Ultrasensitive capacitance sensor to detect amyloid-beta 1-40 in human serum using supramolecular recognition of β-CD/RGO/ITO micro-disk electrode

In this paper, we developed a new ultrasensitive capacitance sensor for detection of amyloid beta 1-40 (a beta 40) protein (one of Alzheimer's disease core biomarkers) in human serum based on the high supramolecular recognition of the beta-cyclodextrin/reduced graphene oxide (beta-CD/RGO) nanohybrid toward the anti-a beta 40 antibody molecule. The sensor was established by immobilizing specific anti-a beta 40 antibody onto the beta-CD/RGO nanohybrid functionalized on indium tin oxide micro-disk electrode (anti-a beta 40/beta-CD/RGO/ITO). Detection of a beta 40 in the human serum (HS) using the sensor anti-a beta 40/beta-CD/RGO/ITO is carried out by capacitance measurement without a redox probe to prevent protein denaturation, serving as a convenient strategy for point-of care diagnosis. In comparison with other studies, the sensor shows a very low limit of detection of 0.69 fg mL(-1) in HS, demonstrating its ability for the ultrasensitive detection of a beta 40. Using this sensor, the dissociation constant K-D of the binding interaction between anti-a beta 40 and a beta 40 in HS is found to be 2.9 x 10(-7) nM, indicating the high binding affinity of antibody-antigen and the suitability of the anti-a beta 40/beta-CD/RGO/ITO sensor for a beta 40 protein detection. The good selectivity of the anti-a beta 40/beta-CD/RGO/ITO sensor in the presence of differential analytes was also performed in this paper.