In immunoassays, non-specific bindings to biosensing surfaces can be effectively prevented by formation of biocompatible and hydrophilic self-assembled monolayer (SAM) on the surfaces. A thin gold (Au) layer on magnetic microspheres, 15 μm in diameter, enables facile SAM formation and thereby accepts second layer of filamentous virus scaffolds for the immobilization of functional proteins. The merger of the virus and SAM-Au protected microspheres not only provides exceptionlly dense antibody loading, but also resembles biological cellular structures that enhance ligand-receptor interactions. Site-specific biotinylation of filamenous viruses allows formation of free-standing virus threads (>1.0 × 1010) on streptavidin-modified SAM-Au microspheres. The augmented yield of antibody loading, due to the increased surface to volume ratio, on virus-modified Au microspheres is confirmed by measuring fluorescence intensities. The bead-based immunoassays for the detection of cardiac marker proteins exhibit increased sensitivity of virus-Au microspheres, as low as 20 pg mL−1 of cardiac troponin I in serum, and extremely low non-specific adsorption when compared with bare polymer beads. This increased sensitivity due to filamentous morphology and SAM-Au layer demonstrates the feasibility of merging viruses with non-biological materials to yield biomimetic tools for the enhanced bead-based immunoassays.
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