Microneedle arrays microfabricated

Whereas solid microneedle arrays present the opportunity to create conduits through the restrictive skin barrier layer, the application of the formulation into the channel through drycoating the microneedle array or coadministration of a solution, suspension, emulsion, or gel containing the medicament generally relies on passive delivery mechanisms. The capacity to microfabricate hollow microneedles, however, allows a controlled quantity of the medicament to be actively delivered from the tip of the inserted microneedle at a defined rate. In addition, hollow microneedles provide the opportunity to not only deliver substances but also to withdraw material from the skin for analysis, monitoring, and responsive purposes. 

Yuzhakov et al. [93] describe the production of an intracutaneous microneedle array and provide an account of its use (microfabrication technology). Various embodiments of this invention can include a microneedle array as part of a closed loop system smart patch to control drug delivery based on feedback information from analysis of body fluids. Dual purpose hollow microneedle systems for transdermal delivery and extraction which can be coupled with electrotransport methods are also described by Trautman et al. [91] and Allen et al. [100]. These mechanical microdevices which interface with electronics in order to achieve a programmed or controlled drug release are referred to as microelectromechanical systems (MEMS) devices. 

The applications of microneedles are many and varied. In the fields of genetic engineering and molecular and cell biology, it is desired to develop a method to introduce peptides, proteins, oligonucleotides, DNA, and other probes into ceDs to alter their functions. For this purpose, microneedles can be applied for the delivery of molecules through impermeable membranes into cells. It has been demonstrated that microfabricated needle arrays could be used to deliver DNA into plant and mammalian cells, inducing cell transformation. 

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