Two-Dimensional Flow Nanometry of Biological Nanoparticles for Accurate Determination of Their Size and Emission Intensity

TL;DR

This paper introduces a novel two-dimensional flow nanometry technique that enables simultaneous high-accuracy measurement of biological nanoparticle size and emission intensity by tracking their motion under flow conditions.

Contribution

The study presents a new method combining surface-sensitive microscopy and flow-induced motion tracking to accurately determine BNP size and emission intensity simultaneously.

Findings

Successfully measured BNP size and emission intensity with high accuracy.

Resolved the radius-squared dependence of vesicle fluorescence intensity.

Demonstrated the method's capability for precise nanoparticle characterization.

Abstract

Biological nanoparticles (BNPs) are of high interest due to their key role in various biological processes and use as biomarkers. BNP size and molecular composition are decisive for their functions, but simultaneous determination of both properties with high accuracy remains challenging, which is a severe limitation. Surface-sensitive microscopy allows one to precisely determine fluorescence or scattering intensity, but not the size of individual BNPs. The latter is better determined by tracking their random motion in bulk, but the limited illumination volume for tracking this motion impedes reliable intensity determination. We here show that attaching BNPs (specifically, vesicles and functionalized gold NPs) to a supported lipid bilayer, subjecting them to a hydrodynamic flow, and tracking their motion via surface-sensitive imaging enable to determine their diffusion coefficients and flow-induced drift velocities and to accurately quantify both BNP size and emission intensity. For vesicles, the high accuracy is demonstrated by resolving the expected radius-squared dependence of their fluorescence intensity.