Water-Soluble Systems of Curcumin Based on Amphiphilic (Co)polymers of N-Vinylpyrrolidone with (Di)methacrylates for Biomedical Applications. Experimental and Theoretical Study

Water-soluble compositions containing up to 4.3% of a curcuminoid mixture with known biological activity were prepared based on amphiphilic copolymers of N-vinylpyrrolidone with (di)methacrylates of various chemical compositions and macromolecular architectures, as well as linear poly-N-vinylpyrrolidone. Dynamic light scattering revealed stable polymer structures in aqueous solution with sizes of approximately 100–1000 nm. Cyclic and square-wave voltammetry revealed differences in the electrooxidation energetics of curcumin– (co)polymer compositions depending on the nature of the polymer, in comparison with native curcumin. UV–Vis spectroscopy was employed to evaluate the stability of the curcuminoid mixture in neutral phosphate-buffered saline as a function of (co)polymer chemical composition; enhanced stability was observed in polymer matrices containing acrylic acid or poly(ethylene glycol) methyl ether methacrylate units. Quantum chemical (DFT) modeling of polymer–curcumin structures indicated the possibility of hydrogen bond formation between functional groups of the carrier and the active compound in both enol and keto forms. The keto–enol tautomerization of curcumin is facilitated in poly-N-vinylpyrrolidone due to cleavage of its intramolecular bond and is hindered in copolymers containing triethylene glycol dimethacrylate and acrylic acid units.