Microwave‐Assisted Preparation of Hydrogel‐Forming Microneedle Arrays for Transdermal Drug Delivery Applications

Abstract

A microwave (MW)‐assisted crosslinking process to prepare hydrogel‐forming microneedle (MN) arrays was evaluated. Conventionally, such MN arrays are prepared using processes that includes a thermal crosslinking step. Polymeric MN arrays were prepared using poly(methyl vinyl ether‐alt‐maleic acid) crosslinked by reaction with poly(ethylene glycol) over 24 h at 80 °C. Polymeric MN arrays were prepared to compare conventional process with the novel MW‐assisted crosslinking method. Infrared spectroscopy was used to evaluate the crosslinking degree, evaluating the area of the carbonyl peaks (2000–1500 cm−1). It was shown that, by using the MW‐assisted process, MN with a similar crosslinking degree to those prepared conventionally can be obtained in only 45 min. The effects of the crosslinking process on the properties of these materials were also evaluated. For this purpose swelling kinetics, mechanical characterisation, and insertion studies were performed. The results suggest that MN arrays prepared using the MW assisted process had equivalent properties to those prepared conventionally but can be produced 30 times faster. Finally, an in vitro caffeine permeation across excised porcine skin was performed using conventional and MW‐prepared MN arrays. The release profiles obtained can be considered equivalent, delivering in both cases 3000–3500 μg of caffeine after 24 h.

Successful application of large microneedle patches by human volunteers

“…While the earliest work was rightly centred on the fundamental science of delivery and understanding of the resulting physiological effects, recent years have seen enhanced emphasis on translation to patient benefit and commercial return, with several notable companies making progress towards commercialisation. Indeed, a number of studies examining patient usability (Birchall et al, 2011, Donnelly et al, 2014a, Vicente-Pérez et al, 2016), scaled-up manufacture and quality control testing (Larrañeta et al, 2015, Larrañeta et al, 2016b, Lutton et al, 2015b), sterile production (McCrudden et al, 2015a) and regulatory considerations (Lutton et al, 2015a) have now been published. MN with applications in improving skin appearance are now available commercially, though it is notable that these are not approved drug products (McCrudden et al, 2015b).…”

“…The needle cavities were filled after applying positive pressure (3–4 bar) to the formulation for 15 min. MN arrays were left to dry for 48 h at room temperature and were then crosslinked by esterification through heating at 80 °C for 24 h (Donnelly et al, 2012a, Donnelly et al, 2014b, Larrañeta et al, 2015, Lutton et al, 2015b). The MN arrays were stored under ambient until assembled into large patches.…”

Hydrogel-Forming Microneedle Arrays Made from Light-Responsive Materials for On-Demand Transdermal Drug Delivery

“…The swelling process of this type of material requires more than 24 hours to reach maximum swelling. The swelling process for this type of material is slower in comparison to other materials used for the preparation of hydrogel-forming MN arrays such as Gantrez ® AN-139 or Gantrez ® S-97 that are able to reach maximum swelling degrees in less than 24 hours (20,42). Moreover, the maximum amount of water that pHEMA hydrogels are able to uptake is substantially smaller than the previously described materials.…”

“…Moreover, the maximum amount of water that pHEMA hydrogels are able to uptake is substantially smaller than the previously described materials. The pHEMA hydrogel shows maximum swelling degrees of around 50% while for Gantrez ® hydrogels the values are higher than 1000% after 24h (20,42). The lower swelling degree combined with the slower swelling process makes this type of material more suitable for the production of prolonged drug delivery systems.…”

Microneedle Manufacture: Assessing Hazards and Control Measures

“…It has been estimated that thumb pressure alone is sufficient to enable successful MN application in almost 90% of cases [21,22]. This facile application and pain-free administration therefore further compounds the risk where accidental puncture could go relatively unnoticed, and it could be argued that the careless handling or disposal of spent patches could be a greater hazard than a conventional hypodermic needle, which, by its visibility, can immediately induce a degree of caution [5].…”