Transdermal delivery of vitamin K using dissolving microneedles for the prevention of vitamin K deficiency bleeding

Current Status of Microneedle Array Technology for Therapeutic Delivery: From Bench to Clinic

In recent years, microneedle (MN) patches have emerged as an alternative technology for transdermal delivery of various drugs, therapeutics proteins, and vaccines. Therefore, there is an urgent need to understand the status of MN-based therapeutics. The article aims to illustrate the current status of microneedle array technology for therapeutic delivery through a comprehensive review. However, the PubMed search was performed to understand the MN's therapeutics delivery status. At the same time, the search shows the number no of publications on MN is increasing (63). The search was performed with the keywords "Coated microneedle," "Hollow microneedle," "Dissolvable microneedle," and "Hydrogel microneedle," which also shows increasing trend. Similarly, the article highlighted the application of different microneedle arrays for treating different diseases. The article also illustrated the current status of different phases of MN-based therapeutics clinical trials. It discusses the delivery of different therapeutic molecules, such as drug molecule delivery, using microneedle array technology. The approach mainly discusses the delivery of different therapeutic molecules. The leading pharmaceutical companies that produce the microneedle array for therapeutic purposes have also been discussed. Finally, we discussed the limitations and future prospects of this technology.

Unravelling Microarray Patch Performance: The Role of In Vitro Release Medium and Biorelevant Testing

The absence of established protocols for studying the in vitro performance of dissolvable microarray patches (MAPs) poses a significant challenge within the field. To overcome this challenge, it is essential to optimize testing methods in a way that closely mimics the skin's environment, ensuring biorelevance and enhancing the precision of assessing MAP performance. This study focuses on optimizing in vitro release testing (IVRT) and in vitro permeation testing (IVPT) methods for MAPs containing the antihistamine drugs loratadine (LOR) and chlorpheniramine maleate (CPM). Our primary objective is to investigate the impact of the composition of in vitro release media on the drug release rate, penetration through the skin, and permeation into the release medium. Artificial interstitial fluid is introduced as a biorelevant release medium and compared with commonly used media in IVRT and IVPT studies. Prior to these studies, we evaluated drug solubility in different release media and developed a method for LOR and CPM extraction from the skin using a design of experiment approach. Our findings highlight the effect of the in vitro release medium composition on both LOR and CPM release rate and their penetration through the skin. Furthermore, we identified the importance of considering the interplay between the physicochemical attributes of the drug molecules, the design of the MAP formulation, and the structural properties of the skin when designing IVRT and IVPT protocols.

Advances in novel biomaterials combined with traditional Chinese medicine rehabilitation technology in treatment of peripheral nerve injury

Peripheral nerve injuries (PNI) represent one of the primary neuropathies leading to lifelong disability. Nerve regeneration and targeted muscle atrophy stand as the two most crucial factors influencing functional rehabilitation post peripheral nerve injury. Over time, traditional Chinese medicine (TCM) rehabilitation approaches such as acupuncture, Tuina, and microneedles serve as pivot means to activate the regeneration of injured nerve Schwann cells. By promoting axon regeneration, these approaches can accomplish nerve repair, reconstruction, and functional rehabilitation. Although TCM rehabilitation approaches have clinically demonstrated effectiveness in promoting the repair and regeneration of PNI, the related molecular mechanisms remain unclear. This significantly hampers the application and promotion of TCM rehabilitation in PNI recovery. Therefore, deeply delving into the cellular and molecular mechanisms of TCM rehabilitation technologies to foster nerve regeneration stands as the most pressing issue. On the other hand, in recent years, novel biomaterials represented by hydrogels, microfluidic platforms, and new chitosan scaffolds have showed their unique roles in treating various degrees of nerve injury. These methods exhibit immense potential in conducting high-throughput cell and organoid culture in vitro and synthesizing diverse tissue engineering scaffolds and drug carriers. We believe that the combination of TCM rehabilitation technology and novel biomaterials can more effectively address precise treatment issues such as identification of treatment target and dosage control. Therefore, this paper not only summarizes the molecular mechanisms of TCM rehabilitation technology and novel biomaterials in treating peripheral nerve injury individually, but also explores the research direction of precise treatment by integrating the two at both macro and micro levels. Such integration may facilitate the exploration of cellular and molecular mechanisms related to neurodegeneration and regeneration, providing a scientific and theoretical foundation for the precise functional rehabilitation of PNI in the future.

Recent advances in delivery of transdermal nutrients: A review

Nutrients provide vital functions in the body for sustained health, which have been shown to be related to the incidence, prevention and treatment of disease. However, limited bioavailability, loss of targeting specificity and the increased hepatic metabolism limit the utilization of nutrients. In this review, we highlight transdermal absorption of nutrients, which represents an opportunity to allow great use of many nutrients with promising human health benefits. Moreover, we describe how the various types of permeation enhancers are increasingly exploited for transdermal nutrient delivery. Chemical penetration enhancers, carrier systems and physical techniques for transdermal nutrient delivery are described, with a focus on combinatorial approaches. Although there are many carrier systems and physical techniques currently in development, with some tools currently in advanced clinical trials, relatively few products have achieved full translation to clinical practice. Challenges and further developments of these tools are discussed here in this review. This review will be useful to researchers interested in transdermal applications of permeation enhancers for the efficient delivery of nutrients, providing a reference for supporting the need to take more account of specific nutritional needs in specific states.

