Paediatricians' opinions of microneedle-mediated monitoring: a key stage in the translation of microneedle technology from laboratory into clinical practice

Fabrication of pure-drug microneedles for delivery of montelukast sodium

Dissolving microneedle (MN) patches are usually formulated with a blend of drug and excipients added for mechanical strength and drug stabilization. In this study, we developed MNs made of pure drug to maximize drug loading capacity. MN patches were fabricated for transdermal delivery of montelukast sodium (MS) which is used to treat asthma and allergic rhinitis. We developed three different fabrication methods - solvent casting, melt casting, and solvent washing - and determined that filling molds with MS powder followed by a solvent washing method enabled MS to be loaded selectively to the MNs. Drug localization was confirmed with Raman imaging. MNs were able to penetrate in vitro and ex vivo skin models, and maintained strong mechanical properties during 6 months' storage at 22 °C. MS was also stable and compatible with the formulation used for the patch backing layer after 3 months' storage at 40 °C. MS delivery efficiency into skin was 55%, which enabled delivery of 3.2 mg MS into porcine skin ex vivo, which is in the range of MS doses in human clinical use. We conclude that the solvent washing method can be used to prepare MNs containing pure drug, such as MS at milligram doses in a ~ 1 cm² MN patch.

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.

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

Microneedles (MNs) are a novel transdermal drug delivery platform, rapidly progressing from a substantive evidence base, towards commercialisation. As part of this transition, it is important to consider the future use of MNs by older people in order to ensure optimal therapeutic outcomes for this unique and increasing population group. This paper, therefore, considers the use of MNs by those aged over 65 years, investigating insertion parameters in ageing skin, alongside the feasibility and acceptability of the technology. Hydrogel-forming MN arrays were applied to seven subjects aged over 65 years, with breach of the stratum corneum confirmed using optical coherence tomography. Insertion depths recorded in each case were similar to a comparative group, aged 20–30 years. Skin recovery was, however, demonstrated to occur at a slower rate in the older subjects, as measured using transepidermal water loss. Qualitative methods, including focus groups and semi-structured interviews, were employed to collect the views and opinions of older people and community pharmacists respectively. The overall consensus was positive, with a number of benefits to MN-mediated drug delivery identified, such as reduced dosing frequency, improved adherence and an alternative delivery route where oral or injectable medication was precluded. Concerns centred on practical issues associated with age-related functional decline, including, for example, reduced dexterity and skin changes. The presentation of this work collectively provides the first convincing report of the importance of further translational research in this area to support future MN use in older people, ensuring an age-appropriate delivery platform.

Tolerability, usability and acceptability of dissolving microneedle patch administration in human subjects

To support translation of microneedle patches from pre-clinical development into clinical trials, this study examined the effect of microneedle patch application on local skin reactions, reliability of use and acceptability to patients. Placebo patches containing dissolving microneedles were administered to fifteen human participants. Microneedle patches were well tolerated in the skin with no pain or swelling and only mild erythema localized to the site of patch administration that resolved fully within seven days. Microneedle patches could be administered by hand without the need of an applicator and delivery efficiencies were similar for investigator-administration and self-administration. Microneedle patch administration was not considered painful and the large majority of subjects were somewhat or fully confident that they self-administered patches correctly. Microneedle patches were overwhelmingly preferred over conventional needle and syringe injection. Altogether, these results demonstrate that dissolving microneedle patches were well tolerated, easily usable and strongly accepted by human subjects, which will facilitate further clinical translation of this technology.

The Use of a Pressure-Indicating Sensor Film to Provide Feedback upon Hydrogel-Forming Microneedle Array Self-Application In Vivo

PURPOSE

To evaluate the combination of a pressure-indicating sensor film with hydrogel-forming microneedle arrays, as a method of feedback to confirm MN insertion in vivo.

METHODS

Pilot in vitro insertion studies were conducted using a Texture Analyser to insert MN arrays, coupled with a pressure-indicating sensor film, at varying forces into excised neonatal porcine skin. In vivo studies involved twenty human volunteers, who self-applied two hydrogel-forming MN arrays, one with a pressure-indicating sensor film incorporated and one without. Optical coherence tomography was employed to measure the resulting penetration depth and colorimetric analysis to investigate the associated colour change of the pressure-indicating sensor film.

RESULTS

Microneedle insertion was achieved in vitro at three different forces, demonstrating the colour change of the pressure-indicating sensor film upon application of increasing pressure. When self-applied in vivo, there was no significant difference in the microneedle penetration depth resulting from each type of array, with a mean depth of 237 μm recorded. When the pressure-indicating sensor film was present, a colour change occurred upon each application, providing evidence of insertion.

CONCLUSIONS

For the first time, this study shows how the incorporation of a simple, low-cost pressure-indicating sensor film can indicate microneedle insertion in vitro and in vivo, providing visual feedback to assure the user of correct application. Such a strategy may enhance usability of a microneedle device and, hence, assist in the future translation of the technology to widespread clinical use.