A Novel DNAzyme Walker Biosensor for the Determination of Chromium(III)

A new DNAzyme walker biosensor has been constructed to sensitively determine chromium (III). The DNAzyme walker consisted of enzyme strands (ES) as the walking strand and carboxyfluorescein-labeled substrate strands (SS) carrying a nicking cleavage site on the surface of streptavidin-modified magnetic beads (MB@ES/SS). Cr3+ activates the nicking endonuclease activity of DNAzyme and its corresponding cleavage on SS to drive ES to move autonomously along the MB surface. As a result, FAM-labeled fragments from SS are released, producing the fluorescence signal. The MB@ES/SS walker biosensor provides rapid analysis and a low limit of detection (3.12 nM) within a linear range from 0.01 to 20 µM. This work offers a new method for Cr3+ determination and broadens its application for metal ion analysis.