Indian Institute of Science Team Develops Low-cost Portable Device For Detecting Melamine

(A) Image of the fluorometer (B) Interior of the prototype 

Melamine, a compound that is added to adulterated milk and dairy products, can lead to kidney-related diseases and cause kidney failure. The techniques currently used to detect it typically require expensive and sophisticated equipment and highly trained personnel, and can take time. In order to make this process simpler and faster, researchers from the Indian Institute of Science (IISc) have designed a low-cost, hand-held device that can detect melamine in water and milk.

Using this device, the researchers tested a range of concentrations of melamine and were able to detect up to 0.1 parts per million (ppm) of melamine in water and milk, which is much lower than the acceptable limit of 1 ppm. Detection took just four minutes.

The team, led by Sai Siva Gorthi, Associate Professor in the Department of Instrumentation and Applied Physics (IAP) at IISc, devised a fluorometer that can detect the formation of copper nanoparticles on specified double-stranded DNA (dsDNA) templates, says Radhika Nambannor Kunnath, a PhD student in Gorthi’s lab and the lead author of the study. These nanoparticles are inexpensive to synthesise and possess a property called fluorescence in which a material emits light of a different wavelength (colour) when a particular wavelength of light falls on it.

The presence of melamine in the sample disrupts the synthesis of these copper nanoparticles and causes a reduction in the intensity of fluorescence, which is detected by the proposed fluorometer. The natural fluorescent glow of these nanoparticles is very weak and their detection requires expensive and sophisticated spectrometers. In a study conducted in 2019, the same team led by Gorthi had shown a way to enhance this glow so that it can be detected by off-the-shelf photodiodes. In the present work, they used electronic components that were easily available at a lower cost, such as a simple UV LED to illuminate the nanoparticles and a PIN photodiode to detect the fluorescence.

The device can be modified to detect other substances too, such as lead and mercury. “This fluorometer can also be easily adapted to detect other analytes of interest (like biomolecules and proteins) using these copper nanoparticles, by changing the template sequence of the dsDNA and other reaction components,” says Kunnath. The team believes that this can be deployed as a screening tool for environmental and food quality testing.