Novel 3D Printed Device for Dual-Signaling Ratiometric Pho-toelectrochemical Readout of Biomarker Using λ-Exonuclease-Assisted Recycling Amplification.

A ratiometric photoelectrochemical (PEC) sensing strategy was proposed for monitoring of carcinoembryonic antigen (CEA) based on a homemade 3D printing device with dual-working photoelectrodes (PE1 and PE2), coupling lambda-exonuclease (lambda-Exo)-assisted recycling amplification with CdS quantum dots. Gold nanoparticles-functionalized ZnO nanorods were utilized as PEC substrate for generating initial photocurrent and immobilizing DNA probe. Upon incubation of target with DNA trigger/CEA aptamer-modified magnetic bead (tri/apt-MB), DNA trigger dissociated from magnetic bead and then hybridized with capture probe (cp) on PE1 or opened hairpin probe (hp) on PE2 to form double-stranded DNA (dsDNA). The exonuclease could recognize and cleave two newly generated dsDNA, leading to the release of trigger. The free trigger strand continued to hybridize with the remaining cp/hp, which were cleaved by lambda-Exo, and then trigger was released again and restarted next recycle with the lambda-Exo. After digestion of lambda-Exo, the number of capture probes on PE1 was reduced, and many short DNA fragments were produced on PE2, thereby resulting in the decreasing CdS QDs on PE1 and the increasing CdS QDs on PE2. As a result, it was observed that the ratio value of photocurrents (PE1/PE2) significantly decreased with the increasing CEA. Under optimum conditions, the sensing method showed a good linear relationship toward CEA within the dynamic range of 0.02-10 ng mL(-1) and a detection limit of 6.0 pg mL(-1). Moreover, the ratiometric PEC sensor exhibited good reproducibility, satisfying stability, and remarkable anti-interference performance, which suggests its promising application prospect to detect target CEA.