Dissolving polymer microneedle patches for influenza vaccination

Microneedle Technology: An Insight into Recent Advancements and Future Trends in Drug and Vaccine Delivery

Over the last decade, microneedle (MN) induced microporation multifunctional approaches to enhance the delivery of drugs through the skin. MN technology included micron-sized needles to create microchannels into the Stratum corneum of skin, the most significant protective layer. Delivery of drugs and vaccines through the transdermal route is an alternative route for hypodermic and oral. It overcomes the problems associated with gastrointestinal along with drug deterioration. It is affordable, noninvasive, painless, simple, and self-administered techniques that provide prolonged release of drugs to enhance patient compliance. The MN delivery focused on biopharmaceuticals like proteins or peptides. The novel concepts have drawn interest in using these techniques in tandem with other enhancement approaches. This review article discussed the latest advancements in MN technology. It emphasized types of MNs, methodology, mechanisms, strategies for delivery of several drugs and vaccines, and significant challenges in the marketing of biopharmaceuticals. Furthermore, relevant U.S. patents and clinical trials based on MNs are also accentuated. Therefore, MN techniques will play a pivotal role in promoting clinical applications and innovative research for scientists and researchers working in the pharmaceutical field.

Pharmaceutical assessment of polyvinylpyrrolidone (PVP): As excipient from conventional to controlled delivery systems with a spotlight on COVID-19 inhibition

Polyvinylpyrrolidone (PVP) is a water-soluble polymer obtained by polymerization of monomer N-vinylpyrrolidone. PVP is an inert, non-toxic, temperature-resistant, pH-stable, biocompatible, biodegradable polymer that helps to encapsulate and cater both hydrophilic and lipophilic drugs. These advantages enable PVP a versatile excipient in the formulation development of broad conventional to novel controlled delivery systems. PVP has tunable properties and can be used as a brace component for gene delivery, orthopedic implants, and tissue engineering applications. Based on different molecular weights and modified forms, PVP can lead to exceptional beneficial features with varying chemical properties. Graft copolymerization and other techniques assist PVP to conjugate with poorly soluble drugs that can inflate bioavailability and even introduces the desired swelling tract for their control or sustained release. The present review provides chemistry, mechanical, physicochemical properties, evaluation parameters, dewy preparation methods of PVP derivatives intended for designing conventional to controlled systems for drug, gene, and cosmetic delivery. The past and growing interest in PVP establishes it as a promising polymer to enhance the trait and performance of current generation pharmaceutical dosage forms. Furthermore, the scrutiny explores existing patents, marketed products, new and futuristic approaches of PVP that have been identified and scope for future development, characterization, and its use. The exploration spotlights the importance and role of PVP in the design of Povidone-iodine (PVP-I) and clinical trials to assess therapeutic efficacy against the COVID-19 in the current pandemic scenario.

Polyvinylpyrrolidone microneedles for localized delivery of sinomenine hydrochloride: preparation, release behavior of in vitro & in vivo, and penetration mechanism

Sinomenine (SIN) is an anti-inflammatory alkaloid derived from Sinomenium acutum, and the products sinomenine hydrochloride (SH) tablets and injections have been marketed in China to treat rheumatoid arthritis (RA). Oral administration of SH has shortcomings of gastrointestinal irritation and low bioavailability. The injection may require professional training and higher cost. It is of interest to develop an alternative form that is easier to administer and avoids the first-pass metabolism. In this study, SH-loaded dissolving microneedles (SH-MN) were fabricated using polyvinyl pyrrolidone and chondroitin sulfate with a casting method. In percutaneous permeation studies of In vitro, the cumulative permeation and permeation rate of SH-MN were 5.31 and 5.06 times higher than that of SH-gel (SH-G). In percutaneous pharmacokinetic studies, the values of the area under the curve after administration of SH-MN in the skin and blood were 1.43- and 1.63-fold higher than that of SH-G, respectively. In percutaneous absorption studies, SH-MN could absorb into tissue fluid; and dissolve after skin penetration. The drug was released along the channel and spread to surrounding skin tissue. After 4 h, the needle tip was almost completely dissolved, and the drug could penetrate to a depth of 200 μm under the skin. These results demonstrate that the SH-MN is an effective, safe, and simple strategy for transdermal SH delivery.

Engineering Antiviral Vaccines

Despite the vital role of vaccines in fighting viral pathogens, effective vaccines are still unavailable for many infectious diseases. The importance of vaccines cannot be overstated during the outbreak of a pandemic, such as the coronavirus disease 2019 (COVID-19) pandemic. The understanding of genomics, structural biology, and innate/adaptive immunity have expanded the toolkits available for current vaccine development. However, sudden outbreaks and the requirement of population-level immunization still pose great challenges in today's vaccine designs. Well-established vaccine development protocols from previous experiences are in place to guide the pipelines of vaccine development for emerging viral diseases. Nevertheless, vaccine development may follow different paradigms during a pandemic. For example, multiple vaccine candidates must be pushed into clinical trials simultaneously, and manufacturing capability must be scaled up in early stages. Factors from essential features of safety, efficacy, manufacturing, and distributions to administration approaches are taken into consideration based on advances in materials science and engineering technologies. In this review, we present recent advances in vaccine development by focusing on vaccine discovery, formulation, and delivery devices enabled by alternative administration approaches. We hope to shed light on developing better solutions for faster and better vaccine development strategies through the use of biomaterials, biomolecular engineering, nanotechnology, and microfabrication techniques.

