IIT-Guwahati reseachers use a method with gold nanoclusters and
copper salt
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. The
nanoclusters are very sensitive to the presence of molecules in the
environment.
“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 gold nanoclusters the yellow
luminescence gets quenched or reduced. When bilirubin is added to the medium,
the copper preferentially interacts with bilirubin and forms a complex and the yellow
luminescence of the gold nanoclusters gets restored,” he says.
Luminescence restored
The bilirubin, which forms the complex with copper and restores
the yellow luminescence, 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. “This could be because there is insufficient bilirubin present on
the skin of the thumb after the first impression,” says Prof. Chattopadhyay.
The way to test people with different concentration of bilirubin
on the skin is by changing the amount of copper that is deposited on the
membrane containing gold nanoclusters.
The change in the intensity of luminescence was nearly the same
whether copper ions deposited on the membrane had completely dried or not. The
shelf life of copper ions deposited on gold nanoclusters is not known. “Most of
the experiments were done when the membrane coated with copper is still wet,”
Ms. Basu says. “So the detection kit can have membranes already coated with
gold nanoclusters and copper ions can be added just before a test.”
Source: THE HINDU-5th January,2017