The Use of Nanoneedles in Drug Delivery: an Overview of Recent Trends and Applications

Nanoneedles (NN) are growing rapidly as a means of navigating biological membranes and delivering therapeutics intracellularly. Nanoneedle arrays (NNA) are among the most potential resources to achieve therapeutic effects by administration of drugs through the skin. Although this is based on well-established approaches, its implementations are rapidly developing as an important pharmaceutical and biological research phenomenon. This study intends to provide a broad overview of current NNA research, with an emphasis on existing approaches, applications, and types of compounds released by these systems. A nanoneedle-based delivery device with great spatial and temporal accuracy, minimal interference, and low toxicity could transfer biomolecules into living organisms. Due to its vast potential, NN has been widely used as a capable transportation system of many therapeutic active substances, from cancer therapy, vaccine delivery, cosmetics, and bio-sensing nanocarrier drugs to genes. The use of nanoneedles for drug delivery offers new opportunities for the rapid, targeted, and exact administration of biomolecules into cell membranes for high-resolution research of biological systems, and it can treat a wide range of biological challenges. As a result, the literature has analyzed existing patents to emphasize the status of NNA in biological applications.

Dissolving and Swelling Hydrogel-Based Microneedles: An Overview of Their Materials, Fabrication, Characterization Methods, and Challenges

Polymeric hydrogels are a complex class of materials with one common feature-the ability to form three-dimensional networks capable of imbibing large amounts of water or biological fluids without being dissolved, acting as self-sustained containers for various purposes, including pharmaceutical and biomedical applications. Transdermal pharmaceutical microneedles are a pain-free drug delivery system that continues on the path to widespread adoption-regulatory guidelines are on the horizon, and investments in the field continue to grow annually. Recently, hydrogels have generated interest in the field of transdermal microneedles due to their tunable properties, allowing them to be exploited as delivery systems and extraction tools. As hydrogel microneedles are a new emerging technology, their fabrication faces various challenges that must be resolved for them to redeem themselves as a viable pharmaceutical option. This article discusses hydrogel microneedles from a material perspective, regardless of their mechanism of action. It cites the recent advances in their formulation, presents relevant fabrication and characterization methods, and discusses manufacturing and regulatory challenges facing these emerging technologies before their approval.

Solid implantable devices for sustained drug delivery

Implantable drug delivery systems (IDDS) are an attractive alternative to conventional drug administration routes. Oral and injectable drug administration are the most common routes for drug delivery providing peaks of drug concentrations in blood after administration followed by concentration decay after a few hours. Therefore, constant drug administration is required to keep drug levels within the therapeutic window of the drug. Moreover, oral drug delivery presents alternative challenges due to drug degradation within the gastrointestinal tract or first pass metabolism. IDDS can be used to provide sustained drug delivery for prolonged periods of time. The use of this type of systems is especially interesting for the treatment of chronic conditions where patient adherence to conventional treatments can be challenging. These systems are normally used for systemic drug delivery. However, IDDS can be used for localised administration to maximise the amount of drug delivered within the active site while reducing systemic exposure. This review will cover current applications of IDDS focusing on the materials used to prepare this type of systems and the main therapeutic areas of application.

Microneedle-assisted transdermal delivery of nanoparticles: Recent insights and prospects

Transdermal delivery of drugs offers an interesting alternative for the administration of molecules that present certain troubles when delivered by the oral route. It can produce systemic effects or perform a local action when the formulation exerts an optimal controlled drug release or a targeted delivery to the specific cell type or site. It also avoids several inconveniences of the oral administration such as the hepatic first pass effect, gastric pH-induced hydrolysis, drug malabsorption because of certain diseases or surgeries, and unpleasant organoleptic properties. Nanomedicine and microneedle array patches (MAPs) are two of the trendiest delivery systems applied to transdermal research nowadays. However, the skin is a protective barrier and nanoparticles (NPs) cannot pass through the intact stratum corneum. The association of NPs and MAPs (NPs@MAPs) work synergistically, since MAPs assist NPs to bypass the outer skin layers, and NPs contribute to the system providing controlled drug release and targeted delivery. Vaccination and tailored therapies have been proposed as fields where both NPs and MAPs have great potential due to inherent characteristics. MAPs conception and easy use could allow self-administration and therefore facilitate mass vaccination campaigns in undeveloped areas with weak healthcare services. Additionally, nanomedicine is being explored as a platform to personalize therapies in such an important field as oncology. In this work we show recent insights that prove the benefits of NPs@MAPs association and analyze the prospects and the discrete interest of the industry in NPs@MAPs, evaluating different limiting steps that restricts NPs@MAPs translation to the clinical practice. This article is categorized under: Nanotechnology Approaches to Biology > NA Therapeutic Approaches and Drug Discovery > NA.

