Parathyroid hormone (1-34)-coated microneedle patch system: clinical pharmacokinetics and pharmacodynamics for treatment of osteoporosis

Functional biomacromolecules-based microneedle patch for the treatment of diabetic wound

Diabetic wounds are a common complication of diabetes. The prolonged exposure to high glucose and oxidative stress in the wound environment increases the risk of bacterial infection and abnormal angiogenesis, leading to amputation. Microneedle patches have shown promise in promoting the healing of diabetic wounds through transdermal drug delivery. These patches target the four main aspects of diabetic wound treatment: hypoglycemia, antibacterial action, inflammatory regulation, and tissue regeneration. By overcoming the limitations of traditional administration methods, microneedle patches enable targeted therapy for deteriorated tissues. The design of these patches extends beyond the selection of needle tip material and biomacromolecule encapsulated drugs; it can also incorporate near-infrared rays to facilitate cascade reactions and treat diabetic wounds. In this review, we comprehensively summarize the advantages of microneedle patches compared to traditional treatment methods. We focus on the design and mechanism of these patches based on existing experimental articles in the field and discuss the potential for future research on microneedle patches.

Microneedle patch with pure drug tips for delivery of liraglutide: pharmacokinetics in rats and minipigs

Transdermal delivery of peptide drugs is almost impossible with conventional penetration enhancers because of epidermal barrier function. Microneedle (MN) patches can bypass the epidermal barrier and have been developed for trans- and intradermal delivery of peptide drugs and vaccines. However, dissolving MN patches are limited by low drug loading capacities due to their small size and admixture of drug and water-soluble excipients. Furthermore, few in vivo pharmacokinetic studies, especially in large animals such as pigs, have been performed to assess post-application systemic drug exposure. Here, we developed a dissolving MN patch with pure liraglutide at the needle tips. The MN patch could load up to 2.21 ± 0.14 mg of liraglutide in a patch size of 0.9 cm2, which was nearly two orders of magnitude higher than that obtained with conventional MN patches of the same size. Raman imaging confirmed that liraglutide was localized at the MN tips. The MN had sufficient mechanical strength to penetrate the epidermis and could deliver up to 0.93 ± 0.04 mg of liraglutide into skin with a dosing variability of less than 6.8%. The MN patch delivery enabled faster absorption of liraglutide than that provided by subcutaneous (S.C.) injection, and achieved relative bioavailability of 69.8% and 46.3% compared to S.C. injection in rats and minipigs, respectively. The MN patch also exhibited similar patterns of anti-hyperglycemic effect in diabetic rats and individual variability in pharmacokinetic parameters as S.C. injection. The liraglutide MN application was well tolerated; no skin irritation was observed in minipigs except for mild erythema occurring within 4 h after once daily administration for 7 days at the same site. Our preclinical study suggests that MN patch with pure drug needle tips might offer a safe and effective alternative to S.C. injection for administration of liraglutide.

Anti-Obesity Drug Delivery Systems: Recent Progress and Challenges

Obesity has reached an epidemic proportion in the last thirty years, and it is recognized as a major health issue in modern society now with the possibility of serious social and economic consequences. By the year 2030, nearly 60% of the global population may be obese or overweight, which emphasizes a need for novel obesity treatments. Various traditional approaches, such as pharmacotherapy and bariatric surgery, have been utilized in clinical settings to treat obesity. However, these methods frequently show the possibility of side effects while remaining ineffective. There is, therefore, an urgent need for alternative obesity treatments with improved efficacy and specificity. Polymeric materials and chemical strategies are employed in emerging drug delivery systems (DDSs) to enhance therapy effectiveness and specificity by stabilizing and controlling the release of active molecules such as natural ingredients. Designing DDSs is currently a top priority research objective with an eye towards creating obesity treatment approaches. In reality, the most recent trends in the literature demonstrate that there are not enough in-depth reviews that emphasize the current knowledge based on the creation and design of DDSs for obesity treatment. It is also observed in the existing literature that a complex interplay of different physical and chemical parameters must be considered carefully to determine the effectiveness of the DDSs, including microneedles, for obesity treatment. Additionally, it is observed that these properties depend on how the DDS is synthesized. Although many studies are at the animal-study stage, the use of more advanced DDS techniques would significantly enhance the development of safe and efficient treatment approaches for obese people in the future. Considering these, this review provides an overview of the current anti-obesity treatment approaches as well as the conventional anti-obesity therapeutics. The article aims to conduct an in-depth discussion on the current trends in obesity treatment approaches. Filling in this knowledge gap will lead to a greater understanding of the safest ways to manage obesity.

Drug Delivery and Therapy Strategies for Osteoporosis Intervention

With the advent of the aging society, osteoporosis (OP) risk increases yearly. Currently, the clinical usage of anti-OP drugs is challenged by recurrent side effects and poor patient compliance, regardless of oral, intravenous, or subcutaneous administration. Properly using a drug delivery system or formulation strategy can achieve targeted drug delivery to the bone, diminish side effects, improve bioavailability, and prolong the in vivo residence time, thus effectively curing osteoporosis. This review expounds on the pathogenesis of OP and the clinical medicaments used for OP intervention, proposes the design approach for anti-OP drug delivery, emphatically discusses emerging novel anti-OP drug delivery systems, and enumerates anti-OP preparations under clinical investigation. Our findings may contribute to engineering anti-OP drug delivery and OP-targeting therapy.

