Beijing Institute of Quantum has made new progress in nano-diamond bio-quantum sensing research

Recently, Liu Yan, assistant researcher of the atomic ensemble precision measurement team of Beijing Institute of Quantum Information Science, and collaborators from scientific research institutions in Germany, France, Russia and other countries have completed the fluorescent labeling and sensing of living cells based on nano-diamond silicon-vacancy color centers. The research work, titled "Silicon-Vacancy Nanodiamonds as High Performance Near-Infrared Emitters for Live-Cell Dual-Color Imaging and Thermometry", was published in Nano Letters on March 15, 2022.

Figure 1 Schematic diagram of nanodiamonds containing SiV color centers for live cell imaging and sensing

In addition to its well-known uses such as decorative gemstones and industrial drilling and cutting, diamond is also favored in quantum technology for its high optical transparency and its photoactive color center. Diamond Silicon Vacancy (SiV) color center is one of the color centers with excellent optical properties. Due to the D3d symmetry structure of SiV color center, its energy level transition is relatively less affected by phonons, and more than 70% of its fluorescence emission is concentrated in its zero-phonon line at 738 nm, and the line width at room temperature is less than 5 nm. Other common color centers are usually strongly influenced by phonons, more than 90% of the fluorescence emission is influenced by phonons, and the spectral width at room temperature exceeds 100 nm.

Figure 2  Preparation process of polymer SiV nanodiamonds for intracellular fluorescent labeling

Figure 3 (a) Fluorescence-labeled imaging of SiV nanodiamonds in living cells; (b) spectral shifts of SiV color center zero-phonon lines at different temperatures; (c) the upper figure, the trajectory of a nanodiamond in living cells Tracking, bottom panel, and simultaneous fluorescence intensity tracking show better fluorescence stability.

In the field of biological detection research, the nano-diamond SiV color center has attracted the attention of life science research due to its advantages of low biological toxicity and stable fluorescence emission. etc. In addition, the SiV color center line width is narrow, and its fluorescence signal is easy to filter and extract from the optical noise generated by various types of macromolecules in the living cell environment (as shown in Figure 1). Its fluorescence wavelength of 738 nm belongs to the near-infrared band. It is conducive to the penetration of fluorescent signals into cells and tissues, and is suitable for optical imaging and detection of deeper living cells and tissues.

This paper reports the preparation of micro- and nano-diamond particles with high concentration of SiV color centers by high temperature and high pressure method, and through grinding, pickling, organic molecular coating and other steps to prepare SiV nano-diamonds suitable for intracellular fluorescent labeling ( as shown in picture 2). Subsequently, SiV nanodiamonds were placed in Hela cell culture wells, and the absorption of SiV nanodiamonds by Hela cells was successfully observed by confocal fluorescence microscopy; the intracellular trajectory tracking of single nanodiamonds was also achieved, and zero-phonon lines were also performed. Spectral tracing measurements (shown in Figure 3). The study shows that by measuring the spectral frequency shift of the zero-phonon line of the nanodiamond SiV color center, it can be used for temperature sensing. In this work, it is also found that through temperature control, in a water bath or intracellular environment, not only the spectral frequency shift of the zero-phonon line occurs, but also a certain nonlinear broadening of its line width.

In this research work, Dr. Liu Yan, the precision measurement team of the atomic ensemble of our institute, undertook the construction of the confocal fluorescence microscope, and carried out the fluorescence imaging, motion trajectory tracking, and zero-phonon spectral line measurement and tracking after fluorescent labeling of living cells with nanodiamonds. Automated measurement design, programming, and experimental execution in a variety of processes. In addition, Dr. Liu Yan commented that nanodiamonds can also be used to study the mechanism of molecular drugs in cells, and can also replace luminescent materials such as colloidal gold for in vitro disease diagnosis applications, achieve ultra-sensitive nucleic acid measurement, and is expected to achieve rapid detection of epidemic viruses and early screening of major diseases.

Link:

https://pubs.acs.org/doi/full/10.1021/acs.nanolett.2c00040