Scientists at CSIR-IGIB (Delhi) have developed a paper-based test strip for Covid-19, and named it after the fictional detective, Feluda, created by Satyajit Ray.
About the article: Quoting from the article “(Our strip) uses cutting-edge gene-editing CRISPR-CAS-9 technology to target and identify genomic sequence of the novel coronavirus in suspected individuals. No other laboratory in India is developing test kit using CRISPR technology,” Dr. Shekhar C. Mande, DG-CSIR, said. Team of Scientists at Institute of Genomics and Integrative Biology (IGIB) added: “Unlike Stanford and MIT, which use CAS-12 and CAS-13 proteins to detect the presence of the novel coronavirus, our kit uses CAS-9 protein technology. And unlike the PCR test, there is no need for probes.”
Anurag Agrawal, Director CSIR-IGIB, explained the difference between the ‘Feluda’ paper strip test and others being carried out around the world. “A few other labs have been developing test kits, but they are largely based on PCR technology. The problem with PCR is that it is costly — one machine costs Rs 14-15 lakh, and imported probes have to be used, of which there is a shortage. It takes several hours,” Agrawal said. Dr T.S.Ganesan, Professor Medical Oncology, Cancer Institute (WIA), Chennai, and member of ISRC explains: This is completely different from PCR-machine approaches. In simple terms, this is how it works: similar to current methods, viral RNA is extracted. However, unlike The PCR reaction, these methods to amplify RNA are different and called LAMP (Loop Mediated Isothermal Amplification). This means you do not need a PCR machine and amplification can be performed simply by heating the sample. Once the amplified DNA is ready,a special protein called CAS9 which is guided to detect the SARS-2 gene by a guide-RNA, this works like a homing missile targeted to hit the SARS-CoV-2 gene. If SARS-Cov-2 gene is present then this guide-RNA and CAS9 protein get stuck to the amplified SARS-DNA. To this reaction a fluorescently labelled single stranded DNA reporter is attached. The CAS protein, when bound to SARS-CoV-2 gene, clips it specifically. This releases the fluorophore which leads to increase in fluorescence is measured. The whole procedure takes about two hours. A company called Mammoth Sciences has published a paper in Nature Biotechnology this month using this technology to detect SARS-COV-2. The team from CSIR-ICGEB in India is developing a similar test called Feluda. In the case of ‘Feluda’ test, the LAMP and CAS9-gRNA reaction takes place on a paper strip and instead of fluorescence reporter a coloured reaction takes place which can be easily detected by the human eye.
