Reviewed by Alex SmithMar 31 2023
Nanodiamond fragments that have been optically trapped are being used as intracellular sensors by researchers to create a new method for examining the complex processes within living cells. The study team captured the particles inside the cell at low power while the cell was still alive using custom-designed optical tweezers.
Schematic of the optical setup used for optical trapping (a) with an image of the fluorescent nanodiamond (FND) inside a leukemia cell (b). Image Credit: Fatemeh Kalantarifard, Technical University of Denmark
The research marks a significant step forward in quantum sensing, which uses quantum mechanics to examine atomic-level changes.
The scientists showed how the nanodiamond particles can be used to detect magnetic noise inside the cell after using optical tweezers to capture the particles inside single leukemia cells.
The study will be presented by Fatemeh Kalantarifard from the Technical University of Denmark at the Optica Biophotonics Congress, which will take place online from April 23–27, 2023, and in Vancouver, British Columbia. The presentation by Kalantarifard is slated to be on Monday, April 24th, 2023, from 15:00 to 15:15 PDT. (UTC–07:00).
Optically Trapped Nanodiamonds
Interest in fluorescent nanodiamonds (FNDs) has grown as potential emitters and sensors for a variety of uses. The ability of FNDs to sense physical factors using quantum sensings, such as temperature and magnetic field, is one of their most remarkable characteristics.
The nitrogen-vacancy (NV) center, a paramagnetic flaw in a diamond that enables reading out temperature and magnetic field-dependent electron spin at the nanoscale, is the foundation of diamond quantum sensing.
Recently, scientists have developed fluorescent nanodiamonds with NV centers for use as intracellular sensors. In the study that was presented at the conference, scientists merged the trapping of FNDs with spin-based photoluminescence detection methods typical of diamond-based sensing in a single cell.
Cells from a human leukemia cell line were used to endocytose FNDs, which were then captured by the living cell while it was exposed to a low-power near-IR laser (1064 nm wavelength).
Nanoscale Sensing
The researchers performed T1 relaxometry measurements after the nanodiamonds were positioned inside the cells or on the cell surface to evaluate their sensing abilities. By periodically turning on and off a Green (532 nm wavelength) laser pulse, this technique polarizes the NV centers’ electron spins before allowing them to return to equilibrium.
The spin relaxation rate is calculated by optically observing the fluorescence intensity level since the polarized configuration exhibits stronger fluorescence than the equilibrium state.
Researchers can trace the magnetic noise inside the cell by analyzing the spin relaxation rates of nanodiamonds placed in various locations because the magnetic noise in the environment influences these rates.
The demonstration indicates that optically trapped fluorescent nanodiamonds could serve as a precise and customizable method to measure things like temperature and magnetic field within living cells.
The combination of optical trapping of diamond nanoparticles and nanodiamond-based quantum sensing can provide a powerful tool for studying cell mechanical properties. Optical trapping can help hold the nanodiamond-based sensors with high precision, allowing for more accurate measurements at the nanoscale level.
Fatemeh Kalantarifard, Postdoctoral Researcher, Technical University of Denmark
Kalantarifard further added, “In particular, T1 relaxometry measurements of optically trapped nanodiamonds can be used for free radical detection in cells. Free radicals are highly reactive molecules that can cause damage to cells and tissues. They are produced naturally in the body because of metabolism and can also be generated by exposure to environmental factors such as radiation or toxins.”
“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