Label-free single molecule imaging with numerical aperture-shaped interferometric scattering microscopy

TL;DR

This paper introduces a novel optical microscopy technique that uses a spatial mask to enhance contrast, enabling label-free imaging of single molecules by differentiating background from scattered light with high sensitivity.

Contribution

The authors demonstrate a new method using a partially transmissive mask near the back focal plane of a high NA microscope to significantly improve single molecule imaging contrast.

Findings

Contrast enhancement scales with the inverse square root of mask transmissivity

Method enables routine label-free single molecule imaging

Applicable to various nanoscopic objects near interfaces

Abstract

Our ability to optically interrogate nanoscopic objects is controlled by the difference between their extinction cross sections and the diffraction limited area to which light can be confined in the far field. We show that a partially transmissive spatial mask placed near the back focal plane of a high numerical aperture microscope objective enhances the extinction contrast of a scatterer near an interface by approximately $T^{-1/2}$, where T is the transmissivity of the mask. Numerical aperture based differentiation of background from scattered light represents a general approach to increasing extinction contrast and enables routine label free imaging down to the single molecule level.