Computational Modeling for the Diffusion of Biosensor from Collagen Matrix into Aqueous Solution

The collagen fibrils can act as a substrate carrying a biosensor that can detect the presence of date rape drugs in a drink. Vitamin B12 (VB12) was chosen as analogous to methyl red (MR), the indicator of gamma-hydroxybutyric acid, a commonly used date rape drug. VB12 is chosen since it is a larger molecule than MR, but has a similar diffusivity constant. Diffusion of the biosensor from the collagen matrix into the aqueous solution was performed experimentally and modeled using COMSOL Multiphysics 4.4. The concentration profiles obtained for the experimental and COMSOL diffusion models were similar, however, COMSOL provided more precise values. While took about five days to completely diffuse the VB12 into aqueous solution; visually and experimentally the steady state value was reached in about one hour. Using the initial concentration of MR and the minimum concentration needed for a reaction between the drug and indicator, the diffusion of the indicator from collagen matrix into the aqueous solution was modeled on COMSOL for different drink glasses. It took just a minute to produce a color change in a shot glass while it took the longest time to indicate the reaction between the drug and the indicator was with a pint glass at 32 minutes.