Dual quenching ECL strategy based on AgInZnS quantum dots and a new co-reaction promoter oxygen vacancy-modified P5AIn/TiO2 for sensitive CEA detection

Abstract

A novel electrochemiluminescence (ECL) biosensor for the sensitive detection of carcinoembryonic antigen (CEA) was constructed, utilizing environmentally friendly AgInZnS quantum dots (AgInZnS QDs) and a new co-reaction promoter enriched with oxygen vacancies, namely titanium dioxide/poly(5-aminoindole) (Ov-TiO2/P5AIn). The composite of P5AIn and TiO2 significantly enhanced the reaction rate of AgInZnS QDs with tripropylamine (TPrA). In addition, the presence of oxygen vacancies significantly enhances the electron migration rate of the electrode material, leading to more efficient catalysis of TPrA+ generation and a significant enhancement of ECL signals. Furthermore, a dual-quenching sensing strategy was employed using cuprous oxide-triaminophenol (Cu2O@APF) as the quencher, enabling the biosensor to switch. Through dual quenching of the ECL emission from AgInZnS QDs by Cu2O and APF, the biosensor achieves an extremely low “off” state of the ECL signal. Furthermore, a signal amplification strategy driven by the synergistic action of exonuclease III (ExoIII) and restriction endonuclease (Nt.BbvCI) was designed for a dual-site DNA walker, achieving cyclic amplification of the target signal and ECL signal, thereby turning the signal “on” again. The above mechanism significantly improved the specificity and sensitivity of the biosensor for CEA detection. The prepared biosensor exhibits good stability, selectivity, and sensitivity. The linear range for CEA detection is 5 × 10−14 to 10−8 M, with a detection limit of 16 fM. Additionally, the biosensor demonstrates satisfactory analytical capability for CEA in real blood samples. This strategy provides a reliable new approach for the sensitive detection of CEA and other tumor markers.