Nanoparticle Tracking Analysis for the Quantification and Size Determination of Extracellular Vesicles
March 28th, 2021
9.3K views
We demonstrate how to use a novel nanoparticle tracking analysis instrument to estimate the size distribution and total particle concentration of extracellular vesicles isolated from mouse perigonadal adipose tissue and human plasma.
Overview
This article presents a detailed protocol for quantification and size determination of extracellular vesicles (EVs) using nanoparticle tracking analysis (NTA). The protocol emphasizes the importance of standardizing NTA parameters to increase rigor and reproducibility in EV research, and demonstrates the effects of altered NTA settings on data quality. The method is validated using EVs isolated from mouse perigonadal adipose tissue and human plasma, with results confirmed by transmission electron microscopy.
Key Study Components
Area of Science
- Extracellular vesicle research
- Nanoparticle tracking analysis
- Analytical biochemistry
Background
- Extracellular vesicles play significant physiological and pathophysiological roles.
- Multiple EV isolation methods exist, each affecting yield and purity.
- Accurate characterization of EV preparations is essential for reproducibility and cross-laboratory comparison.
- NTA is a widely used technology for high-throughput EV analysis, but results are sensitive to operator technique and instrument settings.
Purpose of Study
- To provide a standardized, reproducible protocol for NTA-based EV quantification and sizing.
- To demonstrate how NTA parameter adjustments impact measurement outcomes.
- To validate the protocol using EVs from different biological sources.
Methods Used
- Preparation of EV samples in cuvettes with careful handling to avoid contamination.
- Serial dilution to achieve optimal particle concentration for NTA.
- Detailed setup of NTA instrument parameters (frame rate, exposure, laser power, gain, etc.).
- Calibration of the instrument using polystyrene beads of known sizes.
- Data acquisition, processing, and reporting using the NTA software.
- Thorough cleaning of cuvettes and accessories post-analysis.
- Validation of results with transmission electron microscopy and recommendation of orthogonal methods (e.g., dynamic light scattering, resistive pulse sensing).
Main Results
- Operator bias and NTA parameter changes significantly affect EV size and concentration measurements.
- Standardized cuvette-based analysis yields reproducible data across a wide size range.
- Instrument calibration is more accurate for smaller particles (~100 nm) than larger ones.
- Adjusting laser power and gain alters reported particle size and concentration.
- Optimal dilution is critical for accurate quantification; technical replicates show low variability.
Conclusions
- Standardization of NTA protocols is essential for rigorous and reproducible EV research.
- The described method provides reliable EV size and concentration data from diverse sources.
- Complementary analytical techniques are recommended for comprehensive EV characterization.
Frequently Asked Questions
Why is standardization important in NTA-based EV analysis?
Standardization minimizes operator bias and variability, ensuring that EV size and concentration measurements are reproducible and comparable across different laboratories.
How does altering NTA parameters affect EV measurement results?
Changes in parameters such as laser power, gain, and dilution can significantly shift the reported particle size and concentration, highlighting the need for consistent settings.
What steps are critical for preparing EV samples for NTA?
Careful sample dilution, avoidance of air bubbles, and thorough cleaning of cuvettes and accessories are essential for accurate and reproducible measurements.
How is the NTA instrument calibrated for accuracy?
Calibration is performed using polystyrene beads of known sizes, confirming that the instrument accurately measures particles, especially those around 100 nm.
What are the limitations of NTA for EV analysis?
NTA is less accurate for larger particles and is sensitive to operator technique and instrument settings. Complementary methods are recommended for comprehensive analysis.
Which orthogonal methods are suggested for EV characterization?
Dynamic light scattering, resistive pulse sensing, transmission electron microscopy, and single-particle interferometric reflectance imaging sensing are recommended to validate NTA results.
How should cuvettes and accessories be cleaned after NTA analysis?
Cuvettes should be rinsed multiple times with deionized water and ethanol, then dried with lint-free materials and compressed air. Inserts and stir bars should be cleaned in ethanol, rinsed, and dried before storage.
