Alteration in Hemoglobin Structure upon Interaction with Titanium Oxide Nanoparticles

Background: The unique properties of titanium oxide nanoparticles (TiO2 NPs) have made them widely used in medical and food applications. However, their probable toxic effects against biomacromolecules especially proteins are not well understood. The present study was aimed to evaluate the effects of TiO2 NPs on the human hemoglobin (Hb) using circular dichroism (CD) and UV-visible (UV-vis) spectroscopic methods. Methods: The far (190-260 nm) circular dichroism bands of Hb (3 mM in phosphate buffer pH 7.4, 10 mM) before and after addition of various concentrations of TiO2 NP with the ranging from 3 to 30 mM were recorded using a spectropolarimeter, model Aviv 215 at room temperature. Also, heat denaturation curves of free Hb and Hb/TiO2 NP complex at various temperatures (25-95ºC) were measured by monitoring the changes of absorbance intensity at 280 nm using Cary spectrophotometer. Results: Far CD spectrum of Hb revealed a strong double-minimum potential at 210 and 222 nm, indicating alpha-helical structure. Upon addition of nanoparticle, a decrease in Hb alpha-helix and increase in B-sheet and random coil contents were observed. In addition, the thermal stability analysis showed that the Tm of free Hb was approximately 60ºC, whereas, the observed Tm of Hb/TiO2 NP was about 50ºC which demonstrates the decline in protein stability after adding NP. Conclusion: The result of this study showed that TiO2 NPs interact with blood proteins, inducing considerable conformational changes and possibly cytotoxic effects, respectively .

Keywords:

Hemoglobin , Titanium Oxide Nanoparticle , Circular Dichroism Spectroscopy , Interaction , Structure