Self-Organized Synthesis of Nanoserpent Clusters on Templated Starch for Sensitive Detection of Pancreatic α-Amylase

Concentration of alpha-amylase in blood serum is one of the very important parameters to measure for the early-stage detection of various pancreatic disorders. Since this enzyme is present in a very small quantity in the serum, it requires the development of an ultrasensitive sensing platform for an accurate quantification with a very lower limit of detection. The study reports the development of a nanobiosensor using 'green' biosynthesis protocol wherein an in situ reduction of gold ions on a starch template yields a nanocluster resembling the shapes of serpents - AuNS. The as-synthesized serpentine AuNS demonstrates superior reaction rate kinetics when exposed to a solution loaded with the enzyme alpha-amylase to engender rapid starch digestion. Importantly, the enzymatic degradation of the surface-bound starch on AuNS exposes the electrically conducting gold nanoclusters, which eventually leads to a significant enhancement of the electrical conductance of the substrate. Subsequently, the large differences in the electrical conductance before and after the addition of alpha-amylase have been translated into an electrochemical sensor to quantitatively determine the alpha-amylase levels in human serum. The proposed sensor yields linear responses in the relevant physiological range of alpha-amylase levels (12-120 U/L) with a significantly lower limit of detection (LoD) of 6 U/L. This sensor exhibits high analytical sensitivity (0.03 (U/L)(-1)) and exceptional specificity with a rapid response time. The results obtained from the laboratory scale prototype have been validated against the results obtained from the clinical autoanalyzer to assess the accuracy. The nanobiosensor has shown a significant potential to translate into a portable, rapid, ultrasensitive, specific, and affordable point-of-care-testing device for the diagnosis of pancreatic disorders at the patients' site.