Microneedle mediated drug delivery is an amalgam of the conventional transdermal patch and the hypodermic needle injection. It offers an improved drug delivery technique without the limitations of the above methods. The ability of microneedles to increase permeability of substances in the skin has been established in the literature. However, a quantitative method for predicting the performance of microneedle devices prior to their fabrication is yet to be fully developed. The contribution of this research is a theoretical framework for modelling and optimizing microneedle array design to obtain desired drug delivery rate while taking into account the transport and mechanical properties of the skin. This is achieved by exploring various theories surrounding transdermal drug transport. The existing theories are then used to develop models to link the microneedle array design parameters with drug transport properties such as permeability and drug concentration in blood.
Numerical simulations and theoretical analyses that are carried out in this PhD research indicate that microneedle design has a significant effect on drug delivery. An algorithm was developed for solving the series of equations presented, thus obtaining a framework which is applied to predict performance of microneedle arrays in vivo. Some practical scenarios are also simulated to demonstrate the applicability of the developed framework. For example, numerical simulations of transdermal delivery of Fentanyl show that varying the design parameters such as penetrated length of microneedle and the tip radius of microneedles affected the peak blood concentration. Similarly, the developed framework was used to obtain the optimum microneedle design to calculate the desired peak blood concentration similar to that obtained using conventional patch system. This study is relevant as it provides a better understanding of microneedle mediated drug delivery process and it orchestrates the design and hence, fabrication of more efficient microneedle based drug delivery devices.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.