A sensitive sandwich-type immunosensor for the detection of galectin-3 based on N-GNRs-Fe-MOFs@AuNPs nanocomposites and a novel AuPt-methylene blue nanorod

We are presenting an electrochemical immunosensor for the determination of Galectin-3 (Gal-3), a biomarker of heart failure. A glassy carbon electrode (GCE) was modified with a film of a composite made from the N-doped graphene nanoribbons immobilized Fe-based-Metal-organic frameworks deposited with Au nanoparticles (N-GNRs-Fe-MOFs@AuNPs). Primary antibody against Gal-3 (Gal-3-Ab 1 ) was immobilized on the Au nanoparticles on the surface of the modified GCE which then was blocked with bovine serum albumin . Signal amplification is crucial for obtaining low detection limits in biosensors. Here, a relatively simple and ultrasensitive sandwich-type electrochemical immunosensor based on novel signal generation and amplification was developed for the determination of Gal-3. A kind of novel redox-active species, AuPt-Methylene blue (MB) (AuPt-MB) nanocomposites , was synthesized by a one-pot method for the first time. Wherein, MB as a kind of the electron transfer mediators in an amperometric biosensor is responsible for electron production and signal amplification. The rod-like AuPt-MB nanohybrids displayed uniform morphology and good electrochemical activity and can combine with the second antibodies against Gal-3 (Gal-3-Ab 2 ). And the AuPt-MB-Ab 2 coupled with the N-GNRs-Fe-MOFs@AuNPs-Ab 1 to form the sandwich type format that can greatly enhance the biosensor's sensitivity. Under optimal conditions, the designed immunosensor exhibited a linear concentration range from 100   fg   mL −1 to 50   ng   mL −1 , with a low detection limit of 33.33   fg   mL −1 (S/N = 3) for Gal-3 in spiked serum. Additionally, the designed immunosensor showed acceptable selectivity, reproducibility and stability. The satisfactory results in analyzing human serum samples indicated potential application promising in monitoring biomarkers.