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ABSTRACT: Single-stranded DNA aptamers recognizing human hepatocarcinoma were isolated by means of a systematic evolution of ligands by exponential enrichment using whole cells as targets (cell-SELEX). After 11 rounds of cell-SELEX procedure using human hepatoma HepG2 cells as targets and human normal hepatocyte cells as counterparts, 12 independent DNA aptamer candidate sequences were obtained. The specific interaction between selected DNA aptamers and targeted cell was confirmed. Dissociation constants of the 12 sequences obtained were also estimated in the range of 19-450nM. Moreover, the consensus secondary structure was found in the isolated aptamers, which was responsible to the recognition of HepG2 cells.
Bioorganic & medicinal chemistry letters 03/2013; 23(6):1797-802. · 2.65 Impact Factor
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ABSTRACT: Atomic force microscopy (AFM) can dynamically detect the adhesion or affinity force between a sample surface and a cantilever. This feature is useful as a detection method using aptamers--single-strand DNA that recognizes its target with very high affinity. The present study proposes a novel DNA aptamer-based sensing system using AFM. In this study, thrombin was chosen as the target molecule, and a DNA aptamer-based AFM sensing system based on competition was developed. The affinity force between the gold chip and the cantilever decreased as the concentration of thrombin increased. Moreover, a low detection limit of 0.2 nM was achieved. Therefore, the AFM sensing system used would be appropriate for the measurement of various chemical compounds.
Journal of Bioscience and Bioengineering 08/2011; 112(5):511-4. · 1.79 Impact Factor
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ABSTRACT: Recently, our group discovered an alternative titanium dioxide (TiO(2)) activation method that uses ultrasound irradiation (US/TiO(2)) instead of ultraviolet irradiation. The pre-S1/S2 protein from hepatitis B virus, which recognizes liver cells, was immobilized to the surface of TiO(2) nanoparticles using an amino-coupling method. The ability of the protein-modified TiO(2) nanoparticles to recognize liver cells was confirmed by surface plasmon resonance analysis and immuno-staining analyses. After uptake of TiO(2) nanoparticles by HepG2 cancer cells, the cells were injured using this US/TiO(2) method; significant cell injury was observed at an ultrasound irradiation intensity of 0.4 W/cm(2). Together with these results, this strategy could be applied to new cell injuring systems that use ultrasound irradiation in place of photodynamic therapy in the near future.
Bioorganic & medicinal chemistry letters 09/2010; 20(17):5320-5. · 2.65 Impact Factor
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ABSTRACT: Atomic force microscopy (AFM) can detect the adhesion or affinity force between a sample surface and cantilever, dynamically. This feature is useful as a method for the selection of aptamers that bind to their targets with very high affinity. Therefore, we propose the Systematic Evolution of Ligands by an EXponential enrichment (SELEX) method using AFM to obtain aptamers that have a strong affinity for target molecules. In this study, thrombin was chosen as the target molecule, and an 'AFM-SELEX' cycle was performed. As a result, selected cycles were completed with only three rounds, and many of the obtained aptamers had a higher affinity to thrombin than the conventional thrombin aptamer. Moreover, one type of obtained aptamer had a high affinity to thrombin as well as the anti-thrombin antibody. AFM-SELEX is, therefore, considered to be an available method for the selection of DNA aptamers that have a high affinity for their target molecules.
Nucleic Acids Research 12/2009; 38(4):e21. · 8.03 Impact Factor
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ABSTRACT: DNA aptamers, which bind specific molecule, such as 8-OHdG, with high affinity were investigated using an in vitro selection strategy called systematic evolution of ligands by exponential enrichment (SELEX). However, 8-OHdG was difficult to immobilize on a carrier for SELEX. Therefore, a DNA aptamer binding to 8-OHdG was selected using GMP-agarose as an analogue from a library of about 4(60) random ssDNA sources. As a result, three aptamer candidates were selected. Among the selected DNA aptamers, the No. 22 DNA aptamer exhibited a high affinity for 8-OHdG. The dissociation constant, K(D), of No. 22 DNA aptamer was on the order of 0.1micromol/L. This result suggests that using an analogue will be a useful new SELEX method for obtaining various aptamers that are difficult to immobilize on a matrix.
Bioorganic & medicinal chemistry letters 06/2009; 19(13):3619-22. · 2.65 Impact Factor
