Human studies with microneedles for evaluation of their efficacy and safety

Translation from Preclinical Research to Clinical Trials: Transdermal Drug Delivery for Neurodegenerative and Mental Disorders

Neurodegenerative diseases (NDs), particularly dementia, provide significant problems to worldwide healthcare systems. The development of therapeutic materials for various diseases has a severe challenge in the form of the blood-brain barrier (BBB). Transdermal treatment has recently garnered widespread favor as an alternative method of delivering active chemicals to the brain. This approach has several advantages, including low invasiveness, self-administration, avoidance of first-pass metabolism, preservation of steady plasma concentrations, regulated release, safety, efficacy, and better patient compliance. Topics include the transdermal method for therapeutic NDs, their classification, and the mechanisms that allow the medicine to enter the bloodstream through the skin. The paper also discusses the obstacles and potential outcomes of transdermal therapy, emphasizing the benefits and drawbacks of different approaches.

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.

An antioxidative, green and safe nanofibers-based film containing pullulan, sodium hyaluronate and Ganoderma lucidum fermentation for enhanced skincare

Dry masks made of natural active ingredients that are packaged in sustainable paper and free of irritating additives (e.g. preservatives, stabilizers) are a trend in the concept of healthy skincare, which possess the advantages of portability, safety and environmental friendliness. The bioactive ingredients obtained from natural plant fermentation are gradually becoming an important alternative additive for facial skincare. Herein, a novel dry facial healthcare mask was fabricated by electrospinning incorporating natural ingredients including pullulan (Pu), sodium hyaluronate (SH), and Ganoderma lucidum fermentation (GLF). The morphology, dissolving capacity, bioactivity, and safety of the obtained masks were investigated in vitro, and their antioxidation and moisturizing activities were verified at the cellular level. The results indicated that the fibrillary films based on pullulan could be dissolved in water within 20 s with good water retention capacity and film with high concentration of GLF (Pu/SH/GLF-3) could scavenge 79 % of DPPH. The films had good ability to resist microbial contamination and non-eye irritation via observing colony growth for 12 months after ultraviolet sterilization and the ocular irritation test of chicken chorioallantoic membrane. Meanwhile, cell experiments further confirmed that they did not exhibit cytotoxicity and could increase the expression of proteins related to moisturizing and antioxidation. The fascinating films have promising application prospects in cosmetic masks. This work may enrich the use of natural materials in skincare products and provide a green development direction for the light chemical industry.

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.

Industrial perspectives for personalized microneedles

Microneedles and, subsequently, microneedle arrays are emerging miniaturized medical devices for painless transdermal drug delivery. New and improved additive manufacturing methods enable novel microneedle designs to be realized for preclinical and clinical trial assessments. However, current literature reviews suggest that industrial manufacturers and researchers have focused their efforts on one-size-fits-all designs for transdermal drug delivery, regardless of patient demographic and injection site. In this perspective article, we briefly review current microneedle designs, microfabrication methods, and industrialization strategies. We also provide an outlook where microneedles may become personalized according to a patient's demographic in order to increase drug delivery efficiency and reduce healing times for patient-centric care.

Microneedles and Their Application in Transdermal Delivery of Antihypertensive Drugs-A Review

One of the most cutting-edge, effective, and least invasive pharmaceutical innovations is the utilization of microneedles (MNs) for drug delivery, patient monitoring, diagnostics, medicine or vaccine delivery, and other medical procedures (e.g., intradermal vaccination, allergy testing, dermatology, and blood sampling). The MN-based system offers many advantages, such as minimal cost, high medical effectiveness, comparatively good safety, and painless drug application. Drug delivery through MNs can possibly be viewed as a viable instrument for various macromolecules (e.g., proteins, peptides, and nucleic acids) that are not efficiently administered through traditional approaches. This review article provides an overview of MN-based research in the transdermal delivery of hypertensive drugs. The critical attributes of microneedles are discussed, including the mechanism of drug release, pharmacokinetics, fabrication techniques, therapeutic applications, and upcoming challenges. Furthermore, the therapeutic perspective and improved bioavailability of hypertensive drugs that are poorly aqueous-soluble are also discussed. This focused review provides an overview of reported studies and the recent progress of MN-based delivery of hypertensive drugs, paving the way for future pharmaceutical uses. As MN-based drug administration bypasses first-pass metabolism and the high variability in drug plasma levels, it has grown significantly more important for systemic therapy. In conclusion, MN-based drug delivery of hypertensive drugs for increasing bioavailability and patient compliance could support a new trend of hypertensive drug delivery and provide an alternative option, overcoming the restrictions of the current dosage forms.

