A biocompatible technique for magnetic field sensing at (sub)cellular scale using Nitrogen-Vacancy centers

Abstract

We present an innovative experimental set-up that uses Nitrogen-Vacancy centres in diamonds to measure magnetic fields with the sensitivity of $\eta =68\pm 3~\mathrm{nT}/\sqrt{\mathrm{Hz}}$ η = 68 ± 3 nT / Hz at demonstrated (sub)cellular scale. The presented method of magnetic sensing, utilizing a lock-in based ODMR technique for the optical detection of microwave-driven spin resonances induced in NV centers, is characterized by the excellent magnetic sensitivity at such small scale and the full biocompatibility. The cellular scale is obtained using a NV-rich sensing layer of 15 nm thickness along z axis and a focused laser spot of $(10 \times 10)~\mu\mathrm{m}^{2}$ ( 10 × 10 ) μ m 2 in x-y plane. The biocompatibility derives from an accurate choice of the applied optical power. For this regard, we also report how the magnetic sensitivity changes for different applied laser power and discuss the limits of the sensitivity sustainable with biosystem at such small volume scale. As such, this method offers a whole range of research possibilities for biosciences.

Laser stimulation of muscle activity with simultaneous detection using a diamond colour centre biosensor

“…Using optomechanical mirror mounts, the laser spot could be moved at sub-millimeter precision to any position on the muscle, with a travel of 2 × 2 cm 2 across the chamber. This represents an improvement over a confocal/inverted widefield microscopy configuration where stimulation is limited only to the centre of the objective field of view 7,41 . We positioned the stimulation laser spot approximately 0.5 mm (Figure 1,b) along the muscle away from the diamond, to ensure we recorded signal propagation in only one direction (towards one end of the muscle).…”

The Optimization of Microwave Field Characteristics for ODMR Measurement of Nitrogen-Vacancy Centers in Diamond

“…For example, living cells can cause internal temperature changes when responding to environmental changes [1,2], but the temperature changes generated by this process are usually small and brief [3], posing a challenge to temperature measurement technology. In recent years, existing intracellular temperature measurement technologies, such as fluorescent proteins [4], organic dyes [5], and rare earth particles [6], have generally suffered from low measurement accuracy [7], insufficient temporal and spatial resolution, and unstable fluorescence [8]. The method of NV centers in diamond stands out due to its stable physical and chemical properties, good biocompatibility [9,10], and ultra-high sensitivity in electronic spin measurement [11].…”

Limitations of Bulk Diamond Sensors for Single-Cell Thermometry

“…Considering ODMR measurements on NV ensembles, nanodiamonds present a lower sensitivity compared to bulk diamonds, because of their shorter coherence time (as already mentioned), the lower density of their color centers, and the difficulty in taking advantage of the field alignment [ 39 ] and laser polarization [ 40 ]. On the contrary, a bulk diamond allows ODMR measurements with micrometric spatial resolution on the x-y plane using a focused laser beam and nanometric resolution along the z-direction using a diamond with a thin layer of NV centers [ 41 ]. Furthermore, a bulk diamond can be nanostructured to form an array of diamond nanopillars, leading to the possibility of guiding the growth of the cell network [ 42 ] and to further improvements in sensitivity due to the pillars acting as optical waveguides [ 43 ].…”