formulations enabled transportation of 5-FU through a rat's skin. The combination (T80, PEG) formulation showed a good penetration profile. Different surfactants showed variable degrees of skin drug retention. The ATR-FTIR spectrograms revealed that the emulsions mainly affected the fluidization of lipids and proteins of the stratum corneum (SC) that lead to enhanced drug permeation and retention across the skin. The present study concludes that the emulsions containing a combination of surfactants (Tween) and a co-surfactant (PEG) exhibited the best penetration profile, prevented the premature release of drugs from the nano droplet, enhanced the permeation and the retention of the drug across the skin and had great potential for transdermal drug delivery. Therefore, chitosan-coated 5-FU emulsions represent an excellent possibility to deliver a model drug as a transdermal delivery system.

A Comprehensive Review of Microneedles: Types, Materials, Processes, Characterizations and Applications

Drug delivery through the skin offers many advantages such as avoidance of hepatic first-pass metabolism, maintenance of steady plasma concentration, safety, and compliance over oral or parenteral pathways. However, the biggest challenge for transdermal delivery is that only a limited number of potent drugs with ideal physicochemical properties can passively diffuse and intercellularly permeate through skin barriers and achieve therapeutic concentration by this route. Significant efforts have been made toward the development of approaches to enhance transdermal permeation of the drugs. Among them, microneedles represent one of the microscale physical enhancement methods that greatly expand the spectrum of drugs for transdermal and intradermal delivery. Microneedles typically measure 0.1-1 mm in length. In this review, microneedle materials, fabrication routes, characterization techniques, and applications for transdermal delivery are discussed. A variety of materials such as silicon, stainless steel, and polymers have been used to fabricate solid, coated, hollow, or dissolvable microneedles. Their implications for transdermal drug delivery have been discussed extensively. However, there remain challenges with sustained delivery, efficacy, cost-effective fabrication, and large-scale manufacturing. This review discusses different modes of characterization and the gaps in manufacturing technologies associated with microneedles. This review also discusses their potential impact on drug delivery, vaccine delivery, disease diagnostic, and cosmetics applications.

Wearable patch delivery system for artificial pancreas health diagnostic-therapeutic application: A review

The advanced stimuli-responsive approaches for on-demand drug delivery systems have received tremendous attention as they have great potential to be integrated with sensing and multi-functional electronics on a flexible and stretchable single platform (all-in-one concept) in order to develop skin-integration with close-loop sensation for personalized diagnostic and therapeutic application. The wearable patch pumps have evolved from reservoir-based to matrix patch and drug-in-adhesive (single-layer or multi-layer) type. In this review, we presented the basic requirements of an artificial pancreas, surveyed the design and technologies used in commercial patch pumps available on the market and provided general information about the latest wearable patch pump. We summarized the various advanced delivery strategies with their mechanisms that have been developed to date and representative examples. Mechanical, electrical, light, thermal, acoustic and glucose-responsive approaches on patch form have been successfully utilized in the controllable transdermal drug delivery manner. We highlighted key challenges associated with wearable transdermal delivery systems, their research direction and future development trends.

Interdependency of influential parameters in therapeutic nanomedicine

Introduction:Current challenges to successful clinical translation of therapeutic nanomedicine have discouraged many stakeholders, including patients. Significant effort has been devoted to uncovering the reasons behind the less-than-expected success, beyond failures or ineffectiveness, of therapeutic nanomedicine products (e.g. cancer nanomedicine). Until we understand and address the factors that limit the safety and efficacy of NPs, both individually and in combination, successful clinical development will lag.Areas covered:This review highlights the critical roles of interdependent factors affecting the safety and therapeutic efficacy of therapeutic NPs for drug delivery applications.Expert opinion:Deep analysis of the current nanomedical literature reveals ahistory of unanticipated complexity by awide range of stakeholders including researchers. In the manufacture of nanomedicines themselves, there have been persistent difficulties with reproducibility and batch-to-batch variation. The unanticipated complexity and interdependency of nano-bio parameters has delayed our recognition of important factors affecting the safety and therapeutic efficacy of nanomedicine products. These missteps have had many factors including our lack of understanding of the interdependency of various factors affecting the biological identity and fate of NPs and biased interpretation of data. All these issues could raise significant concern regarding the reproducibility- or even the validity- of past publications that in turn formed the basis of many clinical trials of therapeutic nanomedicines. Therefore, the individual and combined effects of previously overlooked factors on the safety and therapeutic efficacy of NPs need to be fully considered in nanomedicine reports and product development.

