Arrays of hollow out-of-plane microneedles made by metal electrodeposition onto solvent cast conductive polymer structures

Abstract

Transdermal drug delivery using microneedles is a technique to potentially replace hypodermic needles for injection of many vaccines and drugs. Fabrication of hollow metallic microneedles so far has been associated with time-consuming steps that restrict batch production of these devices. Here, we are presenting a novel method for making metallic microneedles with any desired height, spacing, and lumen size. In our process, we use solvent casting to coat a mold, which contains an array of pillars, with a conductive polymer composite layer. The conductive layer is then used as a seed layer in a metal electrodeposition process. To characterize the process, the conductivity of the polymer composite with respect to different filler concentrations was investigated. In addition, plasma etching of the polymer was characterized. The electroplating process was also studied further to control the thickness of the microneedle array plate. The strength of the microneedle devices was evaluated through a series of compression tests, while their performance for transdermal drug delivery was tested by injection of 2.28 μm fluorescent microspheres into animal skin. The fabricated metallic microneedles seem appropriate for subcutaneous delivery of drugs and microspheres.

Development and Validation of an Artificial Mechanical Skin Model for the Study of Interactions between Skin and Microneedles

“…MN Insertions Profi ling : Single hollow nickel MNs were fabricated according to Mansoor et al [ 36 ] Single MN insertions onto FT skin samples were performed using a Q400 TMA instrument at 35% RH and 100% RH. Single MNs were mounted onto the penetration probe (cylindrical tip with a diameter of 2.54 mm) and applied normal to the skin surface at 10 N min −1 to a maximum force of 2 N. During the insertions, the displacement of the MN into the skin and the forces exerted by the MN on the skin were recorded, as shown in Figure 3 B.…”

Microneedles for drug delivery: trends and progress

“…(Sinha & Kaur, 2000). Metals traditionally used for MN fabrication consist of stainless steel, nickel coated in gold, titanium, platinum and palladium (Martanto et al, 2004;Wang et al, 2006;Mansoor et al, 2013). Although numerous journal papers have been published on the use of silicon as a primary substituent of MN DOI: 10.3109/10717544.2014.986309 formulation, the material itself has yet to be FDA approved (Park et al, 2005).…”

“…They also differ in shape, ranging from square, circular, flat tipped, sharp tipped, etc. (Henry et al, 1998;Park et al, 2005;Gupta et al, 2009;Swain et al, 2011;Kommareddy et al, 2013;Mansoor et al, 2013;Torrisi et al, 2013;Pierre & Rossetti, 2014). There has been a lot of research conducted on MNs for the delivery and monitoring of various drugs such as glucose control for diabetics (Ito et al, 2006;Nordquist et al, 2007;Ainslie & Desai, 2008;El-Laboudi et al, 2013;Taylor & Sahota, 2013;Ita, 2014), Alzheimer's disease (Wei-Ze et al, 2010), anticancer (Fang et al, 2008) and other conditions (Ezan, 2013).…”

Fluid absorption by skin tissue during intradermal injections through hollow microneedles

“…Previously, the use of OCT had been limited to imaging microneedle penetration into skin tissue 29 , 30 , or dissolution of polymeric microneedles 31 . Other reported imaging of tissue were mostly carried out post-injection or post-insertion using confocal microscopy 5 , 32 – 34 , ultrasound echography 12 , fluorescence microscopy 10 , 35 , histology 10 , 11 , 33 , 36 , 37 , x-ray computed tomography (micro-CT) 38 , 39 , or two-photon microscopy 40 . Fluorescence and confocal microscopy have adequate spatial and temporal resolutions to image injections, but have low imaging depths in skin (up to few hundred micrometers) that only allow visualizing the upper layers of skin after injections.…”