Modeling and optimization of drug release from diffusion-controlled spherical devices

This work presents an optimization approach for achieving desirable drug release from diffusion-controlled spherical devices. A mathematical model was established for description of drug release in these devices. Initial drug concentration and diffusivity profiles were optimized using a mixed Newton-Tikhonov regularization method to study various targeted release performances. Pseudo constant release, linear decrease release and linear increase followed by a constant release profiles were achieved under constant diffusivity with optimized initial drug concentration distributions, while the diffusivity profiles in devices with different initial concentration profiles were optimized to establish a pseudo constant release profile. The results show that the targeted drug release in the spherical devices can be fulfilled by optimizing the initial drug concentration or diffusivity profile. Moreover, burst effects could be minimized by maintaining low or no drug at the outer layer of the spherical devices with optimized diffusivity profiles.