Dynamic Light Scattering

Dynamic light scattering (DLS) is historically known as photon correlation spectroscopy or quasi-elastic light scattering. It is routinely used to detect hydrodynamic sizes and aggregation of nanoparticles in suspension. In a given environment, the diffusion speed of the nanoparticle is inversely correlated with its hydrodynamic size according to the Stokes-Einstein equation. In DLS analysis, a beam of laser light is directed through the dispersed nanoparticles and the nanoparticles scatter the laser light. The scattered light intensity is detected at a fixed angle over time to detect nanoparticle diffusion speed, and thus the hydrodynamic size can be obtained. Protein nanocages belong to nanoparticles and their hydrodynamic sizes can be conveniently measured by DLS analysis. Hydrodynamic size distribution analysis of protein nanocages is a fast and precise method to check if the protein nanocages are in assembly form and if any aggregates are formed. Non-assembled subunits or oligomers are unable to function well in vivo. Aggregation can lead to bioactivity loss and side effects.

Fig 1. Dynamic Light Scattering Configuration (Lim, J.K., et al., 2013)

Aside from hydrodynamic size analysis, zeta potential determination is another usage of the DLS technique. When a nanoparticle is dispersed in a solution, its surface net charge attracts a tight layer (Stern phase) and a loose layer (slipping plane) of the opposite charges. The charge at the interface of the slipping plane and the solvent is the zeta potential. Zeta potential is measured by electrophoretic light scattering, in which an electrical field is added to the dispersed nanoparticles. The charged nanoparticles then move towards the opposite electrode with a certain velocity related to their zeta potential. Zeta potential is closely related to nanoparticle stability. Protein nanocages with negative or positive net charges will be more likely to maintain their well-dispersed status in a given solution whilst those bearing no net charges tend to aggregate and even precipitate. Zeta potential determination gives valuable information about the storage conditions and formulation for protein nanocages.

Fig 2. Schematics of Electrical Double Layer (Feng, Y., et al., 2020)

Our service

Creative BioMart Nanocage conducts both hydrodynamic size distribution analysis and zeta potential analysis for protein nanocages. We cover hydrodynamic size distribution analysis of protein nanocages ranging from 1 nm to 10 μm. Zeta potential can be measured at a fixed pH value or at different pH values to obtain the isoelectric point of protein nanocages. Our service consists of the following 4 steps.

1. Online Inquiry. If you are interested in our DLS service, please contact us through online inquiry. Our DLS scientists will help you with sample preparation and sample delivery.
2. Sample delivery. Simply deliver your protein nanocage in solution or freeze-dried protein nanocages to us. We perform free sample pretreatments including sample concentration, sample buffer exchange, and sample centrifugation before DLS measurement.
3. DLS detection and result analysis. Each sample will be measured at least 5 times to guarantee the accuracy of results. We offer a discount for multiple samples.
4. Report generation. We will give you a detailed report containing the DLS method, DLS results, and discussion.

References

• Lim, J.K., et al. (2013). "Characterization of magnetic nanoparticle by dynamic light scattering." Nanoscale research letters, 8(1), 1-14.
• Feng, Y., et al. (2020). "Surface charge (zeta-potential) of nanoencapsulated food ingredients." Characterization of Nanoencapsulated Food Ingredients. Academic Press, 213-241.