hypocrellin-b and titanium-dioxide

The binding of Hypocrellin B-TiO(2) chelate with DNA has been studied by using absorption, steady state fluorescence, cyclic voltammetry, time resolved fluorescence and laser flash photolysis measurements. The experimental results show that the presence of TiO(2) nanoparticles increases the binding of Hypocrellin B with DNA. The groove binding mode is confirmed by spectroscopic and docking studies. Laser flash photolysis studies confirm the presence of electrons in the conduction band of TiO(2) which will produce active oxygen species and results in damage of DNA indicating the potential application of Hypocrellin B-TiO(2) chelate in the field of photodynamic therapy (PDT).

Topics: Animals; Binding Sites; Cattle; Chelating Agents; DNA; DNA Damage; Electrochemistry; Fluorescence; Lasers; Models, Molecular; Molecular Structure; Osmolar Concentration; Perylene; Photolysis; Quinones; Reactive Oxygen Species; Spectrometry, Fluorescence; Titanium

TiO2 semiconductor colloids have been successfully employed in environmental clean-up, antibacterial and bactericidal action under ultraviolet light due to its strong redox ability and high yield of active oxygen species (1O2, O2*-), *OOH) generation. Hypocrellin B, isolated from Hypocrella bambusae (B.et.Br) Sacc, a natural pigment with strong and broad absorption over the visible light region, was used in our work in an attempt to extend the photoresponse of TiO2 to visible light and maintain the high generation of active oxygen under visible light illumination. The formation of the HB-TiO2 chelate was characterized by UV-Vis and surface enhanced raman spectroscopy (SERS) and it was found that the chelate still had high efficiency of active oxygen generation. The possible generation mechanism was explored by Electron Paramagnetic Resonance (EPR) and time-resolved transient spectra techniques, showing that singlet oxygen (1O2) and superoxide radical anion (O2*-)) were produced via energy transfer and electron transfer, respectively. The application of HB-TiO2 chelate in environment protection and bacteria sterilization was implied.

Topics: Chelating Agents; Colloids; Electron Spin Resonance Spectroscopy; Molecular Structure; Perylene; Photosensitivity Disorders; Photosensitizing Agents; Quinones; Singlet Oxygen; Superoxides; Titanium

The cation radical of dye produced from the interfacial electron transfer from a surface chelated dye to the conduction band of the colloidal TiO2 was studied by laser flash photolysis and electron paramagnetic resonance (EPR) techniques. The study employed hypocrellin B (HB), a natural photodynamic pigment with strong absorption over the visible light region, as a sensitizer and titanium dioxide as a colloid semiconductor. HB formed a chelate with this colloid semiconductor and exhibited a red-shifted and strongly enhanced absorption in the visible spectrum. Laser photolysis indicated that the electron excitation in the visible absorption band of the chelate resulted in extremely rapid and efficient electron injection from the excited triplet state of the dye into the conduction band of the semiconductor. A transient absorption of cation radical of HB at 570 nm was observed. The appearance of cation radical of HB was characterized by EPR spectrometry: the photoinduced EPR signal was not quenched by oxygen and its intensity decreased in the presence of NaI, a typical hole scavenger. The generation of conduction band electrons in HB-sensitized TiO2 system was also verified by the spin elimination of a stable cyclic nitroxide, 2,2, 6,6-tetramethylpiperidine-1-oxyl (TEMPO), and by the reduction of methyl viologen (MV2+) to its radical MV+.

Topics: Animals; Colloids; Electron Spin Resonance Spectroscopy; Free Radicals; Lasers; Perylene; Photochemistry; Photolysis; Quinones; Titanium