An ultrasensitive DNA biosensor based on covalent immobilization of probe DNA on fern leaf-like α-Fe2O3 and chitosan Hybrid film using terephthalaldehyde as arm-linker

• Fern leaf-like α-Fe2O3 microparticles was synthesized via a facile template-free method.
• Fe2O3 presents a large accessible surface area and high electrical conductivity.
• A DNA biosensor was fabricated using chitosan–Fe2O3 as matrix and terephthalaldehyde as arm-linker.
• High sensitivity and selectivity were achieved by the biosensor.

In this work, a novel electrochemical DNA biosensor has been developed based on the hybrid film of fern leaf-like α-Fe2O3 microparticles and chitosan (CS). The fern leaf-like α-Fe2O3 microparticles were synthesized via a facile template-free hydrothermal method, and their morphologies were characterized by X-ray diffraction, energy dispersive spectrometry, scanning electron microscope, and transmission electron microscope. Electrochemical characterization assays revealed that the hybrid film modified electrode had remarkable synergistic effects of the large accessible surface area and high electrical conductivity of semiconductive Fe2O3, and the good film stability of CS. Based on the rich amino groups on CS, the CS–Fe2O3 hybrid film was employed as a functional matrix for probe DNA immobilization using terephthalaldehyde (TPA) as a bifunctional arm-linker. The hybridization capacity of the developed biosensor was evaluated with electrochemical impedance spectroscopy (EIS) using [Fe(CN)6]3−/4− as the indicating probe. A wide dynamic detection range from 1.0×10−14 to 1.0×10−10 M with ultralow detection limit of 5.6×10−15 M was achieved for the target DNA. The hybridization selectivity experiments further revealed that the biosensor could discriminate fully complementary sequences from one-base mismatched, three-base mismatched, and non-complementary sequences. Moreover, the biosensor showed the advantage of good regeneration ability and reproducibility.