A novel immunosensor utilizing multi-walled carbon nanotube as label on a lateral flow system for simple and quantitative electrical detection was investigated. Multi-walled carbon nanotubes (MWCNTs) were first modified with polyvinylpyrrolidone (PVP) for uniform dispersion in aqueous solution. Then, the MWCNTs were conjugated with human immunoglobulin G (IgG) using 1-(3-(dimethylamino)-propyl)-3-ethylcarbodiimide hydrochloride (EDC) coupling chemistry. The lateral flow immunosensor was made of nitrocellulose membrane that transports sample and reagents through a porous structure by capillary action. The performance of the immunosensor was demonstrated using human IgG as a model analyte competing with the conjugate (MWCNT-labeled human IgG) at the capture zone. As a result of binding reaction between the conjugate and the immobilized Protein A at the capture zone, the conjugated MWCNTs formed a conducting network at the capture zone providing conductance measurement corresponding to the amount of captured conjugate. Quantitative immunoassay response for the target human IgG was demonstrated in the range of 25 to 200 μg ml~(-1) without an additional amplification step. The presented immunosensing technique could be expanded for the detection of various analyte-specific biomolecules with a potential for simple and rapid tests suitable for point-of-care diagnostics.
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