Probing the role of peptide adsorption on metal oxide surfaces with synchrotron radiation.

The interaction between biological molecules and inorganic material surfaces is of importance in a number of areas from biomedical devices for implantation, sensors and bioreactors. The required behaviours for each of these applications are slightly different, for example in biomedical implants it is thought that a protein conditioning layer is formed at the surface, prior to cell attachment and growth of new tissue. On the other hand, in pharmaceutical applications where protein therapeutics may be manufactured, interactions with the reactor material surfaces can lead to denaturation or agglomeration of the proteins. This may have the effect of removing the desired action protein, or in the worse case, causing unwanted side effects such as protein aggregation.
Studies of molecular adsorption on well-characterised surfaces using synchrotron techniques have led to an improved understanding of protein-metal interactions. However, in most cases the surface of a metal implant or pipeline will be terminated with a native oxide layer. In addition, these studies are often carried out under vacuum conditions, thus the effect of water on the adsorption process is not well understood. Obviously in a real biomedical device or pharmaceutical plant, water will be a major component of the surrounding media. Recent advances in photoelectron spectroscopy now allow measurements to be made in the presence of water and water vapour. Photoelectron spectroscopy is an extremely powerful probe of surface chemistry and the adsorption mechanism of molecules, since it is capable of studying just the top 1 - 10 nm of a material surface.
In this proposal we will study the adsorption processes of five different amino acids which exhibit varying degrees of acidity/basicity and two small peptides on idealised titanium dioxide surfaces. Rutile titanium dioxide is the native oxide formed on titanium which is widely used both as a metal and alloy in biomedical implants, and is believed to be a key factor in the success of these devices.

Planned Impact
The proposed work will determine the adsorption mechanism of some important amino acids and tripeptide moieties on metal oxide surfaces. The information gained will be important in a number of biomedical related areas from biomedical implants, biosensors, and protein therapeutics as well as in other industries such as maritime, where an understanding of peptide adsorption may enable novel strategies for prevention of biofouling to occur.

These areas are important for a number of reasons, as an ageing population is likely to see an increase in implants. Protein therapeutics may be a solution to the increase in antibiotic resistance in bacteria. In addition, marine fouling is a costly issue which leads to downtime of vessel usage and expensive clean up processes. The work proposed in this travel grant is of a fundamental nature and is likely to contribute to the areas outlined above, informing the choice of materials or design of materials and coatings which enhance or retard protein adsorption. This if developed further, in the longer term would have impact both nationally and internationally. Previous work by the investigators, following an award of a travel grant, led to publications which have been cited in work linked to sensing, cancer therapeutics, novel coatings technology and photocatalyst applications as well as in more fundamental science.

The proposal will also assist in the training of PhD students in state of the art spectroscopic techniques we will use here, and ensure the UK maintains a body of highly-skilled people in complex photoelectron spectroscopy and emerging techniques in photoelectron spectroscopy as well as in the use of synchrotron radiation.