Combination of Dissolving Microneedles with Nanosuspension and Co-Grinding for Transdermal Delivery of Ketoprofen

Ketoprofen is an anti-inflammatory agent that may cause gastric irritation if administered orally. Dissolving microneedles (DMN) can be a promising strategy to overcome this issue. However, ketoprofen has a low solubility; therefore, it is essential to enhance its solubility using certain methods, namely nanosuspension (NS) and co-grinding (CG). This research aimed to formulate DMN containing ketoprofen-loaded NS and CG. Ketoprofen NS was formulated with poly(vinyl alcohol) (PVA) at concentrations of 0.5%, 1%, and 2%. CG was prepared by grinding ketoprofen with PVA or poly(vinyl pyrrolidone) (PVP) at different drug–polymer ratios. The manufactured ketoprofen-loaded NS and CG were evaluated in terms of their dissolution profile. The most promising formulation from each system was then formulated into microneedles (MNs). The fabricated MNs were assessed in terms of their physical and chemical properties. An in vitro permeation study using Franz diffusion cells was also carried out. The most promising MN-NS and MN-CG formulations were F4-MN-NS (PVA 5%-PVP 10%), F5-MN-NS (PVA 5%-PVP 15%), F8-MN-CG (PVA 5%-PVP 15%), and F11-MN-CG (PVA 7.5%-PVP 15%), respectively. The cumulative amounts of drug permeated after 24 h for F5-MN-NS and F11-MN-CG were 3.88 ± 0.46 µg and 8.73 ± 1.40 µg, respectively. In conclusion, the combination of DMN with nanosuspension or a co-grinding system may be a promising strategy for delivering ketoprofen transdermally.

Two-photon polymerization based reusable master template to fabricate polymer microneedles for drug delivery

Microneedle patches have been widely used in a minimally invasive manner for various drug delivery applications. However, for developing these microneedle patches, master molds are required, which are generally made of metal and are very expensive. Two-photon polymerization (2PP) technique can be used for fabricating microneedles more precisely and at a much lower cost. This study reports a novel strategy for developing microneedle master templates using the 2PP method. The main advantage of this technique is that there is no requirement for post-processing after laser writing, and that for the fabrication of polydimethylsiloxane (PDMS) molds, harsh chemical treatments such as silanization are not required. This is a one-step process for manufacturing of microneedle templates which allows easy replication of negative PDMS molds. This is done by adding resin to the master-template and annealing at a specific temperature, thereby making the PDMS peel-off easy and allowing re-use of the master template multiple times. Using this PDMS mold, two types of polyvinyl alcohol (PVA)-rhodamine (RD) microneedle patches were developed, namely, dissolving (D-PVA) and hydrogel (H-PVA) patches and were characterized using suitable techniques. This technique is affordable, efficient and does not require post-processing for development of microneedle templates required for drug delivery applications.•Two photon polymerization can be used for cost-effective fabrication of polymer microneedles for transdermal drug delivery.•Post-processing or surface-modification procedures are not required for these master templates.•Using a simple annealing step, the master template becomes reusable and robust for peeling off polymers like PDMS.

Microneedle-Mediated Permeation Enhancement of Chlorhexidine Digluconate: Mechanistic Insights Through Imaging Mass Spectrometry

PURPOSE

Chlorhexidine digluconate (CHG) is a first-line antiseptic agent typically applied to the skin as a topical solution prior to surgery due to its efficacy and safety profile. However, the physiochemical properties of CHG limits its cutaneous permeation, preventing it from reaching potentially pathogenic bacteria residing within deeper skin layers. Thus, the utility of a solid oscillating microneedle system, Dermapen®, and a CHG-hydroxyethylcellulose (HEC) gel were investigated to improve the intradermal delivery of CHG.

METHODS

Permeation of CHG from the commercial product, Hibiscrub®, and HEC-CHG gels (containing 1% or 4% CHG w/w) was assessed in intact skin, or skin that had been pre-treated with microneedles of different array numbers, using an Franz diffusion cells and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS).

RESULTS

Gels containing 1% and 4% CHG resulted in significantly increased depth permeation of CHG compared to Hibiscrub® (4% w/v CHG) when applied to microneedle pre-treated skin, with the effect being more significant with the higher array number. ToF-SIMS analysis indicated that the depth of dermal penetration achieved was sufficient to reach the skin strata that typically harbours pathogenic bacteria, which is currently inaccessible by Hibiscrub®, and showed potential lateral diffusion within the viable epidermis.

CONCLUSIONS

This study indicates that HEC-CHG gels applied to microneedle pre-treated skin may be a viable strategy to improve the permeation CHG into the skin. Such enhanced intradermal delivery may be of significant clinical utility for improved skin antisepsis in those at risk of a skin or soft tissue infection following surgical intervention.

Preparation and characterization of fast dissolving ulvan microneedles for transdermal drug delivery system

Dissolving microneedles made from natural polymers recently have gained much attention as an efficient transdermal drug delivery system (TDDS). For the first time, ulvan, a sulfated polysaccharide extracted from Ulva lactuca, was applied to fabricate dissolving microneedles through a two-step casting method. The ulvan microneedles (UMNs) made from 4% ulvan solution were in a pyramidal shape with an average height of 655 μm and an aspect ratio of 2.63. The in vitro skin insertion study showed the UMNs could totally penetrate into the porcine skin to the dermis layer and rapidly dissolved as the needle height was reduced by 90.3% after post-insertion of only 2 min. The rapid dissolution of UMNs in situ thus could release the loaded model drugs of rhodamine 6G (R6G) and bovine serum albumin-fluorescein isothiocyanate conjugate (FITC-BSA) in the skin tissue. The in vitro drug release profiles through porcine skin revealed the UMNs markedly enhanced the cumulative release of FITC-BSA. In addition, the UMNs had good biocompatibility towards normal cells of HaCaT and NIH3T3. Briefly, this study demonstrates the rapidly dissolving UMNs could effectively carry the drug into skin and thus can be developed as a potential TDDS in the pharmaceutical and cosmeceutical fields.

