In vivo and qualitative studies investigating the translational potential of microneedles for use in the older population

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.

Advance and Challenges in the Treatment of Skin Diseases with the Transdermal Drug Delivery System

Skin diseases are among the most prevalent non-fatal conditions worldwide. The transdermal drug delivery system (TDDS) has emerged as a promising approach for treating skin diseases, owing to its numerous advantages such as high bioavailability, low systemic toxicity, and improved patient compliance. However, the effectiveness of the TDDS is hindered by several factors, including the barrier properties of the stratum corneum, the nature of the drug and carrier, and delivery conditions. In this paper, we provide an overview of the development of the TDDS from first-generation to fourth-generation systems, highlighting the characteristics of each carrier in terms of mechanism composition, penetration method, mechanism of action, and recent preclinical studies. We further investigated the significant challenges encountered in the development of the TDDS and the crucial significance of clinical trials.

Dissolving Microneedles Loaded with Gestodene: Fabrication and Characterization In Vitro and In Vivo

Background

Gestodene (GEST) is widely used in female contraception. It is currently being used as an oral contraceptive. However, unfortunately, oral contraceptives are often associated with several bothersome side effects and poor compliance. Therefore, a sustained delivery system for GEST to overcome these shortcomings is highly desirable.

Objectives

The present study successfully developed a kind of novel dissolving microneedles (DMNs) with a potential for sustained release and a minimally invasive intradermal treatment of GEST.

Methods

The dissolving microneedles containing GEST were fabricated using polyvinylpyrrolidone as the base material. The characteristics in vitro and pharmacokinetics in vivo of GEST-loaded DMNs were investigated.

Results

The results showed that the microneedle could pierce the porcine skin and release the drug at an average dose of 20µg/cm2 daily for seven days. The pharmacokinetic experiment of the microneedles indicated that the plasma level of GEST in rats increased with increasing drug dosage, and the plasma drug concentration-time curves were much flatter compared with subcutaneous injection and oral administration. In addition, no cutaneous irritation was observed.

Conclusions

GEST-loaded DMNs may be a promising intradermal sustained delivery system for contraceptive use.

Nanomedicines and microneedles: a guide to their analysis and application

The fast-advancing progress in the research of nanomedicine and microneedle applications in the past two decades has suggested that the combination of the two concepts could help to overcome some of the challenges we are facing in healthcare. They include poor patient compliance with medication and the lack of appropriate administration forms that enable the optimal dose to reach the target site. Nanoparticles as drug vesicles can protect their cargo and deliver it to the target site, while evading the body's defence mechanisms. Unfortunately, despite intense research on nanomedicine in the past 20 years, we still haven't answered some crucial questions, e.g. about their colloidal stability in solution and their optimal formulation, which makes the translation of this exciting technology from the lab bench to a viable product difficult. Dissolvable microneedles could be an effective way to maintain and stabilise nano-sized formulations, whilst enhancing the ability of nanoparticles to penetrate the stratum corneum barrier. Both concepts have been individually investigated fairly well and many analytical techniques for tracking the fate of nanomaterials with their precious cargo, both in vitro and in vivo, have been established. Yet, to the best of our knowledge, a comprehensive overview of the analytical tools encompassing the concepts of microneedles and nanoparticles with specific and successful examples is missing. In this review, we have attempted to briefly analyse the challenges associated with nanomedicine itself, but crucially we provide an easy-to-navigate scheme of methods, suitable for characterisation and imaging the physico-chemical properties of the material matrix.

cGAMP/Saponin Adjuvant Combination Improves Protective Response to Influenza Vaccination by Microneedle Patch in an Aged Mouse Model

Current strategies for improving protective response to influenza vaccines during immunosenescence do not adequately protect individuals over 65 years of age. Here, we used an aged mouse model to investigate the potential of co-delivery of influenza vaccine with the recently identified combination of a saponin adjuvant Quil-A and an activator of the STING pathway, 2’3 cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) via dissolving microneedle patches (MNPs) applied to skin. We demonstrate that synergy between the two adjuvant components is observed after their incorporation with H1N1 vaccine into MNPs as revealed by analysis of the immune responses in adult mice. Aged 21-month-old mice were found to be completely protected against live influenza challenge after vaccination with the MNPs adjuvanted with the Quil-A/cGAMP combination (5 µg each) and demonstrated significantly reduced morbidity compared to the observed responses in these mice vaccinated with unadjuvanted MNPs. Analysis of the lung lysates of the surviving aged mice post challenge revealed the lowest level of residual inflammation in the adjuvanted groups. We conclude that combining influenza vaccine with a STING pathway activator and saponin-based adjuvant in MNPs is a novel option for skin vaccination of the immunosenescent population, which is at high risk for influenza.

