Quantitative lateral flow immunosensor using carbon nanotubes as label

Abstract

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 mg ml À1 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.

Achieving Ultra-Low Detection Limit Using Nanofiber Labels for Rapid Disease Detection

“…Several demonstrations confirming the possibilities of incorporating CNTs have been reported [11] [13]- [15]. However, the utilization of individual CNTs continues to pose a challenge due to signal repeatability and higher false-alarm rates.…”

“…This comparison study was based on an earlier findings by Abera et al using individual CNTs as label [11]. To highlight the signal amplification potential that NMBs are offering for low detection limit, similar tests were repeated using individual CNTs on our immunosensor.…”

“…The surfaces of NMB-IgG conjugates were coated with PEG. The formation of a polyethylene oxide chains resulted in a highly hydrophilic, neutrally charged, sterically hindering layer at the surfaces of the NMBs [11] [21] [22]. The PEG-coated NMB-IgG conjugates were reacted by IgG-FITC.…”

“…This method is incapable of producing quantitative analysis of the results and is also limited by high false-alarm rates leading to inconclusive or wrong diagnostics [8]. Fluorescent techniques also suffer from photo bleaching and the need for a sophisticated reader device [11]. In addition, an incubation period of at least few minutes is necessary prior to the fluorescence emission.…”

“…These labels are often designed to generate signals for optical detection using colorimetric or fluorescent techniques. Colorimetric detection while simple and cost-effective lacks in the high sensitivity required for early diagnosis [10] [11]. This method is incapable of producing quantitative analysis of the results and is also limited by high false-alarm rates leading to inconclusive or wrong diagnostics [8].…”