## 1 Introduction  
The social, economic, and healthcare challenges posed by the COVID-19 pandemic have been unprecedented. As of January 2023, worldwide COVID-19 cases have surpassed over half a billion, with an associated death toll of more than 6.6 million [1]. Early in the pandemic, large-scale testing, timely detection, and isolation were identified as vital elements to control the spread [2]. The 2019 COVID pandemic has demonstrated the need for easy, fast, cost-effective, and accurate virus detection techniques. Recently, viral outbreaks such as Monkeypox, Marburg, Ebola, and COVID-19 variants have been of concern. Such outbreaks highlight the need for effective and inexpensive point-of-care (POC) diagnostic tools for surveillance and to deploy rapid medical countermeasures. Since December 2021, the FDA has authorized two oral antiviral medications for COVID-19. While vaccinations remain the primary and potent tool against COVID-19, antiviral drugs have been found to be effective if administered as soon as possible after diagnosis (within five days of developing symptoms) [3]. Polymerase chain reaction (PCR) remains the gold standard for COVID-19 detection. However, centralized laboratory-based PCR testing involves long turnaround times (up to several days) [4]. Currently authorized COVID-19 antiviral drugs are effective if administered within five days of symptom onset. Hence, widespread access to rapid and accurate point-of-care companion diagnostic tests is essential for the success of antiviral drugs against SARS-CoV-2 infections [5]. Antigen-based immunoassays have been extensively utilized to test for COVID-19. Detection methods include electrochemical, optical, piezoelectric, magnetic, and plasmonics-based methods to detect the COVID-19 antigen [6,7]. Among these, electrochemical immunoassay-based biosensors are a practical approach given their capability for rapid, inexpensive, sensitive, and selective detection at the point of care [8]. Electrochemical (EC) biosensors recognize the interaction between an analyte (e.g., a pathogen or a label) and a recognition element (e.g., a capture antibody), producing an electrical signal that is monitored by a transducer [9]. Often, EC biosensors are combined with metal nanomaterials such as silver (Ag) and gold (Au) nanoparticles (NPs). Such nanomaterials provide distinct advantages such as a high surface-to-volume ratio, superior electron transfer properties, and stability in immobilized biomolecules. EC biosensors utilizing screen-printed carbon electrodes (SPCEs) modified with such nanomaterials offer improved analytical and miniaturization capabilities for POC use [10]. Further, the addition of an immunomagnetic step enables the capture and concentration of the analyte of interest, especially from larger-volume samples [11]. A \"sandwich approach\" combining immunomagnetic beads for analyte capture and an antibody-conjugated EC label has been utilized to detect pathogens [12]. The use of immunomagnetic beads enables the preconcentration of analytes from complex biological samples and the magneto-controlled transport of the sandwich to the surface of an SPCE for detection [13; 14; 15]. The secondary component of the sandwich involves antibodies that are labeled with an EC marker. These antibodies are designed to bind to the target analyte at a different site than the immunomagnetic bead-conjugated antibodies. The use of secondary EC labels enables the amplification of the detection signal [16]. Thus, the sandwich approach combines two advantages: preconcentration from large sample volumes and signal amplification. [PERSON] et al. reported the use of magnetic beads combined with AuNPs for the detection of the SARS-CoV-2 spike protein in saliva [17]. [PERSON] et al. developed an AuNP-based biosensor that was utilized for the detection of the SARS-CoV-2 spike antigen in spiked saliva samples [18]. More broadly, EC biosensors for detecting SARS-CoV-2 have been well described, and readers can refer to recent reviews on the same [19; 20; 21].