DFT Study of Chitosan Ascorbate Nanoparticles Structure

In recent years, use of chitosan (CS) nanoparticles as nanocarriers has received much attention due to their biodegradability, biocompatibility and non-toxicity. CS nanoparticles containing drugs, flavors, enzymes and antimicrobial agents can maintain their activity. Such nanoparticles can stimulate the stabilization of ascorbic acid (AA) and improve controlled release. This study investigates the interaction of CS monomer with AA and sodium tripolyphosphate (TPP) using density functional theory (DFT) during the formation of chitosan ascorbate (CA) nanostructure (CAN). On the basis of existing results, the formation of the CS monomer from the complexes occurs due to the donor-acceptor interaction, which is energetically favorable in all considered interactions according to the calculations. At close range, proton transfer has been identified with interaction energies, namely CS-AА (-6.82 kcal/mol), CS-TPP (-4.56 kcal/mol) in the aqueous phase, which indicates that in the process of CAN formation, in most cases, the formation of a donor-acceptor bond occurs between the amino groups of CS with the enol group of AA and the relative coordination of CS with TPP. The introduction of the aqueous phase led to a drop in the interaction energy. On the basis of our results for the linking types (interaction energies), we propose a simple mechanism for their impact on the CAN formation process.