This paper introduces the electrically detected displacement assay (EDDA), a electrical biosensor detection principle for applications in medical and clinical diagnosis, and compares the method to currently available microarray technologies in this field. The sensor can be integrated into automated systems of routine diagnosis, but may also be used as a sensor that is directly applied to the polymerase chain reaction (PCR) reaction vessel to detect unlabeled target amplicons within a few minutes. Major aspects of sensor assembly like immobilization procedure, accessibility of the capture probes, and prevention from nonspecific target adsorption, that are a prerequisite for a robust and reliable performance of the sensor, are demonstrated. Additionally, exemplary results from a human papillomavirus assay are presented.

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Sensible DNA: An electrochemical DNA assay based on specific Salmonella spp. capture probes and enzyme labeling with alkaline phosphatase was optimized by using a 48-electrode microarray and scanning electrochemical microscopy (SECM). SECM was further used to evaluate potential amplification strategies due to redox cycling. Due to insufficient detection limits and selectivity, electrochemical DNA sensors are not yet used as everyday tools in diagnostics. Here, we present an electrochemical DNA assay that is based on specific Salmonella spp. capture probes. Our optimization strategies and the specific features of related electrochemical DNA sensor arrays, which are comprised of a chip with 48 gold electrodes, are also described. A ssDNA monolayer is formed by chemisorption of the thiol-modified capture strand on the different gold electrodes of the array after spotting with a needle spotter. The assay parameters were optimized for the use of minimum amounts of sample and reagents and short assay times. Scanning electrochemical microscopy (SECM) has been used to visualize the local activity of an enzyme label used for amplified hybridization detection at high lateral resolution. The potential of SECM to further amplify the sensor signal by means of redox cycling is demonstrated by using single-stranded DNA capture probe modified gold microelectrodes as SECM tips. The detection limit of the proposed DNA sensor is shown to be in the femtomolar range without redox cycling amplification.

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Functional cellulose derivatives are very versatile materials for the creation of mono‐ and multilayer systems. Hydrophobic alkyl and trimethylsilyl celluloses form highly ordered Langmuir‐Blodgett multilayers on hydrophobic substrates. Cellulose thiosulfates and methyl thio ethers were self‐assembled on gold and silver surfaces to form hydrophilic monolayers. Cellulose layer systems are capable for chemical transformations under conservation of the structural order. They are suitable platforms for the investigation of molecular recognition at surfaces and the construction of sensor devices. Both biological ligands, e.g. biotin, and enzymes, e.g. horse radish peroxidase, could be attached to cellulose under conservation of their biological function.