ATR-IR spectroscopic studies of the influence of phosphate buffer on adsorption of immunoglobulin G to TiO2

In situ attenuated total reflectance infrared (ATR-IR) spectroscopy has been applied to the study of the influence of phosphate on the extent of protein adsorption onto TiO2. Immunoglobulin G (Ig.G) was adsorbed onto a TiO2 sol–gel film from solutions containing phosphate or NaCl. Monitoring of the amide II absorbance (v=1545 cm−1) confirmed reduced protein adsorption from the phosphate containing solution. In situ ATR-IR spectroscopy was also used to study phosphate induced desorption of Ig.G. Solutions containing various phosphate concentrations were passed over a TiO2 film with Ig.G adsorbed to it. As the concentration of phosphate increased the amide II absorbance decreased confirming the removal of bound Ig.G from the TiO2 surface. As the amide II absorbance decreased the phosphate absorbance (v=1080 cm−1) increased suggesting accumulation of phosphate at the TiO2 surface. Not all of the bound protein could be displaced from the TiO2 surface by phosphate suggesting the presence of weakly and strongly bound Ig.G.