Multiplexing of injury codes for the parallel operation of enzyme logic gates

Abstract

The development of a highly parallel enzyme logic sensing concept employing a novel encoding scheme for the determination of multiple pathophysiological conditions is reported. The new concept multiplexes a contingent of enzyme-based logic gates to yield a distinct 'injury code' corresponding to a unique pathophysiological state as prescribed by a truth table. The new concept is illustrated using an array of NAND and AND gates to assess the biomedical significance of numerous biomarker inputs including creatine kinase, lactate dehydrogenase, norepinephrine, glutamate, alanine transaminase, lactate, glucose, glutathione disulfide, and glutathione reductase to assess soft-tissue injury, traumatic brain injury, liver injury, abdominal trauma, hemorrhagic shock, and oxidative stress. Under the optimal conditions, physiological and pathological levels of these biomarkers were detected through either optical or electrochemical techniques by monitoring the level of the outputs generated by each of the six logic gates. By establishing a pathologically meaningful threshold for each logic gate, the absorbance and amperometric assays tendered the diagnosis in a digitally encoded 6-bit word, defined as an 'injury code'. This binary 'injury code' enabled the effective discrimination of 64 unique pathological conditions to offer a comprehensive high-fidelity diagnosis of multiple injury conditions. Such processing of relevant biomarker inputs and the subsequent multiplexing of the logic gate outputs to yield a comprehensive 'injury code' offer significant potential for the rapid and reliable assessment of varied and complex forms of injury in circumstances where access to a clinical laboratory is not viable. While the new concept of parallel and multiplexed enzyme logic gates is illustrated here in connection to multi-injury diagnosis, it could be readily extended to a wide range of practical medical, industrial, security and environmental applications.