# 3D positioning and optically detected magnetic resonance of intracellular fluorescent nanodiamonds using a multi-plane microscope

## TL;DR

A new microscope platform enables 3D tracking of fluorescent nanodiamonds inside cells, advancing quantum sensing in biological systems.

## Contribution

A multi-plane microscope platform enables 3D correlated quantum sensing with nanoscale precision in biological systems.

## Key findings

- The platform achieves 3D positioning of fluorescent nanodiamonds with 9 nm lateral and 12 nm axial precision.
- Correlated 3D positioning and optically detected magnetic resonance were demonstrated in mouse cardiomyocytes.
- The system supports single-particle tracking and correlated quantum sensing in intracellular environments.

## Abstract

Wide-field quantum sensing with fluorescent nanodiamonds (FNDs) in biological systems offers significant potential for understanding intracellular dynamics at the nanoscale. However, current wide-field quantum sensing methods are limited to 2D correlated measurements. 3D correlated quantum sensing remains challenging due to the inherent properties of wide-field microscopy. Here, we have developed a multi-plane wide-field microscope platform that achieves an imaging volume of 50 × 50 × 5 μm³. This is accomplished by simultaneously imaging eight focal planes at varying sample depths using a beam-splitting prism. By employing a Fourier-transform-based fluorescent particle positioning method, the platform attains lateral positioning precision of 9 nm and axial precision of 12 nm. Using this platform, we performed correlated 3D positioning of FNDs in mouse cardiomyocytes and conducted optically detected magnetic resonance on nitrogen-vacancy color centers within intracellular FNDs. Our results demonstrate the potential of this platform for single-particle tracking and highlight its capability to achieve correlated 3D quantum sensing.