Microdroplet based disposable sensor patch for detection of α-amylase in human blood serum

Concentration of alpha-amylase in human serum is a key indicator of various pancreatic ailments and an affordable point-of-care detection of this biomarker can benefit millions suffering from these diseases. In view of this situation, we report the development of a flexible patch-sensor, which simply requires a microdroplet of aqueous starch-FeSO4 solution to detect alpha-amylase in serum. The detection is achieved through the generation of mixing vortices (similar to 12 rpm) inside the droplet with the help of an imposed thermal gradient. Such vortices due to Marangoni and natural convections are found to be strongest at an optimal temperature difference of similar to 18 degrees C - 23 degrees C across the droplet which in turn facilitate mixing and promote the specific starch-amylase enzymatic reaction. Subsequently, the large (similar to 80%) variation in the electrical resistance across the droplet is correlated to detect the level of the alpha-amylase in the analyte. Importantly, the sensor can detect even in the limits of 15-110 units/liter. Further, the sensitivity of flexible sensors is similar to 8.6% higher than the non-flexible one. Interestingly, the sensitivity of the proposed sensor has been nearly three-times than the previously reported optical ones. The results of patch-sensor match very closely with the standard path-lab tests while detecting unknown level of amylase in serum. The prototype has shown significant potential to translate into an affordable device for the real-time detection and easy prognosis of pancreatic disorders.