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.

Multi-omics analysis of bone marrow mesenchymal stem cell differentiation differences in osteoporosis

Osteoporosis is a systemic skeletal disease characterized by low bone mass and degradation of bone tissue microarchitecture, leading to enhanced bone fragility and increased fracture risk. However, the pathogenesis of osteoporosis is unclear. Our results showed that BMSCs dervied from ovariectomized rats had a higher capacity for osteogenesis and lipogenic differentiation compared to the control group. In the meantime, we identified a total of 205 differentially expressed proteins and 2294 differentially expressed genes in BMSCs isolated from ovariectomized rats by proteomics analysis and transcriptome sequencing, respectively. These differentially expressed proteins and genes were mainly involved in ECM-receptor interaction signaling pathway. We speculate that BMSCs derived from ovariectomized rats have a higher potential for bone formation because expression of ECM collagen or genes encoding collagen in the bone ECM in BMSCs isolated from ovariectomized rats are increased compared with that from control group, which provided the prerequisite for the increased bone turnover effect. To conclusion, our results may provid new ideas for further research on the pathogenesis of osteoporosis.

Advances in microneedle-based therapy for bone disorders

Bone-related disorders treatment is a serious public health concern, imposing a significant social and economic burden on patients and healthcare systems. Although conventional drug delivery systems have made advances in bone diseases prevention and management, the limited delivery efficiency and convoluted focal environment lead to inadequate drug absorption and lack of specificity to achieve the intended therapeutic impact. Microneedle-based therapy represents an extraordinarily safe and well-tolerable therapeutic approach for treating bone disorders, providing improved efficacy by breaking down the barriers and delivery of therapeutic components to the target sites with programable release profiles in a less invasive manner. Over the past decades, numerous significant achievements in the development of various types of drug-carried microneedles have been made to address the obstacles encountered in the bone-treating procedure, enabling the microneedle-based therapy to take an important step in practical applications. In this light, this review summarizes these remarkable researches in terms of microneedles types and drug delivery strategies, with the goal of demonstrating the benefits of exploiting microneedle-based therapy as a novel strategy for treating bone-related disorders. The remaining challenges and future perspectives are also discussed in the hope of inspiring more efficient and intelligent bone treatment strategies.

Microneedle-enabled therapeutics delivery and biosensing in clinical trials

Microneedles (MNs) are micron-sized protrusions attached to a range of devices that are used in therapeutic delivery and diagnosis. Because MNs can be self-applied, are painless, and can carry multiple therapeutic agents, they have received extensive attention, and have been widely investigated, for local and systemic therapy. Many researchers are currently working to extend the use of MNs to clinical applications. In this review, we provide an update and analysis on MN-based clinical trials since their inception in 2007. The MNs in clinical trials are classified into five types based on their appearance and properties, including: hollow MNs, MN patches, radiofrequency MNs, MN rollers, and other MNs. The various aspects of MN trials are summarized, such as MN types, clinical trial time, and trial regions. This review aims to present an overview of MN development and provide insights for future research in this field. To our knowledge, this is the first review focused on MN clinical trials which showcases the latest applications of this advanced technology in medicine.

The promising application of hydrogel microneedles in medical application

OBJECTIVES

Hydrogel microneedles are emerging, and promising microneedles mainly composed of swelling polymers. This review is intended to summarize the preparation materials, formation mechanisms, applications and existing problems of hydrogel microneedles.

METHODS

We collected the literature on the materials, preparation and application of hydrogel microneedles in recent years, and summarized their mechanism and application in drugs delivery.

KEY FINDINGS

Hydrogel microneedles have higher safety and capabilities of controlled drug release, and have been mainly used in tumour and diabetes treatment, as well as clinical monitoring. In recent years, hydrogel microneedles have shown great potential in drug delivery, and have played the role of whitening, anti-inflammatory and promoting healing.

CONCLUSIONS

As an emerging drug delivery idea, hydrogel microneedles for drug delivery has gradually become a research hotspot. This review will provide a systematic vision for the favourable development of hydrogel microneedles and their promising application in medicine, especially drug delivery.

Research progress of advanced microneedle drug delivery system and its application in biomedicine

Transdermal drug delivery is an effective way of drug delivery in addition to oral and intravenous administration. Among them, microneedle administration is a new type of subcutaneous drug delivery, which forms micron-level pores on the surface of the skin, making the drug enter the dermis through the cuticular layer of the skin in the least invasive way. This mode of drug delivery not only increases the permeation efficiency of transdermal drug delivery but also improves the bioavailability of drug delivery. At present, there are many kinds of research on microneedles, such as solid microneedles, hollow microneedles, soluble polymer microneedles, etc. However, some new microneedle drug delivery systems have been gradually developed and applied with the development of microneedle drug delivery technology, for meeting the more complex pathological environment. In this review, we focus on the principle, structure, and function of some new types of microneedles, such as stimulus-response microneedles, iontophoresis microneedles, and bionic microneedles. We summarize the effects of materials, geometry, and size on the properties of microneedles as well as their applications and potential developments in the field of biomedicine. We hope that this review can provide new ideas and help with the development of new microneedle drug delivery systems.

