Static Light Scattering

Measure particle properties like protein aggregation and empty/full capsid ratio

Learn more with light

Static Light Scattering (SLS) might seem simple at first — a laser goes into a sample, hits particles, and bounces back out — but SLS is actually one of the most powerful techniques to detect particles in solution. The intensity of reflected light is the main readout of an SLS experiment and, if you know what you expect of your sample, that intensity can tell you a lot. SLS can be used to calculate titers of viral particles, or as the most sensitive way to keep an eye on when aggregation begins in a sample.

SLS is able to do all this through the power of light.

How does SLS work?

With SLS, laser light is directed at your sample and the scattered light is measured at one or more angles around the sample. Because the intensity of scattered light can be affected by a number of properties of your sample and setup, such as:

  • Particle molecular weight
  • Particle size (Rg)
  • Particle concentration
  • Interactive forces between particles
  • Refractive indices of the particle and solvent
  • Angle between the laser and detector
  • Laser wavelength

We can use the measured intensity to characterize the particles in your sample. Here’s how it works:

Shine the right light

Particles that are small relative to the light wavelength will scatter light evenly in all directions (Rayleigh scattering). For UV and visible lasers, biologics like proteins and AAV are considered small.

SLS Laser
Measure intensity

The intensity of the scattered light will depend on a number of factors related to your sample, your light source, and your detection setup. For small, dilute particles, intensity is proportional to:

  • Particle molecular weight (M)
  • Particle concentration (C)
  • Refractive index of the buffer (no)
  • Differential refractive index of the particle relative to concentration (dn/dc)2
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Turn up the heat

With SLS and a thermal ramp, you can measure the aggregation temperature (Tagg)—that’s the temperature when SLS intensity begins to increase and aggregation gets out of hand.

Turn up the heat
…or get a two-for-one

With simultaneous SLS and DLS, you can figure out just the intensity coming from AAV capsids. That’s the first step to getting easy and quick AAV titers.

DLS_or get two for one_r2_crop4
SLS_or get two for one_r2_crop2
SLS vs DLS—What’s the difference?

Instruments often offer SLS and DLS data side-by-side, so you may be wondering about the differences between the techniques and when to use each one.

SLS is all about average intensity and can tell us about particle molecular weight and concentration in certain setups. In contrast, DLS reads how fast scattered light intensity changes over time, which provides information on diffusion rates and particle size. You can say it’s like listening to a rock concert—SLS would tell you how loud the music is and DLS would tell you what song is being played.

So when you're thinking about choosing the right kind of light scattering, SLS is ideal for detecting the moment when aggregation begins because it is a direct measurement that increases the moment molecular weight increases. By contrast, DLS looks at size based on the diffusion of particles in solution, so DLS needs a bit of time to detect particles that are moving around.

But on the plus side, DLS is more quantitative when you know less about your sample, so it’s great for comparing sizes from day-to-day or batch-to-batch, and for measuring how the size of your particles change over long isothermal experiments.

DLS vs SLS
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Uncle

Uncle combines DSF, static light scattering, and dynamic light scattering measurements to deliver results for protein unfolding and aggregation problems, all done on the same sample. Add in customizable analysis across full-spectrum fluorescence detection and you’ve got a flexible tool that is ready to answer almost any protein stability question. Seeing the whole story on when proteins unfold and aggregate reveals exactly what’s going on with protein samples.

Stunner

Stunner is the only system that pulls together UV/Vis concentration, DLS and SLS data from the same 2 μL sample. Dig in to your AAV to get the total capsid titer and empty/full ratio, or rack up payload concentration and size data on any nanoparticle all at once. Nail down your protein quality by knocking concentration, hydrodynamic size, polydispersity, and detection of aggregates off your list in one shot. Without skipping a beat, you’ll know if your AAV, nanoparticle or protein is good to go.

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Ready for more?

Biopharma scientists can now use the right tool for protein aggregation and capsid characterization with instruments that combine SLS with DLS, fluorescence, and UV/Vis. Have a question or ready to find out more?