NEW DELHI: Researchers at the Indian Institute of Technology (IIT), Guwahati, have found that clay particles interact differently in the presence of SARS-CoV-2 — the virus that causes COVID-19 — a finding they used for developing a simple, affordable testing alternative.The approach developed looks at how quickly particles of clay settle in a salt water solution containing the virus.“Due to changes in inter-particle forces of clay in the presence of the virus, the sedimentation rate of the clay-electrolyte system changed,” the authors wrote in the study published in the journal Applied Clay Science.The findings offer a “simple and affordable” alternative to the complex, expensive methods currently used for detecting SARS-CoV-2, the team said.“Current methods, such as Polymerase Chain Reaction (PCR), are highly sensitive but time consuming and require heavy equipment. Similarly, the antigen testing is fast but lacks accuracy, while antibody testing is used after the infection has occurred, highlighting limitations at various levels,” lead author T.V. Bharat, professor at IIT Guwahati‘s department of civil engineering, said.Further, many of the currently available methods are not practical in resource-limited settings or during large-scale outbreaks. The COVID-19 pandemic revealed a critical gap in how we detect and track viral infections, he added.For the study, the researchers used Bentonite clay because its unique chemical structure allows pollutants and heavy metals to be easily absorbed.“Previous studies have shown that clay particles can bind with viruses and bacteriophages, making it a promising material for virus detection,” Bharat said.The team looked at particles of Bentonite clay interacted with viral material in a saline solution.They found that a Coronavirus surrogate and Infectious Bronchitis Virus (IBV) bind to the negatively charged clay surfaces at a controlled room temperature and neutral pH of 7.Bharat said the study offers a “faster, more affordable, and an accurate” alternative method — “as simple as watching sand settle in water” — to current methods, paving the way for a better disease monitoring and treatment strategies, especially during pandemics.The method also “holds great promise for improving how viral outbreaks are monitored and controlled, especially in regions where expensive lab equipment and trained personnel are not readily available,” the lead author said.