MICRONEEDLE PATCHES FOR TRANSDERMAL DRUG DELIVERY: A REVIEW

Most medicines cannot penetrate the skin at therapeutically useful rates, which has significantly hindered the success of transdermal drug delivery. It has recently been suggested that using micron-scale needles to increase skin permeability can significantly improve transdermal delivery, particularly for macromolecules. Microneedles of various sizes, forms, and materials have been created using the instruments of the microelectronics industry. Solid microneedles, which have been demonstrated to enhance skin permeability to a wide variety of molecules and nanoparticles in vitro, have been the focus of the majority of drug delivery investigations. Oligonucleotide delivery, insulin-induced blood glucose reduction, and protein and DNA vaccine-induced immune response stimulation have all been shown in in vivo experiments. In these investigations, needle arrays have been employed as drug carriers that release medication into the skin from a microneedle surface coating or to puncture holes in the skin to enhance transport by diffusion or iontophoresis. It has also been demonstrated that hollow microneedles can microinject insulin into diabetic rats. The ratio of microneedle fracture force to skin insertion force, or margin of safety, was determined to be ideal for needles with a small tip radius and a thick wall in order to address practical uses of microneedles. Human volunteers reported no pain when microneedles were put into their skin. All of these findings point to microneedles as a potentially useful technique for delivering medicinal substances into the skin for a variety of potential uses.