How Label-Free Nanoparticle Trapping Illuminates Biotech's Future

A team at Ohio State University led by William B. Carpenter has developed the Interferometric Scattering Anti-Brownian ELectrokinetic (ISABEL) trap, a novel instrument for analyzing individual biomolecular nanoparticles. ISABEL is an evolution of Anti-Brownian ELectrokinetic (ABEL) traps that uses interferometric scattering as a highly sensitive, fluorophore-label-free detection scheme.

This addresses the limitations of traditional, fluorescent-label based ABEL traps, where photobleaching causes the particle to "go dark." Interferometric scattering boosts the weak light scattered by a small nanoparticle by allowing it to interfere with light reflected from the substrate, making the particle visible and locatable.

The key goal is to achieve tailored control and observation of single nanoparticles, overcoming the chaotic movement (Brownian motion) in a liquid environment. Unlike optical traps, which use a laser beam's momentum transfer and are less effective for objects smaller than 100 nm, electrokinetic traps like ISABEL use an active feedback mechanism. Based on the particle's detected position, high-speed electronics apply precise electric voltages via electrodes in a microfluidic cell to push the particle back to the center of the field of view.

This control allows researchers to answer fundamental questions about complex systems, such as how molecular contacts affect cargo loading or how a particle's physical assembly impacts access to its internal components, with potential applications in drug delivery and synthetic nanocontainers.