Structural Conformations of Monoclonal Antibodies at Oil/Water Interfaces

Antibodies are proteins that bind to specific targets, helping the immune system fight infections and foreign substances. Monoclonal Antibodies (mAbs) are important in many biotechnology applications and are increasingly important in medicine, with treatments like immunotherapy and antibody chemotherapy resulting in a market worth over $100 billion.

Drugs containing mAbs or other proteins are often stored in pre-filled syringes to allow easier and less risky application. The barrel of these syringes is coated with oil, to allow the plunger to move without jamming. However, mAbs will often adsorb (stick) to the interface between oil and solution, which can disrupt their structure and thus their functionality. The presence of the oil/water interface can also cause disrupted proteins to form together into aggregates that can cause unwanted immune reactions in patients. To determine the full effect of the oil on the protein, and to find ways to minimise this effect, it is important to be able to determine the structure of proteins at these oil/water interfaces.

Currently, the investigation of proteins at oil/water interfaces is difficult, as the technique must be able to distinguish nanometre-scale structures through both solution and oil. Neutron reflection is a technique which is sensitive to nanometre scales, but until recently work at the oil-water interface was extremely difficult, as the beam of neutrons must pass through either a thick oil or solution layer, both of which will heavily attenuate the beam.

Prior to this project, work by M. Campana showed that this can be overcome by spin-coating the block to produce a thin oil layer, and deuterating the oil (replacing hydrogen in the oil with deuterium) to reduce the attenuation of the layer. However, this technique currently uses hexadecane, which is toxic but easy to deuterate, as a model oil. The method had also not yet been shown to work with mAbs, only reference proteins. Thus this project's goal is to develop the oil-water neutron reflection technique, along with other techniques like ellipsometry, to allow accurate investigation of mAbs at oil/water interfaces, and to investigate different the behaviour of different mAbs at the interface.

So far this project has shown that the hexadecane method also works with mAbs, giving a useful model system for mAbs at the oil/water interface. The focus of the project is now moving to measuring mAb adsorption to a more biologically compatible oil.