Systematic characterization of drug release profiles from finite-sized hydrogels

Diffusion is often used as the primary method of molecular transport in drug delivery schemes. We present a systematic investigation of the Weibull and Peppas functions as useful tools in quantifying drug release profiles. The data is obtained from 2D simulated hydrogels and diffusion is modeled using an exact enumeration scheme. We show the fitting parameters to be largely time-dependent and therefore unreliable in indicating fundamental characteristics of the underlying physical mechanism. The parameters in the Weibull function however, have a stable regime when characterizing release profiles; we propose a simple iterative test that can be used to ensure that one is in this stable regime. Also, the mechanism of diffusion is shown to be independent of obstacle density in hydrogels that are larger than their respective characteristic lengths; a homogeneous obstacle distribution can therefore be replaced by an effective viscosity.