Structured illumination multimodal 3D-resolved quantitative phase and fluorescence sub-diffraction microscopy

TL;DR

This paper introduces a novel structured illumination technique that enables simultaneous sub-diffraction resolution imaging of both quantitative phase and fluorescence in 3D, bridging a significant gap in multimodal biological microscopy.

Contribution

The authors demonstrate the first multimodal 3D sub-diffraction imaging system combining quantitative phase and fluorescence using structured illumination, with applications to biological cells.

Findings

Enhanced lateral and axial resolution over diffraction limit.

Striking parallels between structured illumination and optical diffraction tomography.

Successful 3D multimodal imaging of biological cells.

Abstract

Sub-diffraction resolution imaging has played a pivotal role in biological research by visualizing key, but previously unresolvable, sub-cellular structures. Unfortunately, applications of far-field sub-diffraction resolution are currently divided between fluorescent and coherent-diffraction regimes, and a multimodal sub-diffraction technique that bridges this gap has not yet been demonstrated. Here we report that structured illumination (SI) allows multimodal sub-diffraction imaging of both coherent quantitative-phase (QP) and fluorescence. Due to the conventional fluorescent applications of SI, we first demonstrated the principle of SI-enabled three-dimensional (3D) QP sub-diffraction imaging with calibration microspheres. Image analysis confirmed enhanced lateral and axial resolutions over diffraction-limited QP imaging, and established striking parallels between coherent SI and conventional optical diffraction tomography. We next introduce an optical system utilizing SI to achieve 3D sub-diffraction, multimodal QP/fluorescent visualization of A549 biological cells fluorescently tagged for F-actin. Our results suggest that SI has unique utility in studying biological phenomena with significant molecular, biophysical, and biochemical components.