Trap remediation of CuBi 2 O 4 nanopolyhedra via surface self-coordination by H 2 O 2 : an innovative signaling mode for cathodic photoelectrochemical bioassay.

This work conveys a new philosophy of surface self-coordination mediated trap remediation for innovative cathodic photoelectrochemical (PEC) signal transduction. Initially, the surface trap states of CuBiO nanopolyhedra resulting from dangling bonds can function as charge carrier recombination centers, which suppress the carrier separation efficiency and result in a low photocurrent output. Particularly, hydrogen peroxide (HO) spontaneously interacts with the uncoordinated Cu(II) on the surface of CuBiO, enabling efficient elimination of dangling bonds and remedy of trap states, thereby outputting intensified photocurrent readout. Exemplified by Flap endonuclease 1 (FEN1) as a model target, a tetrahedron DNA (THD)-based strand displacement amplification (SDA) was introduced to manipulate the formation of hemin impregnated G-quadruplex (G-quadruplex/hemin) DNAzyme and the resultant catalytic reduction for HO. In addition, a highly efficient and ultra-sensitive PEC sensing platform was achieved for FEN1 detection with a wide linear range from 1.0 fM to 100.0 pM and a detection limit of 0.3 fM (S/N = 3). This work not only establishes a new idea of cathodic PEC signal transduction, but also offers an efficient biosensing platform for FEN1.