L-lactate is a key metabolite indicative of physiological state, glycolysis pathways, and various diseases such as sepsis, heart attack, lactate acidosis, and cancer. Detection of lactate has been relying on a few enzymes that need other substrates. In this work, DNA aptamers for L-lactate were obtained using a library-immobilization selection method and the highest affinity aptamer reached a Kd of 0.43 mM as determined using isothermal titration calorimetry. The aptamers showed up to 50-fold selectivity for L-lactate over D-lactate and had no measurable response to other closely related analogs such as pyruvate and 3-hydroxybutyrate. A fluorescent biosensor based on the strand displacement method showed a limit of detection of 0.55 mM. Simultaneous detection of L-lactate and D-glucose in the same serum solution was achieved. This work has broadened the scope of aptamers to very simple metabolites and provided a useful probe for the continuous and multiplexed monitoring.
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