Abstract
Aptamer-based sensors have emerged as a major platform for detecting small-molecular targets, because aptamers can be selected to bind these small molecules with higher affinity and selectivity than other receptors such as antibodies. However, portable, accurate, sensitive, and affordable detection of these targets remains a challenge. In this work, we developed an aptasensing platform incorporating magnetic beads and a DNAzyme for signal amplification, resulting in high sensitivity. The biosensing platform was constructed by conjugating a biotin-labeled aptamer probe of small-molecular targets such as toxins and a biotin-labeled substrate strand on magnetic beads, and the DNAzyme strand hybridized with the aptamer probe to block the substrate cleavage activity. The specific binding of the small-molecular target by the aptamer probe can replace the DNAzyme strand and then induce the hybridization between the DNAzyme strand and substrate strand, and the iterative signal amplification reaction of hydrolysis and cleavage of the substrate chain occurs in the presence of a metal ion cofactor. Using invertase to label the substrate strand, the detection of small molecules of the toxin is successfully transformed into the measurement of glucose, and the sensitive analysis of small molecules such as toxins can be realized by using the household portable glucose meter as a readout. This platform is shown to detect ochratoxin, a common toxin in food, with a linear detection range of 5 orders of magnitude, a low detection limit of 0.88 pg/mL, and good selectivity. The platform is easy to operate and can be used as a potential choice for quantitative analysis of small molecules, at home or under point-of-care settings. Moreover, by changing and designing the aptamer probe and the arm of DNAzyme strand, it can be used for the analysis of other analytes.