The outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) threatens global medical systems and economies and rules our daily living life. Controlling the outbreak of SARS-CoV-2 has become one of the most important and urgent strategies throughout the whole world. As of October 2020, there have not yet been any medicines or therapies to be effective against SARS-CoV-2. Thus, rapid and sensitive diagnostics is the most important measures to control the outbreak of SARS-CoV-2. Homogeneous biosensing based on magnetic nanoparticles (MNPs) is one of the most promising approaches for rapid and highly sensitive detection of biomolecules. This paper proposes an approach for rapid and sensitive detection of SARS-CoV-2 with functionalized MNPs via the measurement of their magnetic response in an ac magnetic field. For proof of concept, mimic SARS-CoV-2 consisting of spike proteins and polystyrene beads are used for experiments. Experimental results demonstrate that the proposed approach allows the rapid detection of mimic SARS-CoV-2 with a limit of detection of 0.084 nM (5.9 fmole). The proposed approach has great potential for designing a low-cost and point-of-care device for rapid and sensitive diagnostics of SARS-CoV-2.

A detailed signal generation of the magnetization response of magnetic nanoparticles (MNPs) as a result of externally applied magnetic fields with flux densities of several millitesla is of high interest for biomedical applications such as magnetic resonance imaging or magnetic particle imaging (MPI). Although, MNPs are already frequently used as contrast agents or tracer materials, experimental data are rarely compared to model predictions because of distinct deviations. In this article, we use a customized Brownian-dominated CoFe 2 O 4 particle system to compare experimental magnetic particle spectroscopy data with Fokker−Planck simulations considering the Brownian relaxation. The influences of viscosity, size distribution, excitation frequency, and field amplitude are studied. We show that the effective magnetic moment and cluster sizes can be determined using a sample viscosity series. As introduced, such particle systems can serve as model systems to evaluate mathematical expressions and to study dependences on physical influencing factors. Investigations of defined MNP systems and detailed characterizations enable a wide field of improved diagnosis and therapy applications, for example, mobility MPI and magnetic hyperthermia.

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