Investigation on Interaction and Sonodynamic Activity of Chlorophyll-Magnesium-Metronidazole (Chl-Mg-MTZ) with Bovine Serum Albumin (BSA) in Aqueous Solution

Abstract

Sonodynamic therapy (SDT) is an innovative cancer treatment involving a tumor-localizing sonosensitizer. The synthesis, modification and activity of novel sonosensitizers have attracted more and more researchers’ attention. In the present study, chlorophyll-magnesium (Chl-Mg) and metronidazole (MTZ) were used as reactants and the chlorophyll-magnesium linked metronidazole complex (chlorophyll-magnesium-metronidazole, Chl-Mg-MTZ) was synthesized and characterized. Bovine serum albumin (BSA) was selected as the target protein; the biomolecule affinity and sonodynamic activity of Chl-Mg-MTZ were assessed by their UV–vis and fluorescence spectra. The results indicate that the interaction of Chl-Mg-MTZ to BSA is comparable with that of chlorophyll-magnesium (Chl-Mg). However, during damage of BSA, Chl-Mg-MTZ shows a higher sonodynamic activity than chlorophyll-magnesium (Chl-Mg). Moreover, synchronous fluorescence spectroscopy indicates that Chl-Mg-MTZ has similar binding ability with the tyrosine (Tyr) and tryptophan (Trp) residues of BSA molecules. However, the damage is mainly focused on the Trp residues. In addition, the production of reactive oxygen species (ROS) in the sonodynamic process was detected through the oxidation-extraction of 1,5-diphenylcarbazide (DPCI). The results promote the potential of Chl-Mg-MTZ as a new sonosensitive drug for use in SDT, encouraging further study on tumor treatment.