Portable device detects a diabetic biomarker in tears

• 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.
• References: 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 Source: https://www.natureasia.com

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