The Cvs of the Modified Immunosensor in the Solution of 0

Electronic supplementary material

1. Fig.1S Shows the SEM of nano-gold produced by electro-depositing HAuCl4.

Fig.1S The SEM of nano-gold

2. Electrochemical characteristics of the modified electrode at different scan rate.

The CVs of the modified immunosensor in the solution of 0.025 mol· L-1 PBS (pH 6.5) at different scan rates are shown in Figure 2S, the scan rates were from 40 to 230 mV·s -1. In addition, the peak current versus the square of root of sweep rate plot, shown in the inset, exhibits a linear relationship, suggesting that the reaction is a diffusion controlled process.

Fig.2S: Show CVs of the immunosensor at various scan rates (from inner to outer): 40, 60, 80, 100, 120, 140, 160, 180, 200 and 230 mV·s -1 in 0.025 mol· L-1 PBS (pH 6.5), respectively. Inset: plots of peak currents versus ν1/2.

3. Electrochemical impedance characterization of the modified electrode

The processes of modified electrode were characterized by using impedance measurements (EIS). The semicircle portion observed in the EIS spectrum, corresponds to the electron-transfer-limited process and a linear part at lower frequency range representing the diffusion limited process. The diameter of semicircle equals the electron-transfer resistance, Ret. Fig.3S shows the EIS of different modified electrode performed in the presence of a 2.5 mM Fe(CN)64−/3− as a redox probe in 0.025 M PBS. The bare GCE exhibited a small semicircle at high frequencies and a linear part at low frequencies, which implied the characteristic of a diffuse limiting step of the electrochemical process (Fig.3S a). After the PB film was electrodeposited on the bare GCE, the EIS of the resulting film showed a lower Ret (Fig.3S b), which indicated that PB is beneficial to the electrons transfer. Fig. 3S c shows the EIS of nano-gold/nano-CaCO3/PB modified electrode. The semicircle of curve c increased slightly compared with that of curve b, may be due to that the presence of nano-CaCO3 and the compactness and tightness film of electrode surface is not benefical for the transfer of electrons. When the anti-CEA was immobilized on the surface of electrode, the semicircle obviously increased (Fig.3S d).

Fig.3S

Fig.3S. EIS of the different electrodes: bare GCE (a); PB (b);nano-gold/ nano-CaCO3 /PB(c); anti-CEA / nano-gold / nano-CaCO3/PB(d) modified electrode. Supporting electrolyte, 0.025M PBS + 2.5 mM Fe(CN)64-/3- solution (pH 6.5).

3. Influence of the temperature on the immunsensor

Temperature is another important factor which affects the amperometric response signal. Fig.4S shows the changed amperometric response of the immunosensor incubated with 20 ng·mL-1 CEA at the temperature range from 15 ºC to 45 ºC. When the temperature added to 37 ºC, the amperometric response signal was optimal. But, considering the activity of the biomolecules and the stability of the immunosensor, the experiment was performed at room temperature.

Fig. 4S

Fig.4S: Show the effect of the temperature on the immunoreaction.

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