Effect of gamma sterilization on the properties of microneedle array transdermal patch system

Applications and prospects of microneedles in tumor drug delivery

As drug delivery devices, microneedles are used widely in the local administration of various drugs. Such drug-loaded microneedles are minimally invasive, almost painless, and have high drug delivery efficiency. In recent decades, with advancements in microneedle technology, an increasing number of adaptive, engineered, and intelligent microneedles have been designed to meet increasing clinical needs. This article summarizes the types, preparation materials, and preparation methods of microneedles, as well as the latest research progress in the application of microneedles in tumor drug delivery. This article also discusses the current challenges and improvement strategies in the use of microneedles for tumor drug delivery.

Overcoming challenges in dermal and transdermal delivery of herbal therapeutics with polymeric microneedles

Natural products are generally preferred medications owing to their low toxicity and irritancy potential. However, a good number of herbal therapeutics (HT) exhibit solubility, permeability and stability issues that eventually affect oral bioavailability. Transdermal administration has been successful in resolving some of these issues which has lead in commercialization of a few herbal transdermal products. Polymeric Microneedles (MNs) has emerged as a promising platform in transdermal delivery of HT that face problems in permeating the skin. Several biocompatible and biodegradable polymers used in the fabrication of MNs have been discussed. MNs have been exploited for cutaneous delivery of HT in management of skin ailments like skin cancer, acne, chronic wounds and hypertrophic scar. Considering the clinical need, MNs are explored for systemic delivery of potent HT for management of diverse disorders like asthma, disorders of central nervous system and nicotine replacement as it obviates first pass metabolism and elicits a quicker onset of therapeutic response. MNs of HT have found good number of aesthetic applications in topical delivery of HT to the skin. Interestingly, MNs have emerged as an attractive option as a minimally invasive diagnostic aid in sampling biomarkers from plants, skin and ocular interstitial fluid. The review updates the progress made by MN technology of HT for multiple therapeutic interventions along with the future challenges. An attempt is made to illustrate the challenging formulation strategies employed in the fabrication of polymeric MNs of HT. Efforts are on to extend the potential applications of polymeric MNs to HT for diverse therapeutic applications.

Rapidly Dissolving Trans-scleral Microneedles for Intraocular Delivery of Cyclosporine A

Cyclosporine A (CsA) is a cyclic peptide immunosuppressant drug that is beneficial in the treatment of various ocular diseases. However, its ocular bioavailability in the posterior eye is limited due to its poor aqueous solubility. Conventional CsA formulations such as a solution or emulsion permeate poorly across the eye due to various static and dynamic barriers of the eye. Dissolvable microneedle (MN)-based patches can be used to overcome barrier properties and, thus, enhance the ocular bioavailability of CsA in the posterior eye. CsA-loaded dissolvable MN patches were fabricated using polyvinylpyrrolidone (PVP) and characterized for MN uniformity and sharpness using SEM. Further characterization for its failure force, penetration force, and depth of penetration were analyzed using a texture analyzer. Finally, the dissolution time, ex vivo permeation, and ocular distribution of cyclosporine were determined in isolated porcine eyes. PVP MNs were sharp, uniform with good mechanical properties, and dissolved within 5 min. Ocular distribution of CsA in a whole porcine eye perfusion model showed a significant increase of CsA levels in various posterior segment ocular tissues as compared to a topically applied ophthalmic emulsion (Restasis®) (P < 0.001). Dissolving MNs of CsA were prepared, and the MN arrays can deliver CsA to the back of the eye offering potential for treating various inflammatory diseases.

Glass Microneedles: A Case Study for Regulatory Approval Using a Quality by Design Approach

In this paper, a roadmap is provided for the regulatory approval of one of the exciting and dynamic drug delivery fields, microneedles, by using a Quality by Design approach to pharmaceutical product development. In this regard, a quality target product profile (QTPP) and the critical quality attributes (CQA) of microneedles are identified. A case study of the recently patented method of fabricating glass microneedles entirely from a therapeutic agent, thus eliminating the requirement for additional excipients is discussed. The glass microneedle, ArrayPatch, is a propriety wearable device with platform potential consisting of an array of sharp, but painless, dissolvable microneedles manufactured with 100% drug. The microneedles penetrate the skin on application and dissolve to deliver a locally effective dose. The in vitro characterization of the microneedle CQAs under WHO-guided stability conditions will be described to assess the manufacturing readiness of ArrayPatch.  A live technical video is also provided, presenting a unique procedure of jugular vein cannulation through the ear vein of a pig animal model to study the in vivo pharmacokinetics of ArrayPatch compared to standard-of-care marketed products.

