Probing the interaction of magnetic iron oxide nanoparticles with bovine serum albumin by spectroscopic techniques.

The interaction of magnetic iron oxide nanoparticles (MNPs) with bovine serum albumin (BSA) was investigated by fluorescence (FL), ultraviolet visible (UV-vis) absorption, Raman, and circular dichroism (CD) spectroscopy. Results indicated that MNPs quench BSA FL mainly by a static quenching mechanism. The FL quenching constants KSV were obtained as 2.44x10(8), 2.41x10(8), and 2.40x10(8) L.mol(-1) at 291, 298, and 313 K, respectively. The thermodynamic parameters of enthalpy change DeltaH(theta), entropy change DeltaS(theta), and free energy change DeltaGtheta were -0.90 kJ.mol(-1), 157.38 J.mol(-1).K(-1), and -47.80 kJ.mol(-1) (298 K), respectively. The association constant (KA) and the number of binding sites (n) were 7.64x10(7) L.mol(-1) and 46.55 at higher concentration of MNPs, and 1.35x10(6) L.mol(-1) and 284.74 at lower concentration of MNPs. The analysis results suggested that the interaction was spontaneous and the electrostatic interactions played key roles in the reaction process. In addition, the Raman and CD spectra proved secondary structure alteration of BSA in the presence of MNPs.