Clinical Benefit and Safety of Microneedle Patches Composed of Magnesium: A Pilot Study in Acne Patients

Magnesium (Mg) is a newly investigated biomaterial that corrodes physiologically in water, resulting in evolved hydrogen with beneficial effects of anti-inflammation and acceleration of the wound healing process. In addition, Mg itself has antimicrobial activity against Cutibacterium acnes, which play a pathogenic role in developing inflammatory acne. This study aimed to evaluate efficacy and safety of a newly developed magnesium microneedle (Mg MN) patch, with a needle length of 0.25 mm, on acne and widened pores. A total of 19 patients with mild to moderate acne and receiving no topical or oral treatment was enrolled in the study. Mg MN patches were applied to inflammatory acne lesions and widened pores on both cheeks and nose. Researchers evaluated efficacy by counting acne lesions and measuring pore sizes, porphyrin level, and sebum secretion. Any objective or subjective adverse events were recorded during the study. The number of acne lesions and scores improved significantly within seven days ( $p<0.01$ ). The porphyrin level tended to decrease over 12 weeks, although pore size and sebum secretion showed unsatisfactory results. No adverse reactions were noted during the study period. Mg MN patches can be useful in treating inflammatory acne lesions, and they are safe to use. For the improvement of widened pores, modification of needle length or a combination of topical agents may be required.

Magnesium microneedle patches for under‐eye wrinkles

Microneedling is a common cosmetic procedure for improvement of wrinkles, acne, scars, and other conditions. Various microneedle (MN) patches have been developed as home care therapy for wrinkles and skin texture. Most of them are made of soluble and absorbable needles. To evaluate the efficacy and safety of non‐absorbable magnesium (Mg) MN patches on under‐eye wrinkles. A total of 20 subjects aged 27–58 years was enrolled in the study. The subjects applied Mg MN patches on the under‐eye wrinkle area for 1–2 h every other night for 12 weeks. The evaluation comprised grading by clinicians, measuring the wrinkle index with a facial analyzer, and measuring the dermal thickness of the under‐eye area with ultrasonography. Any adverse events and discomfort were addressed during the study. The application of Mg MN patches on under‐eye areas showed improvements in under‐eye grading scale, wrinkle index, and dermal thickness after 12 weeks. The mean grading scale significantly improved after 8 weeks of application (p < 0.01). The wrinkle index showed significant improvement after 12 weeks on the right under‐eye area (p < 0.05). The dermal thickness of the under‐eye area tended to increase, but no statistically significant changes were observed. Non‐absorbable Mg MN patches can be used for under‐eye wrinkles with minimal discomfort.

Microneedle-Based Vaccine Delivery: Review of an Emerging Technology

Vaccination has produced a great improvement to the global health by decreasing/eradicating many infectious diseases responsible for significant morbidity and mortality. Thanks to vaccines, many infections affecting childhood have been greatly decreased or even eradicated (smallpox, measles, and polio). That is why great efforts are made to achieve mass vaccination against COVID-19. However, developed vaccines face many challenges with regard to their safety and stability. Moreover, needle phobia could prevent a significant proportion of the population from receiving vaccines. In this context, microneedles (MNs) could potentially present a solution to address these challenges. MNs represent single dose administration systems that do not need reconstitution or cold-chain storage. Being self-administered, pain-free, and capable of producing superior immunogenicity makes them a more attractive alternative. This review explores microneedles’ types, safety, and efficacy in vaccine delivery. Preclinical and clinical studies for microneedle-based vaccines are discussed and patent examples are included.

