Enzyme-linked aptamer-based sandwich assay (ELASA) for detecting lactate dehydrogenase, a malarial biomarker.

Herein, we report a sensitive and selective enzyme-linked aptamer-based sandwich assay (ELASA) to detect lactate dehydrogenase (LDH), which is an attractive biomarker for malaria diagnosis and antimalarial medication. We performed the sandwich assay with a single aptamer sequence, called 2008s, owing to the structural properties of the LDH tetramer instead of using a conventional sandwich assay with two different aptamers (or antibodies) for capturing and probing a target molecule. First, the biotinylated LDH aptamer was linked with immobilized streptavidin on a microwell plate for binding flexibility, and then LDH was bound to the aptamer. Next, a horseradish peroxidase-conjugated aptamer of the same sequence was used to analyze LDH quantitatively. Using this approach, the limit of detection (LOD) of LDH with the naked eye was 100 ng mL, and the LOD and limit of quantification from the absorbance measurements were 34.9 ng mL and 95.5 ng mL, respectively, based on LDH spiked blood samples. Our proposed method selectively binds LDH, not human lactate dehydrogenase. Therefore, this method may be a valuable tool for diagnosing, monitoring, and quarantining malaria cases easily and rapidly.