A unique, sensitive, and highly specific fluoroimmunoassay system for antigen detection using quantum dot and gold nanoparticles has been developed. The assay is based on the fluorescence quenching of quantum dots caused by gold nanoparticles coated with antibody. To demonstrate its analytical capabilities, the quantum dots were coated with anti-HBsAg monoclonal antibodies (QDs-MAb1) and gold nanoparticles coated with another anti-HBsAg monoclonal antibodies (GNPs-MAb2) which specifically bound with HBsAg could sandwich the HBsAg captured by the immunoreactions. The sandwich-type immunocomplex was formed and the energy of quantum dots was transferred to gold nanoparticles as they were within a short distance, so that the fluorescence intensity of quantum dots was quenched. The fluorescence intensity of quantum dots at 570 nm was negative linear proportional to HBsAg concentration logarithm. The result showed that the limit of detection of the HBsAg was 0.928 ng/mL. This new system can be extended to detect target molecules with matched antibodies and has broad potential applications in immunoassay and disease diagnosis.

Herein we reported that polyamidoamine dendrimer (PAMAM) modified single walled carbon nanotubes (PSWCNTs) were successfully used for high efficient delivery and intracellular imaging of survivin siRNA vector. No.4 generation of PAMAM dendrimers were used to modify single walled carbon nanotubes, and characterized by high resolution transmission electron microscopy (HR-TEM), and atom force microscopy (AFM), survivin shRNA vectors were constructed and identified, and then dendrimer-modified SWCNTs were mixed with survivin shRNA vectors, resultant dendrimer-SWCNTs-survivin shRNA vector mixtures co-cultured with human gastric cancer MGC803 cells, then the expression of survivin shRNA vectors in MGC803 cells was observed by fluorescent microscopy, cell viability was analyzed by MTT method. Results showed that survivin shRNA vector was successfully expressed in MGC803 cells, and MGC 803 cell growth was markedly inhibited. In conclusion, dendrimer (PAMAM) modified single walled carbon nanotubes can be used for high efficient delivery and intracellular imaging of siRNA, and own great potential in applications such as gene or drug delivery and tumor targeted imaging and simultaneous therapy in near future.