Quantum Optics INRIM
Color centers in diamond
A biocompatible technique for magnetic field sensing at (sub)cellular scale using Nitrogen-Vacancy centers
We present an innovative experimental set-up that uses Nitrogen-Vacancy centres in diamonds to measure magnetic fields with the sensitivity of 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 (10×10) μm2 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.
Nanodiamond–Quantum Sensors Reveal Temperature Variation Associated to Hippocampal Neurons Firing
Temperature is one of the most relevant parameters for the regulation ofintracellular processes. Measuring localized subcellular temperature gradientsis fundamental for a deeper understanding of cell function, such as thegenesis of action potentials, and cell metabolism. Notwithstanding severalproposed techniques, at the moment detection of temperature fluctuations atthe subcellular level still represents an ongoing challenge. Here, for the firsttime, temperature variations (1°C) associated with potentiation and inhibitionof neuronal firing is detected, by exploiting a nanoscale thermometer basedon optically detected magnetic resonance in nanodiamonds. The resultsdemonstrate that nitrogen-vacancy centers in nanodiamonds provide a toolfor assessing various levels of neuronal spiking activity, since they are suitablefor monitoring different temperature variations, respectively, associated withthe spontaneous firing of hippocampal neurons, the disinhibition ofGABAergic transmission and the silencing of the network. Conjugated withthe high sensitivity of this technique (in perspective sensitive to<0.1°Cvariations), nanodiamonds pave the way to a systematic study of thegeneration of localized temperature gradients under physiological andpathological conditions. Furthermore, they prompt further studies explainingin detail the physiological mechanism originating this effect.