Executive Industry Relevance
Reliable quantification and sizing of extracellular vesicles (EVs) are critical for early discovery and translational research, as EV characteristics can reflect disease states and therapeutic responses. Nanoparticle tracking analysis (NTA) offers high-throughput, quantitative EV profiling, but standardization is essential to ensure reproducibility and cross-laboratory comparability. This protocol addresses key challenges in EV analytics, supporting predictive confidence and portfolio decision-making in biopharma R&D.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables rigorous hypothesis testing by providing quantitative EV concentration and size data.
- Supports biological de-risking through reproducible measurement of EV characteristics across samples.
- Facilitates functional target validation by linking EV profiles to disease or treatment conditions.
Screening & Assay Development
- Prepares validated EV samples for downstream screening and mechanistic assays.
- Standardizes assay conditions to ensure reproducibility and comparability of quantitative outputs.
- Enables reliable evaluation of compound effects on EV release or composition.
Translational & Preclinical Research
- Aligns EV analytics with disease-relevant biomarker discovery and validation.
- Provides continuity from discovery through preclinical studies by supporting consistent EV measurement.
- Reduces translational risk by enabling robust cross-study and cross-site data integration.
Pipeline & Workflow Integration
NTA-based EV quantification and sizing fit within the discovery-to-preclinical continuum, supporting both early-stage hypothesis testing and translational biomarker development.
- Discovery Biology: Delivers quantitative EV data for pathway clarification and mechanistic de-risking.
- Screening: Provides standardized, reproducible EV measurements for assay readiness and compound evaluation.
- Analytics: Generates size distribution and concentration outputs for robust statistical comparison across conditions.
- Translational Research: Supports biomarker alignment and preclinical continuity when EVs are disease-relevant.
- Enterprise Reuse: Establishes a standardized, reusable workflow for EV analytics across programs and sites.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in EV-based studies.
- Operational Value: Enhances reproducibility, standardization, and scalability of EV analytics.
- Strategic Value: Improves go/no-go decisions and capital efficiency by reducing biological risk.
- Portfolio Impact: Enables risk-adjusted prioritization and advancement of EV-related programs.
Implementation Considerations
- Requires expertise in EV isolation, NTA operation, and data interpretation.
- Needs access to calibrated NTA instrumentation and analytical infrastructure.
- Demands rigorous cross-team standardization of sample preparation and analysis parameters.
- May require adaptation of dilution and cleaning protocols for different sample types.
- Accuracy is highest for smaller particles; orthogonal methods are recommended for comprehensive EV characterization.
Biopharma FAQs
Why does null hypothesis testing matter for NTA-based EV quantification?
Null hypothesis testing enables objective evaluation of whether observed differences in EV size or concentration are statistically significant, supporting robust target validation and reducing false discovery risk in early discovery pipelines.
How does independent variable isolation fit into NTA parameter optimization?
Systematically altering one NTA parameter at a time, such as laser power or gain, isolates its effect on EV measurement outputs, ensuring that observed changes are attributable to specific variables and not confounded by operator bias.
What do quantitative dependent variable measurements enable in EV analytics?
Quantitative outputs such as mean, median, and mode particle size, along with concentration, allow for rigorous comparison across samples, conditions, and studies, facilitating data-driven decision-making in biopharma R&D.
Why are replication requirements critical for cross-functional EV studies?
Technical replicates and standardized protocols ensure that EV measurement results are reproducible and comparable across teams and sites, supporting collaborative research and enterprise-wide data integration.
What statistical analysis capabilities are required before implementing NTA-based EV workflows?
Teams must be able to perform calibration, dilution factor adjustments, and statistical comparisons of EV size and concentration distributions to validate measurement accuracy and support reliable downstream analyses.
Chapters in this video
0:04
Introduction
0:58
Cuvette Preparation
1:53
Particle Tracking Instrument Preparation and Nanoparticle Tracking Analysis
4:01
NTA Data Processing, Display, and Interpretation
5:29
Cuvette Cleaning
6:33
Results: Using a Novel NTA Instrument to Estimate EV Size Distribution and Total Particle Concentration
8:33
Conclusion