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.

Design and fabrication of r-hirudin loaded dissolving microneedle patch for minimally invasive and long-term treatment of thromboembolic disease

Cardiovascular disease is the leading cause of global mortality, with anticoagulant therapy being the main prevention and treatment strategy. Recombinant hirudin (r-hirudin) is a direct thrombin inhibitor that can potentially prevent thrombosis via subcutaneous (SC) and intravenous (IV) administration, but there is a risk of haemorrhage via SC and IV. Thus, microneedle (MN) provides painless and sanitary alternatives to syringes and oral administration. However, the current technological process for the micro mould is complicated and expensive. The micro mould obtained via three-dimensional (3D) printing is expected to save time and cost, as well as provide a diverse range of MNs. Therefore, we explored a method for MNs array model production based on 3D printing and translate it to micro mould that can be used for fabrication of dissolving MNs patch. The results show that r-hirudin-loaded and hyaluronic acid (HA)-based MNs can achieve transdermal drug delivery and exhibit significant potential in the prevention of thromboembolic disease without bleeding in animal models. These results indicate that based on 3D printing technology, MNs combined with r-hirudin are expected to achieve diverse customizable MNs and thus realize personalized transdermal anticoagulant delivery for minimally invasive and long-term treatment of thrombotic disease.

Role of Vitamin K in Intestinal Health

Intestinal diseases, such as inflammatory bowel diseases (IBDs) and colorectal cancer (CRC) generally characterized by clinical symptoms, including malabsorption, intestinal dysfunction, injury, and microbiome imbalance, as well as certain secondary intestinal disease complications, continue to be serious public health problems worldwide. The role of vitamin K (VK) on intestinal health has drawn growing interest in recent years. In addition to its role in blood coagulation and bone health, several investigations continue to explore the role of VK as an emerging novel biological compound with the potential function of improving intestinal health. This study aims to present a thorough review on the bacterial sources, intestinal absorption, uptake of VK, and VK deficiency in patients with intestinal diseases, with emphasis on the effect of VK supplementation on immunity, anti-inflammation, intestinal microbes and its metabolites, antioxidation, and coagulation, and promoting epithelial development. Besides, VK-dependent proteins (VKDPs) are another crucial mechanism for VK to exert a gastroprotection role for their functions of anti-inflammation, immunomodulation, and anti-tumorigenesis. In summary, published studies preliminarily show that VK presents a beneficial effect on intestinal health and may be used as a therapeutic drug to prevent/treat intestinal diseases, but the specific mechanism of VK in intestinal health has yet to be elucidated.

Sustained Release Biodegradable Microneedles of Difluprednate for Delivery to Posterior Eye

Purpose: Difluprednate ophthalmic emulsion (Durezol^®) is currently used for the treatment of anterior uveitis; however, recent studies have shown that difluprednate can treat posterior eye conditions. Topical formulations limit the amount of drug capable of permeating to the posterior segment due to permeation barriers, lacrimation, and lymphatic clearance. Methods: Resomer^®-based microneedle patches were fabricated for difluprednate using poly(acrylic acid) (PAA) for the rapidly dissolvable backing. The patches were analyzed for microneedle uniformity and sharpness using scanning electron microscopy, and the penetration depth was analyzed by confocal microscopy. Failure force necessary to break the microneedles and force needed to penetrate the sclera were analyzed by the texture analyzer. Difluprednate release and trans-scleral permeation studies on microneedles were performed using Franz diffusion cells. Results: The microneedles were uniform, sharp, and penetrated to 500 μm depth on sclera. The microneedles have a failure force proportional to the molecular weight (MW) of the polymer used. There was no correlation between failure force and the penetration force of the microneedles. The PAA backing dissolved within 30-40 min, while release studies showed a matrix diffusion-controlled release over the 7-day study. The amount of drug permeation and retention in the sclera were decreased with an increase in the MW of the Resomer and failure force of each array. Conclusions: Resomer-based microneedles have a potential application for the sustained release of difluprednate for posterior segment conditions.

