Heavily bio-engineered monoclonal antibodies (mAbs) are an increasingly important trend in the biopharmaceutical industry. However, these mAbs are often destabilised by the silicone oil found in pre-filled syringes, which are the preferred storage and application method for these drugs. This effect can be reduced by adding biologically safe surfactants to the formulation, but the mechanism by which this protects the mAb is currently not proven. This study will investigate the mAb-surfactant-silicone oil interaction, using several contrasts to isolate of each component's SLD profile. An ensemble of potential conformations created from Monte-Carlo simulations of the protein's structure will be compared to this profile. This study will investigate mAb-surfactant stabilisation in detail, proving that complex four-phase protein systems can be studied in depth by Neutron Reflection.