Abstract
We have performed computational modeling studies to explore the properties of functionalized Mg-Al layered double hydroxides (LDHs) for drug (heparin) delivery applications. Using molecular dynamics (MD) simulations, we investigated the intercalation of heparin into a Mg:Al 2:1 LDH system, for which some limited experimental data have been reported (Gu, Z. Chem. Mater. 2008, 20, 3715). Counterions and explicit water molecules have been included in order to simulate the experimental conditions performed for the related hybrid LDH systems. An ab initio force field (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies: COMPASS) was used for the MD simulations of the hybrid organic-inorganic systems. The interlayer structure, arrangement, and orientation of the intercalated species were examined and contrasted with the geometry of the isolated systems. The close contacts and hydrogen bonds between drug heparin and its surroundings in the hybrid system were analyzed, and the self-diffusion coefficients of both heparin and water molecules were estimated to be 5.6 x 10(-9) cm(2)/s and 8.5 x 10(-8) cm(2)/s at 300 K on the basis of 2 ns MD simulations. Implications for the stability of the hybrid LDH-drug systems were also discussed. Computed powder X-ray diffraction patterns were compared with those of related LDH-drug experiments.