Development and optimisation of the biosensor for aspartate aminotransferase blood level determination.

This work presents the development and optimisation of an amperometric biosensor for determining aspartate aminotransferase (AST) activity in blood serum, using glutamate oxidase and platinum disc electrodes. AST is a key biomarker for diagnosing cardiovascular and liver diseases. The biosensor's bioselective membrane composition and formation protocol and the working solution (aspartate 8 mM, α-ketoglutarate 2 mM, pyridoxal-5-phosphate 100 µM) were optimised. The sensor demonstrated high selectivity, stability (70% retention over 2 months at - 18 °C), and sensitivity (2.37 nA min⁻ per 10 U L⁻), with a dynamic range of 0-500 U L⁻ and a limit of detection of 1 U L⁻. Comparative analysis showed the calibration curve method outperforms the standard addition method for AST measurement in serum samples. Additionally, a reference spectrophotometric technique was adapted for AST level determination, showing a strong correlation (r = 0.989) with the biosensor results. This research offers a fast, affordable, and accurate tool for early check-ups of liver and heart conditions. The biosensor's flexibility and ease of use make it suitable for further development into point-of-care testing and personalised healthcare techniques.