Silk Fibroin Microneedles for Transdermal Drug Delivery: Where Do We Stand and How Far Can We Proceed?

Microneedles are a patient-friendly technique for delivering drugs to the site of action in place of traditional oral and injectable administration. Silk fibroin represents an interesting polymeric biomaterial because of its mechanical properties, thermal stability, biocompatibility and possibility of control via genetic engineering. This review focuses on the critical research progress of silk fibroin microneedles since their inception, analyzes in detail the structure and properties of silk fibroin, the types of silk fibroin microneedles, drug delivery applications and clinical trials, and summarizes the future development trend in this field. It also proposes the future research direction of silk fibroin microneedles, including increasing drug loading doses and enriching drug loading types as well as exploring silk fibroin microneedles with stimulation-responsive drug release functions. The safety and effectiveness of silk fibroin microneedles should be further verified in clinical trials at different stages.

Microneedle-Mediated Transdermal Delivery of Biopharmaceuticals

Transdermal delivery provides numerous benefits over conventional routes of administration. However, this strategy is generally limited to a few molecules with specific physicochemical properties (low molecular weight, high potency, and moderate lipophilicity) due to the barrier function of the stratum corneum layer. Researchers have developed several physical enhancement techniques to expand the applications of the transdermal field; among these, microneedle technology has recently emerged as a promising platform to deliver therapeutic agents of any size into and across the skin. Typically, hydrophilic biomolecules cannot penetrate the skin by passive diffusion. Microneedle insertion disrupts skin integrity and compromises its protective function, thus creating pathways (microchannels) for enhanced permeation of macromolecules. Microneedles not only improve stability but also enhance skin delivery of various biomolecules. Academic institutions and industrial companies have invested substantial resources in the development of microneedle systems for biopharmaceutical delivery. This review article summarizes the most recent research to provide a comprehensive discussion about microneedle-mediated delivery of macromolecules, covering various topics from the introduction of the skin, transdermal delivery, microneedles, and biopharmaceuticals (current status, conventional administration, and stability issues), to different microneedle types, clinical trials, safety and acceptability of microneedles, manufacturing and regulatory issues, and the future of microneedle technology.

Egg Microneedle for Transdermal Delivery of Active Liraglutide

Liraglutide, a human glucagon-like peptide-1 (GLP-1) analog, is promising for safely treating type 2 diabetes mellitus (T2DM), compared to insulin, by significantly reducing the risk of glucose-dependent hypoglycemia. Concerns related to injection prevent T2DM patients from taking liraglutide regularly, even though once-a-day subcutaneous (SC) injections. Dissolving microneedles (DMNs) are promising substitutes for SC injection and for improving patient convenience. However, there are two fundamental limitations: the low drug delivery due to incomplete insertion and loss of drug activity during DMN fabrication. Here, it is shown that an egg microneedle (EMN) designed with three functional layered structures can maintain the maximum activity of the loaded compound during DMN fabrication and deliver it completely into the skin, with the base layer allowing the complete delivery of liraglutide, and the shell layer maintaining the drug activity by mimicking the role of albumin in eggs. In a diabetic mouse model, liraglutide administration via EMN exhibited similar effect when compared to that of injection. Therefore, EMN-mediated liraglutide administration is a good potential option for replacing liraglutide injections in T2DM treatment.

Actively separated microneedle patch for sustained-release of growth hormone to treat growth hormone deficiency

Growth hormone deficiency (GHD) has become a serious healthcare burden, and presents a huge impact on the physical and mental health of patients. Here, we developed an actively separated microneedle patch (PAA/NaHCO₃-Silk MN) based on silk protein for sustained release of recombinant human growth hormone (rhGH). Silk protein, as a friendly carrier material for proteins, could be constructed in mild full-water conditions and ensure the activity of rhGH. After manually pressing PAA/NaHCO₃-Silk MN patch to skin for 1 min, active separation is achieved by absorbing the interstitial fluid (ISF) to trigger HCO₃ ^‒ in the active backing layer to produce carbon dioxide gas (CO₂). In rats, the MN patch could maintain the sustained release of rhGH for more than 7 days, and produce similar effects as daily subcutaneous (S.C.) injections of rhGH in promoting height and weight with well tolerated. Moreover, the PAA/NaHCO₃-Silk MN patch with the potential of painless self-administration, does not require cold chain transportation and storage possess great economic benefits. Overall, the PAA/NaHCO₃-Silk MN patch can significantly improve patient compliance and increase the availability of drugs, meet current unmet clinical needs, improve clinical treatment effects of GHD patients.

Development of Clinical Weekly-Dose Teriparatide Acetate Encapsulated Dissolving Microneedle Patch for Efficient Treatment of Osteoporosis

Teriparatide acetate (TA), which directly promotes bone formation, is subcutaneously injected to treat osteoporosis. In this study, TA with a once-weekly administration regimen was loaded on dissolving microneedles (DMNs) to effectively deliver it to the systemic circulation via the transdermal route. TA activity reduction during the drying process of various TA polymer solutions formulated with hyaluronic acid and trehalose was monitored and homogeneities were assessed. TA-DMN patches fabricated using centrifugal lithography in a two-layered structure with dried pure hyaluronic acid on the base layer and dried TA polymer solution on the top layer were evaluated for their physical properties. Rhodamine-B-loaded TA-DMNs were found to form perforations when inserted into porcine skin using a shooting device. In addition, 87.6% of TA was delivered to the porcine skin after a 5-min TA-DMN patch application. The relative bioavailability of TA via subcutaneous injection was 66.9% in rats treated with TA-DMN patches. The maximal TA concentration in rat plasma was proportional to the number of patches used. Therefore, the TA-DMN patch fabricated in this study may aid in the effective delivery of TA in a patient-friendly manner and enhance medical efficacy in osteoporosis treatment.

