Micromoulding microneedle array patches under vacuum, hands-free!

Our hands-free, ‘vac-and-fill’ micromoulding technique prevented air entrapment and bubble formation in viscous formulations when degassed under vacuum. Image from Smith E, et al. Int J Pharm 2024;650:123706. Licence: CC BY 4.0 Deed.

Our latest paper, Vac-and-fill: A micromoulding technique for fabricating microneedle arrays with vacuum-activated, hands-free mould-filling, has been published in the International Journal of Pharmaceutics. It’s open access, so head over there to read the full-text article for free!

This paper reports the solution to a problem that took us several months to solve. We were trying to mould a microneedle array patch. There are basically two ways to do it: you fill the mould with the liquid formulation and either centrifuge it or degas it under vacuum. Both techniques are widely reported in the literature. They have been designed to force any air out of the microcavities in the mould, so that the formulation can enter them to form the microneedles. We didn’t have the right rotor to go with the centrifuge, so we opted for the vacuum degassing technique, fully expecting it to be a walk in the park. What a disappointment that turned out to be! We discovered that our formulation was too viscous to allow the air to escape. We ended up with a lot of air bubbles trapped in the liquid formulation.

We quickly realised that the vacuum degassing technique reported in the literature had used low polymer concentrations, which meant that their liquid formulations were not as viscous as ours. To micromould the microneedle array patch successfully from our viscous formulation, we had to remove the air first before filling the formulation into the mould. But how would one fill the mould under vacuum?

The answer: a modified syringe, a 3D-printed part, some painstaking calibration, and viola! The paper describes our solution in full, but here’s a peek of the contraption in action.

This is Emma’s first paper and our first together with Dr Katarina Novakovic‘s group. Congratulations, Emma, and thank you team for the hard work!

PolyU collaborators visit Newcastle to conduct joint microneedle study

2023 seemingly left in a haste. Stepping into 2024, we welcomed our collaborators from The Hong Kong Polytechnic University (PolyU) to Newcastle, to conduct a joint study on microneedle formulation for drug delivery and diagnostics. Merab Naveed, Hubert Chan and Dr Thomas Lee from PolyU’s Biomedical Engineering Department spent nearly two weeks with us, running experiments and exchanging ideas with us. Newcastle University students, Begho Obale and Jakub Masloch, who completed their MPharm research projects with us, also lent their expertise to this joint study. Among other things, Begho made a dancing microneedle mould – the first ever reported. It was a most wonderful way to start the new year.

So how did our guests find it? I know Hubert enjoyed the unique learning experience – his words, not mine. I’m really pleased that we’re able to organise this research exchange programme. Thanks also go to Dr Wing Man Lau and Dr Hin Chung Lau of PolyU, the other two academic advisors on the project, for making this happen.

Biosensors special issue: Microneedle diagnostics

I am guest-editing a special issue of the Biosensors journal with Professor Ryan Donnelly of Queens University Belfast. We would like to invite manuscripts from colleagues who work in this area. The submission deadline is 30 November 2021. Please see the special issue announcement on the journal website for details.

If your work concerns polymers for drug delivery or wound healing, then please also check out the Polymers special issue that I am guest-editing with Dr Wing Man Lau, which is still open for submission.

Review: Microneedle-based devices for point-of-care infectious disease diagnostics

We have published a review article on microneedles as a technological platform for diagnosing infectious diseases. In this review, we enumerate the infectious diseases that could potentially be diagnosed in the skin, examine the mechanisms of existing microneedle diagnostic technologies, and evaluate their applications in infectious disease diagnosis. This publication is timely given that we’re in the middle of a infectious disease pandemic.

Figure 1: Microneedles inserted into the skin may extract or detect disease markers in situ. Diagnostic tests for infectious diseases should ideally be both specific and rapid.

Any diagnostic test has to be specific to be useful (Figure 1). For a potentially deadly diseases, the more rapid the diagnosis, the better, because it buys precious time for the patient to seek early treatment, which could save lives. However, for infectious diseases that can be transmitted by close contact, it’s also desirable that the patient can administer the test themselves without too much discomfort. Many tests do better in meeting some of these criteria at the expense of other criteria. For example, I took the PCR test for COVID-19. I am sure the test itself was highly specific, but the nasal and throat swabs were uncomfortable. The diagnosis wasn’t exactly ‘rapid’ either — I got my result several days later (mainly due to limited test capacity at that time, but that has improved significantly since). Microneedle devices are painless to administer on the skin, and tests can produce real-time or near-real-time results. Not all of these studies have been on infectious diseases, of course. The technology is still nascent but the potentials are huge.

