Article

Microneedles: Progress in Developing New Technology for Painless Drug Delivery

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Abstract

Advances in the processing of materials on a micro-scale have led to the development and introduction of devices that employ very small needles. That has significant potential in devices for diagnostics, healthcare monitoring and drug delivery by mechanically perforating the outer skin layer and allowing for transdermal drug absorption or fluid sampling. These processing techniques incorporate one or more technologies that enable the precise machining, extrusion, casting, and/or forming of from one to an array or grid of microneedles. Evolving microneedle systems will be well positioned to address a significant segment of the large –molecule biological drugs expected to emerge from the convergence of automated discovery and genome mapping. To overcome the problems of oral route skin has been extensively studied as an alternative route of drug delivery. Skin is a large and easily accessible organ that can be readily used to administer drugs into the blood capillaries lying just tens of microns beneath the skin’s surface. Despite the advantages offered by skin for drug delivery, clinical drug delivery through the skin is severely limited by the presence of the top most layers of dead cells called the stratum corneum. This layer is just 10-20 µm in depth, but is the rate-limiting barrier and only allows low molecular weight molecules with moderate oil and water solubility to diffuse through. This in turn restricts the drugs that can be delivered via the skin into a very narrow range. As a result, presently only thirteen active molecules are approved for delivery through the skin by the Food and Drug Administration.

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... In this study, we developed a MN array on personalized curved surfaces, or a MN splint via 3DP, that acts as a splint to immobilize the affected trigger finger and delivers NSAIDs through MN-assisted transdermal drug delivery [53,54] for pain relief. ...
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The hand function of patients who suffer from trigger finger can be impaired by the use of traditional splints. There is also a risk of systemic side effects with oral non-steroidal anti-inflammatory drugs (NSAIDs) used for pain relief. Microneedle-assisted transdermal drug delivery offers an attractive alternative for local delivery of NSAIDs. However, traditional microneedle arrays fabricated on flat surfaces are unable to deliver drugs effectively across the undulating skin surface of affected finger(s). In this study, using 3D printing, a dual-function microneedle array has been fabricated on personalized curved surfaces (microneedle splint) for drug delivery and splinting of the affected finger. The novel microneedle splint was assessed for its physical characteristics and the microneedles were shown to withstand up to twice the average thumb force without fracturing. An average skin penetration efficiency of 64% on dermatomed human cadaver skin was achieved and the final microneedle splint showed biocompatibility with human dermal cell lines. A significantly higher amount of diclofenac permeated through the skin by 0.5 h with the use of the microneedle splint as compared to intact skin. The fabricated microneedle splint can thus be a potential new approach to treat trigger finger via personalized splinting without affecting normal hand function.
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