Magnetically Modulated Fluorescence of Nitrogen-Vacancy Centers in Nanodiamonds for Ultrasensitive Biomedical Analysis
Yuen Yung Hui,1 Oliver J. Chen,1 Hsin-Hung Lin,1 Yu-Kai Su,1 Katherine Y. Chen,1 Chih-Yen Wang,1 Wesley W.-W. Hsiao,2 and Huan-Cheng Chang1,2,3,*
1Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
2Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
3Department of Chemistry, National Normal Taiwan University, Taipei 106, Taiwan
Anal. Chem. 93, 7140–7147 (2021).
The negatively charged nitrogen-vacancy (NV–) center in fluorescent nanodiamond (FND) is a point defect with unique magneto-optical properties. It emits far-red fluorescence at ~700 nm and its intensity can be magnetically modulated with a depth of more than 10% at a field strength of 30 mT. We have closely examined this property and illustrated its practical use in biomedicine by applying a periodic, time-varying magnetic field to FNDs deposited on surface or dispersed in solution with a lock-in detection method. We achieved selective and sensitive detection of 100-nm FNDs on nitrocellulose membrane at a particle density of 0.04 ng/mm2 (or ~2 × 104 particles/mm2) and in aqueous solution with a particle concentration of 1 ng/mL (or ~1 fM) in 10 s as the detection limits. The utility and versatility of the technique were demonstrated with an application to background-free detection of FNDs as reporters for FND-based lateral flow immunoassays as well as selective quantification of FNDs in tissue digests for in vivo studies.