# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1702.03582