An Effective Drug Delivery Process Using a Molecular Dynamics-Based Cylindrical Particle Model

This paper attacks the problem of drug particles modeling in their delivery process for better predictions of solubility and absorption rate. Most of the current models treat the particles to be spheres which may not be accurate. The drug particles formed by grinding and milling are usually not spheres but are irregular or spindles in shape. As such, in this paper modeling of drug particles as cylinders is proposed to rigorously study the impact on its solubility. Along the same line, we also delve into the effect on solubility of changing the aspect ratio of a cylindrical drug particle having a constant mass as well as the diffusion coefficient of the solute which dominates the control on the kinetics of drug release. Molecular Dynamics (MD) simulation is employed to calculate the diffusion coefficient of a given particle using one of Einstein’s fluctuation-dissipation equations that relates transport properties to time. The MD approach makes it possible to deal with parameters that are too difficult to be physically measured in a human body. The solubility analysis of a cylindrical drug particle is done using the Noyes-Whitney equation. The rates of change of radius and of mass are analyzed graphically for drug particles of different weights and sizes. Finally the solubility of a sphere versus that of a cylinder for the same mass is investigated. The data reveal that with the same given mass, the solubility of a spherical particle is less than that of the cylindrical shape. As to the effect of the diffusion coefficient, δ on the solubility of a particle, it is found that the increase in δ for a particle with fixed mass increases its solubility. However, the solubility decreases while δ is increased for a particle with fixed radius.