Electrochemical Detection of Alpha-Fetoprotein Based on Black Phosphorus Nanosheets Modification with Iron Ions

Abstract

Black phosphorus nanosheets (BPNSs) were synthesized with liquid exfoliation combined with the ultrasonic method and loaded with Fe³⁺ by simply mixing. The morphology, structure and electrochemical properties of the synthesized Fe³⁺/BPNSs were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV), etc. The load of Fe³⁺ can improve the electrochemical performance of BPNSs and enhance the sensitivity of the detection. Additionally, Fe³⁺/BPNSs display good biocompatibility. In this study, immunosensors based on Fe³⁺/BPNSs were constructed to detect alpha-fetoprotein (AFP). The detection is due to the specific binding between the AFP antigen and antibody on the surface of the immunosensors, which can reduce the current response of Fe³⁺/BPNSs. The immunosensors have a good linear relationship in the range of 0.005 ng·mL^-1 to 50 ng·mL^-1, and the detection limit is 1.2 pg·mL^-1. The results show that surface modification with metal ions is a simple and effective way to improve the electrochemical properties of BPNSs, which will broaden the prospects for the future application of BPNSs in the electrochemical field.

Keywords: Fe3+; alpha-fetoprotein; black phosphorus nanosheets; electrochemical immunosensors.

Scheme 1

Schematic illustration of the electrochemical immunosensors for the detection of AFP.

Figure 1

(a) TEM and (b) SAED images of Fe³⁺/BPNSs; AFM images of (c) BPNSs and (d) Fe³⁺/BPNSs.

Figure 1

(a) TEM and (b) SAED images of Fe³⁺/BPNSs; AFM images of (c) BPNSs and (d) Fe³⁺/BPNSs.

Figure 2

(a) UV–vis absorption spectra of BPNSs, Fe³⁺/BPNSs and Fe³⁺. (b) Raman spectra of BPNSs and Fe³⁺/BPNSs. High-resolution XPS spectra of P element of (c) BPNSs and (d) Fe³⁺/BPNSs, O element of (e) BPNSs and (f) Fe³⁺/BPNSs, (g) Fe element of Fe³⁺/BPNSs.

Figure 3

(a) CV diagrams of BPNSs and Fe³⁺/BPNSs. (b) Cytotoxicity on Hacat cells after treatment with different concentrations of Fe³⁺/BPNSs.

Figure 4

(a) CV diagrams of BPNSs with different concentrations, (b) CV diagram and (c) EIS characterization of Fe³⁺/BPNSs loaded with different concentrations of Fe³⁺. a—0, b—0.005, c—0.01, d—0.05, e—0.1, f—0.2, h—0.4 mg·mL⁻¹. (d) Zeta potentials of BPNSs and Fe³⁺/BPNSs. CV diagrams of (e) Fe³⁺/BPNSs at different pH conditions. (f) Current differences at different antibody concentrations.

Figure 4

(a) CV diagrams of BPNSs with different concentrations, (b) CV diagram and (c) EIS characterization of Fe³⁺/BPNSs loaded with different concentrations of Fe³⁺. a—0, b—0.005, c—0.01, d—0.05, e—0.1, f—0.2, h—0.4 mg·mL⁻¹. (d) Zeta potentials of BPNSs and Fe³⁺/BPNSs. CV diagrams of (e) Fe³⁺/BPNSs at different pH conditions. (f) Current differences at different antibody concentrations.

Figure 5

(a) CV diagram of the build process and (b) Fourier infrared spectroscopy of Fe³⁺/BPNSs and Fe³⁺/BPNSs-Ab. (c) CV diagram of the immunosensors at a series of concentrations of AFP. (d) Linear relationship between logarithm of antigen concentration and current difference. (e) Comparison of current change with different interference factors.