Detection of Few Hydrogen Peroxide Molecules using Self-Reporting Fluorescent Nanodiamond Quantum Sensors

Abstract

Hydrogen peroxide (H2O2) plays an important role in various signal transduction pathways and regulates important cellular processes. However, monitoring and quantitatively assessing the distribution of H2O2 molecules inside living cells requires a nanoscale sensor with molecular-level sensitivity. Herein, we show the first demonstration of sub-10 nm-sized fluorescent nanodiamonds as a catalyst for the decomposition of H2O2 and the production of radical intermediates at the nanoscale. Furthermore, the NV quantum sensors inside the nanodiamonds are employed to quantify the aforementioned radicals. We believe that our method of combining the peroxidase-mimicking activities of the nanodiamonds with their intrinsic quantum sensor showcases their application as a self-reporting H2O2 sensor with molecular-level sensitivity and nanoscale spatial resolution. Given the robustness and the specificity of the sensor, our results promise a new platform for elucidating the role of H2O2 at the cellular level.

Unraveling Eumelanin Radical Formation by Nanodiamond Optical Relaxometry in a Living Cell

“…In general, the shapes of the curves shown in Figure 4d remained similar for all simulated plots despite the differences in the ND shapes. Although the simulated number of radicals may vary because the simulation uses approximations to account for the quantum many-body effects that would otherwise be intractable, previous results 17,24,43 suggest that this simulation method can still provide quantitative (see Figure 1b in details) agreement between the simulated and experimental results. Furthermore, the variation of the number of radicals depends on the different ratio 2r ND /l ND .…”

“…From the T 1 relaxation times, we were able to estimate the number of radicals in the shell of the RGS-NDs. To achieve this, we employed a theoretical model 17,24,43 to simulate the T 1 relaxation times for different radical concentrations in the eumelanin shell. The radicals in the polymer layer produced a fluctuating magnetic field at the position of the NV − center, which was characterized by an amplitude variance of B ⊥ 2 and a temporal correlation time of τ c .…”