Fullerene-doped polyaniline as new redox nanoprobe and catalyst in electrochemical aptasensor for ultrasensitive detection of Mycobacterium tuberculosis MPT64 antigen in human serum

Tuberculosis caused by Mycobacterium tuberculosis (MTB) is still a major threat to global public health. However, the existing methods for MTB detection are usually complicated and time consuming with unsatisfactory sensitivity and specificity. In this work, a relatively simple and ultrasensitive electrochemical aptasensor based on novel signal generation and amplification was constructed for the determination of MTB antigen MPT64. The coil-like fullerene (C₆₀)-doped polyaniline (C₆₀-PAn) nanohybrids with large surface area, abundant active groups and excellent electric performance were synthesized and used both as new redox nanoprobe and catalyst for the generation and amplification of electrochemical signal for the first time. Then gold nanoparticles decorated C₆₀-PAn nanocomposites (GNPs-C₆₀-PAn) were labeled with signal aptamer to form the tracer label. After the sandwich reaction of target MPT64 antigen between capture aptamer and the tracer label, a distinguishing detection signal of C₆₀-PAn would be observed. Moreover, the detection signal could be enormously enhanced towards the efficient electrocatalytic oxidation of ascorbic acid based on C₆₀-PAn, resulting in further improvement of the sensitivity. With the excellent redox and electrocatalytic activity of C₆₀-PAn, a wide detection linear range from 0.02 to 1000 pg/mL was obtained with a detection limit of 20 fg/mL for MPT64. The proposed aptasensor showed high selectivity to target antigen compared with possible interfering substances. More importantly, it also exhibited excellent specificity and sensitivity for MPT64 detection in serum samples of tuberculosis patients, which provided a rapid and efficient detection method for MTB infection.