## 4 Conclusions  
In conclusion, we developed a novel magnetic immuno-capture approach, MICaFVi, for the detection of viral-mimicking and pseudoviral particles as surrogates for MERS-CoV and SARS-CoV-2. MICaFVi is based on capturing the spike proteins exposed on coronaviruses using anti-spike antibody-conjugated MNPs (AS-MNPs), followed by the use of a flow cytometer to detect viral particles (i.e., VM-SPs or pseudoviral particles), enabling efficient, fast, accurate, sensitive, and specific detection. Our method combines the high specificity and efficiency of the capturing functionalized MNPs with the high sensitivity and accuracy of flow cytometry. MICaFVi detected successfully mimic-virus silica particles as well as MERS-CoV pseudoviral particles (MERS-pp) with high efficiencies of ~60% and 90%, respectively, and LOD = 20 pmol/mL. The proposed approach has great potential for designing an alternative approach for the accurate and sensitive diagnosis of SARS-CoV-2 and other viral infections. Moreover, MICaFVi can be adaptable for diverse pathogen detection either separately or simultaneously (Multiplex MICaFVi), and could be potentially used to detect other viruses, bacteria, proteins, and even cells.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/bios13050553/s1](https://www.mdpi.com/article/10.3390/bios13050553/s1)]([https://www.mdpi.com/article/10.3390/bios13050553/s1](https://www.mdpi.com/article/10.3390/bios13050553/s1)), Figure S1: Gating strategy: The first steps consist of NP visualization based on their sorting according to their forward and side scatter properties. To eliminate NP doublets and clumps, that could generate a high fluorescence background and subsequently increases the rate of false positive events, FSC-H vs FSC-A and SSC-H vs SSC-A sequential gating was used as a double discrimination strategy; Figure S2: SEM and TEM images of virus-mimic silica particles (VM-SPs) and anti-spike protein conjugated (AS-MNPs) showing their sizes and morphology; Figure S3: Adaptability of MICaFVi technique that could be easily applied for diverse pathogen detection (viruses, bacteria, proteins, and even cells).  
A.N. conceived the idea, secured funds, and conceptualized and designed the whole study. A.N., [PERSON] and [PERSON] conducted lab experiments. [PERSON], N.S., [PERSON] and A.A. analyzed the data. [PERSON] prepared all of the particles and their functionalization. [PERSON], [PERSON] and [PERSON] wrote the manuscript. [PERSON] performed the microscopic characterization of particles. [PERSON] produced the pseudoviral particles. [PERSON] visualized and supervised the study. All authors have read and agreed to the published version of the manuscript.  
This work was supported by King Abdullah International Medical Research Center (KAIMRC) Institutional Research Grants (grant numbers: RC20/266/R and RC15/143/R) to PI: A.N.  
This study was approved by the IRB at King Abdullah International Medical Research Center, MNGHA, Riyadh, Saudi Arabia. Approval reference number: IRBC/754/15.  
Not applicable.  
The original data presented in the study are included in the article/Supplementary Material; any further data inquiries can be directed to the corresponding author.  
The authors thank all members of the Core Facility Department for their continuous support and advice. [PERSON] would like to thank the Arab Fund for Economic and Social Development (AFESD)--the Arab Fund Fellowship Award Program.  
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.