Portable device detects a diabetic biomarker in tears
doi:10.1038/nindia.2020.105 Published online 6 July 2020
Researchers have designed a portable sensing device that can detect the elevated levels of a specific protein in the tears of diabetic patients1.
The elevated levels of the protein signal the early onset of diabetic retinopathy (DR), a disorder that affects the retina, the light-sensitive part of the eyes.
Currently DR is diagnosed using complex, invasive eye tests. To find a simple one, the scientists from the Indian Institute of Technology in Guwahati, led by Dipankar Bandyopadhyay, fabricated the device by coating a water-based suspension of gold nanoparticles with an antibody that is specific to beta-2 microglobulin (B2M), a protein found in tears and urine.
The device also has microchannels where the antibody-coated nanoparticles mix and react with tears containing B2M.
The levels of B2M increase in tears, urine, blood serum and brain fluids in various disorders, including diabetes.
Tiny drops of tears, when drawn into the microchannels, reacted with the antibody-coated gold nanoparticles, triggering a colour change. On reacting with B2M in tears, the nanoparticles’ colour changed from dark purple to pale purple.
This reaction, happening under an LED light placed on one side of the device, reduced the intensity of rays emanating from the reaction mix. A light detector, on the other side of the device, measures such changes in light intensity and generates a digital signal.
A signal-processing unit then converts the signal into a readable one, revealing the concentration of B2M in human tears. This device could also be used to monitor levels of B2M in urine.
1. Maity, S. et al. Microfluidic immunosensor for point-of-care-testing of beta-2-microglobulin in tear. ACS. Sustain. Chem. Eng. (2020) doi: 10.1021/acssuschemeng.0c00289