Interferometric Scattering Enables Fluorescence-Free Electrokinetic Trapping of Single Nanoparticles in Free Solution

Abstract

Anti-Brownian traps confine single particles in free solution by closed-loop feedback forces that directly counteract Brownian motion. The extended-duration measurement of trapped objects allows detailed characterization of photophysical and transport properties, as well as observation of infrequent or rare dynamics. However, this approach has been generally limited to particles that can be tracked by fluorescent emission. Here we present the Interferometric Scattering Anti-Brownian ELectrokinetic trap (ISABEL trap), which uses interferometric scattering rather than fluorescence to monitor particle position. By decoupling the ability to track (and therefore trap) a particle from collection of its spectroscopic data, the ISABEL trap enables S-1

Engineering improved measurement and actuation for nanoscale biophysics

“…Most recently, we pioneered an update to the ABEL trap which employs interferometric scattering (rather than fluorescence) to track a trapped particle (Squires et al 2019b). This will enable future investigations of a much broader class of single particles, including those that are intermittently or dimly fluorescent, or do not fluoresce.…”

Micromirror Total Internal Reflection Microscopy for High-Performance Single Particle Tracking at Interfaces

“…4. The linear scaling of the detected signal for iSCAT with the volume of the scatterer compared to a squared dependence for dark-field detection also implies that sample-specific background that is smaller than the signal of interest plays a more significant role in iSCAT than in dark-field imaging 16 . Conversely, iSCAT is intrinsically more suited to simultaneously imaging a larger range of particle sizes for a given dynamic range in detection.…”

Photothermal Spectro-Microscopy as Benchmark for Optoplasmonic Bio-Detection Assays

“… 15 − 21 At the same time novel microscopic methods make use of plasmonic particles as photostable labels 22 , 23 and combine them with optical, electromagnetic, or electric devices for trapping and manipulation of sensor particles or even of the molecules themselves. 24 − 29 In the following we will exclusively focus on optoplasmonic assays that facilitate analyte recognition via observation of a plasmonic nanostructure’s response to (single) analytes perturbing its dielectric environment. The volume in which such perturbations are recognizable is defined by the extent of the structures’ enhanced near-field and is limited to distances on the order of 10 nm away from the structures’ surface.…”