Metal-Organic Framework Derived Multicomponent Nanoagent as a Reactive Oxygen Species Amplifier for Enhanced Photodynamic Therapy

Intracellular antioxidants such as glutathione (GSH) play a critical role in protecting malignant tumor cells from apoptosis induced by reactive oxygen species (ROS) and in mechanisms of multidrug and radiation resistance. Herein, we rationally design two multicomponent self-assembled photodynamic therapy (PDT) nanoagents, that is, Glup-MFi-c and Glud-MFo-c, which consist of respective GSH-passivation and GSH-depletion linkers in metal-organic frameworks encapsulated with photosensitizers for a deeply comprehensive understanding of GSH-based tumor PDT. Multicomponent coordination, π-π stacking, and electrostatic interactions among metal ions, photosensitizers, and bridging linkers under the protection of a biocompatible polymer generate homogeneous nanoparticles with satisfied size, good colloid stability, and ultrahigh loading capacity. Compared to the GSH-passivated Glup-MFi-c, the GSH-depleted Glud-MFo-c shows pH-responsive release of photosensitizer and [Fe^III(CN)₆] linker in tumor cells to efficiently deplete intracellular GSH, thus amplifying the cell-killing efficiency of ROS and suppressing the tumor growth in vivo. This study demonstrates that Glud-MFo-c acts as a ROS amplifier, providing a useful strategy to deeply understand the role of GSH in combating cancer.

Microneedles with dual release pattern for improved immunological efficacy of Hepatitis B vaccine

In this study, dissolving microneedles (DMNs) with dual-release pattern, capable of both bolus release and slow release, were prepared. These DMNs were used with a hepatitis B vaccine that requires multiple shots to achieve immunological efficacy comparable to that obtained when two separate shots are administered. Dissolving microneedles with HBsAg in PLA tips and CMC coating formulation together (HBsAg-PLA/CMC-DMNs) consist of polylactic acid (PLA) tips for slow release, a carboxy-methyl cellulose (CMC) coating formulation for bolus release, and a dissolving base of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) for dissolution in the skin. The in vitro release pattern of HBsAg from the CMC coating formulation and PLA tips was observed. Through an in vivo test, 1) the delivery efficiency of HBsAg-PLA/CMC-DMNs was observed, and 2) the immunological efficacy of this method was compared with the efficacy of two shots delivered by conventional intramuscular (IM) administration and two shots delivered by HBsAg-coated microneedle (CMNs) administration. HBsAg-PLA/CMC-DMNs punctured the skin successfully. The PVA/PVP base was completely dissolved within 10 min of insertion, resulting in the delivery of all microneedle tips into the skin. In the in vitro release experiment, all of the HBsAg in the CMC coating formulation was released within 20 min, and the HBsAg present in the PLA tips was gradually released over more than 55 days. The antibody titer of one shot of HBsAg-PLA/CMC-DMNs was the same as or higher than two shots delivered by conventional IM and CMN methods. DMNs with dual-release pattern can deliver two formulations simultaneously with a single shot, resulting in improved immunological efficacy of HBsAg that requires multiple doses. In addition, this dual-release MN system can be used for the delivery of other drugs that require multiple administrations.

Microneedles loaded with anti-PD-1-cisplatin nanoparticles for synergistic cancer immuno-chemotherapy

Programmed cell death protein-1 (PD-1) on T-cells combined with programmed cell death ligand-1 (PD-L1) critically accounts for tumor immune evasion. Anti-PD-1 (aPD-1) blocks the binding of PD-1 to PD-L1, thus allowing T-cell activation for tumor cell eradication. Currently, the major challenges for cancer immunotherapy are how to improve the response rate and overcome drug resistance. Dermal administration turns out to be a promising route for immunotherapy since skin is a highly active immune organ containing a large population of resident antigen-presenting cells. Microneedle arrays can pierce the immune-cell-rich epidermis, leading to a robust T-cell response in the microenvironment of tumor cells. Herein, we successfully developed a microneedle patch loaded with pH-responsive tumor-targeted lipid nanoparticles (NPs), which allows local delivery of aPD-1 and cisplatin (CDDP) precisely to cancer tissues for cancer therapy. For in vivo studies, aPD-1/CDDP@NPs delivered through microneedles effectively boosted the immune response, thereby a remarkable effect on tumor regression was realized. Synergistic anticancer mechanisms were therefore activated through robust microneedle-induced T-cell response, blockage of PD-1 in T-cells by aPD-1, and an increase in direct cytotoxicity of CDDP in tumor cells. Strikingly, transdermal delivery using MNs increased the response rate in the animal model unresponsive to aPD-1 systemic therapy. This exhibited promise in the treatment of immunotherapy-unresponsive cancers. Taken together, microneedle-mediated local delivery of nano-encapsulated chemotherapeutic and immunotherapeutic agents at tumor skin sites provides a novel treatment strategy and insights into cancer therapy.

