Abstract
A dynamic micromotor-based immunoassay, exemplified by cortisol detection, based on the use of tubular micromotors functionalized with a specific antibody is described. The use of antibody-functionalized micromotors offers huge acceleration of both direct and competitive cortisol immunoassays, along with greatly enhanced sensitivity of direct and competitive immunoassays. The dramatically improved speed and sensitivity reflect the greatly increased likelihood of antibody-cortisol contacts and fluid mixing associated with the dynamic movement of these microtube motors and corresponding bubble generation that lead to a highly efficient and rapid recognition process. Rapid naked-eye detection of cortisol in the sample is achieved in connection to use of horseradish peroxidase (HRP) tag and TMB/H2O2 system. Key parameters of the competitive immunoassay (e.g., incubation time and reaction volume) were optimized. This fast visual micromotor-based sensing approach enables “on the move” specific detection of the target cortisol down to 0.1μgmL−1 in just 2min, using ultrasmall (50µL) sample volumes.
Highlights
Recent advances in nanomotors have paved the way to novel biosensing systems and applications
The micromotors used for detecting cortisol were fabricated by a standard membrane template electrodeposition method
The template-electrodeposition protocol consisted on electropolymerization of the EDOT monomer within the conical micropores of a polycarbonate (PC) membrane used as a template, followed by electrodeposition of Ni and the inner Pt layer (Fig. 2A (a)), and release of the resulting PEDOT/Ni/Pt micromotors by dissolving the membrane (Fig. 2A (b))
Summary
Recent advances in nanomotors have paved the way to novel biosensing systems and applications. Tubular micromotors functionalized with specific antibodies have been incorporated into lab-on-achip diagnostic devices demonstrating efficient recognition and isolation of the model protein IgG [10,11] Such direct “on-the-fly” recognition and isolation processes obviate the need for common sampling and washing procedures. The efficient movement of these micromotors and generated-microbubbles tail has been shown to enhance the fluid mixing of the sample and to greatly increase the analyte–receptor interactions toward faster and more sensitive assays [12,13,14] These dynamic sensing nanosystems have demonstrated important advantages to enhance target-bioreceptor interactions, which hold considerable interest for its implementation as medical diagnostic tools
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