Microneedles: Progress in developing new technology for painless drug delivery

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.