A novel ratio electrochemical biosensor based on multi-functional nanocomposite was developed. Fe3O4 was synthesized in situ on carboxyl functionalized 2D nanomaterial MXene, and then covalently bonded with [Ru(NH3)6]3+ to obtain nanocomposites MXC-Fe3O4-Ru. Fe3O4 and [Ru(NH3)6]3+ can neutralize the electronegativity of the MXene to make the nanocomposites electrically neutral. Combine with the good hydrophilicity and conductivity of MXene, the nanocomposites can be utilized to construct antifouling electrochemical biosensors without modifying with specific antifouling materials. Moreover, Fe3O4 can endow the nanocomposites with magnetism, and [Ru(NH3)6]3+ is used as an internal standard molecule. The strong magnetic MXC-Fe3O4-Ru can be easily separated and firmly modified on the magnetic gold electrode (MGE). DNA double-stranded (dsDNA) containing an ferrocene (Fc)-modified carcinoembryonic antigen (CEA) aptamer can be specifically captured to the surface of the electrode by amido bond. In the presence of CEA, CEA binds to the aptamer and leaves the electrode surface, the electrochemical signal of Fc decreases, while the electrochemical signal of [Ru(NH3)6]3+ is fixed on the electrode surface remains basically unchanged. The ratio of the electrochemical signals of Fc and [Ru(NH3)6]3+ is proportional to the CEA concentration. The linear range of the sensor is 1 pg/mL to 1 μg/mL with a detection limit of 0.62 pg/mL. With the excellent antifouling performance, good conductivity of the nanocomposite, and the application of the ratiometric strategy, the biosensor can achieve high selectivity, accuracy, and sensitivity for the detection of targets even in complex samples, such as FBS and clinical serum.
Keywords: Anti-fouling; Carcinoembryonic antigen; Electrochemical biosensor; MXene; Ratiometric strategy.
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