Now, a thumb imprint is all that is required for detecting hyperbilirubinemia, a condition in which the amount of bilirubin in the blood is in excess and turns the sclera of the eye, urine and even the skin yellow. Hyperbilirubinemia is commonly seen in people with jaundice and newborns; a person is said to have jaundice when the bilirubin concentration in the blood typically exceeds 12 ppm in adults and 50 ppm in a newborn.
Researchers at the Indian Institute of Technology (IIT) Guwahati have tested the sensitivity and specificity of a simple, quick, point-of-care test for detecting excess bilirubin in patients.
While visual observation of yellow colour of the sclera and/or urine is routine for detecting jaundice, it is confirmed by a blood test.
A team led by Prof. Arun Chattopadhyay from the Department of Chemistry and Centre for Nanotechnology, IIT Guwahati, used thumb imprints to detect hyperbilirubinemia. The results were published in the journal Scientific Reports .
“When a person has jaundice, the bilirubin gets deposited on the skin surface. We wanted to develop a quick test to confirm if the bilirubin amount has exceeded the permissible limit in the blood,” says Prof. Chattopadhyay.
The team has been working on nanotechnology for more than 10 years, and, in recent years, on luminiscent atomic nanoclusters.
“Gold nanoclusters that have been functionalised [using chitosan and mercaptopropionic acid] show yellow luminescence under UV light. But when copper salt (copper sulphate) is added to it, the yellow luminescence gets quenched or reduced. When bilirubin is added to the medium, the copper preferentially interacts with it, forming a complex and the luminescence of the gold nanoclusters gets restored,” he says.
Luminescence restored
The bilirubin comes when the thumb is pressed on a gold nanoclusters coated membrane that has copper deposited on it.
“Previous independent studies have shown that luminescence of the gold nanoclusters is quenched by copper and at the same time copper interacts with bilirubin. So that’s why we chose copper ions,” says Srestha Basu from IIT Guwahati and the first author of the paper.
“You need to press the thumb on the membrane for a few minutes to restore the yellow luminescence in the the gold nanoclusters,” he says. Immediately after taking an impression, the same thumb cannot be used on a different membrane to restore the luminescence of copper-deposited gold nanoclusters.
