Walk-up or Automated Measurements of Size, Concentration, and Zeta Potential of Particles

View Podcast Transcript

Tamlyn Oliver: Hi, everyone. Welcome to Biocompare's Tech Insights podcast where we speak to scientific experts about new tools and technology that can help advance your research. I'm Tamlyn Oliver, managing editor of Biocompare. Today's guest is Richard Chung, a product manager at Wyatt Technology. He's going to talk about optimizing the measurement of size particle concentration and zeta potential in biopharmaceutical development. Thanks for joining us today, Richard. We're all for simplifying workflows, so we look forward to hearing what you have to say.

Richard Chung: Hi Tamlyn. I'm excited to be here.

Tamlyn: We have a lot of questions. So we're going to jump right in with some basic questions first and then work up to details of the ZetaStar. All right, let's start with the first question. What is zeta potential and why is it important?

Richard: Zeta potential is a physical property that is often used to optimize formulations, predict interactions and stability via aggregation. Ultimately, it can reduce the time needed to produce formulations and provide an indication of long term stability. This is really important for a lot of pharmaceutical companies and drug manufacturing companies to assess the quality of their formulations. Especially in early development and characterization. And roughly, you know, when we're characterizing zeta potential since it is used as a predictor of how the particle will be in solution. A lot of the times you have to understand a lot of other factors about the sample as well. You know, just relying on the zeta potential is not enough since it is dependent on a multitude of factors. So it's critical to know the ionic strength of your solution. The ph, a lot of other environmental factors. So it is a measurement of how the sample is in its immediate environment. And it can change if if you're looking at the data potential in one formulation versus another.

Tamlyn: So the ZetaStar is used to measure zeta potential? Can you tell us a little more about the ZetaStar?

Richard: The ZetaStar is Wyatt and Water's latest offering, our latest instrument development project And the ZetaStar has a multitude of characterization techniques. It's our first ever instrument that has static light scattering, dynamic light scattering and electrophoretic light scattering capabilities. What does that all mean? Each one of these light scattering techniques enables different characterization modalities. So for example, static light scattering allows us to measure molecular weight turbidity and particle concentration.

Our dynamic light scattering capabilities allow us to measure size size distribution and poly dispersity. And then electrophoretic light scattering allows us to measure electrophrenic mobility, which in turn allows us to get the zeta potential the effective charge, the net charge and the conductivity. So all that combined, this instrument is one of our most versatile and diverse instrumentations.

Tamlyn: One of the ways to determine zeta potential is light scattering. Can you talk about how that's done?

Richard: With the ZetaStar specifically, we're using electrophoretic light scattering. So essentially the sample will be in solution. And with the sample, we'll place two electrodes into the sample and introduce an electric field. And if the particle is charged, once that electric field is introduced, it'll begin to move back and forth. So the charged particles will move in response to the applied field. And that speed is the electrophretic mobility. That's what is directly measured. And from that mobility measurement, we're able to derive the zeta potential, the charge of the particle, and the conductivity of the solution as well.

Tamlyn: I understand it's important to simultaneously take more than one light scattering measurement on the same sample. Can you talk about why that's important? And also the advantages that conveys.

Richard: Unlike other light scattering characterization techniques like dynamic light scattering or static light scattering, electrophoretic light scattering in particular is an invasive technique where once we apply the field, we could potentially alter the sample depending on how strong of a field we apply and how fragile the sample is by applying this field, we could alter the sample. So it's important to simultaneously measure the size of the sample over the course of the measurement. And that way we can monitor in real time if the measured size changes or remains constant, and it'll give us information about how to optimize the method a little bit further. A secondary advantage is by doing both at the same time, we're essentially cutting the measurement time in half.

Tamlyn: You talked about the ZetaStar. Is this a capability unique to the ZetaStar?

Richard: So from all the, you know, we've taken a look at a lot of the competitor instruments and our own legacy product line to try and assess, you know, where can we make the most impact, not just copying what our competitors are doing. And from everything we've seen, this is this is something unique to the ZetaStar.

Tamlyn: I also saw that the ZetaStar can be automated for walkway measurements of multiple samples. Can you tell me why that's important and how it works?

Richard: With scientists in the lab, no one wants to stand in front of an instrument all day, especially a cuvette-based instrument and insert a cuvette and wait for the measurement to complete 10 to 15 minutes later, take it out, clean it do the whole process again after optimizing formulations or looking at a queue of samples that's 20 to 30 plus, you're gonna be standing in front of the instrument all day. And that can, you know, from the scientists point of view, I know that can be extremely painful and time consuming. Another thing is for consistency, you know, we want to by automating the system, we can ensure, you know, everything is automated hands free. So there's no risk of from the way the samples introduce. If you know, if you've touched the optical surfaces of one CT and introduce your fingerprints or introduce the sample and, and in a bad way. And another, you know, this really just takes that part of the human interaction out of it, reduces the likelihood of mess ups that way. And part of how we're able to do this with the ZetaStar is with the flow cell design. We can connect directly to an auto sampler for a stop flow experiment.This is unique in the space of ELS instrumentation. Because all the ELS instruments currently on the market are cuvette based. So by connecting to the auto sampler, we can run the measurement stop flow, we can automate wash steps in between and ensure no carryover and make the whole process automated. So you can set up a sample run of 20 to 30 samples overnight and come back in the morning to view the results.

