Construction of electrochemical biosensor based on magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods for the sensitive detection of MUC1 mucoprotein

Magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods with the saturation magnetization of 69.5 emu/g were prepared via the hydrothermal and calcination-reduction process using β-FeOOH nanorods as precursor and galactose as the reducing agent. The average length and diameter of the nanorods were 81.6 nm and 23.9 nm, respectively. The surfaces of the heterogeneous nanorods were modified with PEI and HAuCl4, resulting in magnetic rod-like Fe3O4/α-Fe2O3@Au nanocomposites. By utilizing the Au–S effect, Apt/ssDNA hybrid double-strands were loaded onto Fe3O4/α-Fe2O3@Au nanocomposites to form Fe3O4/α-Fe2O3@Au-Apt/ssDNA biosensors capable of recognizing mucoprotein-1 (MUC1) mucoprotein. These biosensors could be magnetically assembled onto a magnetic glassy carbon electrode to create a "Turn off" type electrochemical biosensor. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) techniques were used to evaluate the detection performance. Based on the change in DPV signals, the optimal concentrations of magnetic Fe3O4/α-Fe2O3@Au nanocomposites and Apt/ssDNA double-stranded probes were 12 mg/mL and 9 μM, respectively, while the optimal incubation time was 2 h. Under these conditions, the sensor exhibited a linear detection range of 0.1 pg/mL to 1500 pg/mL (R2 = 0.9988), with a limit of detection (LOD) of 0.1 pM and a limit of quantitation (LOQ) of 0.34 pM. The biosensor demonstrated excellent performance in terms of selectivity, reproducibility (RSD = 2.9 %), and stability. When actual serum samples diluted by a factor of 20 in PBS were tested, the recovery rate ranged from 95.65 % to 103.40 %, indicating that this approach for sensitive detection of MUC1 holds promising prospects.