Pharmacokinetic Evaluation of a Novel Donepezil-Loaded Dissolving Microneedle Patch in Rats

Research on the development of dissolving microneedles (DMNs) has focused on bolus drug delivery, with little attention on sustained release. Here, we evaluated the sustained release, absorption pattern, and effective drug permeation of a novel donepezil-loaded DMN patch through an in vivo investigation on rats. The applications of DMN patches to the shaved skin of rats for 1 week and 1 h were compared with oral donepezil administration to assess their sustained release capabilities. We used a validated liquid chromatography–tandem mass spectrometry method to quantify donepezil in the plasma. We found that the microneedle arrays effectively delivered donepezil across the skin, with dissolution observed within 1 h of application. Furthermore, skin irritation test showed that the patches produced no irritation response. The DMN arrays also effectively increased drug permeation and demonstrated sustained release and absorption of donepezil from DMN patches. These patches allow extended dosing intervals, reduced gastrointestinal adverse effects, and convenient self-administration to mitigate poor drug compliance, making them beneficial for the treatment of elderly patients with Alzheimer’s disease.

Microneedles enable the development of skin-targeted vaccines against coronaviruses and influenza viruses

Throughout the COVID-19 pandemic, many have seriously worried that the plus burden of seasonal influenza that might create a destructive scenario, resulting in overwhelmed healthcare capacities and onwards loss of life. Many efforts to develop a safe and efficacious vaccine to prevent infection by coronavirus and influenza, highlight the importance of vaccination to combat infectious pathogens. While vaccines are traditionally given as injections into the muscle, microneedle (MN) patches designed to precisely deliver cargos into the cutaneous microenvironment, rich in immune cells, provide a noninvasive and self-applicable vaccination approach, reducing overall costs and improving access to vaccines in places with limited supply. The current review aimed to highlight advances in research on the development of MNs-mediated cutaneous vaccine delivery. Concluding remarks and challenges on MNs-based skin immunization are also provided to contribute to the rational development of safe and effective MN-delivered vaccines against these emerging infectious diseases.

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.

Continuous monitoring of diabetes with an integrated microneedle biosensing device through 3D printing

Diabetes is a prevalent chronic metabolic disease with multiple clinical manifestations and complications, and it is among the leading causes of death. Painless and continuous monitoring of interstitial glucose is highly desirable for diabetes management. Here we unprecedentedly show continuous monitoring of diabetes with an integrated microneedle biosensing device. The device was manufactured with a 3D printing process, a microfabrication process, an electroplating process, and an enzyme immobilization step. The device was inserted into the dermis layer of mouse skin and showed accurate sensing performance for monitoring subcutaneous glucose levels in normal or diabetic mice. The detection results were highly correlated with those obtained from a commercial blood glucose meter. We anticipate that the study could open exciting avenues for monitoring and managing diabetes, alongside fundamental studies of subcutaneous electronic devices.

Development of a thermostable oxytocin microneedle patch

Oxytocin is a nonapeptide hormone used in labor to initiate uterine contractions and to prevent and treat postpartum hemorrhage. Oxytocin is currently administered by injection and requires refrigerated transport and storage, which limits access, especially during home birth in developing countries. Here, we propose a thermostable, simple-to-administer microneedle (MN) patch for rapid delivery of oxytocin suitable for use by healthcare workers with limited training, like traditional birth attendants. Oxytocin (10 IU, 16.8 μg) coated onto stainless steel MN arrays was released into skin within 1-5 min after manual insertion. Among tested excipients, polyacrylic acid was best at stabilizing oxytocin stored at 75% relative humidity, with no significant loss for up to 2 months at 40 °C. Under desiccated conditions, MNs coated with formulations containing trehalose in a mixture of citrate buffer and ethanol retained 75% oxytocin potency at 40 °C for 12 months; the commercial oxytocin product Pitocin® was reduced to 35% potency under these conditions. These findings support development of MN patches for oxytocin administration with improved ease of use, extended thermostability and simplified logistics to enable greater access to this life-saving medicine.

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.

Immunologic mechanisms of seasonal influenza vaccination administered by microneedle patch from a randomized phase I trial

In a phase 1 randomized, single-center clinical trial, inactivated influenza virus vaccine delivered through dissolvable microneedle patches (MNPs) was found to be safe and immunogenic. Here, we compare the humoral and cellular immunologic responses in a subset of participants receiving influenza vaccination by MNP to the intramuscular (IM) route of administration. We collected serum, plasma, and peripheral blood mononuclear cells in 22 participants up to 180 days post-vaccination. Hemagglutination inhibition (HAI) titers and antibody avidity were similar after MNP and IM vaccination, even though MNP vaccination used a lower antigen dose. MNPs generated higher neuraminidase inhibition (NAI) titers for all three influenza virus vaccine strains tested and triggered a larger percentage of circulating T follicular helper cells (CD4 + CXCR5 + CXCR3 + ICOS + PD-1+) compared to the IM route. Our study indicates that inactivated influenza virus vaccination by MNP produces humoral and cellular immune response that are similar or greater than IM vaccination.

