Photoelectrochemical detection of tumor markers based on a CdS quantum dot/ZnO nanorod/Au@Pt-paper electrode 3D origami immunodevice.

A 3D origami photoelectrochemical (PEC) immunodevice based on CdS quantum dot (QD)-sensitized ZnO nanorods (ZNRs) as a photoactive matrix and glucose oxidase (GOx) functionalized nanoporous silver (NPS) as a label was established for sensitive detection of tumor markers. The ZNRs were grown on a porous Au@Pt core-shell nanoparticle modified paper working electrode (Au@Pt-PWE) via an in situ growth method. The coupling of CdS QDs and the ZNR/Au@Pt-PWE resulted in an enhanced excitation and photo-to-electric conversion efficiency. The large amount of GOx loading on the NPS in situ generated more HO in the glucose substrate for electron donation, which amplified the photocurrent signals. And the good biocompatibility of the Au@Pt-PWE retained good stability for the sandwich-type immunoassay. A 3D origami photoelectrochemical immunodevice for the detection of carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) was successfully developed with linear ranges of over 4 orders of magnitude and with detection limits down to 0.3 pg mL and 0.5 pg mL. This proposed amplification strategy exhibited excellent stability and reproducibility in real human serum assay, and could be applied in point-of-care testing of other cancer markers.