Amperometric immunosensor based on covalent organic frameworks and Pt/Ru/C nanoparticles for the quantification of C-reactive protein.

An ultrasensitive and nonenzymatic electrochemical sandwich-type immunoassay using covalent organic framework (COF-LZU1) material applied as a fixed matrix was developed for the determination of C-reactive protein (CRP). COFs with large specific surface area, good conductivity and stability were employed for functionalisation of the surface. Au nanoparticles were loaded on COF-LZUl to immobilise the CRP antibody (anti-CRP) on the surface of a glassy carbon electrode. Microwave method was employed for the synthesis of the Pt/Ru/C nanoparticles to imitate the protein enzyme with high catalytic activity. The as-synthesised activated carbon-supported bimetallic Pt/Ru/C nanoparticle composite was used to label secondary CRP antibody because it exhibited excellent catalytic behaviour toward hydrogen peroxide. After incubation of CRP, Pt/Ru/C-labelled anti-CRP was combined with CRP through specific antibody-antigen recognition process. The reduction current of H202 at - 0.2 V catalysing by tag Pt/Ru/C as measured by a chronoamperometric method is proportional to the concentration of CRP. Under optimal experimental conditions, employing chronoamperometry to investigate the CRP, the obtained linear range was 0.2 to 20 ng/mL with a detection limit of 0.1 ng/mL. This immunosensor provides an attractive platform for the applicability of COF-LZU1 materials and Pt/Ru/C nanoparticles in electrochemical assays. Graphical abstract An ultrasensitive and nonenzymatic electrochemical immunoassay using covalent organic frameworks (COF-LZU1) material as the fixed matrix was developed for the detection of C-reactive protein (CRP). Microwave method was employed to synthesis the bimetallic metal composites Pt/Ru/C nanoparticles, which exhibited excellent catalytic behavior toward small molecules H2O2. COFs with large specific surface area, good conductivity and stability were employed for surface functionalization. Our proposed biosensor is highly sensitive, with the detection limit of 0.1 ng/mL.