A microneedle platform for buccal macromolecule delivery

Alternative means for drug delivery are needed to facilitate drug adherence and administration. Microneedles (MNs) have been previously investigated transdermally for drug delivery. To date, drug loading into MNs has been limited by drug solubility in the polymeric blend. We designed a highly drug-loaded MN patch to deliver macromolecules and applied it to the buccal area, which allows for faster delivery than the skin. We successfully delivered 1-mg payloads of human insulin and human growth hormone to the buccal cavity of swine within 30 s. In addition, we conducted a trial in 100 healthy volunteers to assess potential discomfort associated with MNs when applied in the oral cavity, identifying the hard palate as the preferred application site. We envisage that MN patches applied on buccal surfaces could increase medication adherence and facilitate the painless delivery of biologics and other drugs to many, especially for the pediatric and elderly populations.

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.

Trends of microneedle technology in the scientific literature, patents, clinical trials and internet activity

The powerful and intriguing idea that drives the emerging technology of microneedles-shrinking the standard needle to a micron scale-has fostered an entire field of microneedle study and subsequent exponential growth in research and product development. Originally enabled by microfabrication tools derived from the microelectronic industry, microneedles are now produced through a number of methods in a variety of forms including solid, coated, dissolvable, and hollow microneedles. They are used to deliver a broad spectrum of molecules, including small molecules, biomolecules, and vaccines, as well as various forms of energy into the skin, eye, and other tissues. Microneedles are also being exploited for use in diagnostics, as well as additional medical, cosmetic, and other applications. This review elucidates the relative roles of different aspects of microneedle technology development, as shown through scientific papers, patents, clinical studies, and internet/social media activity. Considering >1000 papers, 750 patents, and almost 80 clinical trials, we analyze different attributes of microneedles such as usage of microneedles, types of microneedles, testing environment, types of patent claims, and phases of clinical trials, as well as which institutions and people in academia and industry from different locations and in different journals are publishing, patenting, and otherwise studying the potential of microneedles. We conclude that there is robust and growing activity in the field of microneedles; the technology is rapidly developing and being used for novel applications to benefit human health and well-being.

Advances in non and minimal-invasive transcutaneous delivery of immunotherapy for cancer treatment

Cancer research has focused on figuring out what was the difference between cancer cells and the tissues within which cancer arose and developing targeted treatments for those differences. With FDA-approved treatments for more ten different cancers and more than thousand new clinical trials, immunotherapy has recently emerged as the most promising area of cancer research by improving efficacy and controlling the adverse effects. Transcutaneous delivery drug delivery offers a number of advantages for the patient because of not only its noninvasive and convenient nature but also factors such as avoidance of first-pass metabolism and prevention of gastrointestinal degradation. The purpose of this review was to highlight technological recent approaches to non and minimal-invasive delivery of immunotherapy for cancer treatment. Finally, some practical considerations and discussions for future studies in the field of transdermal immunomodulation are also included.

Cutaneous vaccination ameliorates Zika virus-induced neuro-ocular pathology via reduction of anti-ganglioside antibodies

