LIGHT-SCATTERING DETECTORS continued
The ongoing advances in light detectors, especially ones that
improve the ability to work with biological molecules, promise to push this technology into even more medical applications.
The DelsaMax PRO has 32 detectors. According to Jones, “Two major recent advances in light-scattering technology are detector number and pressurization of samples.” For the DelsaMax PRO, says Jones, having so many detectors provides two key benefits: “The first is that if any particu- lar detector generates spurious data, it can be quickly noted as an outlier from the other detectors; the second is that the measurement times can be dramatically reduced, thus preserving the integrity of proteins during the application of electric potential.” With previous technology, measur- ing the zeta potential would probably significantly damage a cell.
More medicines Light detectors can be used to study medicines in more ways than ever, and researchers keep finding new ones. Scientists from Switzerland and the United States used light-scattering technology to measure the excipients—inert substances—in drug formualtions.1
In particular, they
To get the most from the light detection, users need specific controls. “The Waters ACQUITY UPLC ELSD provides flexibility and fine control of temperatures for the nebulizer and drift tube to enable analysts to optimize conditions to maximize sensitivity and selectivity,” Pham explains. “The ELSD flow path has been optimized for the lowest dis- persion to allow scientists to take advantage of the peak widths found in UPLC methods.”
Protein power and more Biological research benefits from today’s light detectors in many ways. “Interesting new uses of light-scattering detectors include size and charge analysis of proteins, exosomes and lipid particles,” says Richard Jones, product manager at Beckman Coulter Life Sciences (Indianapo- lis, Ind.).
Light detectors turn out to be especially useful in developing new ther- apeutics. “As a protein therapeutic is being handed off from R&D to the development team, protein multimerization and aggregation state are impor- tant parameters to be examined,” Jones explains. “Light scattering provides a very rapid method to examine protein size and molecular weight.”
Light detectors can also measure the zeta potential—the charge dif- ference between the surface of a particle and the liquid around it. “The rapid examination of zeta potential is important to gain an understand- ing of the impact of drug formulation on the propensity of a protein to stay in solution,” Jones explains.
Exosomes are vesicles—usually less than 100 nanometers in diam- eter—that cells create and secrete. “Many recent companies have been founded with the aim of designing and manufacturing therapeutic exosomes for delivering therapeutics to specific cell types,” Jones says. Beckman’s DelsaMax PRO Zeta Potential Dynamic Light Scattering Analyzer has been used to characterize the zeta potential of some thera- peutic exosome preparations.
AMERICAN LABORATORY 22
looked at polysorbates (PS), and tested them with three technologies, including mixed-mode (MM)-ELSD and the fluorescence micelle assay (FMA); the results showed that some technologies work better for some uses than others. As the scientists wrote: “For PS20 degraded by chemi- cal oxidation, quantitation results were lower for FMA than MM-ELSD, while the opposite trend was observed with base hydrolysis.”
In developing vaccines, additives can improve efficacy. These adjuvants can be liposomes, which are spherical sacs made of lipids. The amount of lipid in the liposomes can affect a vaccine’s efficacy and stability. U.K. scientists created an HPLC-ELSD “method that allows for the rapid and simultaneous quantification of lipid concentrations within liposomal systems prepared by three liposomal manufacturing techniques (lipid film hydration, high shear mixing, and microfluidics).”2
They used the
system to quantify four lipids, and concluded: “HPLC-ELSD was shown to be a rapid and effective method for the quantification of lipids within liposome formulations without the need for lipid extraction processes.”
The ongoing advances in light detectors, especially ones that improve the ability to work with biological molecules, promise to push this tech- nology into even more medical applications. Some of the same advances will also make this technology more useful in basic research. The use of light as a fundamental method of detection in science will not be going away anytime soon, and advances like the ones described here show us even more of what technology can light up around us—whether the light is used to make better medicines or explore nature.
References 1. Lippold, S.; Koshari; S.H. et al. Impact of mono- and poly-ester frac- tions on polysorbate quantitation using mixed-mode HPLC-CAD/ELSD and the fluorescence micelle assay. J. Pharm. Biomed. Anal. 2016; doi: 10.1016/
j.jpba.2016.09.033.
2. Roces, C.B.; Kastner, E. et al. Rapid quantification and validation of lipid concentrations within liposomes. Pharmaceutics 2016; doi: 10.3390/ pharmaceutics8030029.
Mike May is a freelance writer and editor living in Florida. He can be reached at
mikemay1959@gmail.com.
JANUARY/FEBRUARY 2017
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