IOS Member Research Series
Combined scattering and fluorescence characterization of biomolecular nanoparticles in an anti-Brownian trap
William (Memo) Carpenter, Assistant Professor
Department of Chemistry and Biochemistry, Ohio State University
Time: Friday, August 29th 2025 at 12:45PM
Location: Physics Research Building 1080 & Zoom
Abstract: Biomolecular nanoparticles are increasingly prevalent as therapeutic delivery vehicles and nanoscale reactors, but their characterization is typically limited to ensemble-averaged or steady-state measurements. To understand its assembly dynamics and interaction with the environment, we want to track a single particle for at least several minutes, which is infeasible when the particle diffuses in an aqueous environment according to Brownian motion. To directly observe these single nanoparticle dynamics, we developed an anti-Brownian Electrokinetic (ABEL) trap, which counteracts the particle’s diffusion while maintaining it in solution for up to multiple minutes. This is achieved by monitoring a particle’s position and applying real-time voltage feedback. We extended this trap to detect the particle label-free, without relying on fluorescent tagging strategies. We show that the trapping statistics allow inference of the particle’s diffusion coefficient and electrokinetic mobility, while fluctuations in the interferometric scattering signal provide an orthogonal measure of a particle’s diffusion in the axial direction. Combining the interferometric scattering contrast with fluorescence spectroscopic readouts, we can also read out internal chemical properties. These capabilities provide a unique method to study dynamical properties of biomolecular nanoparticles for extended periods of time, yielding an unprecedented synthesis of physical and chemical insights into these systems.
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