Molecular dynamics of paclitaxel encapsulated by salicylic acid-grafted chitosan oligosaccharide aggregates.

Chitosan oligosaccharide (COS) derivatives have attracted significant interest in drug delivery systems because of their well-known low toxicity, excellent biocompatibility, and biodegradability. Paclitaxel-loaded nanoparticles based on salicylic acid-grafted chitosan oligosaccharide (COS/SA) were synthesized and characterized. Then, in order to understand the mechanism of the actions of the paclitaxel (PTX) encapsulated by COS/SA, all-atom molecular dynamics simulations were performed to analyze the aggregation of COS/SA molecules. The van der Waals and hydrophobic interactions are the major driving forces for the drug encapsulation process. Electrostatic and hydrogen-bonding interactions also play helpful roles in the COS/SA aggregation. Analyses of the radial distribution function and solvent accessible surface area indicate that the COS/SA nanoparticles are highly hydrosoluble and that the nanoparticles can significantly enhance the aqueous solubility of a hydrophobic drug. Different drug loading systems are also investigated in this work, and the best theoretical drug loading is found to be 10% (w/w). The present work provides insights into the mechanism of the atomic structures of drug-loaded polymeric nanoparticles and presents new perspective for the design of drug delivery systems with desirable properties.