Comparing the effects of Fe(III) and Cu(II) on the binding affinity of erlotinib to bovine serum albumin using spectroscopic methods

The interactions between erlotinib (ET) and bovine serum albumin (BSA) in the absence and presence of Cu(II) and Fe(III) in aqueous solution were investigated by using fluorescence, circular dichroism and three-dimensional (3D) fluorescence spectroscopic methods under simulative physiological conditions. Erlotinib effectively quenched the intrinsic fluorescence of BSA with slight redshifts in the absence and presence of Cu(II) and Fe(III). Cu(II) decreased the binding affinity and reduced the binding sites of erlotinib to BSA, while Fe(III) increased the binding affinity and binding sites of erlotinib to BSA. The negative values of ΔH and ΔS illustrate that the binding is mainly driven by the hydrogen bond and van der Waals force. The conformation of BSA was changed through ET binding in the presence of Cu(II) and Fe(III), which was revealed by circular dichroism, synchronous fluorescence and 3D fluorescence spectroscopic methods. The results indicate that the binding capability of erlotinib to BSA is affected by the types of metal ions.