Novel microneedle design and fabrication for improved drug delivery

Abstract

Since its invention in 1853 by the British physicians Alexander Wood, the syringe is a basic transdermal injection tool used over 12 billion injections per year by injection drug users (IDU) worldwide. Transdermal drug delivery can avoid hepatic metabolism and absorption differences in relation to gastrointestinal disorders. In addition, it can produce fast effects with small amounts of drugs, but it is accompanied by several problems. According to world health organization estimates in 2014, about 2 million syringe-induced medical accidents occur each year and 25 types of blood-borne viruses have been reported including hepatitis B, C and HIV. In addition to the economic reasons that vaccination costs increase annually, the use of a syringe should be prescribed by a professional medical practitioner, or at least necessary for undergo relevant profes-sional training. Therefore, development of microneedle is required as a drug delivery technology that can be used by general public without fear of secondary infection. To this end, this thesis first describes the development of a microneedle that mimics the tip of a hypodermic needle and enables efficient drug administration with invasion. In the backside lithography process, the mask design factors are investigated and applied to easily fabricate complex three dimensional structures with a single UV exposure. The suggested microneedle array combines with the fiber sheet to function as an effective transdermal drug delivery system. It can continuously supply the administered drug using capillary forces and wicking of the fibers. Their functionality is visualized and evaluated in drug delivery tests using agarose gels. One step further, we demonstrate production of microneedle by injection molding process capable of realizing a low manufacturing cost and a mass production. We achieve the injection molding process of microneedle while solving limitations such as machining of sharp point, gas trap and generation of burr, etc. Continuous drug administration and diffusion by proposed microneedles can be confirmed in real time through experiments. In addition, in vivo drug delivery is successfully confirmed by inserting into the body of actual adult mouse. The microneedles of this study have various applications as a safe and advanced transdermal drug delivery method that anyone can use. In particular, it will serve as a starting point for solving problems that may arise from drug delivery through existing injections, but also will be a new step for human health and well-being with low production costs and easy accessibility.