title: Carbon nanoparticle-enhanced immunoelectrochemical detection for protein tumor marker with cadmium sulfide biotracers.
abstract: We have developed a sensitive electrochemical immunoassay system for the detection of a protein tumor marker, carcinoembryonic antigen (CEA), that is based on a carbon nanoparticle (CNP)/poly(ethylene imine) (PEI)-modified screen-printed graphite electrode (CNP-PEI/SPGE) covered with anti-CEA antibodies. The signal amplification strategy--using CdS nanocrystals as biotracers and CNPs to enhance electron transfer--improves the sensitivity and detection limit for CEA, suggesting that this system holds promise for development into a point-of-care or disposable home-care self-diagnostic tool. This biosensor is based on a sandwich complex immunoassay, which we assembled from sequential layers of the anti-CEA antibody (alphaCEA) on CNP-PEI/SPGE, the CEA sample, and the CdS nanocrystal quantum dots (QDs) sensitized with alphaCEA (alphaCEA-CdS QD). We used square wave anodic stripping voltammetry (SWASV) to amplify the signal current response obtained from the dissolved alphaCEA-CdS QDs. The calibration curve for CEA concentration was linear in the range of 0.032-10 ng/mL; the detection limit (estimated as the mean of the blank sample plus three times the standard deviation obtained on the blank sample) was 32 pg/mL (equivalent to 160 fg in a 5 microL sample). This method is suitably precise and sensitive to function as a means of determining urinary CEA, which is a better marker than serum CEA for the early detection of urothelial carcinoma.
authors.affiliation: BioAnalytical Chemistry Laboratory, Department of Chemistry, National Tsing Hua University, Hsinchu, 30013 Taiwan. jaho@mx.nthu.edu.tw
authors.forename: Ja-an Annie
authors.initials: JA
authors.lastname: Ho
authors.forename: Yeh-Chun
authors.initials: YC
authors.lastname: Lin
authors.forename: Li-Sheng
authors.initials: LS
authors.lastname: Wang
authors.forename: Kuo-Chu
authors.initials: KC
authors.lastname: Hwang
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
mesh_terms: D055910:Antibodies, Immobilized / Q000737:chemistry / Q000276:immunology; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000737:chemistry / Q000276:immunology; D019187:Cadmium Compounds / Q000737:chemistry*; D002138:Calibration; D002244:Carbon / Q000737:chemistry*; D002272:Carcinoembryonic Antigen / Q000032:analysis* / Q000737:chemistry / Q000276:immunology; D004563:Electrochemistry; D004566:Electrodes; D006108:Graphite / Q000737:chemistry; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D011094:Polyethyleneimine / Q000737:chemistry; D045663:Quantum Dots; D013440:Sulfides / Q000737:chemistry*
chemical_list: D055910:Antibodies, Immobilized; D014408:Biomarkers, Tumor; D019187:Cadmium Compounds; D002272:Carcinoembryonic Antigen; D013440:Sulfides; C034939:cadmium sulfide; D002244:Carbon; D006108:Graphite; D011094:Polyethyleneimine