Energy-Dependent Endocytosis Is Responsible for Skin Penetration of Formulations Based on a Combination of Indomethacin Nanoparticles and l-Menthol in Rat and Göttingen Minipig

We previously designed a Carbopol gel formulation (N-IND/MEN) based on a combination of indomethacin solid nanoparticles (IND-NPs) and l-menthol, and we reported that the N-IND/MEN showed high transdermal penetration. However, the detailed mechanism for transdermal penetration of IND-NPs was not clearly defined. In this study, we investigated whether endocytosis in the skin tissue of rat and Göttingen minipig is related to the transdermal penetration of IND-NPs using pharmacological inhibitors of endocytosis. The pharmacological inhibitors used in this study are as follows: 54 µM nystatin, a caveolae-mediated endocytosis (CavME) inhibitor; 40 µM dynasore, a clathrin-mediated endocytosis (CME) inhibitor; and 2 µM rottlerin, a micropinocytosis (MP) inhibitor. The N-IND/MEN was prepared by a bead mill method, and the particle size of solid indomethacin was 79–216 nm. In both rat and Göttingen minipig skin, skin penetration of approximately 80% IND-NPs was limited by the stratum corneum (SC), although the penetration of SC was improved by the combination of l-menthol. On the other hand, the treatment of nystatin and dynasore decreased the transdermal penetration of indomethacin in rats and Göttingen minipigs treated with N-IND/MEN. Moreover, in addition to nystatin and dynasore, rottlerin attenuated the transdermal penetration of IND-NPs in the Göttingen minipigs’ skin. In conclusion, we found that l-menthol enhanced the SC penetration of IND-NPs. In addition, this study suggests that the SC-passed IND-NPs are absorbed into the skin tissue by energy-dependent endocytosis (CavME, CME, and/or MP pathways) on the epidermis under the SC, resulting in an enhancement in transdermal penetration of IND-NPs. These findings provide significant information for the design of nanomedicines in transdermal formulations.

Drug Delivery Approaches for Managing Overactive Bladder (OAB): A Systematic Review

Overactive bladder syndrome (OAB) is characterised by urgency symptoms, with or without urgency incontinence, usually with frequency and nocturia and severely affects the quality of life. This systematic review evaluates the various drug delivery strategies used in practice to manage OAB. Advanced drug delivery strategies alongside traditional strategies were comprehensively analysed and comparatively evaluated. The present review was conducted according to the preferred reporting items for systematic reviews and meta-analyses guidelines. A total of 24 studies reporting the development of novel formulations for the treatment of OAB were considered eligible and were further categorised according to the route of drug administration. The review found that various drug delivery routes (transdermal, intravesicular, oral, vaginal and intramuscular) are used for the administration of drugs for managing OAB, however, the outcomes illustrated the marked potential of transdermal drug delivery route. The findings of the current review are expected to be helpful for pharmaceutical scientists to better comprehend the existing literature and challenges and is anticipated to provide a basis for designing and fabricating novel drug delivery systems to manage OAB.

The Current Status of Clinical Research Involving Microneedles: A Systematic Review

In recent years, a number of clinical trials have been published on the efficacy and safety of drug delivery using microneedles (MNs). This review aims to systematically summarize and analyze the current evidence including the clinical effect and safety of MNs. Three electronic databases, including PubMed, were used to search the literature for randomized controlled trials (RCTs) and clinical controlled trials (CCTs) that evaluated the therapeutic efficacy of MNs from their inception to 28 June 2018. Data were extracted according to the characteristics of study subjects; disorder, types, and details of the intervention (MNs) and control groups; outcome measurements; effectiveness; and incidence of adverse events (AEs). Overall, 31 RCTs and seven CCTs met the inclusion criteria. Although MNs were commonly used in skin-related studies, evaluating the effects of MNs was difficult because many studies did not provide adequate comparison values between groups. For osteoporosis treatment, vaccine, and insulin delivery studies, MNs were comparable to or more effective than the gold standard. Regarding the safety of MNs, most AEs reported in each study were minor (grade 1 or 2). A well-designed RCT is necessary to clearly evaluate the effectiveness of MNs in the future.