Current trends in polymer microneedle for transdermal drug delivery

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

Progress and perspective of microneedle system for anti-cancer drug delivery

Transdermal drug delivery exhibited encouraging prospects, especially through superficial drug administration routes. However, only a few limited lipophilic drug molecules could cross the skin barrier, those are with low molecular weight and rational Log P value. Microneedles (MNs) can overcome these limitations to deliver numerous drugs into the dermal layer by piercing the outermost skin layer of the body. In the case of superficial cancer treatments, topical drug administration faces severely low transfer efficiency, and systemic treatments are always associated with side effects and premature drug degradation. MN-based systems have achieved excellent technical capabilities and been tested for pre-clinical chemotherapy, photothermal therapy, photodynamic therapy, and immunotherapy. In this review, we will focus on the features, progress, and opportunities of MNs in the anticancer drug delivery system. Then, we will discuss the strategies and advantages in these works and summarize challenges, perspectives, and translational potential for future applications.

Technological approaches to streamline vaccination schedules, progressing towards single-dose vaccines

Vaccines represent the most successful medical intervention in history, with billions of lives saved. Although multiple doses of the same vaccine are typically required to reach an adequate level of protection, it would be advantageous to develop vaccines that induce protective immunity with fewer doses, ideally just one. Single-dose vaccines would be ideal to maximize vaccination coverage, help stakeholders to greatly reduce the costs associated with vaccination, and improve patient convenience. Here we describe past attempts to develop potent single dose vaccines and explore the reasons they failed. Then, we review key immunological mechanisms of the vaccine-specific immune responses, and how innovative technologies and approaches are guiding the preclinical and clinical development of potent single-dose vaccines. By modulating the spatio-temporal delivery of the vaccine components, by providing the appropriate stimuli to the innate immunity, and by designing better antigens, the new technologies and approaches leverage our current knowledge of the immune system and may synergize to enable the rational design of next-generation vaccination strategies. This review provides a rational perspective on the possible development of future single-dose vaccines.

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

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

Active Microneedle Administration of Plant Virus Nanoparticles for Cancer in situ Vaccination Improves Immunotherapeutic Efficacy

The solid tumor microenvironment (TME) poses a significant structural and biochemical barrier to immunotherapeutic agents. To address the limitations of tumor penetration and distribution, and to enhance antitumor efficacy of immunotherapeutics, we present here an autonomous active microneedle (MN) system for the direct intratumoral (IT) delivery of a potent immunoadjuvant, cowpea mosaic virus nanoparticles (CPMV) in vivo. In this active delivery system, magnesium (Mg) microparticles embedded into active MNs react with the interstitial fluid in the TME, generating a propulsive force to drive the nanoparticle payload into the tumor. Active delivery of CPMV payload into B16F10 melanomas in vivo demonstrated substantially more pronounced tumor regression and prolonged survival of tumor-bearing mice compared to that of passive MNs and conventional needle injection. Active MN administration of CPMV also enhanced local innate and systemic adaptive antitumor immunity. Our approach represents an elaboration of conventional CPMV in situ vaccination, highlighting substantial immune-mediated antitumor effects and improved therapeutic efficacy that can be achieved through an active and autonomous delivery system-mediated CPMV in situ vaccination.

Layered double hydroxide nanostructures and nanocomposites for biomedical applications

Layered double hydroxide (LDH) nanostructures and related nanocomposites have attracted significant interest in biomedical applications including cancer therapy, bioimaging and antibacterial treatment. These materials hold great advantages including low cost and facile preparation, convenient drug loading, high drug incorporation capacity, good biocompatibility, efficient intracellular uptake and endosome/lysosome escape, and natural biodegradability in an acidic environment. In this review, we summarize the development of three types of LDH nanostructures including pristine LDH, surface modified LDH, and LDH nanocomposites for a range of biomedical applications. The advantages and disadvantages of LDH nanostructures and insights into the future development are also discussed.

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.

Advances in Sweat Wearables: Sample Extraction, Real-Time Biosensing, and Flexible Platforms

Wearable biosensors for sweat-based analysis are gaining wide attention due to their potential use in personal health monitoring. Flexible wearable devices enable sweat analysis at the molecular level, facilitating noninvasive monitoring of physiological states via real-time monitoring of chemical biomarkers. Advances in sweat extraction technology, real-time biosensors, stretchable materials, device integration, and wireless digital technologies have led to the development of wearable sweat-biosensing devices that are light, flexible, comfortable, aesthetic, affordable, and informative. Herein, we summarize recent advances of sweat wearables from the aspects of sweat extraction, fabrication of stretchable biomaterials, and design of biosensing modules to enable continuous biochemical monitoring, which are essential for a biosensing device. Key chemical components of sweat, sweat capture methodologies, and considerations of flexible substrates for integrating real-time biosensors with electronics to bring innovations in the art of wearables are elaborated. The strategies and challenges involved in improving the wearable biosensing performance and the perspectives for designing sweat-based wearable biosensing devices are discussed.

