Vertically-Ordered Mesoporous Silica Film Based Electrochemical Aptasensor for Highly Sensitive Detection of Alpha-Fetoprotein in Human Serum

Abstract

Convenient and rapid detection of alpha fetoprotein (AFP) is vital for early diagnosis of hepatocellular carcinoma. In this work, low-cost (0.22 USD for single sensor) and stable (during 6 days) electrochemical aptasensor was developed for highly sensitive and direct detection of AFP in human serum with the assist of vertically-ordered mesoporous silica films (VMSF). VMSF has silanol groups on the surface and regularly ordered nanopores, which could provide binding sites for further functionalization of recognition aptamer and also confer the sensor with excellent anti-biofouling capacity. The sensing mechanism relies on the target AFP-controlled diffusion of Fe(CN)₆^3-/4- redox electrochemical probe through the nanochannels of VMSF. The resulting reduced electrochemical responses are related to the AFP concentration, allowing the linear determination of AFP with a wide dynamic linear range and a low limit of detection. Accuracy and potential of the developed aptasensor were also demonstrated in human serum by standard addition method.

Keywords: alpha fetoprotein; aptasensor; electrochemistry; vertically-ordered mesoporous silica films.

Figure 1

Schematic illustration for the fabrication of electrochemical aptasensing interface (a) and AFP detection (b).

Figure 2

Cross-sectional SEM (a) and top-view TEM (b) images of VMSF. (c) CV curves obtained at SM@VMSF/ITO and VMSF/ITO electrodes in 0.1 M KCl solution containing 2.5 mM K₃Fe(CN)₆/K₄Fe(CN)₆. (d) Nyquist plots of SM@VMSF/ITO and VMSF/ITO electrodes obtained in 0.1 M KCl solution containing 2.5 mM K₃Fe(CN)₆/K₄Fe(CN)₆.

Figure 3

CV curves (a) and EIS plots (b) of VMSF/ITO, O-VMSF/ITO, Apt/O-VMSF/ITO, BSA/Apt/O-VMSF/ITO and AFP/BSA/Apt/O-VMSF/ITO electrodes obtained in 0.1 M KCl containing 2.5 mM K₃Fe(CN)₆/K₄Fe(CN)₆. The concentration of AFP is 1 ng/mL.

Figure 4

Effect of coupling time for aptamer immobilization (a), aptamer concentration (b) and incubation time for AFP (c) on current signal value.

Figure 5

(a) DPV curves of the developed electrochemical aptasensor in the presence of different concentrations of AFP (1 pg/mL–1 μg/mL). (b) Corresponding calibration curve.

Figure 6

(a) Electrochemical responses of BSA/Apt/O-VMSF/ITO sensor to CEA, S-100, CA199, CA125, AFP or their mixture. I₀ and I denote the anodic peak current before (I₀) and after (I) incubation with AFP or other antigens and ΔI = I − I₀. The concentration of AFP and other proteins are 0.1 ng/mL and 1 ng/mL, respectively. (b) Anodic peak currents obtained at five different electrodes. (c) Stability of the developed electrochemical aptasensor after storage for different days. The concentration of AFP in (b,c) is 1.0 ng/mL.