Dynamic light scattering: a powerful risk-management method
From protein expression to storage and delivery, protein aggregation is a process that can occur at any stage in the lifetime of a therapeutic protein. Although the specific mechanisms by which protein aggregation occurs are still not fully understood, various aspects of the manufacturing process, such as microbial contamination during cell culture or inappropriate storage conditions, have been found to increase the risk of physical and chemical degradation due to aggregation.
As protein formation plays a highly critical role in ensuring the usability and efficacy of an injectable biopharmaceutical product, initial formation or aggregation could affect immunogenicity—an important factor in ensuring safety, usability and stability. Incorporating appropriate detection tools at an early stage is a vital step in monitoring potential aggregation.
DLS: beyond current limitations
DLS, a prevalent technique that has been used in both colloidal sciences and protein characterization studies, is the appropriate technique to address the limitations of traditional protein aggregation testing methods.
• Measurements occur directly in the cuvette
• No pretreatment needed
• Only small sample amounts required (< 5 µL per replicate, sample concentration ≥ 0.1 mg/mL)
• Samples are reusable
• Analysis time: 2 min/sample, resulting in 30 samples/h
• Easy and quick data evaluation
• Highly sensitive to only small amounts of aggregates
• Efficient, high-throughput method
Common measurement techniques vs. dynamic light scattering
Various analytical methods, such as the Coulter counter (CC) method, micro-flow imaging (MFI), dynamic imaging particle analysis (DIPA), and light obscuration (LO), can be applied to evaluate the presence of protein aggregates within the micrometer (μm) range. Multi-angle static light scattering (MALS) allows researchers to measure the presence of protein aggregates early in the formation process. Other common separating methods include asymmetrical flow field-flow fractionation (AF4), analytical ultracentrifugation (AUC) and size-exclusion chromatography (SEC).
Although each of these methods has been proven to be efficient, none of them can directly measure protein aggregates in solution. The specific handling and preparation requirements for the sample, either before or during measurement, can alter the state of sample aggregation.
Dynamic light scattering is simple, fast and non-destructive. A mature and very powerful technique, DLS is based on an analysis of the scattered light fluctuations that occur as a result of Brownian motion. DLS measures the Brownian motion of particles in a dispersion and uses this information to determine their hydrodynamic size.
DLS allows researchers to detect the presence of aggregates, even at very low concentrations. Measurements occur directly in the cuvette and are performed without separation or dilution (preventing potential dissociation of reversible aggregates). No information about concentration or molecular composition is needed.
Applications of DLS
DLS is a high-throughput method suitable for ensemble measurements ranging from Rh values of 0.5 nm up to 1,000 nm. The DynaPro® Nanostar® equipped with DYNAMICS software (Wyatt Technology) is a cuvette-based batch DLS system that enables fast and precise characterization of proteins and requires only small sample volumes.
One of the main application fields for DLS is the detection of aggregates even in trace amounts. Since DLS is a uniquely fast technique, its use for screening during formulation development is particularly common.
The following are some of the diverse applications supported by DLS:
- Tracing protein aggregation
- Estimating populations of aggregates in small and large molecules, proteins or liposomes
- Checking the quality of biomolecules prior to running costly analyses such as SOR or SANS
- Formulation studies
- Analyzing thermal stability and denaturation
- Differentiating pure unfolding from aggregation
- Measuring the sizes of viruses and VLPsQuantifying self-assembly processes of polypeptides or DNA
Developers particularly benefit from DLS as one of the most sensitive techniques for the detection of aggregates. As a simple, fast, non-destructive, high-throughput screening method, dynamic light scattering yields clear results in a short time and makes it easy to estimate a project’s chances of success.