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In this work, a novel dot-blot DNAzyme-linked aptamer assay (DLAA) for protein detection is developed with thrombin as a model protein. A peroxidase-like DNAzyme which serves as the catalytic label is tethered to a 15-mer thrombin-binding aptamer to form a label-free DNAzyme-linked aptamer probe. Based on specific interaction of the aptamer with target protein immobilized on nitrocellulose membrane, a DNAzyme layer is introduced onto the membrane. The DNAzyme can catalyze the H(2)O(2)-mediated oxidation of 3,3',5,5'-tetramethylbenzidine to produce a colored insoluble product that is apt to be adsorbed onto the nitrocellulose membrane. As a result, blue dots appear on the membrane, in contrast to the colorless background. As the concentration of thrombin increases, the color of dots gets deep. Such a protein concentration-dependent color change can be quantified via an image-processing software, with a detection limit of 0.6 microM. Furthermore, this assay has been applied successfully to the detection of thrombin in biological samples (e.g., human serum), indicating its practicality for bioanalysis.

The pure titanium disks were divided into three groups and etched for 30 minutes with HNO3, hot H2SO4/H2O2 or hot H2SO4/HCl respectively. The treated disks were studied and analyzed with scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The disks etched with HNO3 had a smooth surface, while those etched with hot H2SO4/H2O2 or hot H2SO4/HCl had rough surfaces, and the surface etched with hot H2SO4/HCl had larger micropores. The XPS analysis demonstrated that the main elements of the surface in three groups were titanium, oxygen and carbon. The carbon concentration was the lowest on the surface etched with hot H2SO4/H2O2 and the highest on that etched with hot H2SO4/HCl. The substances were TiO2, Ti2O3, TiO and metal Ti on the surface etched with HNO3 or hot H2SO4/H2O2. Only TiO2 was detected on the surface etched with hot H2SO4/HCl.

The high SNR (Signal-to-Noise) spectra from 20 cases of gastric carcinoma and normal mucosa were obtained by confocal Raman microspectroscopy. Consistent spectral features were observed at different sites of one tissue slice for both typical tissues. Raman spectra of normal gastric mucosa shows two peaks which are assigned to amide I vibration of proteins in 1640-1670(cm(-1)) spectral region. However, in gastric carcinoma, only one peak of amino I vibrational mode of proteins can be observed. The obviously different spectral characters of the two types of tissues are in accordance to clinicopathologic diagnosis. The result shows Raman spectroscopy might be a potential method in the diagnosis of gastric carcinoma.

For the first time, the feasibility of a molecularly imprinted liquid phase deposition (LPD) thin film has been demonstrated. Thin films of titanium oxide imprinted with L-glutamic acid were prepared by the LPD method on a gold-coated quartz crystal microbalance. The imprinted molecule could be removed upon treatment with immersion in deionized water. A sensor was developed on the basis of this method and showed good sensitivity, selectivity, and reproducibility to the template molecule. An equation was deduced to characterize the interaction between molecularly imprinted films and the template by virtue of Scatchard analysis. X-ray photoelectron spectroscopy was introduced to show the evidence for the molecular imprinting phenomenon. The linear relationship between the frequency shifts and the concentration of analyte in the range of 10-200 microM was obtained. LPD proves to be a powerful method for imprinting titanium oxide thin films.