Snake fang-inspired stamping patch for transdermal delivery of liquid formulations

A flexible microneedle patch that can transdermally deliver liquid-phase therapeutics would enable direct use of existing, approved drugs and vaccines, which are mostly in liquid form, without the need for additional drug solidification, efficacy verification, and subsequent approval. Specialized dissolving or coated microneedle patches that deliver reformulated, solidified therapeutics have made considerable advances; however, microneedles that can deliver liquid drugs and vaccines still remain elusive because of technical limitations. Here, we present a snake fang-inspired microneedle patch that can administer existing liquid formulations to patients in an ultrafast manner (<15 s). Rear-fanged snakes have an intriguing molar with a groove on the surface, which enables rapid and efficient infusion of venom or saliva into prey. Liquid delivery is based on surface tension and capillary action. The microneedle patch uses multiple open groove architectures that emulate the grooved fangs of rear-fanged snakes: Similar to snake fangs, the microneedles can rapidly and efficiently deliver diverse liquid-phase drugs and vaccines in seconds under capillary action with only gentle thumb pressure, without requiring a complex pumping system. Hydrodynamic simulations show that the snake fang-inspired open groove architectures enable rapid capillary force-driven delivery of liquid formulations with varied surface tensions and viscosities. We demonstrate that administration of ovalbumin and influenza virus with the snake fang-inspired microneedle patch induces robust antibody production and protective immune response in guinea pigs and mice.

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.

Mathematical Modelling, Simulation and Optimisation of Microneedles for Transdermal Drug Delivery: Trends and Progress

In the last two decades, microneedles (MNs) have received significant interest due to their potential for painless transdermal drug delivery (TDD) and minimal skin damage. MNs have found applications in a range of research and development areas in drug delivery. They have been prepared using a variety of materials and fabrication techniques resulting in MN arrays with different dimensions, shapes, and geometries for delivery of a variety of drug molecules. These parameters play crucial roles in determining the drug release profiles from the MNs. Developing mathematical modelling, simulation, and optimisation techniques is vital to achieving the desired MN performances. These will then be helpful for pharmaceutical and biotechnological industries as well as professionals working in the field of regulatory affairs focusing on MN based TDD systems. This is because modelling has a great potential to reduce the financial and time cost of both the MNs' studies and manufacturing. For example, a number of robust mathematical models for predicting the performance of the MNs in vivo have emerged recently which incorporate the roles of the structural and mechanical properties of the skin. In addressing these points, this review paper aims to highlight the current status of the MN modelling research, in particular, the modelling, simulation and optimisation of the systems for drug delivery. The theoretical basis for the simulation of MN enhanced diffusion is discussed within this paper. Thus, this review paper provides a better understanding of the modelling of the MN mediated drug delivery process.

Rapid biodegradable microneedles with allergen reservoir for skin allergy test

With the increasing allergy cases worldwide, this study introduces a biodegradable microneedle system to facilitate allergy testing process. Dissolving microneedle provides a minimally invasive manner to go through skin barrier while avoiding needle phobia among patents, especially children. The microneedles were fabricated using copolymer polyvinylpyrrolidone-co-methacrylic acid (PVP-MAA) material. To ensure the successful insertion of microneedles into the skin, we tailored the mechanical strength of the copolymer by adjusting the weight ratio of two constituted polymers. A reservoir was designed to load allergy specimen for the allergy test. This system is expected to offer a simple and effective allergy testing that can facilitate the allergy testing protocol.

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.

Bioresorbable, Miniaturized Porous Silicon Needles on a Flexible Water-Soluble Backing for Unobtrusive, Sustained Delivery of Chemotherapy

Conventional melanoma therapies suffer from the toxicity and side effects of repeated treatments due to the aggressive and recurrent nature of melanoma cells. Less-invasive topical chemotherapies by utilizing polymeric microneedles have emerged as an alternative, but the sustained, long-lasting release of drug cargos remains challenging. In addition, the size of the microneedles is relatively bulky for the small, curvilinear, and exceptionally sensitive cornea for the treatment of ocular melanoma. Here, we report a design of bioresorbable, miniaturized porous-silicon (p-Si) needles with covalently linked drug cargos at doses comparable to those of conventional polymeric microneedles. The p-Si needles are built on a water-soluble film as a temporary flexible holder that can be intimately interfaced with the irregular surface of living tissues, followed by complete dissolution with saline solution within 1 min. Consequently, the p-Si needles remain embedded inside tissues and then undergo gradual degradation, allowing for sustained release of the drug cargos. Its utility in unobtrusive topical delivery of chemotherapy with minimal side effects is demonstrated in a murine melanoma model.

