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Updated: Aug 11, 2026
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Sample Preparation for Single Virion Atomic Force Microscopy and Super-resolution Fluorescence Imaging
Published on: January 2, 2014
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Exploring poly-L-lysine-based particle capture for atomic force microscopy studies of extracellular vesicles
L Conti1,2, A Ridolfi1,2, A Borup3
1Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), University of Florence, Florence, Italy.
Journal of Microscopy
|January 6, 2026
Summary
This study optimizes extracellular vesicle (EV) immobilization for atomic force microscopy (AFM). We introduce a new parameter Q to estimate sample concentration and propose an improved protocol for EV morphometry.
Area of Science:
- Biophysics
- Materials Science
- Nanotechnology
Background:
- Extracellular vesicles (EVs) require precise immobilization for accurate atomic force microscopy (AFM) analysis.
- Current protocols for EV immobilization present challenges in quantitative morphometry and nanoindentation.
- Understanding substrate interactions is crucial for reliable EV characterization.
Purpose of the Study:
- To investigate the impact of experimental variables on EV immobilization for AFM.
- To introduce a quantitative measure (Q) for adsorbed material and sample concentration estimation.
- To develop an optimized AFM protocol for EV morphometry in air.
Main Methods:
- Systematic variation of experimental parameters for EV immobilization on various substrates.
- Introduction and application of parameter Q to quantify adsorbed material.
- Comparison of EV morphometry results obtained in liquid and air using optimized protocols.
Main Results:
- Parameter Q quantifies total adsorbed material and estimates relative sample concentrations in AFM experiments.
- Q shows a logarithmic dependence on substrate charge density.
- EV contact angle (CA) does not correlate with substrate charge density as expected.
- An optimized air-based AFM protocol achieves EV size distributions comparable to liquid-based methods.
Conclusions:
- The parameter Q provides a reliable method for estimating sample concentration in EV immobilization studies.
- Substrate charge density significantly influences EV adsorption, but contact angle is less predictable.
- An optimized air protocol offers a viable alternative for EV morphometry, simplifying experimental procedures.
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