Directly Compressed Tablets: A Novel Drug-Containing Reservoir Combined with Hydrogel-Forming Microneedle Arrays for Transdermal Drug Delivery

Microneedle (MN) patches consist of a hydrogel-forming MN array and a drug-containing reservoir. Drug-containing reservoirs documented in the literature include polymeric films and lyophilized wafers. While effective, both reservoir formulations are aqueous based, and so degradation can occur during formulation and drying for drugs inherently unstable in aqueous media. The preparation and characterization of novel, nonaqueous-based, directly compressed tablets (DCTs) for use in combination with hydrogel-forming MN arrays are described for the first time. In this work, a range of drug molecules are investigated. Precipitation of amoxicillin (AMX) and primaquine (PQ) in conventional hydrogel-forming MN arrays leads to use of poly(vinyl alcohol)-based MN arrays. Following in vitro permeation studies, in vivo pharmacokinetic studies are conducted in rats with MN patches containing AMX, levodopa/carbidopa (LD/CD), and levofloxacin (LVX). Therapeutically relevant concentrations of AMX (≥2 µg mL^-1 ), LD (≥0.5 µg mL^-1 ), and LVX (≥0.2 µg mL^-1 ) are successfully achieved at 1, 2, and 1 h, respectively. Thus, the use of DCTs offers promise to expand the range of drug molecules that can be delivered transdermally using MN patches.

From the laboratory to the end-user: a primary packaging study for microneedle patches containing amoxicillin sodium

Abstract

As microneedle (MN) patches progress towards commercialisation, there is a need to address issues surrounding their translation from the laboratory to the end-user. One important aspect of MN patches moving forward is appropriate primary packaging. This research focuses on MN patches containing amoxicillin (AMX) sodium for the potential treatment of neonatal sepsis in hot and humid countries. A MN patch consists of a hydrogel-forming MN array and a drug-containing reservoir. Improper primary packaging in hot and humid countries may result in degradation of active pharmaceutical ingredients, with the use of substandard medicines a major health concern. The research presented here, for the first time, seeks to investigate the integrity of MN patches in different primary packaging when stored under accelerated storage conditions, according to international guidelines. At pre-defined intervals, the performance of the MN patch was investigated. Major causes of drug instability are moisture and temperature. To avoid unnecessary degradation, suitable primary packaging was sought. After 168 days, the percentage of AMX sodium recovered from drug-containing reservoirs packaged in Protect™ 470 foil was 103.51 ± 7.03%. However, packaged in poly(ester) foil, the AMX sodium content decreased significantly (p = 0.0286), which is likely due to the degradation of AMX sodium by the imbibed moisture. Therefore, convincing evidence was provided as to the importance of investigating the stability of MN patches in primary packaging intended for MN-mediated transdermal delivery so that they are ‘fit for purpose’ when it reaches the end-user. Future work will include qualitative studies to assess MN patch usability.

Graphical abstract

Exploration into the opinions of patients with HIV, healthcare professionals and the lay public of the use of microneedles in clinical practice: highlighting the translational potential for their role in HIV infection

Poor adherence to oral antiretroviral therapy (ART) remains an important challenge in the treatment of HIV. Microneedles (MN) potentially could offer a non-invasive long-acting (LA) delivery approach, avoiding the need for daily dosing of ART. However, this claim has yet to be explored amongst its potential end-users. The aim of this mixed methods study was to investigate the perspectives from various end-users surrounding the translation of MN technology to general clinical practice, with a particular focus on delivery of ART. Quantitative postal questionnaires were distributed amongst healthcare professionals (HCPs) and the lay public (LP). A total of 208 responses were obtained (HCP, 69; LP, 139), with a completion rate of 34.7%. The consensus on MN technology was positive from both demographics (HCP, 97.1%; LP, 98.6%), with further strong support of postulated MN use within HIV (HCP, 97.1%; LP, 98.6%). Qualitative focus groups were employed to investigate in-depth, the perspectives of 12 patients with HIV. Again, consensus on MN technology was positive, highlighting benefits pertinent to HIV, including discreet self-application and potential sustained release thus avoiding daily oral ART and associated side effects. Patient concerns focused on the need for varied MN dosing schedules and a reluctance to change from established ART. The findings of this study provide an initial indication of MN acceptability, particularly for use within HIV, from various end-user demographics. Furthermore, concerns raised advocate the importance of continued translational research in this area and should act as motivators for those in MN development to ensure a patient-centred MN product is delivered.

