Ultra-sensitive label-free detection of haptoglobin using Au-rGO decorated electrochemical sensing platform: Towards endometriosis diagnostic application

In this research, for the first time, one-step electrodeposition of simultaneously gold nanoparticles (AuNPs) and reduced graphene oxide (rGO) on the surface of a glassy carbon electrode (GCE) was used as a sensing platform of highly sensitive and label-free immunosensing for the rapid voltammetric analysis for haptoglobin (HP) at ultra-trace levels. 11-mecaptoundecanoic acid (11-MUA) was self-assembled onto Au substrate, which was coupled to the antibody (ab-HP) via ethyl-N’-(3-dimethyl aminopropyl) carbodiimide hydrochloride–N-hydroxysuccinimide (EDC-NHS) coupling. The interaction between the antigen (HP) and antibody (ab-HP) is measured by square wave voltammetry in [Fe (CN)6]3−/4− solution. The proposed immunosensor exhibits a concentration that ranges from 10 fg mL−1 to 1000 ng mL−1, and 3.47 fg mL−1 of low detection limit (LOD). Moreover, an immunosensor has high sensitivity, selectivity, reproducibility, stability, and reusability. Ultimately, this system was successfully applied for the detection of HP in different positive and negative serum samples (positive: n = 40, negative: n = 10), whereas negligible change was observed in control samples and was compared with commercial ELISA kits. The specificity and sensitivity of the assay were 100% and 98%, respectively. The coincidence rate using the HP ELISA kit was 95.30% and 92.20%. The result demonstrated that the sensing platform could be used for clinical diagnosis of HP in clinical laboratories.