Expanding the glucose meter’s repertoire

Personal glucose meters have previously been repurposed to detect other biological targets. But those studies have typically been limited to a single target. Now, Yi Lu and Jingjing Zhang of the University of Illinois, Urbana-Champaign, use a glucose meter as a biocomputing platform for logic gates that produce glucose or the reduced form of nicotinamide adenine dinucleotide (NADH) in response to various biological substances (Angew. Chem. Int. Ed. 2018, DOI: 10.1002/anie.201804292). For example, they designed a NOR logic gate that responds to two inputs, adenosine triphosphate and adenosine diphosphate, which are coenzymes for many enzymes. The logic gate consists of a series of enzymatic reactions, or an enzyme cascade, with creatine kinase, pyruvate kinase, and lactate dehydrogenase. The presence of either ADP or ATP triggers the reaction cascade and consumption of NADH. The level of NADH is high only in the absence of both inputs. For all other combinations of ADP and ATP, the NADH level is low, satisfying the requirements of a NOR gate. Lu and Zhang made seven logic gates using a variety of inputs, including metal ions, metabolites, coenzymes, and native enzymes. They anticipate that similar devices could be made for many other medically relevant analytes to transform biomolecular logic gates into a convenient, portable, resettable, and quantitative sensing system for inexpensive point-of-care diagnostics.