Dynamic Light Scattering (DLS) is a widely implemented technique for characterisation of proteins and their formulations; allowing not only the determination of molecular size but also an assessment of stability. In recent years, the stability of proteins in solution has attracted significant scientific and commercial interest, due to the exponential growth in the use of proteins as biotherapeutic drugs. Since knowledge of formulation stability and behaviour are paramount for delivery of a safe and commercially viable product, the demand for tools that can characterize these formulation properties has increased. Protein mobility – measured using electrophoretic light scattering (ELS) – is one property that has been identified as a promising indicator of formulation stability, viscosity and behaviour.
While biologic drugs are often formulated at high concentrations, e.g. 100mg/ml, the desire to make measurements early in the biopharmaceutical development cycle means that measurements at lower concentrations are also desirable, with a view to predicting behaviour at formulation concentrations.
Acquiring protein mobility measurements requires the application of an electric field to the sample – a physical process that itself can cause damage to the protein by stimulating aggregation. Consequently, the resultant mobility measurements reflect that of the aggregate molecules rather than the protein of interest.
Accurate and high quality measurements of protein mobility require an instrument with sufficient sensitivity to measure both the low count rates and low electrophoretic mobilities associated with dilute protein solutions, as well as a measurement technique that reduces the risk of aggregate generation.
This poster describes the work carried out by scientists at Malvern Instruments, which shows that much of the aggregation that occurs during electrophorectic measurements takes place at the electrodes. It also describes a new measurement technique invented and patented by Malvern Instruments, the Diffusion Barrier Method, which protects the protein sample by isolating it from the cell electrodes, and increases the reliability of the data generated from the measurement.