Comparison of different models of motion in a crowded environment: a Monte Carlo study

Diffusion Behavior of Drug Molecules in Acrylic Pressure-Sensitive Adhesive

Acrylic pressure-sensitive adhesive (PSA) is widely used in transdermal drug delivery systems, while the diffusion behavior of drug molecules in PSA is of great importance. In this paper, PSAs with different cross-link densities were prepared by adjusting the ratio of cross-linkers. The effects of cross-link density and temperature on the diffusion of drugs in PSA were investigated by Fourier transform infrared attenuated total reflectance and molecular dynamics simulation. The consistency between the experimental and simulation results demonstrated that molecular dynamics simulation could be used to predict the diffusion behavior of drugs in PSA. The results showed that free volume and the wriggling of polymer chains are positively related to the diffusion coefficient of drug molecules, while hydrogen bonds hinder drug diffusion.

Molecular transport in systems containing binding obstacles

We studied the movement of particles in crowded environments by means of extensive Monte Carlo simulations. The dynamic lattice liquid model was employed for this purpose. It is based on the cooperative movement concept and allows the study of systems at high densities. The cooperative model of molecular transport is assumed: the motion of all moving particles is highly correlated. The model is supposed to mimic lateral motion in a membrane and therefore the system is two-dimensional with moving objects and traps placed on a triangular lattice. In our study the interaction (binding) of traps with moving particles was assumed. The conditions in which subdiffusive motion appeared in the system were analysed. The influence of the strength of binding on the dynamic percolation threshold was also shown. The differences in the dynamics compared to systems with impenetrable obstacles and with systems without correlation in motion were presented and discussed. It was shown that in the case of correlated motion the influence of deep traps is similar to that of impenetrable obstacles. If the traps are shallow a recovery to normal diffusion was observed for longer time periods.