Ping Geng

Development of an electrochemical immunoassay for rapid detection of E. coli using anodic stripping voltammetry based on Cu@Au nanoparticles as antibody labels

A sensitive electrochemical immunoassay for rapid detection of Escherichia coli has been developed by anodic stripping voltammetry (ASV) based on core-shell Cu@Au nanoparticles (NPs) as anti-E. coli antibody labels. The characteristics of Cu@Au NPs before and after binding with antibody were confirmed by transmission electron microscopy (TEM). After Cu@Au-labeled antibody reacted with the immobilized E. coli on Polystyrene (PS)-modified ITO chip, Cu@Au NPs were dissolved by oxidation to the metal ionic forms, and the released Cu(2+) ions were determined at GC/Nafion/Hg modified electrode by ASV. The utilization of GC/Nafion/Hg modified electrode could enhance the sensitivity for Cu(2+) detection with a concentration as low as 9.0 x 10(-12)mol/L. Since Cu@Au NPs labels were only present when antibody reacted with E. coli, the amount of Cu(2+) directly reflected the number of E. coli. The technique could detect E. coli with a detection limit of 30CFU/mL and the overall analysis could be completed in 2h. By introducing a pre-enrichment step, a concentration of 3CFU/10mL E. coli in surface water was detected by the electrochemical immunoassay.

An electrochemical glycan biosensor based on a thionine-bridged multiwalled carbon nanotube/gold nanoparticle composite-modified electrode

Glycans that attached to glycoproteins on cell surfaces are known to be functionally important and they have potential diagnostic values. The development of effective methods to analyze glycan expression on living cell surface is desirable for understanding their functions in disease progression and providing a powerful tool for early diagnosis. In this paper, thionine-bridged multiwalled carbon nanotube/gold nanoparticle (MWCNT/Th/AuNP) as a mediator/nanomaterial composite was synthesized to develop an electrochemical biosensor for glycan assay on living cancer cells. The MWCNT/Th/AuNP composite was fabricated by binding AuNPs to the surface of Th-coated MWCNTs, in which thionine acted as a linker to enable the negatively charged AuNPs to bind to the anionic MWCNT surface. When compared with conventional nanomaterial-based electrochemical biosensors, the MWCNT/Th/AuNP-modified electrode contained thionine as an electron mediator and simplified the electrochemical process based on enzymatic catalysis for signal amplification. Under a sandwich-type assay format, the MWCNT/Th/AuNP-based biosensor facilitated highly sensitive and specific detection of mannose on human liver and prostate cancer cells and offered great promise for the analysis of other glycans on living cells by utilizing a greater variety of lectins.