title: Polymer-functionalized silica nanosphere labels for ultrasensitive detection of tumor necrosis factor-alpha.
abstract: A signal amplification strategy for sensitive detection of tumor necrosis factor-alpha (TNF-α) using quantum dots (QDs)-polymer-functionalized silica nanosphere as the label was proposed. In this approach, silica nanospheres with good monodispersity and uniform structure were employed as carriers for surface-initiated atom transfer radical polymerization of glycidyl methacrylate, which is readily available functional monomer that possessing easily transformable epoxy groups for subsequent CdTe QDs binding through ring-open reaction. Then, human anti rabbit TNF-α antibody (anti-TNF-α, Ab2, served as a model protein) was bonded to CdTe QDs-modified silica nanospheres coated with polymer to obtain QDs-polymer-functionalized silica nanosphere labels (Si/PGMA/QD/Ab2). The Si/PGMA/QD/Ab2 labels were attached onto a gold electrode surface through a subsequent "sandwich" immunoreaction. This reaction was confirmed by scanning electron microscopy (SEM) and fluorescence microscopic images. Enhanced sensitivity could be achieved by an increase of CdTe QD loading per immunoassay event, because of a large number of surface functional epoxy groups offered by the PGMA. As a result, the electrochemiluminescence (ECL) and square-wave voltammetry (SWV) measurements showed 10.0- and 5.5-fold increases in detection signals, respectively, in comparison with the unamplified method. The detection limits of 7.0 pg mL(-1) and 3.0 pg mL(-1) for TNF-α antibodies by ECL and SWV measurements, respectively, were achieved. The proposed strategy successfully demonstrated a simple, reproducible, specific, and potent method that can be expanded to detect other proteins and DNA.
authors.affiliation: State Key Laboratory of Bioelectronics, School of Chemistry and Chemical Engineering, Jiangning District, Southeast University, Nanjing, 211189, People's Republic of China.
authors.forename: Liang
authors.initials: L
authors.lastname: Yuan
authors.forename: Xin
authors.initials: X
authors.lastname: Hua
authors.forename: Yafeng
authors.initials: Y
authors.lastname: Wu
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Pan
authors.forename: Songqin
authors.initials: S
authors.lastname: Liu
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D019187:Cadmium Compounds / Q000737:chemistry; D055664:Electrochemical Techniques / Q000379:methods; D004566:Electrodes; D004852:Epoxy Compounds / Q000737:chemistry; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008163:Luminescent Measurements / Q000379:methods*; D008689:Methacrylates / Q000737:chemistry; D054118:Nanospheres / Q000737:chemistry* / Q000648:ultrastructure; D011108:Polymers / Q000737:chemistry*; D045663:Quantum Dots; D011817:Rabbits; D012822:Silicon Dioxide / Q000737:chemistry*; D013691:Tellurium / Q000737:chemistry; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis* / Q000276:immunology
chemical_list: D000906:Antibodies; D019187:Cadmium Compounds; D004852:Epoxy Compounds; D008689:Methacrylates; D011108:Polymers; D014409:Tumor Necrosis Factor-alpha; D012822:Silicon Dioxide; D013691:Tellurium; C007870:glycidyl methacrylate; C028337:cadmium telluride