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The purpose of this work was to fabricate an electrochemical DNA biosensor for detecting hepatitis B virus. Gold nanorods (GNRs), which are known for their conductivity, were used to increase surface area and consequently increase the immobilization of single-stranded DNA (ss-DNA) on the modified gold electrode. The GNRs were characterized via transmission electron microscopy. The morphology of the gold electrode before and after modification with GNRs was characterized by scanning electron microscopy. Atomic-force microscopy was used to evaluate the morphology of the GNR electrode surface before and after interaction with ss-DNA. Cyclic voltammetry was used to monitor DNA immobilization and hybridization, using [Co(phen)] as an electrochemical indicator. The target DNA sequences were quantified at a linear range from 1.0 × 10 to 10.0 × 10 mol L, with a detection limit of 2.0 × 10 mol L by 3 σ. The biosensor had good specificity for distinguishing complementary DNA in the presence of non-complementary and mismatched DNA sequences. [ABSTRACT FROM AUTHOR]

The application of rod‐shaped gold nanoparticles as probes and carriers in biological systems have recently attracted great interest. UV–vis spectroscopy, circular dichroism, Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy were used to study optical and structural properties of rod‐shaped gold nanoparticles when interacting with DNA oligomers in phosphate sodium salt buffer. The morphological transformation process of rod‐shaped gold nanoparticles resulting from the interaction with single‐stranded DNA (ssDNA) showed the role of hexadecyltrimethylammonium bromide (CTAB) in nanostructures as the main interacting agent. The obtained results confirmed that the CTAB coat of rod‐shaped gold nanoparticles have powerful positive charges for conjugations with surface negative charges of phosphate groups on ssDNA oligomers. The CTAB also inhibit the formation of covalent sulphide bonds between the gold core of rod‐shaped nanoparticles and alkanethiol oligonucleotides. The authors found that when the nanorods were exposed to ssDNA oligonucleotides, the gold nanorods changed their shapes and sizes, and exposed some microscopic malformations which could be used in the development of colorimetric assays of nucleic acids. [ABSTRACT FROM AUTHOR]

Objective: In recently air pollution is motivated by many agents and in the aerosol we can distinguish smallest airways, composed by biological particles, such as pollen grains and particulate of anthropogenic origin. During the last decade the size, shape, composition, sources and effect of these particle matters (PM) on human health have been studied by microscopic methods. Atomic force microscopy (AFM) is therefore a valuable complementary microscopy technique for the comparative study of the pollen grains surface morphology. The main goals of this research we investigated to characterize the elemental differences in the composition of the airborne ash pollen exine wall and to describe the particulate matter found adhered to this pollen in the Tehran, capital city of Iran, using an Energy Dispersive X-Ray analysis (EDX) on the SEM and Atomic force microscopy (AFM). Material and Methods: The first stage, pollen grains were collected in pollutant area (Tehran regions) and nonpollutant area (Parand city near the Tehran).Then used SEM/EDX for pollen grains analysis and advantages of two samples for AFM for the imaging of reside in the sticky PM on the ash pollen surface of the high spatial resolution, compared with SEM images, and the unique three-dimensional rendition of the exine surface topography, which avoids cross sectioning of the samples. Results: Images showed of exine units from the tectum of polluted and non- polluted pollen were done by AFM. These units of polluted sample showed were recorded adhered the PM in exine surface as being 250 to 300nm wide. This particle matter size is lower than PM2.5. We have obtained atomically resolved images on single aerosol particles in Tehran at the first on environmental biological samples. Conclusion: Our results showed AFM images method can be used for identifying pollen surface contamination and evaluation of PM size more exact and showed good agreement with light and electron microscopy micrographs. [ABSTRACT FROM AUTHOR]