Long-acting injectable formulation technologies: Challenges and opportunities for the delivery of fragile molecules

INTRODUCTION

The development of long acting injectables (LAIs) for protein and peptide therapeutics has been a key challenge over the last 20 years. If these molecules offer advantages due to their high specificity and selectivity, their controlled release may confer several additional benefits in terms of extended half-life, local delivery, and patient compliance.

AREA COVERED

This manuscript aims to give an overview of peptide and protein based LAIs from an industrial perspective, describing both approved and promising technologies (with exceptions of protein engineering strategies and devices), their advantages and potential improvements to aid their access to the market.

EXPERT OPINION

Many LAIs have been developed for peptides, with formulations on the market for several decades. On the contrary, LAIs for proteins are still far from the market and issues related to manufacturing and sterilization of these products still need to be overcome. In situ forming depots (ISFDs), whose simple manufacturing conditions and easy administration procedures (without reconstitution) are strong advantages, appear as one of the most promising technologies for the delivery of these molecules. In this regard, the approval of ELIGARD® in the early 2000's (which still requires a complex reconstitution process), paved the way for the development of second-generation, ready-to-use ISFD technologies like BEPO® and FluidCrystal®.

Bone Tissue Engineering in the Treatment of Bone Defects

Bones play an important role in maintaining exercise and protecting organs. Bone defect, as a common orthopedic disease in clinics, can cause tremendous damage with long treatment cycles. Therefore, the treatment of bone defect remains as one of the main challenges in clinical practice. Today, with increased incidence of bone disease in the aging population, demand for bone repair material is high. At present, the method of clinical treatment for bone defects including non-invasive therapy and invasive therapy. Surgical treatment is the most effective way to treat bone defects, such as using bone grafts, Masquelet technique, Ilizarov technique etc. In recent years, the rapid development of tissue engineering technology provides a new treatment strategy for bone repair. This review paper introduces the current situation and challenges of clinical treatment of bone defect repair in detail. The advantages and disadvantages of bone tissue engineering scaffolds are comprehensively discussed from the aspect of material, preparation technology, and function of bone tissue engineering scaffolds. This paper also summarizes the 3D printing technology based on computer technology, aiming at designing personalized artificial scaffolds that can accurately fit bone defects.

Recent Advancements in Microneedle Technology for Multifaceted Biomedical Applications

Microneedle (MNs) technology is a recent advancement in biomedical science across the globe. The current limitations of drug delivery, like poor absorption, low bioavailability, inadequate skin permeation, and poor biodistribution, can be overcome by MN-based drug delivery. Nanotechnology made significant changes in fabrication techniques for microneedles (MNs) and design shifted from conventional to novel, using various types of natural and synthetic materials and their combinations. Nowadays, MNs technology has gained popularity worldwide in biomedical research and drug delivery technology due to its multifaceted and broad-spectrum applications. This review broadly discusses MN’s types, fabrication methods, composition, characterization, applications, recent advancements, and global intellectual scenarios.

The Role of 3D Printing Technology in Microengineering of Microneedles

Microneedles (MNs) are minimally invasive devices, which have gained extensive interest over the past decades in various fields including drug delivery, disease diagnosis, monitoring, and cosmetics. MN geometry and shape are key parameters that dictate performance and therapeutic efficacy, however, traditional fabrication methods, such as molding, may not be able to offer rapid design modifications. In this regard, the fabrication of MNs using 3D printing technology enables the rapid creation of complex MN prototypes with high accuracy and offers customizable MN devices with a desired shape and dimension. Moreover, 3D printing shows great potential in producing advanced transdermal drug delivery systems and medical devices by integrating MNs with a variety of technologies. This review aims to demonstrate the advantages of exploiting 3D printing technology as a new tool to microengineer MNs. Various 3D printing methods are introduced, and representative MNs manufactured by such approaches are highlighted in detail. The development of advanced MN devices is also included. Finally, clinical translation and future perspectives for the development of MNs using 3D printing are discussed.

Application of microneedle patches for drug delivery; doorstep to novel therapies

In the past decade, microneedle-based drug delivery systems showed promising approaches to become suitable and alternative for hypodermic injections and can control agent delivery without side effects compared to conventional approaches. Despite these advantages, the procedure of microfabrication is facing some difficulties. For instance, drug loading method, stability of drugs, and retention time are subjects of debate. Besides, the application of novel refining fabrication methods, types of materials, and instruments are other issues that need further attention. Herein, we tried to summarize recent achievements in controllable drug delivery systems (microneedle patches) in vitro and in vivo settings. In addition, we discussed the influence of delivered drugs on the cellular mechanism and immunization molecular signaling pathways through the intradermal delivery route. Understanding the putative efficiency of microneedle patches in human medicine can help us develop and design sophisticated therapeutic modalities.

