Optically Stuck Nanodiamonds to Measure Properties Inside Living Cells

The optically trapped nanodiamond fragments are being used as intracellular sensors by researchers to create new methods for examining complex processes inside living cells. The research team captured particles inside the cells at low power while the cells were alive using specially designed optical tweezers.

Schematic of the optical setup used for optical trapping (a) with nanodiamond fluorescent (FND) images inside leukemic cells (b). Image Credit: Fatemeh Kalantarifard, Danish Technical University

This research marks a significant step forward in quantum sensing, which uses quantum mechanics to examine changes at the atomic level.

The scientists demonstrated how nanodiamond particles could be used to detect magnetic noise inside cells after using optical tweezers to capture the particles inside a single leukemia cell.

The study will be presented by Fatemeh Kalantarifard of the Technical University of Denmark at the Optica Biophotonics Congress, which will take place online from 23-27 April 2023, and in Vancouver, British Columbia. The Kalantarifar presentation is scheduled for Monday, April 24thth, 2023, from 15.00 to 15.15 WIB. (UTC–07:00).

Optically Trapped Nanodiamonds

Interest in fluorescent nanodiamonds (FNDs) has been growing as potential emitters and sensors for a variety of uses. The FND’s ability to sense physical factors using quantum sensing, such as temperature and magnetic fields, is one of its most remarkable characteristics.

Nitrogen vacancy centers (NV), paramagnetic defects in diamond that allow magnetic field-dependent readings of temperature and electron spin at the nanoscale, are the basis of diamond quantum sensing.

More recently, scientists have developed a fluorescent nanodiamond with an NV center for use as an intracellular sensor. In the study presented at the conference, the scientists combined FND trapping with a spin-based photoluminescence detection method typical for diamond-based sensing in a single cell.

Cells from a human leukaemic cell line were used for endocytosis of FND, which were then captured by live cells when exposed to a low-power near IR laser (wavelength 1064 nm).

Nanoscale Sensing

The researchers performed T1 relaxometry measurements after the nanodiamonds were placed either inside the cells or on the cell surface to evaluate their sensing abilities. By periodically turning on and off the Green laser pulse (532 nm wavelength) this technique polarizes the electron spins of the NV center before allowing them to return to equilibrium.

The spin relaxation rate is calculated by optically observing the fluorescence intensity level because the polarized configuration shows stronger fluorescence than the equilibrium state.

The researchers were able to track the magnetic noise inside the cell by analyzing the relaxation rate of the nano-diamond spins placed at various locations as magnetic noise in the environment affects that rate.

The demonstration shows that optically trapped fluorescent nanodiamonds can serve as a precise and adaptable method for measuring things like temperature and magnetic fields inside living cells.

The combination of diamond nanoparticle optical trapping and nanodiamond-based quantum sensing could provide a powerful tool for studying the mechanical properties of cells. Optical trapping can help maintain nanodiamond-based sensors with high precision, enabling more accurate measurements at the nanoscale level.

Fatemeh Kalantarifard, Postdoctoral Researcher, Technical University of Denmark

Kalantarifar further added, “In particular, T1 relaxometric measurements of optically trapped nanodiamonds can be used for the detection of free radicals in cells. Free radicals are highly reactive molecules that can cause damage to cells and tissues. They are produced naturally in the body due to metabolism and can also be produced by exposure to environmental factors such as radiation or poisons.

The use of optically trapped nanodiamonds for free radical detection offers several advantages, including high sensitivity, non-invasiveness, and the ability to monitor real-time changes in T1 relaxation time. This technique can be used to study the effects of oxidative stress on cells and may have potential applications in the diagnosis and treatment of diseases such as cancer and neurodegenerative disorders.

Fatemeh Kalantarifard, Postdoctoral Researcher, Technical University of Denmark


Researchers use tiny diamonds to create intracellular sensors | News Release | Optics (2023). Available in:

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