Point-of-Care Optical Device for Estimation of α-Amylase Using Carbon Quantum Dots

Alpha-amylase (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-amylase) is an enzyme released by the pancreas, and it converts starch into sugar. Pancreatitis or inflammation of the pancreas is detected by elevated levels of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-amylase in blood. It is one of the biomarkers for pancreatitis. This study investigated the development of an optical point-of-care (POC) device for the detection of pancreatitis by estimating <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-amylase, using a light-emitting diode and a light-dependent resistor (LDR). We synthesized carbon quantum dots (CDs) by pyrolyzing the citric acid at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~^{\circ }$ </tex-math></inline-formula>C for 16 min and subsequently conjugated CDs with starch. The conjugation of starch to CD was conducted using the EDC-NHS protocol. We observed a quantum quenching effect when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-amylase was added to the starch-conjugated CD. The study utilized artificial blood serum (ABS) with an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-amylase range of 42–420 U/L. The CDs’ potential as sensitive fluorescent probes for detecting enzymatic activity was indicated by the negative correlation disclosed by the measurements with enzyme concentration. The device developed obtained a sensitivity of 0.079 a.u.L/U and an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{{2}}$ </tex-math></inline-formula> of 0.99 for its calibration curve. This illustrates a potential POC implementation of the device to identify acute pancreatitis, using CD as a fluorescent probe.