Xinhua Ma

Simultaneous and combined detection of multiple tumor biomarkers for prostate cancer in human serum by suspension array technology

Tumor markers (TMs) play an important role in clinical rapid screening and diagnosis for prostate cancer (PCa). In this study, we describe a competitive method to establish the multiplex suspension array by tumor biomarkers coated on distinguishable microbeads which competing with free biomarkers for their complementary antibodies (Ab) in one single reaction system for simultaneous and combined detection of prostate TMs in human serum. The volumes of the targets coupled onto the beads and their complementary Abs were optimized. The suspension array standard curves correlated well with PCa biomarkers (R(2)>0.9968). PCa biomarker levels were quantified using median fluorescent intensities. The working ranges of prostate-specific antigen (PSA), prostate stem cell antigen (PSCA), prostate-specific membrane antigen (PSMA) and prostatic acid phosphatase (PAP) were 0.47-502.94, 1.00-923.35, 1.00-524.79, and 1.73-176.07ngmL(-1) in serum samples, respectively. This method was compared to indirect competitive enzyme linked immunosorbent assay. It was found that high concordance between the two technologies resulted from serum samples of the eight PCa patients. The multiplex suspension array technology is specific to PCa biomarkers, displayed no significant cross-reactivity, and remains stable for 6 months. We also characterized the bead surface microstructures under different conditions employing a field emission scanning electron microscope. The suspension array is a straightforward and reliable method for analysis of multiple TMs with simple operation, high sensitivity at a low cost.

Simultaneous and rapid detection of multiple pesticide and veterinary drug residues by suspension array technology

Suspension array technology is proposed for the simultaneous quantitative determination of seven kinds of pesticide and veterinary drug residues, namely, atrazine, chloramphenicol, carbaryl, clenbuterol, 17-β-estradiol, imidacloprid, and tylosin. The assay is simple and can be accomplished within 2h without repeated pumping and washing steps unlike conventional suspension arrays. The hapten-protein conjugate-coated beads bind to their complementary biotinylated antibodies using a competitive immunoassay format. The coefficients of determination R(2) for six targets were greater than 0.992, whereas that for atrazine was 0.961, which indicate good logistic correlations. The dynamic ranges for the seven targets in the 7-plex assay ranged from 2 log units to 4 log units(1.60×10(0)-1.64×10(3), 5.12×10(-2)-1.60×10(2), 1.00×10(0)-3.13×10(3), 4.00×10(-1)-4.10×10(2), 4.00×10(-1)-4.10×10(2), 5.12×10(-2)-1.60×10(2), and 2.00×10(0)-4.00×10(2)ngmL(-1)). The minimum detection concentrations of chloramphenicol, carbaryl, clenbuterol and 17-β-estradiol in the suspension array (0.05, 1.00, 0.40 and 0.40 ng mL(-1)) were lower than the corresponding limits of detection (0.25, 6.60, 24.23 and 13.96 ng mL(-1)) of using an indirect competitive enzyme-linked immunosorbent assay. Environmental scanning electron microscope was employed to characterize the bead surface, which directly confirmed the reactions on the beads. The suspension array is more flexible and feasible than ELISA for the fast quantitative analysis of pesticide and veterinary drug residues.

A novel label-free fluorescence assay for one-step sensitive detection of Hg 2+ in environmental drinking water samples

A novel label-free fluorescence assay for detection of Hg2+ was developed based on the Hg2+-binding single-stranded DNA (ssDNA) and SYBR Green I (SG I). Differences from other assays, the designed rich-thymine (T) ssDNA probe without fluorescent labelling can be rapidly formed a T-Hg2+-T complex and folded into a stable hairpin structure in the presence of Hg2+ in environmental drinking water samples by facilitating fluorescence increase through intercalating with SG I in one-step. In the assay, the fluorescence signal can be directly obtained without additional incubation within 1 min. The dynamic quantitative working ranges was 5–1000 nM, the determination coefficients were satisfied by optimization of the reaction conditions. The lowest detection limit of Hg2+ was 3 nM which is well below the standard of U.S. Environmental Protection Agency. This method was highly specific for detecting of Hg2+ without being affected by other possible interfering ions from different background compositions of water samples. The recoveries of Hg2+ spiked in these samples were 95.05–103.51%. The proposed method is more viable, low-costing and simple for operation in field detection than the other methods with great potentials, such as emergency disposal, environmental monitoring, surveillance and supporting of ecological risk assessment and management.