SNC‐TIRS: Label‐free Single Nanoparticle Characterization System Based on Total Internal Reflection Scattering Signal

Nanoparticles are used in various biomedical applications like in vitro diagnostics, imaging, drug delivery, and other therapeutic uses. The performance of such applications requires accurate knowledge of size distribution that needs precise characterization techniques. In this study, a single-nanoparticle characterization system based on the total internal reflected scattering signal (SNC-TIRS) is demonstrated for the size estimation of synthetic nanoparticles and exosomes. A compact waveguide-based evanescent field illumination is used to convert a digital microscope into a nanoparticle characterization system based on scattering signals from diffusing nanoparticles in Brownian motion. By analyzing single-particle trajectories, the system estimates the hydrodynamic size, average number of particles observed per unit volume, and the distribution of sample heterogeneity. SNC-TIRS is benchmarked with inorganic nanoparticles and biomaterials in size range of 80-250 nm. Its utility to characterize the size of exosomes isolated from plasma using magnetic nanoparticles (MNPs) is shown. The hydrodynamic size of bare MNPs (123.83 +/- 29.19 nm), antibody-bound-MNPs (161.33 +/- 29.47 nm), and antibody-exosome-bound-MNP conjugates (224.82 +/- 25.89) are estimated and the results obtained agree with standard methods such as dynamic light scattering and nanoparticle tracking analysis. SNC-TIRS can enable the label-free characterization of nanomaterials and clinically relevant biomarkers.