Zika virus (ZIKV) causes moderate to severe neuro-ocular sequelae, with symptoms ranging from conjunctivitis to Guillain-Barré Syndrome (GBS). Despite the international threat ZIKV poses, no licensed vaccine exists. As ZIKV and DENV are closely related, antibodies against one virus have demonstrated the ability to enhance the other. To examine if vaccination can confer robust, long-term protection against ZIKV, preventing neuro-ocular pathology and long-term inflammation in immune-privileged compartments, BALB/c mice received two doses of unadjuvanted inactivated whole ZIKV vaccine (ZVIP) intramuscularly (IM) or cutaneously with dissolving microneedle patches (MNP). MNP immunization induced significantly higher B and T cell responses compared to IM vaccination, resulting in increased antibody titers with greater avidity for ZPIV as well as increased numbers of IFN-γ, TNF-α, IL- and IL-4 secreting T cells. When compared to IM vaccination, antibodies generated by cutaneous vaccination demonstrated greater neutralization activity, increased cross-reactivity with Asian and African lineage ZIKV strains (PRVABC59, FLR, and MR766) and Dengue virus (DENV) serotypes, limited ADE, and lower reactivity to GBS-associated gangliosides. MNP vaccination effectively controlled viremia and inflammation, preventing neuro-ocular pathology. Conversely, IM vaccination exacerbated ocular pathology, resulting in uncontrolled, long-term inflammation. Importantly, neuro-ocular pathology correlated with anti-ganglioside antibodies implicated in demyelination and GBS. This study highlights the importance of longevity studies in ZIKV immunization, and the need of exploring alternative vaccination platforms to improve the quality of vaccine-induced immune responses.

Patchless administration of canine influenza vaccine on dog's ear using insertion-responsive microneedles (IRMN) without removal of hair and its in vivo efficacy evaluation

Microneedles provide the advantages of convenience and compliance by avoiding the pain and fear of needles that animals often experience. Insertion-responsive microneedles (IRMN) were used for administration to a hairy dog without removing the dog's hair. Canine H3N2 vaccine was administered with IRMN attached to the dog's ears ex vivo and the conventional microneedle system (MN) was administered for 15 min to compare puncture performance and delivery efficiency. The vaccine was also administered to compare antibody formation using IRMN with the use of intramuscular injection. The veterinarian observed the behavior of the dog during the course of the administration and compared the response to IRMN with that of intramuscular administration. The tips of IRMN were separated from the base and delivered into the hairy skin successfully. Puncture performance of IRMN were the same as that of coated microneedles (95%), but delivery efficiency of IRMN were 95% compared to less than 1% for coated microneedles. The H3N2 vaccine inoculated into the dog's ears showed the same antibody formation as the intramuscular injection. The dog appeared to be more comfortable with IRMN administration compared to syringe administration. IRMN are the first microneedle system to deliver a canine vaccine successfully into a hairy dog without removal of the dog's hair. The use of IRMN can provide both convenience and compliance for both the dog and the owner.

Safe Coated Microneedles with Reduced Puncture Occurrence after Administration

The goal of this study is the preparation of safer coated microneedles so that tips remaining after the initial use are less likely to be reinserted on a second use. Twelve groups of uncoated microneedles (u-MNs) were prepared from the combination of three different aspect ratios (height to base width) and four kinds of polymer (polyethylene (PE), polypropylene (PP), nylon and polylactic acid (PLA)). After coating the u-MNs with polyvinyl alcohol formulation to make coated MNs (c-MNs), the force displacement of the u-MNs and the c-MNs was measured. The aspect ratio was reduced from 2.2, 2.5 and 3.0 with u-MNs to 1.3, 1.4 and 1.6 with c-MNs, respectively, after the coating formulation was applied to the MNs. All PLA MNs had a puncture performance of more than 95%. However, the puncture performance of u-MNs made of PE and of PP with a 3.0 aspect ratio was only 8% and 53%, respectively, whereas the rates of c-MNs made of PE and of PP were 82% and 95%, respectively. In animal experiments with PP MNs with a 3.0 aspect ratio, the 59% rate of puncture performance with u-MNs increased to above 96% with c-MNs and fell to 13% for r-MNs. Safe c-MNs can overcome the disadvantages of standard c-MNs by reducing the probable contamination of remaining tips after use. Safe c-MNs have advantages over standard c-MNs in terms of humidity resistance, reasonable cost, sterilization process and short processing time through the separate process of u-MN preparation and simple dip-coating.

