Immunosensing of C-reactive protein in pleural fluid using electrodeposited silver nanoparticles

C-reactive protein (CRP) is a member of the acute phase reactants. CRP is generally used as a biomarker of inflammation and tissue injury. Here, CRP detection is performed in pleural fluid caused by pleural effusion. For this aim, Anti-CRP was conjugated on silver nanoparticle (AgNP)-modified electrodes to prepare immunosensors. To carry out AgNP electrodeposition, a novel ligand, mannose 4-aminophenyl L-alanine (Man-4APA), was synthesized and characterized using NMR and MS analysis. Then, AgNPs were synthesized in the presence of Man-4APA. After that, AgNPs/P (Man-4APA) was formed by electrodeposition on the electrodes. The success of the coating of the surfaces with AgNPs/P (Man-4APA) was confirmed using SEM and EDS analysis. Covalent conjugation was carried out between the amine groups of AgNPs/P (Man-4APA) and the carboxyl groups of Anti-CRP. The formation of the obtained amide bond was examined using XPS analysis. Using the designed AgNPs/P (Man-4APA)/Anti-CRP, the linear range for CRP was 0.5-100 ng/mL with a LOD of 0.38 ng/mL. After testing the effect of some potential interfering compounds on the current signal of AgNPs/P (Man-4APA)/Anti-CRP, the determination of CRP in pleural fluid collected from patients with pleural effusion was carried out successfully.