Properties and energetics for design and characterization of chitosan nanoparticles used for drug encapsulation
Abstract
This work presents a theoretical study of the energetics, as well as the optical and mechanical properties of chitosan nanoparticles, supported by experimental findings. A thorough investigation, by means of all electron density functional theory, is performed on the effects of protonation of the ionic cross-linked polyanion tripolyphosphate on the interaction energies with chitosan oligomers. Depending on the protonation of chitosan and the relative orientation, the interaction energies of chitosan with tripolyphosphate are computed as 12.3 kcal mol−1 (H4P3O10−), 15.4 kcal mol−1 (H3P3O102−), 17.7 kcal mol−1 (H2P3O103−), 30.8 kcal mol−1 (HP3O104−), and 68.3 kcal mol−1 (P3O105−, before proton transfer), 21.2 kcal mol−1 (after proton transfer). The reported theoretical IR and UV/Vis spectra are in good agreement with the corresponding experimental spectra. Through vibrational analysis modes are identified and assigned to prominent peaks. The calculated value for the Young's modulus of (protonated) chitosan oligomers is 115 GPa, while for crystalline (unprotonated) chitosan it is 79.6 GPa. These values are compared with experimental ones.