Sensitive detection of cardiac troponin T based on superparamagnetic bead-labels using a flexible micro-fluxgate sensor

In this study, we describe an innovative micro-fluxgate immunosensor based on superparamagnetic Dynabeads for the detection of cardiac troponin T (cTnT), an important biomarker for cardiovascular diseases. The fluxgate sensor developed in this study uses a double layer of Co-based amorphous ribbons as a sensing element and three-dimensional solenoid copper coils to control the sensitive core. The system was fabricated through a standard micro-fabrication process, including thick photoresist lithography and electroplating. Superparamagnetic Dynabeads were employed as recognition tags and double polyclonal antibody pairs combined using streptavidin–biotin binding were employed to specifically capture and label the cTnT coupled with magnetic beads on a separate Au film-coated wafer via a classical sandwich immunoassay process. Series optimization of the assay parameters was performed to achieve optimal detection parameters. Under optimal conditions, the detection and quantification of cTnT was performed by sensing the magnetic signal of the cTnT-labeled Dynabeads with the micro-fluxgate sensor. The resulting biosystem successfully detected cTnT with satisfactory sensitivity, reproducibility, stability, and specificity. A minimum detectable limit of 0.01 ng mL−1 was achieved with a linearity range of 0.01–10 ng mL−1, demonstrating the high sensitivity of this novel system. In addition to the superior detection performance, the proposed sensor is convenient to manipulate, entirely lab-free, provides a quick result, and is portable. These factors suggest that this system has the potential to be applied as a point-of-care diagnostic tool for cardiovascular disease.