Nanoparticle Tracking Analysis

What is nanoparticle tracking analysis?

Nanoparticle tracking analysis is a characterization technique that follows the movement of individual particles in suspension to determine their size distribution and concentration. Commonly known as NTA, it combines optical microscopy, laser illumination, video acquisition, and image-processing software to visualize and track particles undergoing Brownian motion.

NTA provides a number-based particle size distribution, which can help reveal different populations within polydisperse samples. Depending on the instrument configuration, it can also report concentration in particles per milliliter and perform fluorescence-based measurements of labeled subpopulations.

How does nanoparticle tracking analysis work?

A liquid sample is introduced into a measurement chamber and illuminated by a laser beam. Light scattered by the particles is collected through a microscope and recorded by a sensitive camera. The analysis software identifies visible points of scattered light and tracks their positions frame by frame throughout the recorded video.

Smaller particles generally undergo faster Brownian motion, whereas larger particles move more slowly. Using the diffusion coefficient calculated for each tracked particle, together with the temperature and viscosity of the dispersing medium, the software estimates hydrodynamic diameter through the Stokes-Einstein equation.

Reliable measurements depend on sample dilution, particle concentration, dispersion stability, particle refractive index, medium viscosity, and acquisition settings. Excessively concentrated samples can produce overlapping tracks and optical interference, while highly diluted samples may provide insufficient statistical representation. Consistent sample preparation and standardized settings are therefore important for comparing measurements.

Laboratory and industrial applications of NTA

• Measurement of extracellular vesicles, including small vesicles commonly described as exosomes.
• Characterization of polymeric, lipid, metallic, and inorganic nanoparticles.
• Development and assessment of drug-delivery systems.
• Investigation of viruses, virus-like particles, and other biological materials.
• Monitoring of particle aggregation, colloidal stability, and formulation changes.
• Research involving biotechnology, nanomedicine, vaccines, biopharmaceuticals, and materials science.

In industrial settings, nanoparticle tracking analysis can support research and development, formulation comparison, process investigations, and quality control. Its use for batch release or regulated testing requires an appropriately validated method, documented repeatability, suitable reference materials, and compliance with applicable requirements.

Frequently asked questions about NTA

What is the difference between NTA and dynamic light scattering?

NTA tracks individual particles and generates a number-based distribution. Dynamic light scattering evaluates fluctuations in scattered light from the particle population and commonly reports an intensity-weighted distribution. Consequently, the techniques may produce different results for broad or multimodal samples.

Can NTA identify nanoparticle composition?

Conventional NTA primarily measures hydrodynamic size and particle concentration; it does not directly determine chemical composition. Fluorescence-capable instruments can detect selected subpopulations when particles are labeled with suitable fluorescent markers.

Can NTA measure every type of nanoparticle?

Detection depends on particle size, concentration, refractive index, and instrument sensitivity. Low-refractive-index biological or polymeric particles may need to be larger to produce detectable scattering than metallic particles, which usually scatter light more strongly.