Description
Nanoparticle Tracking Analysis with the ZetaView®
The ZetaView® is a nanoparticle tracking analysis (NTA) instrument for measuring hydrodynamic particle size, zeta potential and concentration.
With nanoparticle tracking analysis, you measure what you see. Each individual particle in the field of view is counted and tracked in short video clips, creating accurate concentration calculations and particle size distributions. The ZetaView® combines these measurements with classical micro-electrophoresis, for determination of zeta-potential. All of these parameters can be measured both in scattering mode and in fluorescence mode, for determination of fluorescently-labelled sub-populations. The result is one compact instrument capable of measuring size, concentration, zeta-potential and fluorescence.
The main advantage of the ZetaView® system is that the optical setup can be moved. The laser and microscope objective can be moved both synchronously and independently.
- Moving the laser and objective synchronously allows sub-volume scanning of the sample cell. Measurements can be taken at 11 different positions across the cell, meaning measurements are based on having tracked thousands of individual particles, giving a more representative analysis than single-point measurements, and adding more power to the statistical analyses.
- Moving the optics independently allows the system to automatically align the laser and objective, therefore automatically focussing the image of the particles and significantly minimising setup time. Once the the focussing is done, there is no need to repeat the procedure for the rest of the day.
Zeta Potential
Zeta potential is effectively a measure of the surface charge of a particle and the ZetaView® uses micro-electrophoresis to calculate it.
The zeta potential distribution is calculated from the electrophoretic mobility results at the two stationary layers in the sample cell, or from an electrokinetic velocity profile obtained by scanning at all 11 positions throughout the sample cell.
The zeta-potential is calculated from the Smoluchowski or Henry equation – see the “Theory” tab, above. In addition to the particle zeta potential result, the curvature of a profile delivers information on the polarity and amount of ionic coating on the cell walls.
Zeta Potential Distributions
The below example highlights the capability of the ZetaView® and zeta potential, as well as the importance of measuring zeta potential and its relationship with hydrodynamic particle size.
A 60 nm gold dispersion was studied for size and zeta potential distribution (pictures on the right). The sample is slightly bi-modal.
Curve A (red) represents gold particles in a 2m KCl environment, curve B (blue/green) the same sample but dispersed in distilled water.
The zeta potential distribution of curve B shows a peak near 0 mV, which is making the suspension unstable, due to a lack of repulsive force between the particles (no charge). The majority of the 60 nm particles are therefore agglomerated, which is clearly seen in the size distribution of curve B.
ZetaView and Fluorescence (F-NTA)
With NTA, particles are viewed by detection of the light that they scatter. Due to the physical nature of this detection method, a chemical discrimination is not provided. In order to add specificity to particle characterisation, Fluorescent Nanoparticle Tracking Analysis (F-NTA) can be employed.
Nanoparticle such as vesicles can be labelled with a specific antibody bearing a fluorescent molecule (fluorophore). The ZetaView® is fitted with a slide-in filter to block scattered light from the laser, allowing past only fluorescence of a longer wavelength, generated by excitation of the fluorophores by the laser. Therefore, only the fluorescently-labelled particles will be detected and measured by the camera.
NEW Zetaview TWIN and QUATT
The ZetaView is now available as Twin and Quad Laser models, incorporating two and four different laser modules and corresponding filters which can all be automatically switched at the click of a button. As well as giving the user a choice of two or four different lasers to use for their fluorescence measurements, the TWIN/QUATT Laser ZetaView allows detection and characterisation of TWO or FOUR different fluorescently labelled sub-populations, adding extra layers of specificity to NTA measurements.
Both models arrive in the same small, compact, highly-engineered chassis as the standard ZetaView. On top of the twin fluorescence emission detection capabilities, the standard size, concentration and zeta potential capabilities remain, making the Twin Laser ZetaView a completely unique offering and very much the next generation of NTA technology.
Interested in the Zetaview®? Request a quote or call us on +44(0)1954 232 776 to discuss your requirements.
