The assay provides high-throughput testing combining antigenCantibody interaction with automated image capture [90]. 4.?Radiological diagnostic approaches Radiology is the field of medicine where imaging technologies are applied for the diagnosis and treatment of diseases. of detection. The review provides a deep insight into the current diagnostic methods and future trends to combat this deadly menace. Keywords: SARS-CoV-2, Diagnosis, Molecular detection, Immunological detection, Radiological approach, Nanoparticles 1.?Introduction The COVID-19 pandemic has affected 606 million individuals, killing around 6.4 million people worldwide as of September 2022 [1]. The most highly impacted regions include America, Europe, Eastern Mediterranean, South-east Asia, Western Pacific and Africa according to World Health Organization (WHO) [1]. The etiological agent of COVID-19 is severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a positive-sense single-stranded ribonucleic acid (+ssRNA) virus from the family Coronaviridae. Under the electron microscope, it appears as crown shaped virus due to the surface proteins. The SARS-CoV-2 genome is approximately 30 kilobases, of which 66.6?% codes for open reading frame 1a and 1b and 33.3?% encodes proteins such as spike protein (S), membrane protein (M), an envelope protein (E), nucleocapsid protein (N), and RNA-dependent RNA polymerase (RdRP) [2], [3]. The variants of SARS-CoV-2 have been identified to Rabbit Polyclonal to ARHGEF5 have mutations in these structural proteins. The Centers for Disease Control and Prevention (CDC) has classified these variants as variants of concern and variants of interest [4]. Alpha, Beta, Gamma, and Delta are the variants of concern [3], [4] whereas Epsilon, Zeta, Eta, Theta, Iota, and Kappa are the variants of interest [5]. Recently, the new variant Omicron with 32 mutations in spike protein alone is also designated as a variant of concern. These variants have specific mutations in structural proteins and exhibit either an increased infection rate or facilitate replication of the virus in the host cell [6]. Available data indicates that the virus primarily transmits via air droplets. The spike protein of SARS-CoV-2 recognizes the angiotensin-converting enzyme 2 (ACE2) present on the host cell surface causing its entry into the cell [7]. The viral RNA is then translated to produce viral replicase polyproteins that are self-cleaved to produce nonstructural proteins. Some of the nonstructural proteins coalesce with each other to form a replicase/transcriptase complex. The complex facilitates the transcription to produce genomic and sub-genomic mRNA. The sub-genomic mRNA gives rise to S, E, M, and N structural proteins. The assembly of genomic RNA and structural proteins takes place in the ER-Golgi apparatus component and the newly formed SARS-CoV-2 are released from the cell via exocytosis (Fig. 1 ) [8], [9]. Some of the symptoms that an active patient displays are fever, fatigue, smell Phthalylsulfacetamide loss, dry cough, anorexia, and breathing trouble. Several others remain Phthalylsulfacetamide asymptomatic for a long time and can transmit the virus to immune suppressed population. Thus, testing Phthalylsulfacetamide on a large platform is necessary to win the battle against the virus [10], [11]. Open in a separate window Fig. 1 Life cycle of SARS-CoV-2. The SARS-CoV-2 virus recognizes the ACE-2 receptor present on the host surface. Post-receptor interaction, the virus particles enter the cell via endocytosis. The envelope of the virus fuses with the cell membrane releasing the viral RNA into the cell. The viral genome is translated to produce polyproteins. Self-proteolysis of polyproteins forms non-structural proteins. These non-structural proteins amalgamate to form a replicase/transcriptase complex (RTC) which facilitates the replication of genomic RNA. Transcription of the viral genome generates sub-genomic RNA that is translated to produce the S, M, E, N, and ORF1a proteins by the ERGIC (Endoplasmic reticulum-Golgi intermediate compartment) complex. The newly assembled viral particles are released out of the cell through exocytosis. After sequencing the whole genome of the virus, molecular testing approaches were put forward to carry out the testing and diagnosis. The approaches where specific SARS-CoV-2 sequences are targeted and detected were seen as the gold standard to segregate the infected ones from the unaffected population and provide them with the appropriate care and medications to eliminate the transmission chain. Examining the sera of the individual for SARS-CoV-2 antigen or antibodies against the virus complemented the molecular approaches by providing a rapid point-of-care diagnosis. To combat the global pandemic, the application of nanotechnology has also been scrutinized for rapid testing [12]. Herein, various diagnostic approaches for SARS-CoV-2 detection are discussed in detail. The methods are classified as molecular biology-based techniques, Phthalylsulfacetamide immunology-based techniques, radiology diagnostics, and nanomaterial-based diagnostics. The methods are compared based on their specificity, sensitivity, the limit of detection, and turnaround time. 2.?Molecular biology-based diagnostics approaches The application of molecular biology approaches has upgraded the diagnostic procedure and is currently one of the most relied diagnostic platforms for COVID-19. The early sequencing of the SARS-CoV-2 genome accelerated the use of molecular diagnostic.