Search

An electrochemical indirect competitive immunoassay protocol as a promising cytosensing strategy was developed to detect integrin β1 expression on human breast cancer MCF-7 cells and adriamycin-resistant human breast cancer MCF-7 (MCF-7/ADR) cells and quantify the cell number. Integrin α5β1 was adsorbed on the gold-nanoparticle modified glassy carbon electrode to bind integrin β1 monoclonal antibody (anti-CD29 mAb). A sandwich structure was then formed using nanocomposites which consisted of horseradish peroxidase (HRP) labeled anti-antibody and gold nanoparticles. HRP bound on the electrode surface could cause an amperometric response of the hydroquinone-H(2)O(2) system. The assembly of the sandwich structure was inhibited by tumor cells to give decreased enzyme-catalytic signals due to the capture of anti-CD29 mAb by integrin β1 on cell membranes. Under optimal conditions the relative current change (S) was proportional to the cell concentration from 1.6 × 10(3) to 2.0 × 10(6) cells mL(-1) with a detection limit of 700 cells mL(-1). Integrin β1 expression in MCF-7/ADR cells was found to be significantly higher than that in MCF-7 cells, indicating the increased adhesion ability of MCF-7/ADR cells.

Conducting polymer nanocomposites have attracted a wide attention in material chemistry and analytical chemistry. In this work, poly(methylene blue) doped silica nanocomposites (PMB@SiO2(nano)) on glassy carbon electrode (GCE) were synthesized based on a two-step electropolymerization. Compared with poly(methylene blue) film, PMB@SiO2(nano) had more advantages in facilitating electron transfer between glucose oxidase (GOx) and the electrode surface. GOx immobilized on PMB@SiO2(nano) underwent a direct and reversible electrochemical reaction involving two-electron and two-proton exchange. A reagentless glucose biosensor using the nanocomposite modified electrode was developed. The calibration curve was linear over a glucose concentration range of 0.01–1.11 mM with a correlation coefficient of 0.998 and a detection limit (3σ) of 3 μM. The apparent Michalis–Menten constant, Km, for the enzymatic reaction was 0.50 mM. The developed biosensor presented good accuracy, repeatability, reproducibility and stability as well as an excellent ability to resist interference from ascorbic acid and uric acid species. The investigation indicates that PMB@SiO2(nano) has a good potential for application in construction of the third-generation enzyme biosensor as a conducting matrix material.

The quartz crystal microbalance (QCM) dynamic measurements indicate that ginsenoside Rh(2) (G-Rh(2)) could inhibit the proliferation of adriamycin-resistant human breast cancer MCF-7 cells (MCF-7/ADR) in a concentration-dependent way. The combined treatment of G-Rh(2) with adriamycin (ADR) at non-effect dosage resulted in the higher inhibition efficiencies and the increased cell-death velocity, suggesting excellent ability of G-Rh(2) for reversal of multidrug resistance in MCF-7/ADR cells. The cytotoxic effect of the ADR-G-Rh(2) combination was evaluated with the modified Burgi formula (Jin equation) based on the QCM responses. It presented apparent synergism, indicating the potential ability of G-Rh(2) in tumor therapy. Fluorescent microscopic inspection and methyl thiazolyl tetrazolium (MTT) assay were also carried out and exhibited the comparable results to QCM analysis. The present work may lay an experimental foundation for the application of ginsenosides in cancer therapy, especial in multidrug resistance research.