FTIR/ATR for protein adsorption to biomaterial surfaces

It is now well accepted that the initial rapid adsorption of blood proteins to biomaterial surfaces is important in the long-term performance of the implant. Cells that interact with the implant will be reacting to a layer (single or multiple) of adsorbed protein. The parameters of importance in a study of protein adsorption to surfaces of biomaterial interest include total amounts of different adsorbed proteins and the conformation and orientation of these adsorbed proteins. Researchers have developed a number of techniques with which we can now address all these questions. In this paper, we have discussed how Fourier transform infrared (FTIR) attenuated total internal reflection (ATR) techniques can be used for the study of biomaterial surfaces and events at biomaterial surfaces such as protein adsorption. FTIR spectroscopy offers higher signal-to-noise and speeds than spectrometers that use gratings and hence offers the capability of observing the critical early events when proteins interact with surfaces. Perhaps the biggest advantage of the FTIR technique over dispersive spectrometers is wavelength precision. This allows the subtraction of water, a strong infrared absorber, from the spectra of proteins in aqueous solutions. This review starts with an introduction of how ATR can be used to provide information about proteins on surfaces. Equations to calculate the amount of proteins adsorbed to surfaces from analysis of ATR spectra are presented. A discussion of the kinds of surfaces that can be analyzed by FTIR/ATR and difficulties with the subtraction of H2O is given. The rest of the review deals with how information of interest to biomaterials researchers such as kinetics of protein adsorption, changes in protein secondary structure and orientation upon adsorption to surfaces can be obtained by FTIR/ATR.