Preparation of Label-free C-Reactive Protein Immunosensor Based on the Palladium-coordinated Covalent Organic Frameworks(Pd/COF-LZU1) Material†

doi:10.7503/cjcu20150344

Abstract

Abstract:

A new imine-linked covalent organic framework(COF) material was synthesized using organic monomer via solvothermal methods. Pd(Ⅱ)-coordinated COF, Pd/COF-LZU1, was accordingly synthesized through simple post-treatment at ambient conditions, which showed excellent catalytic activity. Then, a label-free C-reactive protein(CRP) immunosensor was constructed using the Pd/COF-LZUI porous composite material to immobilize anti-CRP on the surface of GCE. When anti-CRP binds with CRP antigen, the formed immuno complex obstruct the electric signal of Fe(CN)₆^4-/3-, which can be used to realize label-free detection of CRP. Electrochemical impedence spectroscopy(EIS) and differential pulse voltammetry(DPV) were employed to characterize the immunosensor. The experimental conditions such as scanning rate, pH value of testing solution, the concentration of anti-CRP and incubation time were also optimized. Under the optimal experimental conditions, the linear range was 5—180 ng/mL, the detection limit was 1.66 ng/mL, with the linear correlation coefficient of 0.992. This immunosensor provides a novel and simple way to detect CRP, and develops the application of the COFs in the electrochemical immunosensor.

Key words: Pd/covalent organic frameworks(COFs), C-Reactive protein(CRP), Immunosensor, Label-free

CLC Number:

O657.1

TrendMD:

LIU Tingzhi, XIA Jieren, LI Yao, CHEN Wenkai, ZHANG Shuai, LIU Yi, ZHENG Li, YANG Yunhui. Preparation of Label-free C-Reactive Protein Immunosensor Based on the Palladium-coordinated Covalent Organic Frameworks(Pd/COF-LZU1) Material^†[J]. Chem. J. Chinese Universities, 2015, 36(10): 1880.

Figures/Tables 14

Flow chart of the synthesis of COF-LZU1 and Pd/COF-LZU1

Scheme 2 Stepwise procedure of immunosensor

Fig.1 13C CP/MAS NMR spectrum of COF-LZU1

Fig.2 IR spectrum of COF-LZU1

Fig.3 PXRD patterns of COF-LZU1(a) and Pd/COF-LZU1(b)

Fig.4 TEM images of COF-LZU1(A, B) and Pd/COF-LZU1(C, D)

Fig.5 Differential pulse voltammetries(A) and electrochemical impedance spectroscopies(B) of different electrodesa. Pd/COF-LZU1/CHIT/GCE; b. Pd/CHIT/GCE; c. COF-LZU1/CHIT/GCE; d. bare GCE.

Fig.6 Electrochemical impedance spectroscopies(EIS) using different modified electrodes in 5 mmol/L [Fe(CN)6]4-/3- solutiona. Bare GCE; b. Pd/COF-LZU1/CHIT/GCE; c. anti-CRP/Pd/COF-LZU1/CHIT/GCE; d. CRP/anti-CRP/Pd/COF-LZU1/CHIT/GCE.

Fig.7 Electrochemical impedance spectroscopies of the immunosensor after incubated 40 μg/mL anti-CRP containing different concentrations of CRPConcentration of CRP/(ng·mL-1), a—i: 0, 5, 10, 20, 30, 60, 80, 100, 150.

Fig.8 CV curves of the immunosensor at various scan rates after incubated 40 ng/mL CRPScan rate/(mV·s-1), a—e: 20, 40, 60, 80, 100. Inset is plots of peak current vs. v1/2.

Fig.9 Influences of pH(A), concentration of anti-CRP(B)and CRP antigen incubation time(C) on the current responds of the immunosensor after incubated 40 ng/mL CRP

Fig.10 Calibration curve of immunosensor(A) and DPV response of different concentrations of CRP(B) Base solution: PBS(0.01 mol/L, pH=7.4) containing 0.5 mmol/L [Fe(CN)6]3-/4-.Concentration of CRP/(ng·mL-1): a—h. 0; 5; 30; 60; 90; 120; 150; 180.

Table 1 Selectivity of the immunosensor

Interferent	I_{interferent+CRP}/μA	I_CRP /μA	I_{interferent+CRP}/I_CRP
BSA	-3.748	-3.618	1.035
HCG	-3.821	-3.618	1.056
Gly	-3.501	-3.618	0.967
Glu	-3.815	-3.618	1.054

Table 2 Recovery of the immunosensor

Sample	Added/(ng·mL^-1)	Found/(ng·mL^-1)	Recovery(%)	Average recovery(%)
1	5.0	4.5	90.0
2	40.0	37.6	94.0	94.47
3	50.0	49.7	99.4

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