Engelmann Ulrich M, Simsek Beril, Shalaby Ahmed, Krause Hans-Joachim
Medical Engineering and Applied Mathematics, FH Aachen University of Applied Sciences, 52428 Jülich, Germany.
Institute of Biological Information Processing, Bioelectronics (IBI-3), Forschungszentrum Jülich, 52428 Jülich, Germany.
Sensors (Basel). 2024 Mar 18;24(6):1945. doi: 10.3390/s24061945.
Frequency mixing magnetic detection (FMMD) is a sensitive and selective technique to detect magnetic nanoparticles (MNPs) serving as probes for binding biological targets. Its principle relies on the nonlinear magnetic relaxation dynamics of a particle ensemble interacting with a dual frequency external magnetic field. In order to increase its sensitivity, lower its limit of detection and overall improve its applicability in biosensing, matching combinations of external field parameters and internal particle properties are being sought to advance FMMD. In this study, we systematically probe the aforementioned interaction with coupled Néel-Brownian dynamic relaxation simulations to examine how key MNP properties as well as applied field parameters affect the frequency mixing signal generation. It is found that the core size of MNPs dominates their nonlinear magnetic response, with the strongest contributions from the largest particles. The drive field amplitude dominates the shape of the field-dependent response, whereas effective anisotropy and hydrodynamic size of the particles only weakly influence the signal generation in FMMD. For tailoring the MNP properties and parameters of the setup towards optimal FMMD signal generation, our findings suggest choosing large particles of core sizes dC>25 nm with narrow size distributions (σ<0.1) to minimize the required drive field amplitude. This allows potential improvements of FMMD as a stand-alone application, as well as advances in magnetic particle imaging, hyperthermia and magnetic immunoassays.
频率混合磁检测（FMMD）是一种灵敏且具有选择性的技术，用于检测作为结合生物靶点探针的磁性纳米颗粒（MNP）。其原理依赖于与双频外部磁场相互作用的粒子集合体的非线性磁弛豫动力学。为了提高其灵敏度、降低检测限并总体上改善其在生物传感中的适用性，正在寻找外部场参数和内部粒子特性的匹配组合以推进FMMD。在本研究中，我们通过耦合尼尔 - 布朗动力学弛豫模拟系统地探究上述相互作用，以研究关键的MNP特性以及应用的场参数如何影响频率混合信号的产生。研究发现，MNP的核心尺寸主导其非线性磁响应，最大的粒子贡献最强。驱动场幅度主导场依赖响应的形状，而粒子的有效各向异性和流体动力学尺寸仅对FMMD中的信号产生微弱影响。为了针对最佳FMMD信号产生调整MNP特性和设置参数，我们的研究结果建议选择核心尺寸dC>25 nm且尺寸分布窄（σ<0.1）的大颗粒，以最小化所需的驱动场幅度。这有望改善FMMD作为一种独立应用，以及在磁性粒子成像、热疗和磁性免疫分析方面取得进展。
