(570d) Design of a Biocompatible Oil Dispersant for Deep Water Applications Using Discontinuous Molecular Dynamics

Oil spills have caused major environmental incidents several times over the past 50 years, and similar occurrences are likely to happen in the future.  Dispersants are commonly used to clean up oil spills, however current dispersants show mild to moderate toxicity to aquatic wildlife.  The goal of this research is to develop a biocompatible oil dispersant, that effectively stabilizes the oil/water interface, allowing ocean bacteria to naturally degrade hydrocarbons.  The backbone of the dispersants is chitosan, a naturally occurring polysaccharide found in the exoskeletons of ocean crustaceans, with hydrocarbon groups attached at selective locations on the backbone to achieve amphiphilic behavior.  We will describe our efforts based in discontinuous molecular dynamics (DMD) simulations to explore ways to selectively attach the hydrocarbon groups such that the resulting hydrophobically modified chitosan will tend to wrap around oil molecules.  Our first DMD simulations are being performed on a system of 200 aldehyde molecules (each containing 12 carbons) in water to observe the formation of micelles.  The aldehyde molecules micellize in water to hide the hydrophobic alkane chains and expose the reactive hydroxide group.    Our next simulations will add 50 chitosan molecules to the system, which surround the micelles creating hydrophically modified chitosan.  After the amine groups of the chitosan bond to the hydroxide groups of the aldehyde, the chitosan will cause the micelle to open, exposing the hydrocarbon chains that are bonded to the chitosan.  Finally, 150 hydrocarbon molecules (each containing 15 carbons) are added to the system representing oil droplets.  The hydrocarbon molecules bonded to the chitosan backbone penetrate the oil droplets, causing the hydrophobically modified chitosan molecule to completely surround the oil droplet.   We are investigating the micelle’s ability to remember its original micelle structure when it is exposed to hydrocarbon molecules. The use of DMD over traditional molecular dynamics (MD) simulations drastically reduces the simulation time, and allows for the study of larger systems over longer periods of real time.  This research could reveal an effective, environmentally friendly, alternative to current oil dispersants.