Boolean-format biocatalytic processing of enzyme biomarkers for the diagnosis of soft tissue injury

The development of a novel enzyme logic sensing concept for the detection of soft tissue injury (STI) is reported. The new biocatalytic scheme employs creatine kinase (CK) and lactate dehydrogenase (LDH) as enzyme biomarker inputs to a biochemical cascade that mimics the operational functionality of a NAND Boolean logic gate. Under the optimal conditions, physiological and pathological levels of CK and LDH are detected optically and electrochemically by monitoring the level of reduced nicotinamide adenine dinucleotide (NADH) as an output of the logic gate. The latter technique employs a flexible carbon screen-printed electrode (SPE) to facilitate the on-site detection of STI. By establishing a pathologically meaningful threshold, relatively simple optical and amperometric assays tendered the diagnosis in a straightforward ‘True’/‘False’ digital format. Only the simultaneous presence of elevated levels of both enzyme inputs would thus trigger a positive diagnosis. Moreover, an interference investigation is performed that employs circulating levels of potential interferents. Such an enzyme cascade and enzymatically-processed biochemical information offer promise for point-of-care injury screening where a rapid determination of pathological situations is a prime consideration.