Impedimetric immunosensor for electronegative low density lipoprotein (LDL−) based on monoclonal antibody adsorbed on (polyvinyl formal)–gold nanoparticles matrix

Monoclonal antibodies (MAb) have been commonly applied to measure LDL in vivo and to characterize modifications of the lipids and apoprotein of the LDL particles. The electronegative low density lipoprotein (LDL−) has an apolipoprotein B-100 modified at oxidized events in vivo. In this work, a novel LDL− electrochemical biosensor was developed by adsorption of anti-LDL− MAb on an (polyvinyl formal)–gold nanoparticles (PVF–AuNPs)-modified gold electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to characterize the recognition of LDL−. The interaction between MAb–LDL− leads to a blockage in the electron transfer of the [Fe(CN)6]4−/K4[Fe(CN)6]3− redox couple, which may could result in high change in the electron transfer resistance (RCT) and decrease in the amperometric responses in CV analysis. The compact antibody–antigen complex introduces the insulating layer on the assembled surface, which increases the diameter of the semicircle, resulting in a high RCT, and the charge transferring rate constant κ0 decreases from 18.2 × 10−6 m/s to 4.6 × 10−6 m/s. Our results suggest that the interaction between MAb and lipoprotein can be quantitatively assessed by the modified electrode. The PVF–AuNPs–MAb system exhibited a sensitive response to LDL−, which could be used as a biosensor to quantify plasmatic levels of LDL−.