The sensor is made by coating a silk-fibroin protein nano-layer, derived from Bombyx mori silk cocoons

The Institute of Advanced Study in Science and Technology (IASST), an autonomous institute of the Department of Science and Technology developed an affordable, user-friendly, portable smartphone-based optical sensor system utilising a fluorescence turn-on mechanism to instantly detect low levels of L-dopa in biological samples.

The sensor is made by coating a silk-fibroin protein nano-layer, derived from Bombyx mori silk cocoons, onto the surface of reduced graphene oxide nanoparticles. This system forms core-shell graphene-based quantum dots with outstanding photoluminescence properties, making it an effective fluorescent turn-on sensor probe for detecting L-dopa in real samples such as blood plasma, sweat, and urine within a linear range of 5 μM to 35 μM. The corresponding detection limits were determined to be 95.14 nM, 93.81 nM, and 104.04 nM, respectively.

The researchers have designed a smartphone-based electronic device with an electric circuit connected to a 365nm LED powered by a 5V smartphone charger. The whole setup is immersed in a dark chamber to isolate it from external light. Visual colour changes during the sensing process were observed by illuminating the sensor probe with the 365 nm LED and capturing images with a smartphone camera.

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