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Abstract: An electrochemiluminescent (ECL) biosensor was constructed for selective assay of alanine aminotransferase (ALT) based on the enzymatically catalyzed oxidation of pyruvate by pyruvate oxidase (PYOD). The composite of potassium ferricyanide and carbon nanotube was adopted to pre-functionalize the basal platinum electrode while the potassium ferricyanide acted as the activator of PYOD. The ALT catalyzed the reaction of L-alanine and α-ketoglutarate to produce pyruvate which could be further enzymatically oxidized by PYOD to yield H2O2 to intensify the ECL of luminol. The biosensor showed rapid response for real-time measurement of ALT in the linear concentration range from 0.00475 to 350 U/L (r = 0.993) with a relatively standard deviation of 2.5% (C ALT = 47.5 U/L, n = 6). The biosensor was applied to assay the ALT in rat serum with average recovery of 90.5%.

In this paper, the sensitization on electrochemiluminescent (ECL) reaction of luminol from reactive oxygen species (ROSs) in neutral medium was studied. The powerful sensitization from ROSs even related with organics and organisms were examined under selected conditions which were suitable for biochemical analysis. The results indicated that whether the enhancers were dissolved in solutions or immobilized on the surface of conventional electrodes, stronger ECL intensity of luminol could be obtained. Enhanced ECL helped to provide groundwork for the detection of biomolecules for which would further enhance or quench the ECL signals. The technique may provide new means in a variety of fields such as clinical diagnostics, immunological analysis and environmental monitoring due to its simplicity and high efficiency.