A highly sensitive label-free electrochemical immunosensor based on AuNPs-PtNPs-MOFs for nuclear matrix protein 22 analysis in urine sample

A reliable and non-invasive electrochemical immunosensor for nuclear matrix protein 22 (NMP22) was presented based on reduced graphene oxide-tetraethylenepentamine (rGO-TEPA) and gold nanoparticles‑platinum nanoparticles-metal organic frameworks (AuNPs-PtNPs-MOFs) nanomaterial. rGO-TEPA is a promising template to enhance the loading ability of electrode for its large specific surface area and abundance in amino groups. AuNPs-PtNPs-MOFs nanomaterial was synthesized by NaBH4 reduction method and applied to immobilize biomolecules due to their good biocompatibility, well conductivity, and excellent H2O2 electrocatalytic ability. The electrochemical response signal was primarily originated from the obstruction of immobilized NMP22 antigen towards electrocatalytic reduction of H2O2 and the signal was recorded by differential pulse voltammetry. Under optimum conditions, the immunosensor showed a sensitive response towards NMP22 at a broad concentration range from 0.005 ng·mL−1 to 20 ng·mL−1. Two strong linear ranges could be observed at 0.005 ng·mL−1 to 0.5 ng·mL−1 (R2 = 0.9833), and 0.5 ng·mL−1 to 20 ng·mL−1 (R2 = 0.9909), with a low LOD of 1.7 pg·mL−1 (S/N = 3). Satisfactory reproducibility, stability and selectivity were obtained for NMP22 detection in real urine samples compared with standard ELISA assay, demonstrating the good analytical performance and potential non-invasive clinical application of this label-free electrochemical immunosensor.