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

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

Assessing the risk of a clinically significant infection from a Microneedle Array Patch (MAP) product

Microneedle Array Patches (MAPs) are an emerging dosage form that creates transient micron-sized disruptions in the outermost physical skin barrier, the stratum corneum, to facilitate delivery of active pharmaceutical ingredients to the underlying tissue. Numerous MAP products are proposed and there is significant clinical potential in priority areas such as vaccination. However, since their inception scientists have hypothesized about the risk of a clinically significant MAP-induced infection. Safety data from two major Phase 3 clinical trials involving hundreds of participants, who in total received tens of thousands of MAP applications, does not identify any clinically significant infections. However, the incumbent data set is not extensive enough to make definitive generalizable conclusions. A comprehensive assessment of the infection risk is therefore advised for MAP products, and this should be informed by clinical and pre-clinical data, theoretical analysis and informed opinions. In this article, a group of key stakeholders identify some of the key product- and patient-specific factors that may contribute to the risk of infection from a MAP product and provide expert opinions in the context of guidance from regulatory authorities. Considerations that are particularly pertinent to the MAP dosage form include the specifications of the finished product (e.g. microbial specification), it's design features, the setting for administration, the skill of the administrator, the anatomical application site, the target population and the clinical context. These factors, and others discussed in this article, provide a platform for the development of MAP risk assessments and a stimulus for early and open dialogue between developers, regulatory authorities and other key stakeholders, to expedite and promote development of safe and effective MAP products.

Microneedles as a momentous platform for psoriasis therapy and diagnosis: A state-of-the-art review

Psoriasis is a chronic, autoimmune, and non-communicable skin disease with a worldwide prevalence rate of 2-3%, creating an economic burden on global health. Some significant risk factors associated with psoriasis include genetic predisposition, pathogens, stress, medications, etc. In addition, most patients with psoriasis should also deal with comorbidities such as psoriatic arthritis, inflammatory bowel diseases, cardiovascular diseases, and psychological conditions, including suicidal thoughts. Based on its severity, the treatment approach for psoriasis is categorised into three types, i.e., topical therapy, systemic therapy, and phototherapy. Topical therapy for mild-to-moderate psoriasis faces several issues, such as poor skin permeability, low skin retention of drug formulation, greasy texture of topical vehicle, lack of controlled release, and so on. On the other arrow, systemic therapy via an oral or parenteral route of drug administration involves numerous drawbacks, including first-pass hepatic metabolism, hepatotoxicity, gastrointestinal disturbances, needle pain and phobia, and requirement of healthcare professional to administer the drug. To overcome these limitations, researchers devised a microneedle-based drug delivery system for treating mild-to-moderate and moderate-to-severe psoriasis. A single microneedle system can deliver the anti-psoriatic drugs either locally (topical) or systemically (transdermal) by adjusting the needle height without involving any pain. In this contemplate, the current review provides concise information on the pathophysiology, risk factors, and comorbidities of psoriasis, followed by their current treatment approaches and limitations. Further, it meticulously discusses the potential of microneedles in psoriasis therapy and diagnosis, along with descriptions of their patents and clinical trials.

The clinical and translational prospects of microneedle devices, with a focus on insulin therapy for diabetes mellitus as a case study

Microneedles have the clinical advantage of being able to deliver complex drugs across the skin in a convenient and comfortable manner yet haven't successfully transitioned to medical practice. Diabetes mellitus is a complicated disease, which is commonly treated with multiple daily insulin injections, contributing to poor treatment adherence. Firstly, this review determines the clinical prospect of microneedles, alongside considerations that ought to be addressed before microneedle technology can be translated from bench to bedside. Thereafter, we use diabetes as a case study to consider how microneedle-based-technology may be successfully harnessed. Here, publications referring to insulin microneedles were evaluated to understand whether insertion efficiency, angle of insertion, successful dose delivery, dose adjustability, material biocompatibility and therapeutic stability are being addressed in early stage research. Moreover, over 3,000 patents from 1970-2019 were reviewed with the search term '"microneedle" AND "insulin"' to understand the current status of the field. In conclusion, the reporting of early stage microneedle research demonstrated a lack of consistency relating to the translational factors addressed. Additionally, a more rational design, based on a patient-centred approach is required before microneedle-based delivery systems can be used to revolutionise the lives of people living with diabetes following regulatory approval.

Recent Advancements in Microneedle Technology for Multifaceted Biomedical Applications

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

Microneedle-mediated transdermal nanodelivery systems: a review

The greatest limitation in the development of transdermal drug delivery systems is that only a few drugs can permeate the skin due to the barrier function of the stratum corneum. Active and passive methods are generally available for improving the ability of drug transdermal delivery. However, nanoparticles, as a passive approach, exhibit capacity-constrained permeation enhancement. Thus, microneedle-mediated nanoparticles possess enormous potential and broad prospects. Microneedles promote the penetration of macromolecules by creating microchannels on the skin surface. In this review, the prevailing subknowledge on microneedles (mechanism, classification, and applications of microneedles combined with nanoparticles) is discussed to provide a guideline for readers and a basic reference for further in-depth studies of this novel drug delivery system.