Measles and rubella microarray array patches to increase vaccination coverage and achieve measles and rubella elimination in Africa

The African Region is committed to measles elimination by 2020 but coverage with the first dose of measles-containing vaccine was only 70% in 2017. Several obstacles to achieving high coverage with measles and rubella vaccines exist, some of which could be overcome with new vaccine delivery technologies. Microarray array patches (MAPs) are single-dose devices used for transcutaneous administration of molecules, including inactivated or attenuated vaccines, that penetrate the outer stratum corneum of the skin, delivering antigens to the epidermis or dermis. MAPs to deliver measles and rubella vaccines have the potential to be a transformative technology to achieve elimination goals in the African Region. MAPs for measles and rubella vaccination have been shown to be safe, immunogenic and thermostable in preclinical studies but results of clinical studies in humans have not yet been published. This review summarizes the current state of knowledge of measles and rubella MAPs, their potential advantages for immunization programs in the African Region, and some of the challenges that must be overcome before measles and rubella MAPs are available for widespread use.

Glucose-responsive insulin patch for the regulation of blood glucose in mice and minipigs

Glucose-responsive insulin delivery systems that mimic pancreatic endocrine function could enhance health and improve quality of life for people with type 1 and type 2 diabetes with reduced β-cell function. However, insulin delivery systems with rapid in vivo glucose-responsive behaviour typically have limited insulin-loading capacities and cannot be manufactured easily. Here, we show that a single removable transdermal patch, bearing microneedles loaded with insulin and a non-degradable glucose-responsive polymeric matrix, and fabricated via in situ photopolymerization, regulated blood glucose in insulin-deficient diabetic mice and minipigs (for minipigs >25 kg, glucose regulation lasted >20 h with patches of ~5 cm2). Under hyperglycaemic conditions, phenylboronic acid units within the polymeric matrix reversibly form glucose-boronate complexes that-owing to their increased negative charge-induce the swelling of the polymeric matrix and weaken the electrostatic interactions between the negatively charged insulin and polymers, promoting the rapid release of insulin. This proof-of-concept demonstration may aid the development of other translational stimuli-responsive microneedle patches for drug delivery.

Microneedle array delivered recombinant coronavirus vaccines: Immunogenicity and rapid translational development

BACKGROUND

Coronaviruses pose a serious threat to global health as evidenced by Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), and COVID-19. SARS Coronavirus (SARS-CoV), MERS Coronavirus (MERS-CoV), and the novel coronavirus, previously dubbed 2019-nCoV, and now officially named SARS-CoV-2, are the causative agents of the SARS, MERS, and COVID-19 disease outbreaks, respectively. Safe vaccines that rapidly induce potent and long-lasting virus-specific immune responses against these infectious agents are urgently needed. The coronavirus spike (S) protein, a characteristic structural component of the viral envelope, is considered a key target for vaccines for the prevention of coronavirus infection.

METHODS

We first generated codon optimized MERS-S1 subunit vaccines fused with a foldon trimerization domain to mimic the native viral structure. In variant constructs, we engineered immune stimulants (RS09 or flagellin, as TLR4 or TLR5 agonists, respectively) into this trimeric design. We comprehensively tested the pre-clinical immunogenicity of MERS-CoV vaccines in mice when delivered subcutaneously by traditional needle injection, or intracutaneously by dissolving microneedle arrays (MNAs) by evaluating virus specific IgG antibodies in the serum of vaccinated mice by ELISA and using virus neutralization assays. Driven by the urgent need for COVID-19 vaccines, we utilized this strategy to rapidly develop MNA SARS-CoV-2 subunit vaccines and tested their pre-clinical immunogenicity in vivo by exploiting our substantial experience with MNA MERS-CoV vaccines.

FINDINGS

Here we describe the development of MNA delivered MERS-CoV vaccines and their pre-clinical immunogenicity. Specifically, MNA delivered MERS-S1 subunit vaccines elicited strong and long-lasting antigen-specific antibody responses. Building on our ongoing efforts to develop MERS-CoV vaccines, promising immunogenicity of MNA-delivered MERS-CoV vaccines, and our experience with MNA fabrication and delivery, including clinical trials, we rapidly designed and produced clinically-translatable MNA SARS-CoV-2 subunit vaccines within 4 weeks of the identification of the SARS-CoV-2 S1 sequence. Most importantly, these MNA delivered SARS-CoV-2 S1 subunit vaccines elicited potent antigen-specific antibody responses that were evident beginning 2 weeks after immunization.

INTERPRETATION

MNA delivery of coronaviruses-S1 subunit vaccines is a promising immunization strategy against coronavirus infection. Progressive scientific and technological efforts enable quicker responses to emerging pandemics. Our ongoing efforts to develop MNA-MERS-S1 subunit vaccines enabled us to rapidly design and produce MNA SARS-CoV-2 subunit vaccines capable of inducing potent virus-specific antibody responses. Collectively, our results support the clinical development of MNA delivered recombinant protein subunit vaccines against SARS, MERS, COVID-19, and other emerging infectious diseases.