Immune Response after Skin Delivery of a Recombinant Heat-Labile Enterotoxin B Subunit of Enterotoxigenic Escherichia coli in Mice

Enterotoxigenic Escherichia coli (ETEC) infections have been identified as a major cause of acute diarrhoea in children in developing countries, associated with substantial morbidity and mortality rates. Additionally, ETEC remains the most common cause of acute diarrhea of international travellers to endemic areas. The heat-labile toxin (LT) is a major virulence factor of ETEC, with a significant correlation between the presence of antibodies against LT and protection in infected patients. In the present work, we constructed a recombinant LTB unit (rLTB) and studied the capacity of this toxoid incorporated in microneedles (rLTB-MN) to induce a specific immune response in mice. MN were prepared from aqueous blends of the polymer Gantrez AN^® [poly (methyl vinyl ether-co-maleic anhydride)], which is not cytotoxic and has been shown to possess immunoadjuvant properties. The mechanical and dissolution properties of rLTB-MNs were evaluated in an in vitro Parafilm M^® model and in mice and pig skin ex vivo models. The needle insertion ranged between 378 µm and 504 µm in Parafilm layers, and MNs fully dissolved within 15 min of application inside porcine skin. Moreover, female and male BALB/c mice were immunized through ear skin with one single dose of 5 μg·rLTB in MNs, eliciting significant fecal anti-LT IgA antibodies, higher in female than in male mice. Moreover, we observed an enhanced production of IL-17A by spleen cells in the immunized female mice, indicating a mucosal non-inflammatory and neutralizing mediated response. Further experiments will now be required to validate the protective capacity of this new rLTB-MN formulation against this deadly non-vaccine-preventable disease.

Dissolving microneedle patches loaded with amphotericin B microparticles for localised and sustained intradermal delivery: Potential for enhanced treatment of cutaneous fungal infections

Fungal infections affect millions of people globally and are often unreceptive to conventional topical or oral preparations because of low drug bioavailability at the infection site, lack of sustained therapeutic effect, and the development of drug resistance. Amphotericin B (AmB) is one of the most potent antifungal agents. It is increasingly important since fungal co-infections associated with COVID-19 are frequently reported. AmB is only administered via injections (IV) and restricted to life-threatening infections due to its nephrotoxicity and administration-related side effects. In this work, we introduce, for the first time, dissolving microneedle patches (DMP) loaded with micronised particles of AmB to achieve localised and long-acting intradermal delivery of AmB for treatment of cutaneous fungal infections. AmB was pulverised with poly (vinyl alcohol) and poly (vinyl pyrrolidone) to form micronised particles-loaded gels, which were then cast into DMP moulds to form the tips. The mean particle size of AmB in AmB DMP tips after pulverisation was 1.67 ± 0.01 μm. This is an easy way to fabricate and load microparticles into DMP, as few steps are required, and no organic solvents are needed. AmB had no covalent chemical interaction with the excipients, but the crystallinity of AmB was reduced in the tips. AmB was completely released from the tips within 4 days in vitro. AmB DMP presented inhibition of Candida albicans (CA) and the killing rate of AmB DMP against CA biofilm inside porcine skin reached 100% within 24 h. AmB DMP were able to pierce excised neonatal porcine skin at an insertion depth of 301.34 ± 46.86 μm. Ex vivo dermatokinetic and drug deposition studies showed that AmB was mainly deposited in the dermis. An in vivo dermatokinetic study revealed that the area under curve (AUC_0-inf) values of AmB DMP and IV (Fungizone® bolus injection 1 mg/kg) groups were 8823.0 d∙μg/g and 33.4 d∙μg/g, respectively (264-fold higher). AmB remained at high levels (219.07 ± 102.81 μg/g or more) in the skin until 7 days after the application of AmB DMP. Pharmacokinetic and biodistribution studies showed that AmB concentration in plasma, kidney, liver, and spleen in the AmB DMP group was significantly lower than that in the IV group. Accordingly, this system addressed the systemic side effects of intravenous injection of AmB and localised the drug inside the skin for a week. This work establishes a novel, easy and effective method for long-acting and localised intradermal drug delivery.

Designing a unique feedback mechanism for hydrogel-forming microneedle array patches: a concept study

Although microneedle array patch (MAP) technology is reaching ever closer to regulatory approval, it remains imperative that approaches to further improve patient acceptance are still explored. Addressing this perception, a water-filled reservoir was incorporated into a hydrogel-forming MAP system to provide a novel feedback mechanism. To confirm successful MAP skin insertion, the end user would both hear and feel the rupture of the water-filled reservoir. Interestingly, a 50-µL water-filled reservoir ruptured at 30.27 ± 0.39 N, which has previously been shown as the mean application force for MN insertion in human subjects following appropriate instruction. Importantly, no significant difference in % cumulative permeation of FITC-dextran 10 kDa and fluorescein sodium after 24 h was observed between a 50-µL reservoir and the current method of application that has been successfully used in both in vitro and in vivo studies (p > 0.05). Therefore, as drug delivery was not affected, this proof-of-concept study has shown that a water-filled reservoir feedback mechanism has the potential to serve as a viable tool for consistent MAP skin insertion.

Translation of Polymeric Microneedles for Treatment of Human Diseases: Recent Trends, Progress, and Challenges

The ongoing search for biodegradable and biocompatible microneedles (MNs) that are strong enough to penetrate skin barriers, easy to prepare, and can be translated for clinical use continues. As such, this review paper is focused upon discussing the key points (e.g., choice polymeric MNs) for the translation of MNs from laboratory to clinical practice. The review reveals that polymers are most appropriately used for dissolvable and swellable MNs due to their wide range of tunable properties and that natural polymers are an ideal material choice as they structurally mimic native cellular environments. It has also been concluded that natural and synthetic polymer combinations are useful as polymers usually lack mechanical strength, stability, or other desired properties for the fabrication and insertion of MNs. This review evaluates fabrication methods and materials choice, disease and health conditions, clinical challenges, and the future of MNs in public healthcare services, focusing on literature from the last decade.

