An update on coating/manufacturing techniques of microneedles

Abstract

Recently, results have been published for the first successful phase I human clinical trial investigating the use of dissolving polymeric microneedles… Even so, further clinical development represents an important hurdle that remains in the translation of microneedle technology to approved products. Specifically, the potential for accumulation of polymer within the skin upon repeated application of dissolving and coated microneedles, combined with a lack of safety data in humans, predicates a need for further clinical investigation. Polymers are an important consideration for microneedle technology-from both manufacturing and drug delivery perspectives. The use of polymers enables a tunable delivery strategy, but the scalability of conventional manufacturing techniques could arguably benefit from further optimization. Micromolding has been suggested in the literature as a commercially viable means to mass production of both dissolving and swellable microneedles. However, the reliance on master molds, which are commonly manufactured using resource intensive microelectronics industry-derived processes, imparts notable material and design limitations. Further, the inherently multi-step filling and handling processes associated with micromolding are typically batch processes, which can be challenging to scale up. Similarly, conventional microneedle coating processes often follow step-wise batch processing. Recent developments in microneedle coating and manufacturing techniques are highlighted, including micromilling, atomized spraying, inkjet printing, drawing lithography, droplet-born air blowing, electro-drawing, continuous liquid interface production, 3D printing, and polyelectrolyte multilayer coating. This review provides an analysis of papers reporting on potentially scalable production techniques for the coating and manufacturing of microneedles.

A simple and cost-effective approach to fabricate tunable length polymeric microneedle patches for controllable transdermal drug delivery

“…Compared to the current state of the art, 24,43,44 the MN patches fabricated with this method exhibit several distinctive advantages. First, the heights of MNs (n ¼ 5) were 1012 AE 13 mm, 768 AE 7 mm and 510 AE 5 mm when applying 50 mL, 100 mL and 150 mL of PDMS pre-polymer solution for spacer fabrication, respectively, ( Fig.…”

“…19 In addition, various functional nanomaterials, such as photothermal nanomaterials, have been incorporated into MNs, to endow new functions or properties to the MNs, 20,21 e.g., to achieve controlled cargo release or self-sterilization. 22,23 Several polymeric MN patch fabrication methods have been developed, 24 including micromoulding, 25 droplet-born air blowing (DAB), 26 photolithography, 27,28 3D printing, 29,30 drawing lithography, 31 and electro-drawing. 32 Among these technologies, micromoulding is the most widely used because of its simple fabrication procedure, scale up feasibility, high reproducibility, and cost-effectiveness.…”

Two-Photon Polymerisation 3D Printing of Microneedle Array Templates with Versatile Designs: Application in the Development of Polymeric Drug Delivery Systems

“…Micromoulding-based manufacture of MN arrays implies the use of a mould, commonly made from poly (dimethylsiloxane) (PDMS), to replicate the MN array structure. These moulds are usually obtained from silicon or metal master templates, which in turn are fabricated by lithography, etching or laser-based techniques (2,9). However, these may prove restrictive in the fabrication of complex MN array designs and geometries.…”

Polymeric Microneedle Arrays: Versatile Tools for an Innovative Approach to Drug Administration

“…A variation on this topic has been recently presented by Tonomo, who used inclined contact UV lithography to fabricate biodegradable PLA microneedles [22] An updated review focused on coating/manufacturing techniques for microneedles has been published by Tarbox et al, taking into account biosafety issues and potentially scalable production. [23] From the analysis of the technological trends in MN fabrication, it is quite clear that two methodologies have consolidated their foundations in this last year: replica molding-based soft imprinting and photolithography. On the other hand, there is no last word in this competition, and only a reasonable principle, such as "the simpler, the better," could be suggested.…”