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Rostock, Germany

Biala K.,University at Albany | Biala K.,University of Rostock | Sedova A.,University at Albany | Flechsig G.-U.,University at Albany | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2015

Understanding complex contributions of surface environment to tethered nucleic acid sensing experiments has proven challenging, yet it is important because it is essential for interpretation and calibration of indispensable methods, such as microarrays. We investigate the effects of DNA sequence and solution temperature gradients on the kinetics of strand displacement at heated gold wire electrodes, and at gold disc electrodes in a heated solution. Addition of a terminal double mismatch (toehold) provides a reduction in strand displacement energy barriers sufficient to probe the secondary mechanisms involved in the hybridization process. In four different DNA capture probe sequences (relevant for the identification of genetically modified maize MON810), all but one revealed a high activation energy up to 200 kJ/mol during hybridization, that we attribute to displacement of protective strands by capture probes. Protective strands contain 4 to 5 mismatches to ease their displacement by the surface-confined probes at the gold electrodes. A low activation energy (30 kJ/mol) was observed for the sequence whose protective strand contained a toehold and one central mismatch, its kinetic curves displayed significantly different shapes, and we observed a reduced maximum signal intensity as compared to other sequences. These findings point to potential sequence-related contributions to oligonucleotide diffusion influencing kinetics. Additionally, for all sequences studied with heated wire electrodes, we observed a 23 K lower optimal hybridization temperature in comparison with disc electrodes in heated solution, and greatly reduced voltammetric signals after taking into account electrode surface area. We propose that thermodiffusion due to temperature gradients may influence both hybridization and strand displacement kinetics at heated microelectrodes, an explanation supported by computational fluid dynamics. DNA assays with surface-confined capture probes and temperature gradients should not neglect potential influences of thermodiffusion as well as sequence-related effects. Furthermore, studies attempting to characterize surface-tethered environments should consider thermodiffusion if temperature gradients are involved. © 2015 American Chemical Society.

Jacobsen M.,University of Rostock | Flechsig G.-U.,University of Rostock | Flechsig G.-U.,Gensoric GmbH
Electroanalysis | Year: 2013

We report about hybridization detection of different nucleic acids on capture probe-modified heated gold wire electrodes. We have compared three kinds of nucleic acid targets: DNA, uracil-conjugated DNA, and RNA. All three sorts of nucleic acids targets could be labeled with osmium tetroxide bipyridine, hybridized with immobilized DNA capture probes and then detected by square-wave voltammetry. Heating the gold electrode instead of the entire bulk hybridization solution leads to improved hybridization efficiency in most cases. The reason could be found in a thermal micro-stirring effect around the heated wire electrode. Also selectivity was improved. Mismatches could be discriminated for DNA and uracil-conjugated DNA targets. Mismatches in RNA strands, however, are more difficult to detect due to relatively stable secondary structures. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Walter A.,University of Rostock | Surkus A.-E.,University of Rostock | Flechsig G.-U.,University of Rostock | Flechsig G.-U.,Gensoric GmbH
Analytical and Bioanalytical Chemistry | Year: 2013

In this report we describe an electrochemical DNA hybridization sensor approach, in which signal amplification is achieved using heated electrodes together with an enzyme as DNA-label. On the surface of the heatable low temperature co-fired ceramic (LTCC) gold electrode, an immobilized thiolated capture probe was hybridized with a biotinylated target using alkaline phosphatase (SA-ALP) as reporter molecule. The enzyme label converted the redox-inactive substrate 1-naphthyl phosphate (NAP) into the redox-active 1-naphthol voltammetrically determined at the modified gold LTCC electrode. During the measurement only the electrode was heated leaving the bulk solution at ambient temperature. Elevated temperature during detection led to increased enzyme activity and enhanced analytical signals for DNA hybridization detection. The limit of detection at 53 C electrode temperature was 1.2 nmol/L. © 2013 Springer-Verlag Berlin Heidelberg.

Woldemichael G.,Adama Science and Technology University | Woldemichael G.,University of Rostock | Tulu T.,Adama Science and Technology University | Flechsig G.-U.,University of Rostock | Flechsig G.-U.,Gensoric GmbH
Microchimica Acta | Year: 2012

The article describes how solar ultraviolet-A radiation can be used to digest samples as needed for voltammetric ultratrace determination of uranium(VI) in river water. We applied adsorptive stripping voltammetry (AdSV) using chloranilic acid as the complexing agent. Samples from the river Warnow in Rostock (Germany) were pretreated with either soft solar UV or wit artificial hard UV from a 30-W source emitting 254-nm light. Samples were irradiated for 12 h, and both methods yielded the same results. We were able to detect around 1 μg·L -1 of uranium(VI) in a sample of river water that also contained dissolved organic carbon at a higher mg·L -1 levels. No AdSV signal was obtained for U(VI) without any UV pre-treatment. Pseudo-polarographic experiments confirmed the dramatic effect of both digestion techniques the the AdSV response. The new method is recommended for use in mobile ultratrace voltammetry of heavy metals for most kinds of natural water samples including tap, spring, ground, sea, and river waters. The direct use of solar radiation for sample pre-treatment represents a sustainable technique for sample preparation that does not consume large quantities of chemicals or energy. © 2012 Springer-Verlag.

Gensoric GmbH | Date: 2012-08-01

This invention relates to an electrochemical sensor (

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