Drug Diffusion Inside a Non-Degradable Hydrogel Microneedle

Microneedles have shown great potential in drug delivery, but further research is needed to improve their performance. Studying drug release and distribution within microneedles using laboratory techniques can be challenging due to the small size of the microneedle and technological limitations. As an alternative, computer simulations can be a helpful method to explore different aspects of drug delivery in microsystems. This paper presented a simulation of drug diffusion inside a non-degradable hydrogel microneedle with a tapered shape. The study investigated the effects of different geometrical parameters, including the height and base diameter of the microneedle. The results indicated that the drug diffusion rate was higher from the tip of the microneedle from the side area near the base. Furthermore, the aspect ratio of the microneedle can notably affect the drug's diffusion time. Long microneedles can significantly accelerate drug discharge compared to short microneedles of the same volume. Based on the obtained data, a nonlinear equation has been developed to estimate the total time required for complete drug diffusion, taking into account various microneedle geometrical parameters such as height, base diameter, and volume. The proposed equation has been found to predict the total drug diffusion time with an error rate of less than 7%. The results obtained were in line with the experimental data available in the literature. The study findings have provided insights into estimating the time required for drug diffusion from the MN body to the tissue, which is crucial in controlled drug release systems, and will be beneficial for the optimum designing, manufacturing, and embedding of the drug.