Progress in microneedle array patch (MAP) for vaccine delivery

A microneedle array patch (MAP) has been developed as a new delivery system for vaccines. Preclinical and clinical trials with a vaccine MAP showed improved stability, safety, and immunological efficacy compared to conventional vaccine administration. Various vaccines can be delivered with a MAP. Currently, microneedle manufacturers can mass-produce pharmaceutical MAP and cosmetic MAP and this mass-production system can be adapted to produce a vaccine MAP. Clinical trials with a vaccine MAP have shown comparable efficacy with conventional administration, and discussions about regulations for a vaccine MAP are underway. However, there are concerns of reasonable cost, mass production, efficacy, and safety standards that meet FDA approval, as well as the need for feedback regarding the best method of administration. Currently, microneedles have been studied for the delivery of many kinds of vaccines, and preclinical and clinical studies of vaccine microneedles are in progress. For the foreseeable future, some vaccines will continue to be administered with syringes and needles while the use of a vaccine MAP continues to be improved because of the advantages of less pain, self-administration, improved stability, convenience, and safety.

A microneedle patch for measles and rubella vaccination: a game changer for achieving elimination

While morbidity and mortality associated with measles and rubella (MR) have dramatically decreased, there are still >100000 estimated deaths due to measles and an estimated 100000 infants born with congenital rubella syndrome annually. Given highly effective MR vaccines, the primary barrier to global elimination of these diseases is low vaccination coverage, especially among the most underserved populations in resource-limited settings. In contrast to conventional MR vaccination by hypodermic injection, microneedle patches are being developed to enable MR vaccination by minimally trained personnel. Simplified supply chain, reduced need for cold chain storage, elimination of vaccine reconstitution, no sharps waste, reduced vaccine wastage, and reduced total system cost of vaccination are advantages of this approach. Preclinical work to develop a MR vaccine patch has proceeded through successful immunization studies in rodents and non-human primates. On-going programs seek to make MR vaccine patches available to support MR elimination efforts around the world.

STAR particles for enhanced topical drug and vaccine delivery

Drug delivery to the skin is highly constrained by the stratum corneum barrier layer¹. Here, we developed star-shaped particles, termed STAR particles, to dramatically increase skin permeability. STAR particles are millimeter-scale particles made of aluminum oxide or stainless steel with micron-scale projections designed to create microscopic pores across the stratum corneum. After gentle topical application for 10 s to porcine skin ex vivo, delivery of dermatological drugs and macromolecules, including those that cannot be given topically, was increased by 1 to 2 orders of magnitude. In mice treated with topical 5-fluorouracil, use of STAR particles increased the efficacy of the drug in suppressing the growth of subcutaneous melanoma tumors and prolonging survival. Moreover, topical delivery of tetanus toxoid vaccine to mice using STAR particles generated immune responses that were at least as strong as delivery of the vaccine by intramuscular injection, albeit at a higher dose for topical than intramuscular vaccine administration. STAR particles were well tolerated and effective at creating micropores when applied to the skin of human participants. Use of STAR particles provides a simple, low-cost and well-tolerated method for increasing drug and vaccine delivery to the skin and could widen the range of compounds that can be topically administered.

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

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

Long-acting reversible contraception by effervescent microneedle patch

To increase access to long-acting contraception, we developed a reversible contraceptive microneedle patch that is simple-to-administer, slowly releases contraceptive hormone (levonorgestrel) for >1 month, and generates no biohazardous sharps waste. After manually pressing the patch to skin for 1 min, microneedles rapidly separate from the patch within the skin due to effervescence triggered by contact with skin's interstitial fluid, as demonstrated in rats and human participants. Long-acting contraception is achieved by formulating microneedles with a biodegradable polymer [poly(lactic-co-glycolic) acid] that slowly releases levonorgestrel for ~1 month in vitro. In rats, the patch maintained levonorgestrel concentration above the human contraceptive threshold level for >1 month, and a placebo microneedle patch was well-tolerated in human participants. Women of reproductive age in three continents demonstrated interest in and preference for long-acting contraception by microneedle patch. These studies indicate that an effervescent microneedle patch could facilitate greater access to long-acting contraception.

