Science & Technology
29th Apr, 2020
Scientists at Delhi’s CSIR-IGIB have developed a paper-based test strip for Covid-19, and named it after the fictional detective created by Satyajit Ray.
- The ‘Feluda’ test strip has been invented by a team led by two Bengali-origin scientists- Dr Souvik Maiti and Dr Debojyoti Chakraborty, at the Council of Scientific & Industrial Research’s Institute of Genomics and Integrative Biology (CSIR-IGIB) in New Delhi.
- The simple paper-based test strip could also reduce Covid-19 testing costs — the real-time polymerase chain reaction test (RT-PCR) used currently requires machinery worth lakhs of rupees and its price is capped at Rs 4,500 in private labs, but the ‘Feluda’ test could cost as little as Rs 500.
- It can be used in a way similar to pregnancy test strips widely available over the counter.
How does it work?
- This strip will be similar to a pregnancy test strip, and will not require any specialised skill and machines to perform, as is the case with other PCR-based tests.
- This strip will just change colour, and can be used in a simple pathological lab. The most important part is it will be 100 per cent accurate.
- The test kit uses CRISPR gene-editing technology to get results, though the difference to the kits being developed at Stanford and MIT is in the proteins used.
- CRISPR technology recognises specific genetic sequences and cuts them in short time.
- The CRISPR reaction is specific, and can be done in 5-10 minutes. It is a powerful technique that worked in detecting the Zika virus too.
Feluda 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.
What are genome editing and CRISPR-Cas9?
- Genome editing (also called gene editing) is a group of technologies that give scientists the ability to change an organism's DNA.
- These technologies allow genetic material to be added, removed, or altered at particular locations in the genome. Several approaches to genome editing have been developed.
- A recent one is known as CRISPR-Cas9, which is short for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9.
- The CRISPR-Cas9 system is faster, cheaper, more accurate, and more efficient than other existing genome editing methods.
- CRISPR-Cas9 was adapted from a naturally occurring genome editing system in bacteria. The bacteria capture snippets of DNA from invading viruses and use them to create DNA segments known as CRISPR arrays.
- The CRISPR arrays allow the bacteria to "remember" the viruses (or closely related ones). If the viruses attack again, the bacteria produce RNA segments from the CRISPR arrays to target the viruses' DNA.
- The bacteria then use Cas9 or a similar enzyme to cut the DNA apart, which disables the virus.
How Feluda is different from others?
- Unlike Stanford and MIT, which use CAS-12 and CAS-13 proteins to detect the presence of the novel coronavirus, Feluda uses CAS-9 protein technology. And unlike the PCR test, there is no need for probes.
- 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.
- Feluda does not require any ‘level 2’ or ‘level 3’ lab to test, unlike most PCR-based tests. This can be done in any simple pathological lab.