Particle Sizing

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Particle-by-particle measurement for accurate particle size and size distribution analysis of sample populations.

  • Absolute size (50nm-10μm+)
  • True Sample Polydispersity
  • Resolve multiple populations
  • Aggregation analysis
  • Individual particle detail

Background

Izon's qNano offers a rapid, accurate and convenient solution for evaluation of particle size and size distribution of nanoparticle samples in a fluid. The particle-by-particle detection methodology ensures an accurate size distribution output without the averaging effects inherent in other size analysis technologies.

A discrete blockade event signal is recorded by the system each time a particle traverses the nanopore. The magnitude of a measured blockade signal is a key indicator of the volume (or equivalent diameter) of the particle that has passed through the pore.

These individually discriminated measurements are built up into a total population view of the sample. This information allows:

  • Evaluation of Absolute Particle Size
  • Accurate Size Distribution of Polydisperse Samples
  • Analysis of Aggregation Effects & Dynamics
  • Size-based Gating of Selected Particle Populations
Background

Particle-by-Particle Sizing

The example on the left demonstrates measurement of a polystyrene nanoparticle sample with three distinct size populations.

Individial particle signals are recorded and displayed in real time. The relationship between measured blockade event magnitude (nA) and particle volume allows the determination of the absolute size of particles in a sample (nm). Particle-by-particle data is displayed as a size-distribution graph for the sample.

The SEM image confirms the presence of three particle populations at 220nm, 400nm and 780nm diameter.

Particle-by-Particle Sizing

Accurate Size Distribution of Polydisperse Samples

qNano enables particle-by-particle collection & assessment of polydisperse mixtures for highly accurate determination of size distribution within a sample.

The figure on the left shows a size distribution histogram of a quad-modal mixture containing four different polymer populations, measured with the Izon qNano's nanopore-based detection (Inset shows particle diameter vs translocation duration). Accurate size distribution output is achieved with individual particle detail.

Accurate Size Distribution of Polydisperse Samples

Size distribution histogram of a quad-modal mixture containing four different polymer populations shows highly accurate resolution of different size fractions within the sample.

Aggregation Analysis

Another key application is the analysis of aggregation within a sample. Mapping of the dynamics of particle suspensions can be made as a function of different conditions, i.e. reaction time, pH, ionic strength, reagent concentrations. The highly accurate particle-by-particle detection method allows detection of subtle changes in aggregation state.

The example on the left shows measurement of a liposomal preparation before and after freezing. The ability to accurately measure sample polydispersity and aggregation effects is a key feature of the qNano system. The same measurement principles can be applied to ensure homogenous and stable sizes of liposome particles during development processes of drug delivery systems.

Aggregation Analysis

Gating and Tunability

Izon's dynamically adjustable nanopores provide a unique tunability to the SIOS measurement system. A sensitive mechanical actuator provides the capability to control the passage of particles through the nanopore sensing zone, allowing selective gating of particles within a sample based on their size.

The system can be tuned to allow particles with a wide variety of sizes to flow through the nanopore under the same conditions, providing the ability to accurately analyse highly poly-disperse samples.

The sensitivity of the system is demonstrated in the figure on the left. As the applied stretch on the nanopore (x value) is reduced from 46.6mm to 44.7mm the particles (polystyrene) are selectively gated from passing through based on their size until at low applied stretch values only the smallest particles are allowed to translocate. The measurement at the largest applied stretch value (46.6mm) displays a wide range of blockade event magnitudes reflecting the full range of particles sizes in the sample.

Gating and Tunability

The dynamic control of particles in the SIOS system is achieved through the unique tunable nature of Izon's dynamically adjustable nanopores. This allows selective gating of particles in a sample based on size as demonstrated in this figure.