Microneedles coated with peanut allergen enable desensitization of peanut sensitized mice

The prevalence of peanut allergies has escalated over the last 20 years, yet there are no FDA approved treatments for peanut allergies. In this study we evaluated the potential of microneedles to deliver peanut protein extract (PE) into skin and assessed if the ensuing immune responses could desensitize mice that were sensitized to peanuts. Peanut sensitized mice were either treated through cutaneous immunotherapy using PE-coated microneedles or not treated, and then orally challenged with PE. After oral challenge, the clinical symptoms of peanut-induced anaphylaxis were significantly lower in the microneedle treated mice as compared to untreated mice, and this was accompanied by down-regulation of systemic anaphylaxis mediators such as histamine and mast cell protease-1 (MCPT-1) in the microneedles treated group. Overall, there was an up-regulation of Th1 cytokines (IL-2 and IFN-γ) as compared to Th2 cytokines (IL-4 and IL-5) in splenocyte culture supernatants of the microneedle treated group as compared to untreated group, suggesting that microneedles promoted immune modulation towards the Th1 pathway. Furthermore, mice treated with PE-coated microneedles were observed to retain integrity of their small intestine villi and had reduced eosinophilic infiltration as compared to the untreated but peanut sensitized mice, which further confirmed the desensitization capability of peanut cutaneous immunotherapy using coated microneedles. Thus, our current study represents a novel minimally invasive microneedle based cutaneous immunotherapy, which may provide a novel route of desensitization for the treatment of peanut allergies.

Plasmonic Paper Microneedle Patch for On-Patch Detection of Molecules in Dermal Interstitial Fluid

Minimally invasive devices to detect molecules in dermal interstitial fluid (ISF) are desirable for point-of-care diagnostic and monitoring applications. In this study, we developed a microneedle (MN) patch that collects ISF for on-patch biomarker analysis by surface-enhanced Raman scattering (SERS). The micrometer-scale MNs create micropores in the skin surface, through which microliter quantities of ISF are collected onto plasmonic paper on the patch backing. The plasmonic paper was prepared by immobilizing poly(styrenesulfonate) (PSS) coated gold nanorods (AuNRs) on a thin strip of filter paper using plasmonic calligraphy. Negatively charged PSS was used to bind positively charged rhodamine 6G (R6G), which served as a model compound, and thereby localize R6G on AuNR surface. R6G bound on the AuNR surface was detected and quantified by acquiring SERS spectra from the plasmonic paper MN patch. This approach was used to measure pharmacokinetic profiles of R6G in ISF and serum from rats in vivo. This proof-of-concept study indicates that a plasmonic paper MN patch has the potential to enable on-patch measurement of molecules in ISF for research and future medical applications.

Microneedle Coating Methods: A Review with a Perspective

A coated microneedle array comprises sharp micrometer-sized needle shafts attached to a base substrate and coated with a drug on their surfaces. Coated microneedles are under investigation for drug delivery into the skin and other tissues, and a broad assortment of active materials, including small molecules, peptides, proteins, deoxyribonucleic acids, and viruses, have been coated onto microneedles. To coat the microneedles, different methods have been developed. Some coating methods achieve selective coating of just the microneedle shafts, whereas other methods coat not only microneedle shafts but also the array base substrate. Selective coating of just the microneedle shafts is more desirable since it provides control over drug dosage, prevents drug waste, and offers high delivery efficiency. Different excipients are added to the coating liquid to modulate its viscosity and surface tension in order to achieve uniform coatings on microneedles. Coated microneedles have been used in a broad range of biomedical applications. To highlight these different applications, a table summarizing the different active materials and the amounts coated on microneedles is provided. We also discuss factors that should be considered when deciding suitability of coated microneedles for new-drug delivery applications. In recent years, many coated microneedles have been investigated in human clinical trials, and there is now a strong effort to bring the first coated microneedle-based product to market.

Recruitment and Collection of Dermal Interstitial Fluid Using a Microneedle Patch

Interstitial fluid (ISF) that surrounds cells in tissues of the body is a novel source of biomarker that complements conventional sources like blood, urine, and saliva. To overcome difficulties in harvesting ISF, a minimally invasive, rapid, simple-to-use, cost-effective method is developed to collect ISF from the skin involving a microneedle (MN) patch. By pressing 650 µm long MNs at an angle just below the skin surface, blood-free ISF flows through micropores to the skin surface and is absorbed into a thin strip of paper on the MN patch backing for subsequent analysis. An optimized method in rat skin in vivo is well tolerated and able to collect >2 µL of ISF within 1 min. Brief skin pretreatment with MNs followed by a 5 min delay dramatically increases subsequent ISF collection by a mechanism believed to involve increased skin hydration. ISF collection using an MN patch has the potential to simplify access to biomarkers in ISF for research and future medical diagnostic and monitoring applications.