Recent Advances in Microneedle Platforms for Transdermal Drug Delivery Technologies

In many clinical applications, the transdermal route is used as an alternative approach to avoid the significant limitations associated with oral drug delivery. There is a long history for drug delivery through the skin utilizing transdermal microneedle arrays. Microneedles are reported to be versatile and very efficient devices. This technique has spurred both industrial and scientific curiosity, due to its outstanding characteristics such as painless penetration, affordability, excellent medicinal efficiency, and relative protection. Microneedles possess outstanding properties for diverse biomedical uses such as the delivery of very large substances with ionic and hydrophilic physicochemical properties. Importantly, microneedles are applicable in numerous biomedical fields such as therapy, diagnosis, and vaccine administration. Microneedles are emerging tools that have shown profound potential for biomedical applications. Transdermal microneedle technologies are likely to become a preferred route of therapeutic substances administration in the future since they are effective, painless, and affordable. In this review, we summarize recent advances in microneedles for therapeutic applications. We explore their constituent materials and fabrication methods that improve the delivery of critical therapeutic substances through the skin. We further discuss the practicality of advanced microneedles used as drug delivery tools.

Peeking into the future: Transdermal patches for the delivery of micronutrient supplements

Adhesive transdermal delivery devices (patches) are the latest advancement in the delivery of micronutrients. A common challenge in this mode of delivery includes surpassing the physical barrier of the skin, while the use of microneedle (MN) arrays, or pretreatment of the skin with MNs can be used for a more successful outcome. Limited evidence from human non-randomized trials point to a sub-optimal delivery of iron through skin patches, although no MNs were used in those trials. Moreover, the use of patches proved inefficient in reducing the prevalence of micronutrient deficiencies in post-bariatric surgery patients. The delivery of minerals was tested in animals using reservoir-type patches, gel/foam patches, MNs and iontophoresis. Results from these studies indicate a possible interplay between the dietary manipulation of mineral intake and the trandermal delivery through patches, as reduced, or regular dietary intake seems to increase absorption of the delivered mineral. Moreover, intervention duration could be an additional factor affecting absorption. Possible adverse events from animal studies include redness or decolorization of skin. In vitro and ex vivo studies revealed an increase in vitamin K, vitamin D and iron delivery, however a variety of methodological discrepancies are apparent in these studies, including the models used, the length of the MNs, the duration of application, temperature control and total micronutrient load in the patches. Data indicate that pre-treating the skin with MNs might enhance delivery; however, a source of variability in the observed effectiveness might include the different molecular weights of the nutrients used, skin factors, the ideal tip radius and MN wall thickness. Non-human studies indicate a potential benefit in combining MN with iontophoresis. Presently, the transdermal delivery seems promising with regard to nutritional supplementation, however limited evidence exists for its efficacy in humans. Future research should aim to control for both intervention duration, possible deficiency status and for the dietary intake of participants.

HPLC method for levothyroxine quantification in long-acting drug delivery systems. Validation and evaluation of bovine serum albumin as levothyroxine stabilizer

Deficiency of thyroid hormones (hypothyroidism) is treated with oral levothyroxine (LEVO). However, the effectiveness of oral administration is highly dependent on the co-administration of food and other drugs. This factor, in combination with the chronic nature of this condition, mean that there are concerns with patient compliance. Development of long acting formulations to treat hypothyroidism could potentially solve this problem. However, LEVO instability in solution could be problematic. In order to develop long acting LEVO delivery systems in vitro drug release experiments should be carried out. However, short term LEVO stability in aqueous solution will prevent this. BSA was used as a stabiliser for LEVO; extending the stability of the drug in aqueous solutions from a few hours to 2 weeks. In order to achieve this, the required concentration of the protein was 0.1% w/v. Subsequently, an HPLC method capable of separating LEVO from the protein was developed and validated following ICH guidelines. The analysis was carried out using a reverse phase HPLC method on an Agilent 1220 Infinity II LC system. The column used to achieve separation was a Zorbax Eclipse plus C18 (95 Å pore size, 250 mm length x 4.6 mm internal diameter; 5 μm particle size). The mobile phase used was composed of acetonitrile and 0.1% trifluoroacetic acid at a ratio of 50:50% v/v. UV detection of LEVO sodium was carried out at 225 nm. The retention time for the drug was 6.6 minutes. The method showed a limit of detection of 0.03 μg/mL and a limit of quantification of 0.09 μg/mL. Finally, this method was used to evaluate the release from implants containing 20% w/w of LEVO. These devices were prepared using a solvent casting method with poly(caprolactone) and LEVO. These devices showed an initial burst release over the first 3 days. Subsequently, they were capable of providing a linear release rate over the following 25 days.

Fabrication, evaluation and applications of dissolving microneedles

In recent years, transdermal preparations have emerged as one of the most promising modes of administration. In particular, dissolving microneedles have attracted extensive attention because of their painlessness, safety, high delivery efficiency and easily operation for patients. This article mainly reviews the preparation methods, the types of matrix polymer materials, the content of dissolving microneedles performance testing, and the applications of dissolving microneedles. It is expected to lay a solid knowledge foundation for the in-depth study of the dissolving microneedles.

