A dual signal-on photoelectrochemical immunosensor for sensitively detecting target avian viruses based on AuNPs/g-C3N4 coupling with CdTe quantum dots and in situ enzymatic generation of electron donor

A sensitive and specific photoelectrochemical (PEC) immunosensor was fabricated for subgroup J avian leukosis viruses (ALV-J) analysis based on a dual signal-on strategy. Gold nanoparticles (AuNPs) decorated graphitic carbon nitride (AuNPs/g-C3N4) as photoelectrochemical species and primary antibody (Ab1) against ALV-J were immobilized onto ITO electrode in turn. An ALP-CdTe-Ab2 bio-conjugant was fabricated by assembling second antibody (Ab2) and alkaline phosphatase (ALP) to CdTe quantum dots (QDs) surface. The PEC immunosensor was fabricated by successively anchoring the target ALV-J and ALP-CdTe-Ab2 bio-conjugants onto electrode surface via the immune recognition. By virtue of the matched energy levels between CdTe QDs and AuNPs/g-C3N4, ALP-CdTe-Ab2 bio-conjugants could serve as the PEC active probes for photocurrent enhancement. Moreover, the photocurrent response could be further enhanced attributed to the ALP catalytic chemistry to in situ produce ascorbic acid for electron donating, achieving an effective dual signal-on mode for PEC assay. On the basis of the ALV-J titers-dependent photocurrent increment, the fabricated PEC immunosensor showed high sensitivity, specificity and stability for ALV-J assay in a wide linear range with a low detection limit of 85 TCID50/mL. This PEC immunosensor with the dual signal-on strategy may open up a promising platform for more target analytes in novel immune analysis and clinical diagnostics.