Multiplexed electrochemical immunoassay using streptavidin/nanogold/carbon nanohorn as a signal tag to induce silver deposition.

An ultrasensitive multiplexed immunoassay method was developed by using streptavidin/nanogold/carbon nanohorn (SA/Au/CNH) as a novel signal tag to induce silver enhancement for signal amplification. The Au/CNH was prepared by in situ growth of nanogold on carboxylated CNH and functionalized with streptavidin. The SA/Au/CNH showed well dispersibility in physiological buffer and could sever as a common tracing tag to recognize biotinylated signal antibody.

Ratiometric electrochemical proximity assay for sensitive one-step protein detection.

This work proposes the concept of ratiometric electrochemical proximity assay (REPA), which can be used for one-step, highly sensitive and selective detection of protein. The assay strategy was achieved on a sensing interface that was formed by hybridization of methylene blue (MB)-labeled antibody-DNA probe (MB-DNA1-Ab1) with ferrocene (Fc)-labeled DNA capture probe (Fc-P) modified gold electrode. On the interface the target protein could trigger the formation of immunocomplex between MB-DNA1-Ab1 and detection antibody-DNA probe (Ab2-DNA2) and subsequently the proximity hybridization of DNA1-DNA2, which led to the departure of MB-DNA1-Ab1 from the interface.

Cellular delivery of quantum dot-bound hybridization probe for detection of intracellular pre-microRNA using chitosan/poly(γ-glutamic acid) complex as a carrier.

A quantum dot (QD)-bound hybridization probe was designed for detection of intracellular pre-miRNA using chitosan (CS)/poly(γ-glutamic acid) (γ-PGA) complex as a gene vector. The probe was prepared by assembling thiolated RNA to gold nanoparticle (Au NP) via Au-S bond and then binding 3'-end amine of the RNA to the carboxy group capped on quantum dot surface. The QD-RNA-Au NP probe was assembled on the vector by mixing with aqueous γ-PGA solution and then CS solution to construct a gene delivery system for highly effective cellular uptake and delivery.

Semiconductor quantum dots for biomedicial applications.

Semiconductor quantum dots (QDs) are nanometre-scale crystals, which have unique photophysical properties, such as size-dependent optical properties, high fluorescence quantum yields, and excellent stability against photobleaching. These properties enable QDs as the promising optical labels for the biological applications, such as multiplexed analysis of immunocomplexes or DNA hybridization processes, cell sorting and tracing, in vivo imaging and diagnostics in biomedicine. Meanwhile, QDs can be used as labels for the electrochemical detection of DNA or proteins.

Inhibition effect of siRNA-downregulated UHRF1 on breast cancer growth.

The UHRF1 gene plays important roles in both cell proliferation through its NIRF_N domains, a PHD domain, an SRA domain, and a RING domain, and multidrug resistance in breast cancer treatment. In this work, a short-hairpin RNA (shRNA) lentiviral system was introduced in two human breast cancer cell lines (MDA-MB-231 and MCF-7) to downregulate the expression of UHRF1 and study the specific inhibition of UHRF1 in breast cancer growth. The effect of UHRF1-shRNA on breast cancer cell proliferation was examined using methylthiazoletetrazolium, bromodeoxyuridine, and colony formation assays.

Disposable immunosensor array for ultrasensitive detection of tumor markers using glucose oxidase-functionalized silica nanosphere tags.

An ultrasensitive multiplexed electrochemical immunoassay method was developed for the detection of tumor markers by combining a newly designed trace tag and a disposable immunosensor array. The array was prepared by immobilizing capture antibodies on gold nanoparticles which were assembled on carbon nanotubes-chitosan modified screen-printed carbon electrodes. The trace tag was prepared by loading signal antibodies and high-content glucose oxidase on amino-functionalized silica nanosphere.

A rapid and simple method for ultrasensitive electrochemical immunoassay of protein by an electric field-driven strategy.

A sensitive, rapid and simple method for analysis of protein was proposed by introducing an electric field-driven technique to the incubation process of immunoassay and immobilizing horseradish peroxidase (HRP) labeled antibody in a newly designed gel matrix to construct an immunosensor. With an electric field-driven technique, the incubation for immuno-recognition could be completed within 2 min. The immobilized HRP showed excellent direct electrochemistry in this new gel matrix, and the detection procedure was greatly simplified by directly monitoring the sensitive electrochemical signal of HRP upon the immunoreaction.

Flow injection immunoassay for carcinoembryonic antigen combined with time-resolved fluorometric detection.

Time-resolved fluorescence has been developed for immunoassay to obtain higher sensitivity than usual immunoassays. In this paper, a simple, sensitive and specific method was developed for immunoassay of serum carcinoembryonic antigen (CEA) by combining time-resolved fluoroimmunoassay (TRFIA) and flow injection analysis. Based on a sandwich immunoassay format, a monoclonal antibody immobilized immunoaffinity column inserted in a flow system was used for immunoreactions.