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

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

Innate local response and tissue recovery following application of high density microarray patches to human skin

The development of microarray patches for vaccine application has the potential to revolutionise vaccine delivery. Microarray patches (MAP) reduce risks of needle stick injury, do not require reconstitution and have the potential to enhance immune responses using a fractional vaccine dose. To date, the majority of research has focused on vaccine delivery with little characterisation of local skin response and recovery. Here we study in detail the immediate local skin response and recovery of the skin post high density MAP application in 12 individuals receiving 3 MAPs randomly assigned to the forearm and upper arm. Responses were characterised by clinical scoring, dermatoscopy, evaporimetry and tissue viability imaging (TiVi). MAP application resulted in punctures in the epidermis, a significant transepidermal water loss (TEWL), the peak TEWL being concomitant with peak erythema responses visualised by TiVi. TEWL and TiVi responses reduced over time, with TEWL returning to baseline by 48 h and erythema fading over the course of a 7 day period. As MAPs for vaccination move into larger clinical studies more variation of individual subject phenotypic or disease propensity will be encountered which will require consideration both in regard to reliability of dose delivery and degree of inherent skin response.

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

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

Microneedle-Based Delivery: An Overview of Current Applications and Trends

Microneedle arrays (MNA) are considered as one of the most promising resources to achieve systemic effects by transdermal delivery of drugs. They are designed as a minimally invasive, painless system which can bypass the stratum corneum, overcoming the potential drawbacks of subcutaneous injections and other transdermal delivery systems such as chemical enhancers, nano and microparticles, or physical treatments. As a trendy field in pharmaceutical and biomedical research, its applications are constantly evolving, even though they are based on very well-established techniques. The number of molecules administered by MNA are also increasing, with insulin and vaccines administration being the most investigated. Furthermore, MNA are being used to deliver cells and applied in other organs and tissues like the eyes and buccal mucosae. This review intends to offer a general overview of the current state of MNA research, focusing on the strategies, applications, and types of molecules delivered recently by these systems. In addition, some information about the materials and manufacturing processes is presented and safety data is discussed.

Novel Design Approaches in the Fabrication of Polymeric Microarray Patches via Micromoulding

The focus on novel systems for transdermal delivery of therapeutic agents has increased considerably over recent years, as this administration route comes with many advantages. Polymeric microarray patches (MAPs) are minimally invasive devices that enable systemic delivery of a wide range of drugs by overcoming the outer skin barrier. Conventionally, MAPs fabricated by micromoulding have a low needle density. In this study, the performance of hydrogel-forming MAPs cast using novel industrially manufactured micromoulds with a high needle density (600 needles/0.75 cm²) was compared to that of MAPs obtained using conventional moulds with a lower density (196 needles/0.89 cm²). Surrounding holders for micromoulds were designed for time-efficient fabrication of MAPs. The influence of needle densities on mechanical strength, insertion efficiency and in vitro permeation of ibuprofen sodium (IBU) was analysed. Insertion of both MAPs into an artificial skin model and neonatal porcine skin was comparable. No significant difference was observed in permeation studies of IBU (p > 0.05), with a delivery of 8.7 ± 1.7 mg for low-density and 9.5 ± 0.1 mg for high-density MAPs within 24 h. This highlights the potential of these novel micromoulds for manufacturing polymeric MAPs with a higher needle density for future applications.

Is Transdermal Multivitamin Patch Effective in Gastric Bypass Patients?

BACKGROUND

Laparoscopic Roux-en-Y gastric bypass (LRYGB) patients are recommended to take multiple oral vitamin supplements daily. Transdermal multivitamin patches are being advertised as an alternative for use in bariatric patients with no data to support their efficacy. The purpose of this study was to evaluate response to daily transdermal use of multivitamin patch after LRYGB and to compare them with a control group of similar patients who used oral supplements.

METHODS

A retrospective review was carried out on patients who had LRYGB at a community hospital from February 2015 to February 2019. Patients who had completed preoperative and annual postoperative bariatric laboratory tests were included. They were divided into patch and pill (control) group.

RESULTS

Seventeen patients were included in the patch and 27 in the pill group. Patients in each group used either patch or pills for 12 months and they were 1 year post LRYGB. Fourteen patients (82.35%) in patch group and 11 patients (40.74%) in pill group had at least 1 deficiency at annual postoperative blood work (P = .0116). Vitamin D deficiency was seen in 81% patients in patch group vs 36% in the pill group (P = .0092). Statistically significant lower postoperative serum concentrations of vitamin D, B1, and B12 were seen in the patch group.

CONCLUSIONS

Multivitamin patch users are more likely to have vitamin D deficiency and lower serum concentration of various vitamins and minerals. Future large studies are needed on the efficacy of multivitamin patches before they can be recommended to bariatric patient population.

