High-Performance Voltammetric Aptasensing Platform for Ultrasensitive Detection of Bisphenol A as an Environmental Pollutant

Abstract

Bisphenol A (BPA) as a pervasive endocrine-disrupting compound (EDC) has been shown to cause multiple detrimental effects including cardiovascular disorders, pregnancy complications, obesity, glucose metabolism disorders, and reproductive toxicity even at a concentration as low as tolerable daily intake (TDI) (4 μg/kg/day). In the present study, a novel ultra-sensitive, electrochemical aptasensor was designed using a screen-printed carbon electrode (SPCE) modified by gold nanoparticles (Au NPs) conjugated to thiolated aptamers for accurate determination of BPA in biological, industrial and environmental samples. To characterize the electrochemical properties of the aptasensor, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were implemented. Detection of BPA was also performed through differential pulse voltammetry (DPV) in [Fe(CN)₆]^3-/4- electrolyte solution. Under optimum condition, the present electrochemical aptasensor demonstrated an outstanding linear response in the concentration range of 1 pM to 10 nM with a remarkably low limit of detection of 0.113 pM. Due to the superb affinity between anti-BPA aptamers and BPA molecules, the designed aptasensor did not show any significant interaction with other analytes in real samples. Also, fabricated biosensor remained perfectly stable in long-term storage. The analytical results of the fabricated aptasensor are well compatible with those obtained by the ELISA method, indicating the trustworthiness and reasonable accuracy of the application of aptasensor in real samples. Overall, the proposed aptasensor would be a credible and economical method of precise, reproducible, and highly selective detection of minimum levels of BPA in food containers and clinical samples. This would be a promising strategy to enhance the safety of food products and reduce the risk of BPA daily exposure.

Keywords: bisphenol A; electrochemical aptasensor; endocrine-disrupting compounds; environmental pollutant; toxicology.

SCHEME 1

The schematic representation of the electrochemical aptasensor fabrication procedure for the detection of BPA.

FIGURE 1

FESEM images of unmodified SPCE (A) and modified (AuNPs) SCPE (B) using electrodeposition method (5 mM HAuCl₄ in 0.5 M H₂SO₄; time: 200 s).

FIGURE 2

Cyclic voltammograms of the untreated SPCE (A), AuNPs/SPCE (B), aptamer/AuNPs/SPCE (C), MCH/aptamer/AuNPs/SPCE (D) and BPA (100 pM)/MCH/aptamer/AuNPs/SPCE (E) in 0.1 M PBS (pH 7.5) containing [Fe(CN)₆]^3–/4–/KCl (5 mM/0.1 M) electrolyte solution.

FIGURE 3

Nyquist spectra of EIS data for intact SPCE (A), AuNPs/SPCE (B), aptamer/AuNPs/SPCE (C), MCH/aptamer/AuNPs/SPCE (D) and BPA (100 pM)/MCH/aptamer/AuNPs/SPCE (E) in 0.1 M PBS (pH 7.4) containing [Fe(CN)₆]^3–/4–/KCl (5 mM/0.1 M) electrolyte solution. The Randles equivalent circuit was employed to model the electrochemical impedance data, (R_s: solution resistance; C_dl: double layer capacitance; R_ct: charge transfer resistance, W: Warburg impedance).

FIGURE 4

(A) DPV peaks of the fabricated aptasensor measuring various BPA concentrations [0, 1, 10, 50, 100 pM, 1 and 10 nM] in 0.1 M PBS (pH 7.5) containing [Fe(CN)₆]^3–/4–/KCl (5 mM/0.1 M) electrolyte solution. (B) BPA standard calibration curve in PBS (0.1 M), the error bars represent the standard deviation of three consecutive measurements.

FIGURE 5

Specificity evaluation of the proposed aptasensor for 100 pM BPA by comparing its DPV signals to 1 nM of well-known interfering agents, including 6F-BPA, HBPA, BPB, and estradiol and the mixture. Error bars represent standard deviations of three sets of parallel experiments.

FIGURE 6

The calibration curve of the designed aptasensor after incubation with various spiked concentrations of BPA in plasma samples. The inset depicts the linear relationship between DPV peak current response and BPA concentration. The error bars indicate the standard deviation of triplicate experiments.