In-Plane Si Microneedles: Fabrication, Characterization, Modeling and Applications

Microneedles are getting more and more attention in research and commercialization since their advancement in the 1990s due to the advantages over traditional hypodermic needles such as minimum invasiveness, low material and fabrication cost, and precise needle geometry control, etc. The design and fabrication of microneedles depend on various factors such as the type of materials used, fabrication planes and techniques, needle structures, etc. In the past years, in-plane and out-of-plane microneedle technologies made by silicon (Si), polymer, metal, and other materials have been developed for numerous biomedical applications including drug delivery, sample collections, medical diagnostics, and bio-sensing. Among these microneedle technologies, in-plane Si microneedles excel by the inherent properties of Si such as mechanical strength, wear resistance, biocompatibility, and structural advantages of in-plane configuration such as a wide range of length, readiness of integration with other supporting components, and complementary metal-oxide-semiconductor (CMOS) compatible fabrication. This article aims to provide a review of in-plane Si microneedles with a focus on fabrication techniques, theoretical and numerical analysis, experimental characterization of structural and fluidic behaviors, major applications, potential challenges, and future prospects.

The Relationship between the Drug Delivery Properties of a Formulation of Teriparatide Microneedles and the Pharmacokinetic Evaluation of Teriparatide Administration in Rats

PURPOSE

Teriparatide is an effective drug for the treatment of osteoporosis. This study examines the relationship between the drug delivery properties of the solid formulation with teriparatide and the pharmacokinetic properties of teriparatide in vivo.

METHODS

Teriparatide microneedles with different dissolution rates were prepared using sucrose and carboxymethylcellulose (CMC). There were three aspects of this study: (1) The dissolution rate of teriparatide from both formulations (sucrose and CMC) was measured in vitro. (2) After administration into porcine skin ex vivo, the diffusion rate of FITC-dextran was observed using a confocal microscope. (3) Pharmacokinetic studies were performed in rats and pharmacokinetic data compared with the release rate and the diffusion pattern.

RESULTS

In the in vitro dissolution experiment, 80% of teriparatide was released within 30 min from the CMC MNs, whereas 80% of teriparatide was released within 10 min from the sucrose MNs. After 30 min, the fluorescence intensity on the surface of the MNs was 40% of the initial intensity for sucrose MNs and 90% for CMC MNs. In the pharmacokinetic study, the C_max values of the CMC and sucrose MNs were 868 pg/mL and 6809 pg/mL, respectively, and the AUC_last values were 6771 pg*hr/mL for the CMC MNs and 17,171 pg*hr/mL for the sucrose MNs.

CONCLUSIONS

When teriparatide is delivered into the skin using microneedles, the release rate from the solid formulation determines the drug's pharmacokinetic properties. The diffusion pattern of fluorescence into the skin can be used to anticipate the pharmacokinetic properties of the drug.

Transdermal Drug Delivery Systems and Their Use in Obesity Treatment

Transdermal drug delivery (TDD) has recently emerged as an effective alternative to oral and injection administration because of its less invasiveness, low rejection rate, and excellent ease of administration. TDD has made an important contribution to medical practice such as diabetes, hemorrhoids, arthritis, migraine, and schizophrenia treatment, but has yet to fully achieve its potential in the treatment of obesity. Obesity has reached epidemic proportions globally and posed a significant threat to human health. Various approaches, including oral and injection administration have widely been used in clinical setting for obesity treatment. However, these traditional options remain ineffective and inconvenient, and carry risks of adverse effects. Therefore, alternative and advanced drug delivery strategies with higher efficacy and less toxicity such as TDD are urgently required for obesity treatment. This review summarizes current TDD technology, and the main anti-obesity drug delivery system. This review also provides insights into various anti-obesity drugs under study with a focus on the recent developments of TDD system for enhanced anti-obesity drug delivery. Although most of presented studies stay in animal stage, the application of TDD in anti-obesity drugs would have a significant impact on bringing safe and effective therapies to obese patients in the future.

Advances of microneedles in hormone delivery

The skin is recognized as a potential target for local and systemic drug delivery and hormone. However, the transdermal route of drug administration seems to be limited by substantial barrier properties of the skin. Recently, delivering hormone via the skin by transdermal patches is a big challenge because of the presence of the stratum corneum that prevents the application of hormone via this route. In order to overcome the limitations, microneedle (MN), consisting of micro-sized needles, are a promising approach to drill the stratum corneum and release hormone into the dermis via a minimal-invasive route. This review aimed to highlight advances in research on the development of MNs-based therapeutics for their implications in hormone delivery. The challenges during clinical translation of MNs from bench to bedside are also discussed.

Microneedle patch designs to increase dose administered to human subjects

Microneedle (MN) patches are being developed for many different kinds of drugs, but are often limited to delivering sub-milligram doses. This is because larger patches can be more difficult to apply to the skin, and acceptability of larger MN patches by human subjects has received limited study. Here, we fabricated 18 different large MN patch designs by laser microfabrication with different MN length (800-1500 μm), number of MNs (225 to 900 MNs per patch), space between MNs (600-1100 μm), and MN base diameter (200-250 μm). After manual application of these patches to human participants, we assessed dose delivery efficiency, total dose delivered, dose delivered per MN, depth of MN penetration and whole-MN delivery efficiency. We found that all of these parameters generally increased with decreased MN length, increased number of MNs (among those ≤1000 μm in length) and increased MN-MN spacing. All MN patch designs caused less pain than a pin prick sensation and were generally considered acceptable by the study participants. The MN patches induced mild, or sometimes moderate, transient erythema on skin. Study participants showed higher preference for MN patches for long-acting contraception compared with conventional options, indicating strong interest and acceptability of MN patches in this study.

