FIGURE 2. Lead DNA sensor with a micro-nanofluidic device.

Immobilized DNAzyme sensor and micro-nanofluidic devices for detection of Pb²⁺ by fluorescently labelled 17E DNAzyme. a, Schematic of immobilized DNAzyme showing catalytic beacon signalling of reaction on the surface, releasing fluorophore into solution for detection. b, Schematic of DNAzyme immobilized within the pores of a nanocapillary array membrane (NCAM) with inset showing the mode of ratiometric fluorescence signalling in the absence or presence of Pb(II). c, Schematic representation of orthogonal microfluidic channels separated by a NCAM flow gate. d, Fluorescence micrographs of the receiving channel before injection of Pb²⁺ sample into a receiving channel containing 1 M 17E DNAzyme, after initial Pb²⁺ injection and after 40 s of total injection time for a DNAzyme–NCAM microfluidic device.