Microswimmer-Based Ultrasensitive Dual-Signal Ratiometric Electrochemical Homogeneous Aptasensor with Functionalized Co-UiO-66 for the Single-Step Detection of HER2 in Whole Blood

The ability to efficiently detect trace disease biomarkers in whole blood remains an enormous challenge. Researchers have paid more attention to the homogeneous electrochemical ratio biosensor due to its self-calibration capability and improved detection accuracy. However, proportional homoge-neous electrochemical sensing is difficult to achieve and typically requires functional modification of the electrode or the preparation of complex materials. Herein, a dual-signal ratiometric aptamer homogeneous electrochemical microswimming detection device with active capture capability and one-step detection of human epidermal growth factor receptor-2 (HER2) is proposed. The homogeneous electrochemical biosensor is fabricated based on a functionalized nanocomposite double-stranded DNA({single-stranded DNA-ferrocene (Fc)-aptamer})@Co-UiO-66 with catalase properties and adsorptive properties to electroactive toluidine blue (TB) molecules. Encapsulation of Co-UiO-66 material with dsDNA (ssDNA-Fc-Apt) containing HER2 aptamer as a gate switch inhibited its ability to adsorb TB molecules. This functionalized Co-UiO-66 material can catalyze hydrogen peroxide. Using hydrogen peroxide as a fuel, it breaks down to release oxygen bubbles, creating a propulsion force that drives dsDNA(ssDNA-Fc-Apt)@Co-UiO-66 target HER2 through whole blood. When the surface dsDNA (ssDNA-Fc-Apt)@Co-UiO-66 recognizes HER2, a strand displacement reaction occurs, and the ssDNA-Fc is released into solution. The HER2 aptamer is coiled because it targets HER2, and the ability to adsorb TB molecules is restored due to the exposed surface of Co-UiO-66. A certain negative voltage is applied to the ITO electrode, and due to the electrostatic attraction, the TB molecules and ssDNA-Fc are adsorbed and enriched on the surface of the electrode by electrostatic attraction, which produces two strong and oppositely changing electrochemical signals, and the electrochemical signals depend on the HER2 concentration. It can sensitively detect HER2 biomarkers in only 40 min with the detection range of 0.0001-10 ng/mL and detection limits as low as 10 fg/mL. The electrochemical microswimmer for the detection of trace disease biomarkers involves a one-step process of capture, signal change, and detection.