Microneedles in Drug Delivery: Progress and Challenges

In recent years, an innovative transdermal delivery technology has attracted great interest for its ability to distribute therapeutics and cosmeceuticals for several applications, including vaccines, drugs, and biomolecules for skin-related problems. The advantages of microneedle patch technology have been extensively evaluated in the latest literature; hence, the academic publications in this area are rising exponentially. Like all new technologies, the microneedle patch application has great potential but is not without limitations. In this review, we will discuss the possible limitations by highlighting the areas where a great deal of improvements are required. Emphasising these concerns early on should help scientists and technologists to address the matters in a timely fashion and to use their resources wisely.

Administration of pilocarpine by microneedle patch as a novel method for cystic fibrosis sweat testing

The sweat test is the gold standard for the diagnosis of cystic fibrosis (CF). The test utilizes iontophoresis to administer pilocarpine to the skin to induce sweating for measurement of chloride concentration in sweat. However, the sweat test procedure needs to be conducted in an accredited lab with dedicated instrumentation, and it can lead to inadequate sweat samples being collected in newborn babies and young children due to variable sweat production with pilocarpine iontophoresis. We tested the feasibility of using microneedle (MN) patches as an alternative to iontophoresis to administer pilocarpine to induce sweating. Pilocarpine-loaded MN patches were developed. Both MN patches and iontophoresis were applied on horses to induce sweating. The sweat was collected to compare the sweat volume and chloride concentration. The patches contained an array of 100 MNs measuring 600 μm long that were made of water-soluble materials encapsulating pilocarpine nitrate. When manually pressed to the skin, the MN patches delivered >0.5 mg/cm2 pilocarpine, which was double that administered by iontophoresis. When administered to horses, MN patches generated the same volume of sweat when normalized to drug dose and more sweat when normalized to skin area compared to iontophoresis using a commercial device. Moreover, both MN patches and iontophoresis generated sweat with comparable chloride concentration. These results suggest that administration of pilocarpine by MN patches may provide a simpler and more-accessible alternative to iontophoresis for performing a sweat test for the diagnosis of CF.

Microneedles for drug delivery: recent advances in materials and geometry for preclinical and clinical studies

INTRODUCTION

A microneedle array patch (MAP) has been studied as a means for delivering drugs or vaccines and has shown superior delivery efficiency compared to the conventional transdermal drug delivery system (TDD). This paper reviews recent advancements in the development of MAPs, with a focus on their size, shapes, and materials in preclinical and clinical studies for pharmaceutics.

AREA COVERED

We classified MAPs for drug delivery into four types: coated, dissolving, separable, and swellable. We covered their recent developments in materials and geometry in preclinical and clinical studies.

EXPERT OPINION

The design of MAPs needs to be determined based on what properties would be effective for the target diseases and purposes. In addition, in preclinical studies, it is necessary to consider not only the novelty of the formulations but also the feasibility of clinical application. Currently, clinical studies of microneedles loaded with various drugs and vaccines are in progress. When the regulation of pharmaceutical microneedles is established and more clinical studies are published, more drugs will be developed as microneedle products and clinical research will proceed. With these considerations, the microneedle array patch will be a better option for drug delivery.

Strategies for transdermal drug delivery against bone disorders: A preclinical and clinical update

The transdermal drug delivery system is an exceptionally safe and well-tolerable therapeutic approach that has immense potential for delivering active components against bone-related pathologies. However, its use is limited in the current clinical practices due to the low skin permeability of most active drugs in the formulation. Thus, innovations in the methodologies of skin permeation enhancement techniques are suggested to overcome this limitation. Although various transdermal drug delivery systems are studied to date, there are insufficient studies comparing the therapeutic efficacy of transdermal delivery systems to oral delivery systems. Thus, creating a decision-making dilemma between oral or transdermal therapies. Therefore, a timely review is inevitable to develop a platform for future researchers to develop next-generation transdermal drug delivery strategies against skeletal diseases that must be convenient and cost-effective for the patients with improved therapeutic efficacy. Here, we will outline the most recent strategies that can overcome the choice limitation of the drug and enhance the transdermal adsorption of various types of drugs to treat bone disorders. For the first time, in this review paper, we will highlight the preclinical and clinical studies on the different transdermal delivery methods. Thus, providing insight into the current therapeutic approaches and suggesting new directions for the advancements in transdermal drug delivery systems against bone disorders.

