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.