The skin, the largest organ in the body, is a highly absorptive organ focused in the transdermal delivery system. Macroscale delivery systems that can be locally implanted on the skin as well as avoid all the complications associated with the systemic delivery of therapeutics have captured researchers’ attention, in recent years. An example of such a system is the microneedle array-based devices that can be used to efficiently deliver both small and macro-molecules and compounds through the skin. Microneedle array-based devices can comprise of dozens to hundreds of micron-sized polymer/metal/glass/ceramic-based needles with different features and advantages benefiting from their potential for tailored and smart designs. These micro-projections generally present dimensions approx. 50 to 250 μm in wide and lengths that can range from few micrometres to those as long as 1500 μm. The microneedle array-based method is far better than conventional transdermal delivery systems because of benefits such as painless, minimally invasive, convenience, improved patient acquiescence and a reduction in the creation of hazardous waste. Furthermore, microneedle arrays can contain the therapeutic in a dried solid form, which increases its thermostability and facilitates the application on the target area.
Research in the field of transdermal delivery system development has progressed rapidly for microneedle array devices and is divided into four major classifications: (1) solid microneedles, (2) hollow microneedles, (3) dissolving microneedles, and (4) coated microneedles. Every type of these microneedles has particular advantages corresponding according to their unique designs and properties. Currently, the applications of microneedle array devices have expanded beyond their representative biomedical applications relating to long-term disease treatment, immunobiological administration, disease diagnosis, and cosmetic ﬁeld. In addition to the small molecule drugs, microneedle arrays can also be used to deliver a large levels of macromolecules in a controllable manner, such as insulin, growth hormones, immunobiological vaccine, receptor agonist, proteins and peptides, which could be transferred into the epidermis directly to improve theirs drug efﬁcacy signiﬁcantly for disease long-term treatment and immunobiological administration.
There is a growing focus on microneedle array devices as transdermal systems to deliver compounds and traditional drugs in academia, and the microneedle array device strategy is a powerful approach to the management of dermatological conditions. Although microneedle array devices have significant advantages in drug delivery in comparison to traditional transdermal methods, it has to be pointed out that microneedle array devices remain a relatively new technology and many procedures in model design and production are not optimal. The performance of matrix material varies in different conditions and needs further investigation. Many factors affect the final commercial price. Microneedle array devices are an invasive technique applied to the skin and the possibility of skin irritation should also be considered. Further investigations on the application of microneedle array devices are required for new solutions to existing challenges and expand the scope of application.
Prof Ryan Donnelly, Chair of Pharmaceutical Technology, at the Queen’s University Belfast in the UK is leading the way in the design and development of polymeric-based microneedle array devices for transdermal drug delivery, with a strong emphasis on improving therapeutic outcomes for patients [1-6]. Additionally, Prof Eoin O’Cearbhaill, from the Science Foundation Ireland Research Centre i-Form, is utilising additive manufacturing technology to push the boundaries of metallic-based microneedle array devices for transdermal drug delivery . Additionally, researchers from Emory University and the Georgia Institute of Technology published reported their finding from a clinical trial to evaluate the safety and efficacy of a flu vaccine delivered via microneedles . The trial showed that microneedle array devices caused less pain and soreness when compared to conventional injections. More importantly, it was demonstrated that the immune responses were similar between people who received the microneedle vaccine and those who received the traditional injection.
An increased focus on the development of microneedle array devices brings considerable confidence that existing challenges will be tackled and that more evidence on the clinical practicality and therapeutic efficacy of this smart method will be found. Moreover, the successful application of microneedle array devices is dependent on several important parameters, such as the therapeutics concentration, the exposure time, and the release sequence. The merging of microneedle array device technology with layer-by-layer production techniques could be a very promising and uncomplicated approach to allow the production of complex and hierarchically organised structures. A revolutionary impact on the drug delivery field from the development and use of microneedle array devices for improving not only the efficacy of therapies but also improve the transdermal drug delivery in the context of other health disorders is envisioned.
Please share your views and opinions on the application of microneedle array-based devices for transdermal drug delivery – where do you see the next research opportunities in this exciting field of biomaterials.
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2. Donnelly et al . Hydrogel‐forming microneedle arrays for enhanced transdermal drug delivery. Advanced Functional Materials. 2012 Dec 5;22(23):4879-90.
3. Alkilani et al . Transdermal drug delivery: innovative pharmaceutical developments based on disruption of the barrier properties of the stratum corneum. Pharmaceutics. 2015 Dec;7(4):438-70.
4. Larraneta et al. Microneedle arrays as transdermal and intradermal drug delivery systems: Materials science, manufacture and commercial development. Materials Science and Engineering: R: Reports. 2016 Jun 1;104:1-32.
5. Ramadon et al . Enhancement strategies for transdermal drug delivery systems: current trends and applications. Drug Delivery and Translational Research. 2021 Jan 20:1-34.
6. Al-Kasasbeh et al . Evaluation of the clinical impact of repeat application of hydrogel-forming microneedle array patches. Drug delivery and translational research. 2020 Jun;10(3):690-705.
7. Krieger et al. Simple and customizable method for fabrication of high-aspect ratio microneedle molds using low-cost 3D printing. Microsystems & Nanoengineering. 2019 Sep 9;5(1):1-4.
8. Rouphael et al . The safety, immunogenicity, and acceptability of inactivated influenza vaccine delivered by microneedle patch (TIV-MNP 2015): a randomised, partly blinded, placebo-controlled, phase 1 trial. The Lancet. 2017 Aug 12;390(10095):649-58.