Materials for Immunotherapy

Breakthroughs in materials engineering have accelerated the progress of immunotherapy in preclinical studies. The interplay of chemistry and materials has resulted in improved loading, targeting, and release of immunomodulatory agents. An overview of the materials that are used to enable or improve the success of immunotherapies in preclinical studies is presented, from immunosuppressive to proinflammatory strategies, with particular emphasis on technologies poised for clinical translation. The materials are organized based on their characteristic length scale, whereby the enabling feature of each technology is organized by the structure of that material. For example, the mechanisms by which i) nanoscale materials can improve targeting and infiltration of immunomodulatory payloads into tissues and cells, ii) microscale materials can facilitate cell-mediated transport and serve as artificial antigen-presenting cells, and iii) macroscale materials can form the basis of artificial microenvironments to promote cell infiltration and reprogramming are discussed. As a step toward establishing a set of design rules for future immunotherapies, materials that intrinsically activate or suppress the immune system are reviewed. Finally, a brief outlook on the trajectory of these systems and how they may be improved to address unsolved challenges in cancer, infectious diseases, and autoimmunity is presented.

Engineering Microneedles for Therapy and Diagnosis: A Survey

Microneedle (MN) technology is a rising star in the point-of-care (POC) field, which has gained increasing attention from scientists and clinics. MN-based POC devices show great potential for detecting various analytes of clinical interests and transdermal drug delivery in a minimally invasive manner owing to MNs' micro-size sharp tips and ease of use. This review aims to go through the recent achievements in MN-based devices by investigating the selection of materials, fabrication techniques, classification, and application, respectively. We further highlight critical aspects of MN platforms for transdermal biofluids extraction, diagnosis, and drug delivery assisted disease therapy. Moreover, multifunctional MNs for stimulus-responsive drug delivery systems were discussed, which show incredible potential for accurate and efficient disease treatment in dynamic environments for a long period of time. In addition, we also discuss the remaining challenges and emerging trend of MN-based POC devices from the bench to the bedside.

Progress in Microneedle-Mediated Protein Delivery

The growing demand for patient-compliance therapies in recent years has led to the development of transdermal drug delivery, which possesses several advantages compared with conventional methods. Delivering protein through the skin by transdermal patches is extremely difficult due to the presence of the stratum corneum which restricts the application to lipophilic drugs with relatively low molecular weight. To overcome these limitations, microneedle (MN) patches, consisting of micro/miniature-sized needles, are a promising tool to perforate the stratum corneum and to release drugs and proteins into the dermis following a non-invasive route. This review investigates the fabrication methods, protein delivery, and translational considerations for the industrial scaling-up of polymeric MNs for dermal protein delivery.

Transdermal cold atmospheric plasma-mediated immune checkpoint blockade therapy

Despite the promise of immune checkpoint blockade (ICB) therapy against cancer, challenges associated with low objective response rates and severe systemic side effects still remain and limit its clinical applications. Here, we described a cold atmospheric plasma (CAP)-mediated ICB therapy integrated with microneedles (MN) for the transdermal delivery of ICB. We found that a hollow-structured MN (hMN) patch facilitates the transportation of CAP through the skin, causing tumor cell death. The release of tumor-associated antigens then promotes the maturation of dendritic cells in the tumor-draining lymph nodes, subsequently initiating T cell-mediated immune response. Anti-programmed death-ligand 1 antibody (aPDL1), an immune checkpoint inhibitor, released from the MN patch further augments the antitumor immunity. Our findings indicate that the proposed transdermal combined CAP and ICB therapy can inhibit the tumor growth of both primary tumors and distant tumors, prolonging the survival of tumor-bearing mice.

[Development of an Immune Regulation Technology Targeting the Skin and Promotion of the Practical Applications of Transcutaneous Vaccination/Immunotherapy]

In the premise of vaccination and allergen-specific immunotherapy, transcutaneous formulations have an advantage over conventional subcutaneous injections in terms of convenience, simplicity of delivery, and painless administration into the skin. Additionally, since transcutaneous formulations can be rendered cold-chain free, they do not require expert handling during transportation, storage, and stockpiling, which enables reductions in costs and distribution to distant areas. Furthermore, transcutaneous formulations are effective for improving adherence in children with phobias toward injection needles and may help in persuading them to perform self-vaccination and home immunotherapy against allergies in the future. We have been promoting the development of innovative "patch-type formulations for vaccination and immunotherapy" which regard skin as an immune organ and utilize our original transcutaneous administration devices (hydrophilic gel patch and microneedle patch) for their delivery. We have confirmed the safety and efficacy of transcutaneous formulations not only in demonstration experiments using animals but also in physician-initiated clinical studies. Additionally, in order to elucidate the mechanism for the induction of immune responses by transcutaneous formulations, we analyzed the immunological events occurring in the skin and regional lymph nodes which accompanied the application of transcutaneous administration devices or the delivery of antigens (vaccines and allergens) to the skin surface layer. This review presents our results from basic to clinical research on the development of transcutaneous formulations for vaccines and allergen-specific immunotherapy.

