Development of C-Reactive Protein Immunosensor Using Thionine/Au Nanoparticles-Covalent Organic Framework-LZU8 as Label

In this paper, an ultrasensitive electrochemical immunoassay based on porous covalent organic framework materials and Au NPs-CoS/graphene oxide (GO) nanocomposite was developed for the detection of C-reactive protein (CRP). Au NPs-CoS/graphene oxide (GO) nanocomposite was synthesized, and employed as substrate because of their high conductivity to immobilize CRP antibody. A new porous covalent organic framework material (COF-LZU8) was functionalized by gold nanoparticles and doped with thionine (Thi) as the electron transfer mediator to obtain nanocomposite. The reduction peak signal of Thi/Au NPs-COF-LZU8 at –0.2 V could be directly detected by highly sensitive differential pulse voltammetry (DPV). Due to the high surface area of COF-LZU8, a great quantity of Thi could be adsorbed on the surface of COF, thus, the signal could be greatly amplified. Moreover, Thi/Au NPs-COF-LZU8 has strong adsorption capacity to the anti-CRP protein macromolecules due to the large specific surface area and good bio-affinity. The concentration of CRP antigen was proportional to the response current, so the quantitative detection of CRP was realized. Under the optimum conditions, the linear range of CRP was 0.05–150 ng/mL with the detection limit of 0.016 ng/mL (S/N = 3). This immunosensor provides a more effective and sensitive method for detection of CRP.