Influence of molecular weight on transdermal delivery of model macromolecules using hydrogel-forming microneedles: potential to enhance the administration of novel low molecular weight biotherapeutics

With a view to improve the current monoclonal antibody-based therapies dominating the pharmaceutical market, low molecular weight (MW) protein-based macromolecules, such as recombinant antibody fragments, typically within the range of 10-70 kDa, have been developed. Previously, our group successfully delivered Avastin®, a monoclonal antibody (mAb) across the skin using hydrogel-forming microneedles (MN). However, it is thought that this delivery system can be further enhanced using novel, lower MW biomolecules. To address this perception, in the current study, FITC-dextran of different MWs (10, 70 and 150 kDa) was used to model the transdermal delivery of low MW biotherapeutics and mAbs with MWs of approximately 150 kDa. Conversely, fluorescein sodium was the compound selected to model hydrophilic, low MW drugs. As expected, fluorescein sodium produced the greatest cumulative permeation (637.4 ± 42.69 μg). The amounts of FITC-dextran 10 kDa and 150 kDa which permeated across neonatal porcine skin in vitro were 462.17 ± 65.85 μg and 213.54 ± 15.19 μg after 24 h, respectively. The results collated here suggest that the delivery of emerging novel biotherapeutics, via'super swelling' hydrogel-forming MNs, have the potential to result in greater permeation across human skin, compared to the delivery of mAbs delivered via the same route.

Vitamin K as a Diet Supplement with Impact in Human Health: Current Evidence in Age-Related Diseases

Vitamin K health benefits have been recently widely shown to extend beyond blood homeostasis and implicated in chronic low-grade inflammatory diseases such as cardiovascular disease, osteoarthritis, dementia, cognitive impairment, mobility disability, and frailty. Novel and more efficient nutritional and therapeutic options are urgently needed to lower the burden and the associated health care costs of these age-related diseases. Naturally occurring vitamin K comprise the phylloquinone (vitamin K1), and a series of menaquinones broadly designated as vitamin K2 that differ in source, absorption rates, tissue distribution, bioavailability, and target activity. Although vitamin K1 and K2 sources are mainly dietary, consumer preference for diet supplements is growing, especially when derived from marine resources. The aim of this review is to update the reader regarding the specific contribution and effect of each K1 and K2 vitamers in human health, identify potential methods for its sustainable and cost-efficient production, and novel natural sources of vitamin K and formulations to improve absorption and bioavailability. This new information will contribute to foster the use of vitamin K as a health-promoting supplement, which meets the increasing consumer demand. Simultaneously, relevant information on the clinical context and direct health consequences of vitamin K deficiency focusing in aging and age-related diseases will be discussed.

Transcutaneous immunization of recombinant Staphylococcal enterotoxin B protein using a dissolving microneedle provides potent protection against lethal enterotoxin challenge

Staphylococcal enterotoxin B (SEB) produced by the Staphylococcus aureus bacteriumis most commonly associated with food poisoning and is known to also cause toxic shock syndrome. Currently, no approved vaccine or specific drug is available to treat SEB intoxication. In this study, we fabricated dissolving microneedles (MNs) loaded with recombinant SEB (rSEB) protein, and evaluated its characteristics, including dissolution profile, protein particle size, insertion depth, antigen retention time in vivo, and skin irritation. Our results showed that rSEB protein-loaded dissolving MNs made of chondroitin sulfate (2%) and trehalose (0.8%) could easily penetrate into the mouse skin within 5 min. The rSEB particle size was unchanged before and after MN fabrication. The skin penetration depth of the MNs was 260 µm. Moreover, the MNs also significantly extended the antigen retention time in vivo. rSEB protein-loaded dissolving MNs also triggered slight erythema at the beginning of administration, but this erythema disappeared within a few hours. More importantly, we investigated the immunogenicity and protective efficacy of rSEB protein-loaded dissolving MNs. Challenge studies in mice revealed that mice in full-dose MN group had a high level of SEB specific antibody response thatprovided100% protection against a lethal SEB toxin challenge. However, there was only 60% protection observed in mice that were in the half-dose MN (dose sparing) group. We also determined the pathological alterations in the tissues of the immunized mice. Taken together, these dissolving MNs may present a promising transcutaneous immunization strategy for treating SEB intoxication.

Priorities in applied research to ensure programmatic success in the global elimination of canine rabies

The elimination of human rabies mediated by dogs is attainable in concept, based upon current sensitive and specific diagnostic methods, existing safe and effective human and veterinary vaccines and a sound virological, pathological and epidemiological understanding of the disease. Globally, all developed countries achieved this goal. Regionally, major progress occurred throughout the Americas. However, less advancement is evident in Africa and Asia. Our objective was to concentrate upon those salient improvements to extant tools and methods over the next five years which could assist and simplify the task for both those developing countries that have already begun the process, as well as other localities in the earlier stages of consideration. We considered several categories of applied research which could be accomplished in the short term, based upon the available scientific evidence and recent recommendations from subject matter experts and key opinion leaders, focused upon perceived major limitations to prior program success. Areas of concentration included: laboratory-based surveillance, pathogen detection and characterization; human rabies prophylaxis; veterinary biologics; implementation of canine vaccination; and oral vaccination of free-ranging community dogs. Further real-time application in these core areas with proven techniques and technology would simplify attaining not only the global goal focused subtly upon human mortality, but the actual elimination of canine rabies as well.