Tamlyn: You just mentioned the cuvettes. Can you talk about the cuvettes and flow cells available for the ZetaStar? And what advantages they offer?

Richard: There are a couple different options available based off of what workflow is of most interest to the user. ZetaStar is our first instrument that has static, dynamic, and electrophoretic light scattering. So it really has a whole suite of workflows available to the instrument. So depending on that we have different cells available. So for zeta potential measurements, for example, we have three options. One is with the dip cell, which enables size and simultaneous zeta potential measurements. This is really ideal if you're limited by sample, since you can make this measurement with only 65 microliters of sample. We have a disposable cell option, which is single use for zeta potential in size as well. So this is really ideal for quick and easy measurements where maybe a user doesn't want to deal with cleaning or potential cross contamination. And then lastly, we have our flow cell, which is ideal for measurements where you want to automate like I had just mentioned or run what we consider high salt measurements. And then for our DLS options, there's a couple different cells as well. You know, these are all carry over options from our DLS-based instrumentation. So for we have extremely low volume cells available like our two microliter and 45 microliter quartz Cuvettes. These enable both size and static light scattering measurements. And then we have a four microliter disposable DLS cuvette as well.

Tamlyn: That sounds very comprehensive.

Richard: Yeah, it can get a little overwhelming but you know, we have easy charts to help map it out. It's really just because the instrument can do so much that we have all these options available.

Tamlyn: Next question… bubbles, why are bubbles detrimental to light scattering measurements? And how are they formed? And how does the ZetaStar deal with them?

Richard: Bubbles are really one of the biggest no-nos for any type of light scattering instrument. Really bubbles are large relative to most samples, they scatter light really well. So it can ruin a measurement essentially. And for zeta potential measurements, in particular, when we're looking at highly conductive solutions, the moment we apply an electric field to induce particle motion, high voltage can produce a couple of negative effects. You know, one it can generate electrolysis at the electrodes, which can cause the formation of gas bubbles. And those bubbles can interfere with the measurement or induce significant amount of noise. Larger voltages can also lead to other issues like sample degradation or joule heating. And to deal with this issue, the ZetaStar does have a couple different design considerations that address this, you know, one is with the specially designed flow cell which can be installed with our Atlas accessory. And this setup essentially allows us to pressurize the entire full path up to 500 PSI. And with the system pressurized the solubility of gas and solution increases and allows the bubbles to dissipate back into solution. And any other bubbles that are formed are essentially collapsed because of the immense pressure within the system. To address the high voltage issue, you know, the the cell design is able to induce strong local fields while applying much lower voltages. Really on the scale of 2 to 3 volts. A lot of the other instruments on the market will regularly apply up to 150 volts. So by applying much lower voltages, we're able to slow electrodegradation and reduce the level of joule heating and overall better preservation of fragile samples.

Tamlyn: My last question is about the dynamics touch software on the ZetaStars' built in touch screen. Can you talk about that? What I can do with it? And if I need to have a specific training to use it?

Richard: One of the big issues with most labs, you know, especially in characterization labs in early development, there is a huge variety of instrumentation needed for characterization. And each setup requires specific training. Depending on the different types of techniques, a user has to just learn how to operate a lot of different software, a lot of different instruments, it's usually limited to experts with zeta potential in particular. So with our new dynamics touch software, we've really significantly lower the barrier of entry and enabled simple touch base workflow operations. You know, we still have our more complex and advanced analytical processes available in the software. But with touch, we're really enabling brand new users to begin collecting data right away. Another key advantage is this allows for extremely fast feedback. So you can insert a cuvette  with your sample and get immediate life readings of the ACF or check the conductivity before you even commit to a big experiment, you can get a quick reading. So if you wanted to do an overnight run, you can just do a quick check to ensure that you have the right sample and everything looks as expected just to give you quick feedback before you even commit to an experiment where you may lose the entire sample or lose a day for that feedback.

Tamlyn: Thank you very much Richard for explaining the advantages of using light scattering to measure multiple key parameters quickly and easily and the benefits of using the start. For more information on ZetaStar, Please read the related article optimizing the measurement of size particle concentration and zeta potential on the Biocompare site.

And thanks so much for listening. For more information on products, technologies and the latest scientific advancements. Please visit biocompare.com and have a great day.

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.