The review article is currently in press, but a pre-proof is already available for download from Acta Pharmaceutica Sinica B. There have been a number of minor corrections to this pre-proof (mainly typographical and referencing error) which will appear in the final publication, but the pre-proof should satisfy the impatient for now.

Congratulations to everyone involved in putting this publication together.

Perspective: The diagnostic potential of microneedles in infectious diseases

The recent COVID-19 pandemic brought the healthcare systems in many countries to their knees. One of the key problems that became evident early on was the lack of diagnostic tools that were rapid and readily accessible to the public.

Diagnostics is what we do as a research team. Naturally, we contemplated what we could do in a situation like this. The result is a perspective article published in Precision Nanomedicine, the official journal of the European Foundation for Nanomedicine.

The conclusion? Microneedle systems excel in many ways as a diagnostic tool. Various microneedle platforms have demonstrated advantages of portability, self-administrability, affordability and scalability over other diagnostic platforms. The potential is huge but the technology is still in its infancy. We need more research to turn that potential into tangible clinical benefits, but we can’t do it alone. Cross-disciplinary collaboration and stakeholder support will be needed to drive this effort forward.

The article is published under the Creative Commons BY-NC-SA 4.0 licence, so please feel free to distribute widely, adapt and reuse for non-commercial purposes, and share any derived work, citing:

Dixon RV, Lau WM, Moghimi SM, Ng KW (2020) The diagnostic potential of microneedles in infectious diseases. Precision Nanomedicine 3(4):629–640 . https://doi.org/10.33218/001c.13658

Welcoming Hassan

Just as we were about to wind down our lab operations for Christmas, we welcomed postdoctoral research associate, Dr Hassan Elsana, into our team this week. Hassan will be working on an EPSRC-funded project researching microneedle-mediated drug delivery in the skin.

This project is a collaboration with Dr Wing Man Lau (School of Pharmacy) and Dr Katarina Novakovic (School of Engineering). We have high hopes for this project.

Exciting times ahead, and I don’t just mean Christmas!

Collaborative paper on 3D cell culture for evaluating biomarker-capturing microneedle devices

Update: Author manuscript available

One of the challenges in developing microneedle devices to capture disease biomarkers from the skin is the lack of suitable skin specimens in which to test the devices. Donor skin specimens that carry the specific target diseases simply do not come by easily.

I first discussed this challenge with Eirini Velliou, Tao Chen and Guoping Lian in April 2016. We decided to tackle it by growing our own model of diseased skin in the lab. Experimental work started shortly after, and continued to develop following my relocation to Newcastle University in 2017. Earlier this week, we described the collaborative work in a joint publication in the journal Sensors and Actuators B: Chemical.

We took a grounds-up approach by growing melanoma skin cancer cells in a three-dimensional (3D) culture, supported structurally by a biocompatible polymer scaffold. This allowed us to simulate not only the biological microenvironment around the cells, but also the three-dimensional structure of the skin for microneedle insertion. Importantly, it was a simple and inexpensive, yet versatile, laboratory model to set up.

In pioneering the 3D cell culture model for evaluating microneedle devices against a skin cancer biomarker, we also demonstrated – for the first time – successful capture of S100B (a biomarker for melanoma skin cancer) in situ using our immunodiagnostic microneedle device.

Stella Totti, formerly a PhD student and now a postdoctoral researcher in Eirini’s research group, is the first author. I am especially pleased that hard work has paid off for Lorraine Dale, a former MSc student of mine, who contributed greatly to this work and is a co-author on this paper.

The paper is free to read until 28 July 2019 via this link: https://authors.elsevier.com/c/1ZBcy3IQMPEdJi

Back in production

I’m pleased to announce that, 2 months after the big move to Newcastle University @UniofNewcastle, the 4D Laboratory is back in production!

Today, the first batch of polymeric microneedle arrays rolled off the production line based in the School of Pharmacy @NCL_Pharmacy. The batch includes some new microneedle designs which we have not reported on before (until now, I guess). These microneedle arrays will now be used in some exciting new projects, which hopefully I will be able to share with you in the not-so-distant future. For now, please savour these teaser images:

Microneedle array: conventional design

Microneedle array: new design