Microneedles for transdermal diagnostics: Recent advances and new horizons

Point-of-care testing (POCT), defined as the test performed at or near a patient, has been evolving into a complement to conventional laboratory diagnosis by continually providing portable, cost-effective, and easy-to-use measurement tools. Among them, microneedle-based POCT devices have gained increasing attention from researchers due to the glorious potential for detecting various analytes in a minimally invasive manner. More recently, a novel synergism between microneedle and wearable technologies is expanding their detection capabilities. Herein, we provide an overview on the progress in microneedle-based transdermal biosensors. It covers all the main aspects of the field, including design philosophy, material selection, and working mechanisms as well as the utility of the devices. We also discuss lessons from the past, challenges of the present, and visions for the future on translation of these state-of-the-art technologies from the bench to the bedside.

The potential role of using vaccine patches to induce immunity: platform and pathways to innovation and commercialization

Introduction: In the last two decades, the evidence related to using vaccine patches with multiple short projections (≤1 mm) to deliver vaccines through the skin increased significantly and demonstrated their potential as an innovative delivery platform.Areas covered: We review the vaccine patch literature published in English as of 1 March 2019, as well as available information from key stakeholders related to vaccine patches as a platform. We identify key research topics related to basic and translational science on skin physical properties and immunobiology, patch development, and vaccine manufacturing.Expert opinion: Currently, vaccine patch developers continue to address some basic science and other platform issues in the context of developing a potential vaccine patch presentation for an existing or new vaccine. Additional clinical data and manufacturing experience could shift the balance toward incentivizing existing vaccine manufactures to further explore the use of vaccine patches to deliver their products. Incentives for innovation of vaccine patches differ for developed and developing countries, which will necessitate different strategies (e.g. public-private partnerships, push, or pull mechanisms) to support the basic and applied research needed to ensure a strong evidence base and to overcome translational barriers for vaccine patches as a delivery platform.

Highly potent intradermal vaccination by an array of dissolving microneedle polypeptide cocktails for cancer immunotherapy

Despite recent advances in cancer therapy using vaccines, the efficacy of vaccine regimens remains to be improved. Cutaneous transportation of biomolecules, particularly DNA vaccines, has potentially improved the therapeutic efficacy and has been found to be an appealing approach in cancer immunotherapy. Nevertheless, the effectiveness of transdermal vaccination is limited by the lack of efficacious immune stimulation. Here, to elicit strong immunogenicity in target cells, we propose an array of dissolving microneedle cocktails for pain-free implantation and triggered release of vaccines and adjuvants at cutaneous tissues. The microneedle cocktails comprising a bioresorbable polypeptide matrix with a nanopolyplex, which include cationic amphiphilic conjugates with ovalbumin-expressing plasmid OVA (pOVA) and immunostimulant-polyinosinic:polycytidylic acid (poly(I:C)), were prepared using a one-pot synthesis. The cationic nanopolyplex effectively transported pOVA and poly(I:C) into the intracellular compartments of dendritic cells and macrophages. Cutaneous implantation of microneedle cocktails on mice elicits a stronger antigen-specific antibody response than subcutaneous administration of the microneedle-free nanopolyplex. Compared with traditional vaccination, the dissolving microneedle cocktails enhanced the antibody recall memory after challenge; remarkably, the cocktail-based therapeutic vaccination also resulted in enhanced lung clearance of cancer cells. The dissolving microneedle cocktail therapy based on the triggered release of immunomodulators and adjuvants synergistically augmented the therapeutic effect in B16/OVA melanoma tumors.

Evaluation of microneedles-assisted in situ depot forming poloxamer gels for sustained transdermal drug delivery

In this study, for the first time, we have reported a sustained transdermal drug delivery from thermoresponsive poloxamer depots formed within the skin micropores following microneedle (MN) application. Firstly, we have investigated the sol–gel phase transition characteristics of poloxamers (PF®127, P108, and P87) at physiological conditions. Rheological measurements were evaluated to confirm the critical gelation temperature (CGT) of the poloxamer formulations with or without fluorescein sodium (FS), as a model drug, at various concentrations. Optimized poloxamer formulations were subjected to in vitro release studies using a vial method. Secondly, polymeric MNs were fabricated using laser-engineered silicone micromolds from various biocompatible polymeric blends of Gantrez S-97, PEG 10000, PEG200, PVP K32, and PVP K90. The MN arrays were characterized for mechanical strength, insertion force determination, in situ dissolution kinetics, moisture content, and penetration depth. The optimized MN arrays with good mechanical strength and non-soluble nature were used to create micropores in the neonatal porcine skin. Microporation in neonatal porcine skin was confirmed by dye-binding study, skin integrity assessment, and histology study. Finally, the in vitro delivery of FS from optimized poloxamer formulations was conducted across non-porated vs microporated skin samples using vertical Franz diffusion cells. Results concluded that permeation of FS was sustained for 96 h across the MN-treated skin samples containing in situ forming depot poloxamer formulations compared to non-microporated skin which sustained the FS delivery for 72 h. Confocal microscopic images confirmed the distribution of higher florescence intensity of FS in skin tissues after permeation study in case of MN-treated skin samples vs intact skin samples.

