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Tehrān, Iran

Dadmehr M.,University of Tehran | Hosseini M.,University of Tehran | Hosseinkhani S.,Tarbiat Modares University | Reza Ganjali M.,University of Tehran | And 2 more authors.
Biosensors and Bioelectronics | Year: 2015

Epigenetic changes such as DNA methylation of CpG islands located in the promoter region of some tumor suppressor genes are very common in human diseases such as cancer. Detection of aberrant methylation pattern could serve as an excellent diagnostic approach. Recently, the direct detection of methylated DNA sequences without using chemical and enzymatic treatments or antibodies has received great deal of attentions. In this study, we report a colorimetric and fluorimetric technique for direct detection of DNA methylation. Here, the DNA is being used as an effective template for fluorescent silver nanoclusters formation without any chemical modification or DNA labeling. The sensitivity test showed that upon the addition of target methylated DNA, the fluorescence intensity is decreased in a linear range when the concentration of methylated DNA has increased from 2.0×10-9 to 6.3 ×10-7M with the detection limit of 9.4×10-10M. The optical and fluorescence spectral behaviors were highly reproducible and clearly discriminated between unmethylated, methylated and even partially methylated DNA in CpG rich sequences. The results were also reproducible when the human plasma was present in our assay system. © 2015 Elsevier B.V.

Borghei Y.-S.,University of Tehran | Hosseini M.,University of Tehran | Dadmehr M.,Payame Noor University | Hosseinkhani S.,Tarbiat Modares University | And 3 more authors.
Analytica Chimica Acta | Year: 2016

A simple but highly sensitive colorimetric method was developed to detect cancer cells based on aptamer-cell interaction. Cancer cells were able to capture nucleolin aptamers (AS 1411) through affinity interaction between AS 1411 and nucleolin receptors that are over expressed in cancer cells, The specific binding of AS 1411 to the target cells triggered the removal of aptamers from the solution. Therefore no aptamer remained in the solution to hybridize with complementary ssDNA-AuNP probes as a result the solution color is red. In the absence of target cells or the presence of normal cells, ssDNA-AuNP probes and aptamers were coexisted in solution and the aptamers assembled DNA-AuNPs, produced a purple solution. UV-vis spectrometry demonstrated that this hybridization-based method exhibited selective colorimetric responses to the presence or absence of target cells, which is detectable with naked eye. The linear response for MCF-7 cells in a concentration range from 10 to 105 cells was obtained with a detection limit of 10 cells. The proposed method could be extended to detect other cells and showed potential applications in cancer cell detection and early cancer diagnosis. © 2015 Elsevier B.V.

Dadmehr M.,University of Tehran | Hosseini M.,University of Tehran | Hosseinkhani S.,Tarbiat Modares University | Ganjali M.R.,University of Tehran | And 5 more authors.
Biosensors and Bioelectronics | Year: 2014

A very sensitive and convenient fluorescence nanobiosensor for rapid detection of DNA methylation based on Fe3O4/Au core/shell nanoparticles has been developed. Specific site of CpG islands of adenomatous polyposis coli (APC), a well studied tumor suppressor gene, was used as the detection target DNA sequence. The characteristics of nanoparticles were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-visible spectroscopy and X-ray diffraction (XRD) spectroscopy. Fe@Au nanoparticles functionalized by bounding of single stranded DNA (ssDNA) probe through sulfhydryl group at the 5' phosphate end. Then unmethylated and methylated complementary target ssDNA were hybridized with the immobilized ssDNA probe. Dipyridamole, a pharmaceutical agent used for the first time as a fluorescence probe which significantly interacted with hybridized unmethylated and methylated DNA. Upon the addition of the target unmethylated and methylated ssDNA, the fluorescence intensity increased in linear range by concentration of unmethylated ssDNA from 1.6×10-15 to 6.6×10-13M with detection limit of 1.2×10-16M and on the other hand, fluorescence intensity declined linearly with concentration of 3.2×10-15-8.0×10-13M methylated DNA and detection limit was 3.1×10-16M. We have also shown that nanobiosensor could distinguish ratio of methylation in series of partially methylated DNA targets with identical sequences. A density functional theory (DFT) calculation was also performed to investigate the interaction between Dipyridamole with unmethylated and methylated cytosine. Finally real sample analysis suggested that nanobiosensor could have practical application for methylation detection in human plasma sample. © 2014 Elsevier B.V.

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