@misc{oai:repo.qst.go.jp:00079549,
 author = {Kuwahata, Akihiro and Kitaizumi, Takahiro and Saichi, Kota and Sato, Takumi and Igarashi, Ryuji and Ohshima, Takeshi and Masuyama, Yuta and Iwasaki, Takayuki and Hatano, Mutsuko and Jelezko, Fedor and Kusakabe, Moriaki and Yatsui, Takashi and Sekino, Masaki and Igarashi, Ryuji and Ohshima, Takeshi and Masuyama, Yuta and Hatano, Mutsuko},
 month = {Nov},
 note = {Magnetic nanoparticles (MNPs) have been widely employed in biomedical applications, such as diagnosis and therapy of various diseases [1]. Advanced clinical studies have demonstrated the feasibility of the detection of MNPs using the magnetometer, as a promising technique alternative to harmful radioactive particles, to diagnose cancer metastasis in breast cancer patients [2,3]. To further expand the applicable clinical regime, there is a need to develop highly sensitive magnetic detection.
The negatively charged nitrogen-vacancy (NV-) color center in a diamond provide immensely a remarkable quantum magnetic sensing, which enables us to detect sub-pico-Tesla at room temperature [4,5]. In this study, we have developed the novel magnetometer with NV- center in a bulk diamond for detecting MNPs (Fig. 1). The optical fiber-based system is employed to fabricate the compact probe system compared with a confocal-based optical system, and the alternating current (AC) magnetic fields (~1 mT) of the excitation coil system to magnetize MNPs yields the highly sensitive detection of MNPs. Figure 2(a) shows the magnetic sensitivity of the developed probe in the Lock-in detection system. The minimum detectable AC magnetic field is approximately 60 nT. The sensitivity of the MNPs detection with the developed probe strongly depends on the remnant excitation fields. We thus produced the magnetic null point at the NV- center location by using an additional cancellation coil for eliminating the remnant fields, and achieved the detectable distances with respect to MNPs of 40 and 5 uL are 9 and 5 mm, respectively, as shown in Fig. 2(b). These results indicate the developed probe can detect the tiny amount of MNPs. We will pursue the further highly sensitive detection by the enhancement of a light collecting efficiency and optimization of the excitation coil system., The 64th Annual Conference on Magnetism and Magnetic Materials (MMM)},
 title = {Development of magnetometer with nitrogen-vacancy center in a bulk diamond for detecting magnetic nanoparticles in biomedical applications},
 year = {2019}
}