3D printed hollow microneedles array using stereolithography for efficient transdermal delivery of rifampicin

A 3D printed assembly of hollow microneedles (HMNs) array, conjoined with a reservoir void, was designed and additively manufactured using stereolithography (SLA) technology utilizing a proprietary class-I resin. The HMNs array was utilized for transdermal delivery of high molecular weight antibiotics, i.e., rifampicin (M_w 822.94 g/mol), which suffers from gastric chemical instability, low bioavailability, and severe hepatotoxicity. HMNs morphology was designed with sub-apical holes present in a quarter of the needle tip to improve its mechanical strength and integrity of the HMNs array. The HMNs array was characterized by optical microscopy and electron microscopy to ascertain the print quality and uniformity across the array. The system was also subjected to mechanical characterization for failure and penetration analyses. The ex vivo permeation and consequent transport of rifampicin across porcine skin were systematically evaluated. Finally, in vivo examinations of rifampicin administration through the microneedle reservoir system in SD rats revealed efficient penetration and desired bioavailability.

Transdermal Route: A Viable Option for Systemic Delivery of Antidepressants

The high rise in the population suffering from depression depicts the need for improved and highly effective treatment options for this condition. Efforts to develop existing drugs into user-friendly dosage forms with a number of advantages in major depressive states, including but not limited to: sustained drug release, reduced drug dosing frequency, improved tolerance and adherence, suitability for use in diverse populations and different treatment scenarios, as well as less central nervous system side effects are required. One such non-invasive drug delivery route that could provide the aforementioned benefits in the treatment of depression is the transdermal route. A number of conventional and emerging transdermal delivery strategies have been investigated for some potent antidepressants and results depict the potential of this route as a viable means for systemic delivery of therapeutically relevant doses of the tested agents, with Emsam®, the commercially available patch of selegiline, being an evidence for the same. The investigated approaches include the formulation of transdermal patches, use of vesicular drug carriers, pro-drug approach, microemulsification, chemical as well as physical enhancement technologies. This review provides a comprehensive account of the rationale, developments made till date, scope and future prospects of delivering antidepressants via the transdermal1 route of administration.

Delivering therapeutic cannabinoids via skin: Current state and future perspectives

Adequate evidence exists in the literature indicating a relatively positive shift with regards to the legal acceptance of cannabis and cannabis-derived products for medicinal purposes in some countries. Concomitantly, scientists are showing renewed interest in cannabis-related research work. Over the years, clinical and preclinical studies have demonstrated the therapeutic significance of cannabinoids for diverse indications. Additionally, efforts are being made to develop cannabis-related products into acceptable prescription products. FDA authorization for the commercial use of four cannabinoid-derived products, available as oral dosage forms is a significant progress already. However, there are certain drawbacks associated with the conventional delivery forms of cannabinoids. These include low oral bioavailability due to hepatic degradation, gastric instability, poor water solubility, and the side effects experienced upon the use of high doses of psychotropic cannabinoids associated with heightened plasma concentrations of the drug. These are however, limitable with the aid of transcutaneous drug delivery. Emerging topical and transdermal strategies could be exploited for the successful development of highly effective delivery systems for cannabinoids. This review discusses the feasibility of delivering therapeutic cannabinoids via skin and provides a comprehensive account of the supporting research studies that have been reported in the literature till date.

Trends in peptide drug discovery

Since the introduction of insulin almost a century ago, more than 80 peptide drugs have reached the market for a wide range of diseases, including diabetes, cancer, osteoporosis, multiple sclerosis, HIV infection and chronic pain. In this Perspective, we summarize key trends in peptide drug discovery and development, covering the early efforts focused on human hormones, elegant medicinal chemistry and rational design strategies, peptide drugs derived from nature, and major breakthroughs in molecular biology and peptide chemistry that continue to advance the field. We emphasize lessons from earlier approaches that are still relevant today as well as emerging strategies such as integrated venomics and peptide-display libraries that create new avenues for peptide drug discovery. We also discuss the pharmaceutical landscape in which peptide drugs could be particularly valuable and analyse the challenges that need to be addressed for them to reach their full potential.

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.

Recent advances in combination of microneedles and nanomedicines for lymphatic targeted drug delivery

Numerous diseases have been reported to affect the lymphatic system. As such, several strategies have been developed to deliver chemotherapeutics to this specific network of tissues and associated organs. Nanotechnology has been exploited as one of the main approaches to improve the lymphatic uptake of drugs. Different nanoparticle approaches utilized for both active and passive targeting of the lymphatic system are discussed here. Specifically, due to the rich abundance of lymphatic capillaries in the dermis, particular attention is given to this route of administration, as intradermal administration could potentially result in higher lymphatic uptake compared to other routes of administration. Recently, progress in microneedle research has attracted particular attention as an alternative for the use of conventional hypodermic injections. The benefits of microneedles, when compared to intradermal injection, are subsequently highlighted. Importantly, microneedles exhibit particular benefit in relation to therapeutic targeting of the lymphatic system, especially when combined with nanoparticles, which are further discussed. However, despite the apparent benefits provided by this combination approach, further comprehensive preclinical and clinical studies are now necessary to realize the potential extent of this dual-delivery platform, further taking into consideration eventual usability and acceptability in the intended patient end-users. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Characterization of microneedles and microchannels for enhanced transdermal drug delivery

Microneedle (MN)-based technologies are currently one of the most innovative approaches that are being extensively investigated for transdermal delivery of low molecular weight drugs, biotherapeutic agents and vaccines. Extensive research reports, describing the fabrication and applications of different types of MNs, can be readily found in the literature. Effective characterization tools to evaluate the quality and performance of the MNs as well as for determination of the dimensional and kinetic properties of the microchannels created in the skin, are an essential and critical part of MN-based research. This review paper provides a comprehensive account of all such tools and techniques.

