Editable TiO₂ Nanomaterial-Modified Paper in Situ for Highly Efficient Detection of Carcinoembryonic Antigen by Photoelectrochemical Method

In this work, a versatile photoelectrochemical paper-based sensor based on N-carbon dots/TiO₂–Pt-modified paper in situ is developed for sensitive detection of carcinoembryonic antigen (CEA) in clinical serum samples. Interconnected cellulose fibers on paper provide a porous, 3D, and flexible substrate for photoelectrochemical sensing. In situ modification of N-carbon dots/TiO₂–Pt with editable structures on paper significantly increases the conductivity, widens the adsorption range, and enhances the photoelectrochemical ability, which enables the higher sensitivity and flexibility compared with traditional rigid sensors. On the basis of this novel protocol, a miniaturized and portable origami device realizes the CEA determination with a low detection limit of 1.0 pg mL^–1 and a wide linear range from 0.002 to 200 ng mL^–1. Thanks to the good biocompatibility, the paper-based device provides a new avenue for the detection of CEA on the cell surface which is promising for portable diagnostics in early tumor warning