This protein attaches to the angiotensin-converting enzyme 2 (ACE2) receptor, which is typically present in epithelial linings, such as the respiratory and gastrointestinal tracts, thereby enabling the virus to enter and infect the host cells [29; 30]. Different point-of-care diagnostic tools and detection techniques have been utilized, including electrochemical, optical, electrochemiluminescence, photoluminescence, colorimetric, immuno-based sensing, and magnetic nano-sensing [22; 23; 31]. In particular, MNPs have shown great potential as detection tools for various virus types. The main advantages of using MNPs for such purposes are as follows: small sizes, facile functionalization, excellent biocompatibility and stabilities, low toxicities, and superior magnetic responsiveness [32]. Most magnetic biosensors fall into major categories, namely, magnetoresistance (MR), magnetic particle spectroscopy (MPS), and nuclear magnetic resonance (NMR) platforms [33]. These materials can be functionalized using specific biotags to capture viruses and target analytes selectively and specifically from complex biological samples, and their magnetic properties can be utilized for efficient separation and purification. In this regard, both surface-(functionalized on surface) and volume-based (dispersed in liquid) magnetic sensing have been exploited to aid in the detection of viruses and pathogens [33]. For instance, the detection of SARS-CoV-2 mimicking using anti-SARS-CoV-2-spike-monoclonal-antibody-functionalized MNPs (80 nm Dextran-coated Bionized NanoFerrite (BNF) particles) was achieved via the measurement of their magnetic responses under an AC magnetic field [34]. The proposed approach allowed for rapid detection (\(\sim\)1 h) with a limit of detection of 0.084 nM. Later on, a five-minute MPS-based bioassay using anti-SARS-CoV-2-spike-polyclonal-antibody-functionalized MNPs (30 nm IPG30 NPs) for the ultrafast detection of the SARS-CoV-2 spike protein at a higher temperature (37 \({}^{\circ}\)C) with a detection limit \(\sim\)5 nM was reported [35]. In another elegant piece of work, [PERSON] et al. illustrated a field-effect transistor (FET)-based biosensor to detect SARS-CoV-2 in clinical samples [36]. The FET biosensor produced by coating graphene sheets of FET with a specific antibody against the SARS-CoV-2 spike protein detected the virus antigen protein with high sensitivity (\(\text{LOD}=100\) fg/mL in biological samples), using only small amounts of analytes. In addition to the above platforms, other platforms that utilize MNPs as auxiliary tools for detecting viruses have also been reported. The combination of MNPs with various analytical techniques (i.e., PCR, ELISA, mass spectrometry, and flow cytometry) has led to an advancement in viral detection techniques. One example is depicted by [PERSON] et al. using viral-antibody-functionalized MNPs as efficient magnetic separation probes for rapid and sensitive virus detection using mass spectroscopy [37]. [PERSON] et al. also demonstrated a portable MInD (magnetic immuno-detection) surface-based immuno-assay approach for SARS-CoV-2 S-protein peptide specific antibody detection in spiked human serum [38]. Furthermore, MNPs have been frequently coupled with several other non-magnetic materials such as Au, silver (Ag), silica, fluorescent probes, and quantum dots in different bioassay platforms. For instance, [PERSON] et al. elegantly reported an ultrasensitive supersandwich-type Au@Fe\({}_{3}\)O\({}_{4}\)/graphene oxide host-guest complexed sensor for SARS-CoV-2 detection in infected COVID-19 patients using a portable electrochemical smartphone [39]. Individual Au and Ag NP-based testing systems were also investigated for SARS-CoV-2 and other forms of viral detection [40]. One commonly used point-of-care (POC) diagnostic tool in this regard is the lateral flow assay (LFA). Examples of SARS-CoV-2 LFA devices utilizing AuNPs for detecting SARS-CoV-2 spike or nucleocapsid proteins have been developed with detection limits ranging from 0.65 ng/mL to 5 \(\upmu\)g/mL [41].