A Quantum Chemical DFTB Study of Curcumin Adsorption on Polycaprolactone and Collagen Surfaces

The adsorption of curcumin on PCL and collagen surfaces modeling the components of coaxial fibers is investigated using the DFTB method. On the PCL surface, curcumin binds weakly (Eb = –0.03 eV), with no appreciable charge transfer and no significant structural reorganization. Water screens the PCL surface and transfers the interaction to the curcumin–water subsystem. On collagen, a more stable complex is formed (Eb = –0.62 eV), stabilized by a hydrogen bond between the phenolic OH group of curcumin and the oxygen of the peptide group. For this complex, a charge transfer of about 0.04 e from collagen to curcumin is revealed. Upon hydration, the additional binding energy on collagen is retained in the range of –0.29… –0.39 eV, and the total stabilization energy reaches –2.80 eV. Replacement of the nearest collagen residues with Arg and Lys does not enhance adsorption. It is concluded that the retention of curcumin in PCL/collagen matrices is governed primarily by the collagen component and the peptide backbone of the protein.