Daliborka Jambrec

Doping Level of Boron-Doped Diamond Electrodes Controls the Grafting Density of Functional Groups for DNA Assays

The impact of different doping levels of boron-doped diamond on the surface functionalization was investigated by means of electrochemical reduction of aryldiazonium salts. The grafting efficiency of 4-nitrophenyl groups increased with the boron levels (B/C ratio from 0 to 20,000 ppm). Controlled grafting of nitrophenyldiazonium was used to adjust the amount of immobilized single-stranded DNA strands at the surface and further on the hybridization yield in dependence on the boron doping level. The grafted nitro functions were electrochemically reduced to the amine moieties. Subsequent functionalization with a succinic acid introduced carboxyl groups for subsequent binding of an amino-terminated DNA probe. DNA hybridization significantly depends on the probe density which is in turn dependent on the boron doping level. The proposed approach opens new insights for the design and control of doped diamond surface functionalization for the construction of DNA hybridization assays.

Potential-Assisted DNA Immobilization as a Prerequisite for Fast and Controlled Formation of DNA Monolayers.

Highly reproducible and fast potential-assisted immobilization of single-stranded (ss)DNA on gold surfaces is achieved by applying a pulse-type potential modulation. The desired DNA coverage can be obtained in a highly reproducible way within minutes. Understanding the underlying processes occurring during potential-assisted ssDNA immobilization is crucial. We propose a model that considers the role of ions surrounding the DNA strands, the distance dependence of the applied potentials within the electrolyte solution, and most importantly the shift of the potential of zero charge during the immobilization due to the surface modification with DNA. The control of the surface coverage of ssDNA as well as the achieved speed and high reproducibility are seen as prerequisites for improved DNA-based bioassays.

Amperometric Detection of dsDNA using an Acridine-Orange-Modified Glucose Oxidase

Invited for this months cover is the group of Prof. Dr. Wolfgang Schuhmann, Dr. Daliborka Jambrec and Dr. Adrian Ruff at Ruhr-Universität in Bochum, Germany. The cover picture shows a novel procedure for the preferential post-hybridization labeling of double-stranded DNA based on the intercalating compound acridine orange, which was covalently bound to glucose oxidase. Labeling with a highly active biocatalyst allows for a simple and sequence-independent amplification of the signal proportional to the amount of hybridized DNA that may be coupled with other amplification strategies. Read the full text of the article at 10.1002/cplu.201700279.