Abstract
An external force-assisted near-field illumination biosensor (EFA-NI biosensor) detects a target substance that is propelled through an evanescent field by an external force. The target substance is sandwiched between an antibody coupled to a magnetic bead and an antibody coupled to a polystyrene bead. The external force is supplied by a magnetic field. The magnetic bead propels the target substance and the polystyrene bead emits an optical signal. The detection protocol includes only two steps; mixing the sample solution with a detection reagent containing the antibody-coated beads and injecting the sample mixture into a liquid cell. Because the system detects the motion of the beads, the sensor allows detection of trace amounts of target substances without a washing step. The detection capability of the sensor was demonstrated by the detection of norovirus virus-like particles at a concentration of ~40 particles per 100 μl in contaminated water.
Highlights
An ideal immunosensor that can overcome the limitations of the current methods should have a wide effective sensing area and detect trace amounts of target substances in the presence of non-specific adsorption
We examined the detection of normal mouse immunoglobulin G (NMIgG) by the EFA-NI biosensor using magnetic beads (MBs) coated with a rabbit anti-mouse IgG and optical signal beads coated with a donkey anti-mouse IgG
We examined the detection of norovirus virus-like particle (VLP) by the EFA-NI biosensor, using MBs coated with an anti-norovirus monoclonal antibody (12A11)[22] and polystyrene beads (PSBs) coated with an anti-norovirus polyclonal antibody
Summary
An ideal immunosensor that can overcome the limitations of the current methods should have a wide effective sensing area and detect trace amounts of target substances in the presence of non-specific adsorption. We developed an “external force-assisted near-field illumination biosensor” (EFA-NI biosensor). The EFA-NI biosensor detects target substances that are propelled through an evanescent field by an external force. Candidates for the application of external force include magnetic force, electric force, and gravity. In the work described in the present report, we employed magnetic force as the external force. The sensing area of the EFA-NI biosensor is not a surface, but a free space near the surface. Using “moving signals” for detection, signal from the target substance can be distinguished from noise. The EFA-NI biosensor has the advantages, but not the disadvantages, of surface-based sensing methods
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