Simplified Interferometric Scattering Microscopy Using Low-Coherence Light for Enhanced Nanoparticle and Cellular Imaging

Interferometric scattering (iSCAT) microscopy is a sensitive optical technique for visualizing nanoscale objects by detecting their elastic scattering through interferometry. iSCAT typically employs laser illumination, which provides high spatial and temporal coherence, enhancing interference contrast and detection sensitivity. However, the use of highly coherent light sources introduces challenges of speckle noise arising from parasitic reflections and scattering within the optical system. In this study, we present an implementation of iSCAT microscopy that employs a mercury lamp as the illumination source. By optimizing the spatial and temporal coherence of this readily available light source, we effectively suppress nonspecific background signals associated with the optical setup while maintaining remarkable sensitivity for sample detection. Our approach achieves nanoparticle detection with scattering cross sections as low as a few 10-16 cm2, allowing the visualization of nanoparticles as small as 10 nm. Furthermore, the low-coherence iSCAT system supports label-free live-cell imaging across a large field of view, capturing dynamic interactions among various cellular organelles. This accessible and robust iSCAT configuration offers a versatile platform for high-sensitivity, high-resolution, label-free imaging and detection of nanoscopic biological entities.