What Is Zeta Potential?

Zeta potential is a specialized term for kinetic potential in colloidal dispersions, also called electromotive potential (ζ-potential), which is used to characterize the surface potential of nanoparticles. Theoretically, zeta potential is the potential of the sliding surface in the interface bilayer relative to a point in the fluid far from the interface. In other words, zeta potential is the potential difference between the dispersion medium and the fluid-fixed layer attached to the dispersed particles. The potential is caused by the net charge in the area around the sliding plane and also depends on the position of the sliding plane. The higher the Zeta potential (positive or negative), the greater the repulsive force between particles and the more stable the system. Conversely, the lower the zeta potential (positive or negative), the smaller the repulsive force between particles and the more they tend to coagulate or agglomerate. Therefore, Zeta potential is an important indicator of the stability of the nanometer drug delivery system. Zeta potential can also affect the drug loading of nanoparticles, as well as the uptake and intracellular transport of nanoparticles by cells.

Zeta potential measurement methods include electrophoresis method, electroosmosis method, flow potential method and ultrasonic method, of which electrophoresis method is the most widely used. The electrophoresis method is to convert the measurement of Zeta potential to the measurement of the mobility of charged particles by using the electrochemical principle. The electrophoretic mobility is measured by electrophoretic light scattering, and then the Henry equation is used to calculate the Zeta potential:

In the formula, UE is the electrophoretic speed; ε is the dielectric constant; ζ is the Zeta potential; f (κa) is the Henry function; η is the viscosity. The method is fast, statistically accurate and reproducible. The early method of mobility measurement was the direct observation method, that is, the voltage was applied across the dispersed system and observed with a microscopic device. At present, the laser Doppler effect method is commonly used for measurement. The principle is that particles moving under the action of an electric field. When the laser light is irradiated on the particles, the frequency of the scattered light changes. After the scattered light and the reference light are superimposed, the frequency change becomes more intuitive and easier to observe. By correlating the frequency change of the light signal with the speed of the particles, the particle mobility can be measured.

There are many commercially available instruments for measuring the Zeta potential of nanoparticles. Among them, the related instruments produced by the British Malvern company are widely used, and their ZetasizerNano series instruments use hybrid mode measurement (combining fast electric field conversion and slow electric field conversion) laser Doppler velocimetry (LDC) and phase analysis off scattering (PALS) Combination. This combination can effectively eliminate electroosmosis and analyze samples in non-aqueous dispersion systems. cd-bioparticles.net uses the most advanced measurement methods to provide fast and accurate nanoparticle zeta potential measurement services.