Dissolving undercut microneedle arrays for multicomponent cutaneous vaccination

The skin is an attractive tissue target for vaccination, as it is readily accessible and contains a dense population of antigen-presenting and immune-accessory cells. Microneedle arrays (MNAs) are emerging as an effective tool for in situ engineering of the cutaneous microenvironment to enable diverse immunization strategies. Here, we present novel dissolving undercut MNAs and demonstrate their application for effective multicomponent cutaneous vaccination. The MNAs are composed of micron-scale needles featuring pyramidal heads supported by undercut stem regions with filleted bases to ensure successful skin penetration and retention during application. Prior efforts to fabricate dissolving undercut microstructures were limited and required complex and lengthy processing and assembly steps. In the current study, we strategically combine three-dimensional (3D) laser lithography, an emerging micro-additive manufacturing method with unique geometric capabilities and nanoscale resolution, and micromolding with favorable materials. This approach enables reproducible production of dissolving MNAs with undercut microneedles that can be tip-loaded with multiple biocargos, such as antigen (ovalbumin) and adjuvant (Poly(I:C)). The resulting MNAs fulfill the geometric (sharp tips and smooth edges) and mechanical-strength requirements for failure-free penetration of human and murine skin to simultaneously deliver multicomponent (antigen plus adjuvant) vaccines to the same cutaneous microenvironment. Cutaneous vaccination of mice using these MNAs induces more potent antigen-specific cellular and humoral immune responses than those elicited by traditional intramuscular injection. Together, the unique geometric features of these undercut MNAs and the associated manufacturing strategy, which is compatible with diverse drugs and biologics, could enable a broad range of non-cutaneous and cutaneous drug delivery applications, including multicomponent vaccination.

Multifunctional Graphene-Oxide-Reinforced Dissolvable Polymeric Microneedles for Transdermal Drug Delivery

Dissolvable polymeric microneedles (DPMNs) are promising transdermal drug delivery systems with minimal invasiveness and improved patient compliance. Incorporation of a small amount of graphene oxide (GO) in the biocompatible polymers for microneedle fabrication results in important new DPMN properties, that is, dramatically enhanced mechanic strength (10-17 times at 500 mg/mL GO), improved moisture resistance, self-sterilization, antibacterial and anti-inflammatory properties (demonstrated in vitro), and near-infrared light-activated controlled drug release (demonstrated in vitro and in vivo), which were exploited for the transdermal delivery of the chemotherapeutic, HA15, to melanoma-bearing mouse models. These new properties improve their efficacy of transdermal drug delivery and ease of use, enhance their capability of controlled drug release, enlarge the scope of the polymers that can be used for DPMN fabrication, prevent microbial contamination during storage and transportation, and reduce infection risk in clinical applications.

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.

Built-In Active Microneedle Patch with Enhanced Autonomous Drug Delivery

The use of microneedles has facilitated the painless localized delivery of drugs across the skin. However, their efficacy has been limited by slow diffusion of molecules and often requires external triggers. Herein, an autonomous and degradable, active microneedle delivery platform is introduced, employing magnesium microparticles loaded within the microneedle patch, as the built-in engine for deeper and faster intradermal payload delivery. The magnesium particles react with the interstitial fluid, leading to an explosive-like rapid production of H2 bubbles, providing the necessary force to breach dermal barriers and enhance payload delivery. The release kinetics of active microneedles is evaluated in vitro by measuring the amount of IgG antibody (as a model drug) that passed through phantom tissue and a pigskin barrier. In vivo experiments using a B16F10 mouse melanoma model demonstrate that the active delivery of anti-CTLA-4 (a checkpoint inhibitor drug) results in greatly enhanced immune response and significantly longer survival. Moreover, spatially resolved zones of active and passive microneedles allow a combinatorial rapid burst response along with slow, sustained release, respectively. Such versatile and effective autonomous dynamic microneedle delivery technology offers considerable promise for a wide range of therapeutic applications, toward a greatly enhanced outcome, convenience, and cost.

Smart Microneedles for Therapy and Diagnosis

Microneedles represent a cutting-edge and idea-inspiring technology in biomedical engineering, which have attracted increasing attention of scientific researchers and medical staffs. Over the past decades, numerous great achievements have been made. The fabrication process of microneedles has been simplified and becomes more precise, easy-to-operate, and reusable. Besides, microneedles with various features have been developed and the microneedle materials have greatly expanded. In recent years, efforts have been focused on generating smart microneedles by endowing them with intriguing functions such as adhesion ability, responsiveness, and controllable drug release. Such improvements enable the microneedles to take an important step in practical applications including household drug delivery devices, wearable biosensors, biomedical assays, cell culture, and microfluidic chip analysis. In this review, the fabrication strategies, distinctive properties, and typical applications of the smart microneedles are discussed. Recent accomplishments, remaining challenges, and future prospects are also presented.