Direct DNA Methylation Profiling with an Electric Biosensor.

DNA methylation is one of the principal epigenetic mechanisms that control gene expression in humans, and its profiling provides critical information about health and disease. Current profiling methods require chemical modification of bases followed by sequencing, which is expensive and time-consuming. Here, we report a direct and rapid determination of DNA methylation using an electric biosensor. The device consists of a DNA-tweezer probe integrated on a graphene field-effect transistor for label-free, highly sensitive, and specific methylation profiling. The device performance was evaluated with a target DNA that harbors a sequence of the methylguanine-DNA methyltransferase, a promoter of glioblastoma multiforme, a lethal brain tumor. The results show that we successfully profiled the methylated and nonmethylated forms at picomolar concentrations. Further, fluorescence kinetics and molecular dynamics simulations revealed that the position of the methylation site(s), their proximity, and accessibility to the toe-hold region of the tweezer probe are the primary determinants of the device performance.

Differential cytotoxicity and internalization of graphene family nanomaterials in myocardial cells.

Given the well-known physical properties of graphene oxide (GO), numerous applications for this novel nanomaterial have been recently envisioned to improve the performance of biomedical devices. However, the toxicological assessment of GO, which strongly depends on the used material and the studied cell line, is a fundamental task that needs to be performed prior to its use in biomedical applications. Therefore, the toxicological characterization of GO is still ongoing. This study contributes to this, aiming to synthesize and characterize GO particles and thus investigate their toxic effects in myocardial cells. Herein, GO particles were produced from graphite using the Tour method and subsequent mild reduction was carried out to obtain low-reduced GO (LRGO) particles. A qualitative analysis of the viability, cellular uptake, and internalization of particles was carried out using GO (~54% content of oxygen) and LRGO (~37% content of oxygen) and graphite. GO and LRGO reduce the viability of cardiac cells at IC50 of 652.1±1.2 and 129.4±1.2µg/mL, respectively. This shows that LRGO particles produce a five-fold increase in cytotoxicity when compared to GO. The cell uptake pattern of GO and LRGO particles demonstrated that cardiac cells retain a similar complexity to control cells. Morphological alterations examined with electron microscopy showed that internalization by GO and LRGO-treated cells (100µg/mL) occurred affecting the cell structure. These results suggest that the viability of H9c2 cells can be associated with the surface chemistry of GO and LRGO, as defined by the amount of oxygen functionalities, the number of graphitic domains, and the size of particles. High angle annular dark-field scanning transmission electron microscopy, dynamic light-scattering, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies were used to characterize the as-prepared materials.

Enhanced Enzymatic Activity of Laccase (from Pycnoporus sanguineus CS43) Immobilized on Sputtered Nanostructured Gold Thin Films.

Functionalization of thin films with organic ligands has been the subject of intense research due to their potential application as heterogeneous molecular nanosystems. In this work, self-assembled monolayers of thiols (16-mercaptohexadecanoic acid and 11-mercaptoundecanol) were used to bind laccase (from Pycnoporus sanguineus CS43) to nanostructured gold thin films obtained by DC sputtering. Sputtering power, sputtering pressure and substrate temperature were optimized to enhance the activity of the immobilized biomolecules. Scanning electron microscopy, confocal microscopy, X-ray diffraction and UV-vis spectroscopy were used to characterize the SAM-functionalized gold substrates. Our results demonstrate that the highest immobilized enzyme activity values can be achieved on substrates of surface roughness ˜200 nm and Au particle size of about 14 nm. The outstanding quality of the as-prepared substrates makes them particularly attractive as bionanosensors.

Fullerene thin films functionalized by 1,5-diaminonaphthalene: preparation and properties.

The gas-phase treatment with 1,5-diaminonaphthalene (DAN) is proposed as an efficient way of chemical functionalization of fullerene C60 thin films in order to modify their electronic properties; a temperature of 190 degrees C and reaction time of 4 h were found to be optimal reaction conditions. Two amino groups of DAN add on two neighboring C60 cages, thus producing cross-links in the fullerene phase. The resulting oligomeric and/or polymeric products exhibit a lower solubility in toluene as compared to pristine C60 films. The functionalized films exhibit lower surface roughness, as found by atomic force microscopy. Raman spectra keep, with some decrease in intensity, the most important features of C60 upon functionalization. The infrared band intensities corresponding to pristine fullerene decrease even stronger, where a number of new absorption bands appear not only due to DAN moieties, but also due to the covalently derivatized C60 cages. The diamine molecules are able to penetrate throughout the entire fullerene phase to provide an efficient and uniform functionalization. As a result, the DAN-functionalized films exhibit higher conductivity as compared to that of pristine films not only along the surface layer, but also through the entire phase of C60, by one and four orders of magnitude, respectively.