Microneedle Mediated Transdermal Delivery of Protein, Peptide and Antibody Based Therapeutics: Current Status and Future Considerations

The success of protein, peptide and antibody based therapies is evident - the biopharmaceuticals market is predicted to reach $388 billion by 2024 [1], and more than half of the current top 20 blockbuster drugs are biopharmaceuticals. However, the intrinsic properties of biopharmaceuticals has restricted the routes available for successful drug delivery. While providing 100% bioavailability, the intravenous route is often associated with pain and needle phobia from a patient perspective, which may translate as a reluctance to receive necessary treatment. Several non-invasive strategies have since emerged to overcome these limitations. One such strategy involves the use of microneedles (MNs), which are able to painlessly penetrate the stratum corneum barrier to dramatically increase transdermal drug delivery of numerous drugs. This review reports the wealth of studies that aim to enhance transdermal delivery of biopharmaceutics using MNs. The true potential of MNs as a drug delivery device for biopharmaceuticals will not only rely on acceptance from prescribers, patients and the regulatory authorities, but the ability to upscale MN manufacture in a cost-effective manner and the long term safety of MN application. Thus, the current barriers to clinical translation of MNs, and how these barriers may be overcome are also discussed.

Evaluation of the clinical impact of repeat application of hydrogel-forming microneedle array patches

Hydrogel-forming microneedle array patches (MAPs) have been proposed as viable clinical tools for patient monitoring purposes, providing an alternative to traditional methods of sample acquisition, such as venepuncture and intradermal sampling. They are also undergoing investigation in the management of non-melanoma skin cancers. In contrast to drug or vaccine delivery, when only a small number of MAP applications would be required, hydrogel MAPs utilised for sampling purposes or for tumour eradication would necessitate regular, repeat applications. Therefore, the current study was designed to address one of the key translational aspects of MAP development, namely patient safety. We demonstrate, for the first time in human volunteers, that repeat MAP application and wear does not lead to prolonged skin reactions or prolonged disruption of skin barrier function. Importantly, concentrations of specific systemic biomarkers of inflammation (C-reactive protein (CRP); tumour necrosis factor-α (TNF-α)); infection (interleukin-1β (IL-1β); allergy (immunoglobulin E (IgE)) and immunity (immunoglobulin G (IgG)) were all recorded over the course of this fixed study period. No biomarker concentrations above the normal, documented adult ranges were recorded over the course of the study, indicating that no systemic reactions had been initiated in volunteers. Building upon the results of this study, which serve to highlight the safety of our hydrogel MAP, we are actively working towards CE marking of our MAP technology as a medical device.

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

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

Preparation and characterization of dissolving hyaluronic acid composite microneedles loaded micelles for delivery of curcumin

In order to improve the bioavailability of curcumin (Cur) and patient compliance, a type of novel hyaluronic acid (HA) composite microneedles containing Cur-loaded micelles was designed in this paper. On the one hand, the microneedles matrix solution was prepared by screening the optimal concentration of HA and the better proportion of HA to sodium carboxymethyl starch (CMS-Na). On the other hand, the amphiphilic polymer, named as Quercetin-Dithiodipropionic Acid-Oligomeric Hyaluronic Acid (Que-DA-oHA), was synthesized and characterized using ¹H-NMR. Subsequently, the dialysis method was used to prepare Cur-loaded Que-DA-oHA micelles with an average size of 172.6 ± 11.4 nm and zeta potential of - 33.71 ± 0.45 mV. A micromolding process was used to prepare the micelle-loaded HA composite microneedles. It had been found that when the concentration of HA was 200 mg/mL and the mass ratio of HA to CMS-Na was 2:1, the prepared HA composite microneedles had good mechanical strength. In-skin dissolution kinetics showed that the micelle-loaded HA composite microneedles could dissolve quickly in the skin. In vitro permeation study indicated that the microneedles delivered 74.7% of their drug load over 6 h, which exhibited remarkable drug permeation properties in a short time. Here, we creatively combined micellar technology with microneedle technology to rapidly deliver Cur transdermally for diseases treatment such as melanoma. Graphical abstract.

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.

Technology update: dissolvable microneedle patches for vaccine delivery

Despite vaccination representing one of the greatest advances of modern preventative medicine, there remain significant challenges in vaccine distribution, delivery and compliance. Dissolvable microarray patches or dissolving microneedles (DMN) have been proposed as an innovative vaccine delivery platform that could potentially revolutionize vaccine delivery and circumvent many of the challenges faced with current vaccine strategies. DMN, due to their ease of use, lack of elicitation of pain response, self-disabling nature and ease of transport and distribution, offer an attractive delivery option for vaccines. Additionally, as DMN inherently targets the uppermost skin layers, they facilitate improved vaccine efficacy, due to direct targeting of skin antigen-presenting cells. A plethora of publications have demonstrated the efficacy of DMN vaccination for a range of vaccines, with influenza receiving particular attention. However, before the viable adoption of DMN for vaccination purposes in a clinical setting, a number of fundamental questions must be addressed. Accordingly, this review begins by introducing some of the key barriers faced by current vaccination approaches and how DMN can overcome these challenges. We introduce some of the recent advances in the field of DMN technology, highlighting the potential impact DMN could have, particularly in countries of the developing world. We conclude by reflecting on some of the key questions that remain unanswered and which warrant further investigation before DMNs can be utilized in clinical settings.