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UBC Theses and Dissertations

Fabrication of out-of-plane microneedles for drug delivery and biosensing Mansoor, Iman


Hollow microneedles can be used to painlessly inject drugs or extract dermal interstitial fluid for biosensing. However, their fabrication so far has been associated with costly and time-consuming steps restricting their batch production as a viable option. This thesis presents novel methods for fabricating inexpensive hollow microneedles, and investigates new methods of characterizing the drug delivery and interstitial fluid sampling using microneedles. First, a method is presented for fabrication of hollow polymer microneedle arrays. Microneedles are formed during a solvent casting process, which leaves a polymer layer around pillars in a pre-fabricated mold. Arrays of microneedles with lengths up to 250 µm have been fabricated. The strength of the microneedles was evaluated to ensure reliable skin penetration and their suitability for drug delivery was demonstrated by injection of fluorescent beads into a skin sample. A second fabrication method is presented for making metallic microneedles with high aspect ratios. Solvent casting was used to coat a mold with a conductive polymer composite layer, which was then used as a seed layer in a metal electrodeposition process to form 500 µm tall microneedles. Some fabrication process steps were characterized and the strength of the microneedles was evaluated. Their usefulness for drug delivery was also demonstrated by injection of fluorescent microspheres into animal skin. Designing effective microneedles requires understanding the drug diffusion process in skin. Here, a novel method is used to characterize diffusion of a chemotherapeutic drug injected with microneedles into skin. Using confocal microscopy, the concentration distribution of the drug was measured over time and then compared to an analytical diffusion model to obtain the drug’s diffusion coefficient. Using this method, different skin storage conditions were evaluated. It was concluded that using previously frozen skin should be avoided for transdermal drug delivery studies. Finally, using the proposed processes, hollow and solid microneedles were fabricated for sampling interstitial fluid for biosensing applications. Minimal removal of the interstitial fluid was achieved with a solid microneedle design as well as a hollow metallic microneedle array attached to a vacuum probe, while no trace of the fluid was observed when using hollow polymer microneedles.

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Attribution-NonCommercial-NoDerivs 2.5 Canada