Hydrogel-Forming Microneedle Arrays Can Be Effectively Inserted in Skin by Self-Application: A Pilot Study Centred on Pharmacist Intervention and a Patient Information Leaflet

To investigate, for the first time, the influence of pharmacist intervention and the use of a patient information leaflet on self-application of hydrogel-forming microneedle arrays by human volunteers without the aid of an applicator device. A patient information leaflet was drafted and pharmacist counselling strategy devised. Twenty human volunteers applied 11 x 11 arrays of 400 mu m hydrogel-forming microneedle arrays to their own skin following the instructions provided. Skin barrier function disruption was assessed using transepidermal water loss measurements and optical coherence tomography and results compared to those obtained when more experienced researchers applied the microneedles to the volunteers or themselves. Volunteer self-application of the 400 mu m microneedle design resulted in an approximately 30% increase in skin transepidermal water loss, which was not significantly different from that seen with self-application by the more experienced researchers or application to the volunteers. Use of optical coherence tomography showed that self-application of microneedles of the same density (400 mu m, 600 mu m and 900 mu m) led to percentage penetration depths of approximately 75%, 70% and 60%, respectively, though the diameter of the micropores created remained quite constant at approximately 200 mu m. Transepidermal water loss progressively increased with increasing height of the applied microneedles and this data, like that for penetration depth, was consistent, regardless of applicant. We have shown that hydrogel-forming microneedle arrays can be successfully and reproducibly applied by human volunteers given appropriate instruction. If these outcomes were able to be extrapolated to the general patient population, then use of bespoke MN applicator devices may not be necessary, thus possibly enhancing patient compliance.