Dissolvable carboxymethyl cellulose/polyvinylpyrrolidone microneedle arrays for transdermal delivery of Amphotericin B to treat cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a significant public health problem caused by different species of Leishmania parasites. Due to low skin permeability, the development of an effective system for delivery of Amphotericin B (AMB), the common effective drug for leishmaniasis treatment, is required to replace the unpleasant and problematic injections. To overcome this problem, a dissolvable microneedle (MN) patch was developed, using biodegradable polymers (a mixture of polyvinylpyrrolidone and carboxymethyl cellulose) for AMB's transdermal delivery. Scanning electron microscopy and fluorescent images showed successful fabrication of the MNs and homogeneous dispersion of the drug into the needles. MNs showed good mechanical properties with the ability to penetrate the rat skin and reach the lower layers. After insertion to the skin, the MNs were rapidly dissolved to release the encapsulated drug, and the resulted micropores in the skin were quickly resealed within 30 min. MN patches showed non-toxicity as exposed to HT-29 cell line. Flow cytometry results showed a potent in vitro leishmanicidal activity of AMB-loaded MN patches against the Leishmania parasites (up to 86% of the parasites' death). Taken together, MN patches might represent a new, efficient and clinically translational approach for transdermal AMB delivery to treat CL.

Design and Evaluation of Dissolving Microneedles for Enhanced Dermal Delivery of Propranolol Hydrochloride

Oral propranolol hydrochloride has been the first-line treatment for infantile hemangioma (IH), whereas systemic exposure to propranolol has the potential of causing serious adverse reactions. Dermal delivery of propranolol is preferable due to high local drug concentration and fewer adverse effects. However, propranolol hydrochloride (BCS class I) is highly hydrophilic and has difficulty in penetrating the stratum corneum (SC) barrier. Dissolving microneedles (MNs) are an efficient tool for overcoming the barrier of the SC and enhancing dermal drug delivery. In this study, propranolol hydrochloride-loaded dissolving MNs were fabricated by using hyaluronic acid and polyvinyl pyrrolidone as matrix materials. Controllable drug loading in needle tips was achieved by a two-step casting procedure. The needles were good in mechanical strength for penetrating the SC while presented excellent dissolving capability for releasing propranolol hydrochloride. In comparison with the solution counterpart, irrespective of being applied to intact skin or solid MNs-pretreated skin, dissolving MNs significantly increased the permeability and skin retention of propranolol. In conclusion, dissolving MNs could be a potential approach for enhancing dermal delivery of propranolol to treat IH.

Development of lysozyme loaded microneedles for dermal applications

Microneedles are being widely explored for dermal delivery of macromolecules. They have the capability and the potential for entrapping enzymes such as lysozyme within a polymeric matrix that do not alter the protein integrity, enable a bolus or a sustained release. In this study, polymeric microneedles have been used to entrap lysozyme (14 kDa) using biodegradable and dissolving polymers such as Polyvinylpyrrolidone (PVP), Hyaluronic acid (HA), and Poly lactic co glycolic acid (PLGA). Microneedles were fabricated using mold casting technique. The structural strength was determined using texture analyzer where PLGA microneedles (16.56 ± 0.23 g) required a significantly higher puncture force as compared to PVP and HA microneedles (12.10 ± 0.04 g and 11.40 ± 0.32 g respectively). The release profile showed an instantaneous release in the case of PVP and HA with almost 50% of the drug released within the first 20 min in both cases and remaining drug was released within the next 2 h whereas Lysozyme entrapped in PLGA showed a release of 29.53 ± 0.78% of lysozyme 72 h. Lysozyme entrapped in microneedles was characterized using circular dichroism and SDS-page analysis for structural stability post microneedle fabrication. The stability studies were performed on these polymeric microneedles for understanding its delivery potential of bio-active lysozyme. At the end of 90 days lysozyme concentration entrapped was 90.35 ± 0.06% 93.76 ± 0.34% 91.74 ± 0.37% for PVP, HA and PLGA respectively. The protein integrity remained intact for three months (α ₊ β) sheets remained intact in the three different polymeric microneedles. The enzyme assay showed that the enzyme entrapped inside microneedles is biologically active and could be used to lyse bacterial infections for dermal applications. However, a detailed analysis of protein formulations would be useful for extending microneedles applications in wounds, skin infections.