Microneedles: Characteristics, Materials, Production Methods and Commercial Development

Although transdermal drug delivery systems (DDS) offer numerous benefits for patients, including the avoidance of both gastric irritation and first-pass metabolism effect, as well as improved patient compliance, only a limited number of active pharmaceutical ingredients (APIs) can be delivered accordingly. Microneedles (MNs) represent one of the most promising concepts for effective transdermal drug delivery that penetrate the protective skin barrier in a minimally invasive and painless manner. The first MNs were produced in the 90s, and since then, this field has been continually evolving. Therefore, different manufacturing methods, not only for MNs but also MN molds, are introduced, which allows for the cost-effective production of MNs for drug and vaccine delivery and even diagnostic/monitoring purposes. The focus of this review is to give a brief overview of MN characteristics, material composition, as well as the production and commercial development of MN-based systems.

Silk Fibroin Microneedle Patches for the Sustained Release of Levonorgestrel

The sustained release of levonorgestrel, a contraceptive, from silk-based microneedle patches was demonstrated for transdermal delivery. Modifications in the formulation of the silk protein and drug loading enabled the tuning of drug loading and release rates from the microneedle patches over time. Sustained drug release reached up to 100 days when the drug was loaded directly inside the microneedles, while release continued for more than a year when the drug was loaded inside microparticles prior to casting inside the microneedle patches. When coupled with the shelf-stable, refrigeration-less features of the silk protein matrix utilized in the microneedle fabrication, these findings suggest that long-acting contraception patches are feasible. This advance could provide practical options for women to have access to new options for protection against unwanted pregnancy.

Development and Study of Semi-Solid Preparations Containing the Model Substance Corticotropin (ACTH): Convenience Application in Neurodegenerative Diseases

Corticotropin (ACTH, previously an adrenocorticotropic hormone) is used in the diagnosis and treatment of pituitary gland disorders, adrenal cortex disorders, and other diseases, including autoimmune polymyositis, systemic lupus erythematosus, rheumatoid arthritis, Crohn’s disease, and ulcerative colitis. So far, the ointment dosage form containing ACTH for use on the skin is unknown. Therefore, it seems appropriate to develop a semi-solid formulation with corticotropin. Emulsion ointments were prepared using an Unguator based on the cream base Lekobaza^® containing corticotropin in different concentrations, and then the physical and chemical parameters of the ointment formulations, such as pH, spreadability, rheological properties, and texture analysis, were evaluated. In addition, a USP apparatus 2 with enhancer cells was utilized to study the in vitro drug release characteristics of the selected formulations. All the ointments obtained were characterized by good spreadability and viscosity. An analysis of the ointment texture was performed and the dependence of the tested parameters on the ACTH content in the ointment was demonstrated. Examination of the structure of the ointment showed that a high concentration of ACTH increases the hardness and adhesiveness of the ointment. In turn, it adversely affects the cohesiveness and elasticity of the ointments tested. The results of the release study showed that ACTH is released the fastest from the formulation with the lowest concentration, while the slowest from the ointment with the highest concentration of ACTH.

Current Status and Challenges in Rotigotine Delivery

Rotigotine is a non-ergoline, high lipophilic dopamine agonist. It is indicated as the first-line therapy for Parkinson's disease (PD) and Restless Leg Syndrome (RLS). However, the precise mechanism of rotigotine is yet to be known. Rotigotine has similar safety and tolerability to the other oral non-ergolinic dopamine antagonists in clinical trials, which include nausea, dizziness and somnolence. Neupro® was the first marketed transdermal patch formulation having rotigotine. The transdermal delivery system is advantageous as it enables continuous administration of the drug, thus providing steady-state plasma drug concentration for 24-hours. Intranasal administration of rotigotine allows the drug to bypass the blood-brain barrier enabling it to reach the central nervous system within minutes. Rotigotine can also be formulated as an extended-release microsphere for injection. Some challenges remain in other routes of rotigotine administration such as oral, parenteral and pulmonary, whereby resolving these challenges will be beneficial to patients as they are less invasive and comfortable in terms of administration. This review compiles recent work on rotigotine delivery, challenges and its future perspective.