Designing of the Diamond-Based NV Quantum Nano-Probe for Biological Applications
This paper presents the application of a quantum sensor nano-probe using the point NV defect in the crystal lattice in the nanodiamond. We aim to showcase the design of a quantum sensor using printed circuit boards (PCBs) and investigate the quantum characteristic response of the NV defect based on simulated temperature and microwave (MW) field. Quantum sensing using the NV centres promises high-resolution nanoscale magnetic imaging and spectroscopic analysis of small ensembles of molecular targets. In this study, we are modelling a nano-probe thermometer based on the NV centre, which offers a theoretical sensitivity of 10mK/ √Hz. This high sensitivity allows us to observe typical temperature gradients in biological systems, particularly the opening of the temperature-sensitive Transient receptor potential (TRP) channels. Many different temperature-sensitive TRP channels are widespread throughout the body, and they are studied as pharmacological targets in various diseases, such as axonal neuropathy, chronic pain, lower urinary tract disorders, and type 2 diabetes. For this purpose, we are using the COMSOL Multiphysics® environment with the RF Module which incorporates the Electromagnetic Waves physics interface, MW heating, and the LiveLink™ for MATLAB® interfacing product. The initial phase of this study involves the design of a printed circuit board (PCB) and microwave (MW) structure that effectively achieves the desired microwave homogeneity. This design aims to create a microwave resonance profile centred around 2.89 GHz, which corresponds to the spin resonance frequency of the NV centre. In the next phase, we create an MW excitation protocol that is suitable for quantum sensing and allows the keeping desired temperature of the liquid media (MW heating physics). For numerical simulation purposes, the frequency-dependent dielectric properties were measured by using a coaxial probe and the measured curve courses were fitted by using the two-pole Cole-Cole model. The second part of this research focuses on probing the quantum response of the NV defect through simulated MW and temperature fields. To assess the quantum response of the simulated field distribution, we employed LiveLink™ for MATLAB®. Utilizing the numerical outcomes obtained from our simulations, we calculated the eigenvalues of the Hamiltonian associated with the ground state spin system of the NV defect. This enabled us to determine the electronic spin resonance shift, providing us with a comprehensive understanding of the quantum response of the nano-probe based on the designed PCB and MW stimulation sequence. In conclusion, we developed the system (PCB and MW protocols) for the thermal and microwave excitation of the NV defect in the nanodiamond particle in the liquid environment for the probing of the selective TRP channel opening. We simulate the MW field and temperature distribution and probe the NV quantum response. This knowledge opens the possibility of manufacturing the nano-probes that can be a powerful tool for developing f.e. multi-temperature probe arrays for in vitro testing, nanoscale probes for in vivo testing and validating TRP channel-related mechanisms of inflammation. As a consequence, the technology and biological knowledge resulting from this work will nurture technological, biomedical, and clinical research.