Modeling Drug Absorption from the Dermis after an Injection

A dermal absorption model for small and macromolecules was previously proposed by Ibrahim et al. This model estimated absorption of therapeutics from the dermal tissue based on their molecular size and protein binding through blood and lymphatics. Blood absorption followed a two-pore theory and the lymphatic absorption was limited by the constant lymphatic flow rate. Current work builds on this steady-state concept by modeling the absorption from the dermis immediately after an injection is given (unsteady state). An injection in the dermis creates a localized pressure gradient which resolves itself over time. This phenomenon is captured in the model to estimate the impact of injection volume on the absorption rate constant. Blood absorption follows the two-pore theory but is time-dependent and the lymphatic absorption is determined based on valve opening and pressure driven convective flow, returning to steady-state as the molecule is absorbed. A direct comparison of the steady-state analysis, experimental data and the current model is made. The results indicate that accounting for the localized time-varying pressure can better predict the experimental absorption rate constants. This work significantly improves the existing understanding of macromolecule uptake from the interstitial fluid following intradermal injection.

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.

Osteocyte apoptosis: the roles and key molecular mechanisms in resorption-related bone diseases

Vital osteocytes have been well known to function as an important orchestrator in the preservation of robustness and fidelity of the bone remodeling process. Nevertheless, some key pathological factors, such as sex steroid deficiency and excess glucocorticoids, and so on, are implicated in inducing a bulk of apoptotic osteocytes, subsequently resulting in resorption-related bone loss. As much, osteocyte apoptosis, under homeostatic conditions, is in an optimal state of balance tightly controlled by pro- and anti-apoptotic mechanism pathways. Importantly, there exist many essential signaling proteins in the process of osteocyte apoptosis, which has a crucial role in maintaining a homeostatic environment. While increasing in vitro and in vivo studies have established, in part, key signaling pathways and cross-talk mechanism on osteocyte apoptosis, intrinsic and complex mechanism underlying osteocyte apoptosis occurs in various states of pathologies remains ill-defined. In this review, we discuss not only essential pro- and anti-apoptotic signaling pathways and key biomarkers involved in these key mechanisms under different pathological agents, but also the pivotal role of apoptotic osteocytes in osteoclastogenesis-triggered bone loss, hopefully shedding new light on the attractive and proper actions of pharmacotherapeutics of targeting apoptosis and ensuing resorption-related bone diseases such as osteoporosis and fragility fractures.

Current trends in polymer microneedle for transdermal drug delivery

Transdermal drug delivery using microneedles is increasingly gaining interest due to the issues associated with oral drug delivery routes. Gastrointestinal route exposes the drug to acid and enzymes present in the stomach, leading to denaturation of the compound and resulting in poor bioavailability. Microneedle transdermal drug delivery addresses the problems linked to oral delivery and to relieves the discomfort of patients associated with injections to increase patient compliance. Microneedles can be broadly classified into five types: solid microneedles, coated microneedles, dissolving microneedles, hollow microneedles, and hydrogel-forming microneedles. The materials used for the preparation of microneedles dictate the different applications and features present in the microneedle. Polymeric microneedle arrays present an improved method for transdermal administration of drugs as they penetrate the skin stratum corneum barrier with minimal invasiveness. The review summarizes the importance of polymeric microneedle and discussed some of the most important therapeutic drugs in research, mainly protein drugs, vaccines and small molecule drugs in regenerative medicine.

Non-invasive drug delivery technology: development and current status of transdermal drug delivery devices, techniques and biomedical applications

Pay-load deliveries across the skin barrier to the systemic circulation have been one of the most challenging delivery options. Necessitated requirements of the skin and facilitated skin layer cross-over delivery attempts have resulted in development of different non-invasive, non-oral methods, devices and systems which have been standardized, concurrently used and are in continuous upgrade and improvements. Iontophoresis, electroporation, sonophoresis, magnetophoresis, dermal patches, nanocarriers, needled and needle-less shots, and injectors are among some of the methods of transdermal delivery. The current review covers the current state of the art, merits and shortcomings of the systems, devices and transdermal delivery patches, including drugs' and other payloads' passage facilitation techniques, permeation and absorption feasibility studies, as well as physicochemical properties affecting the delivery through different transdermal modes along with examples of drugs, vaccines, genes and other payloads.

Development of a novel zolmitriptan intracutaneous microneedle system (Qtrypta™) for the acute treatment of migraine

M207 is an investigational intracutaneous microneedle therapeutic system for nonoral zolmitriptan delivery. In a Phase I trial, M207 provided faster absorption with a higher 2 h exposure than oral zolmitriptan. In the pivotal trial evaluating efficacy, tolerability and safety in moderate-to-severe migraine attacks, M207 3.8 mg was superior to placebo in providing freedom from headache pain (42 vs 14%) and freedom from most bothersome symptom (68 vs 43%) 2 h post-dose. Treatment-emergent adverse events were mild and transient and most commonly concerned the application site. In post hoc analyses: pain freedom was sustained in approximately 1/3 of patients; efficacy was observed in migraine headaches that are typically more difficult to treat.