title: Ultrasensitive electrochemical immunosensor for oral cancer biomarker IL-6 using carbon nanotube forest electrodes and multilabel amplification.
abstract: Squamous cell carcinomas of head and neck (HNSCC) are associated with immune, inflammatory, and angiogenic responses involving interleukin-6 (IL-6). This article reports an ultrasensitive electrochemical immunosensor for human IL-6 and proof-of-concept studies of IL-6 detection in HNSCC cells. Single wall carbon nanotube (SWNT) forests with attached capture antibodies (Ab(1)) for IL-6 were used in an electrochemical sandwich immunoassay protocol using enzyme label horseradish peroxidase (HRP) to measure very low (<or=30 pg mL(-1)) and elevated levels of IL-6. Two levels of multienzyme labeling were used to measure a broad concentration range of IL-6 in a representative panel of HNSCC cells. Secondary antibodies (Ab(2)) attached to carboxylated multiwall carbon nanotubes with 106 HRP labels per 100 nm gave the highest sensitivity of 19.3 nA mL (pg IL-6)(-1) cm(-2) and the best detection limit (DL) of 0.5 pg mL(-1) (25 fM) for IL-6 in 10 microL of calf serum. For more concentrated samples, biotinylated Ab(2) bound to streptavidin-HRP to provide 14-16 labels per antigen was used. These immunosensors accurately measured secreted IL-6 in a wide range of HNSCC cells demonstrated by excellent correlations with standard enzyme-linked immunosorbent assays (ELISA), suggesting that SWNT immunosensors combined with multilabel detection have excellent promise for detecting IL-6 in research and clinical applications.
authors.affiliation: Department of Chemistry and Institute of Materials Science, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269, USA.
authors.forename: Ruchika
authors.initials: R
authors.lastname: Malhotra
authors.forename: Vyomesh
authors.initials: V
authors.lastname: Patel
authors.forename: Jose Pedro
authors.initials: JP
authors.lastname: Vaqué
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
authors.forename: James F
authors.initials: JF
authors.lastname: Rusling
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D015374:Biosensing Techniques; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis*; D045744:Cell Line, Tumor; D004566:Electrodes; D004797:Enzyme-Linked Immunosorbent Assay; D006258:Head and Neck Neoplasms / Q000175:diagnosis*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D015850:Interleukin-6 / Q000032:analysis*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D013194:Staining and Labeling
chemical_list: D014408:Biomarkers, Tumor; D015850:Interleukin-6; D037742:Nanotubes, Carbon