Jörg Albers

Electric chips for rapid detection and quantification of nucleic acids

A silicon chip-based electric detector coupled to bead-based sandwich hybridization (BBSH) is presented as an approach to perform rapid analysis of specific nucleic acids. A microfluidic platform incorporating paramagnetic beads with immobilized capture probes is used for the bio-recognition steps. The protocol involves simultaneous sandwich hybridization of a single-stranded nucleic acid target with the capture probe on the beads and with a detection probe in the reaction solution, followed by enzyme labeling of the detection probe, enzymatic reaction, and finally, potentiometric measurement of the enzyme product at the chip surface. Anti-DIG-alkaline phosphatase conjugate was used for the enzyme labeling of the DIG-labeled detection probe. p-Aminophenol phosphate (pAPP) was used as a substrate. The enzyme reaction product, p-aminophenol (pAP), is oxidized at the anode of the chip to quinoneimine that is reduced back to pAP at the cathode. The cycling oxidation and reduction of these compounds result in a current producing a characteristic signal that can be related to the concentration of the analyte. The performance of the different steps in the assay was characterized using in vitro synthesized RNA oligonucleotides and then the instrument was used for analysis of 16S rRNA in Escherichia coli extract. The assay time depends on the sensitivity required. Artificial RNA target and 16S rRNA, in amounts ranging from 10(11) to 10(10) molecules, were assayed within 25 min and 4 h, respectively.

Electrical microarrays for highly sensitive detection of multiplex PCR products from biological agents.

For the sensitive detection of amplicons derived from diagnostic PCR, a novel electrical low-density microarray is applied and compared to state-of-the-art quantitative real-time PCR. The principle of the electrochemical method and the effective use for analysis are described. Interdigitated array gold electrodes (IDA-E) embedded into a silicon chip are the core technology of the fully automated compact biosensor system, basing on enzyme coupled electrochemical detection. The biointerface is built up with thiol-modified capture oligonucleotides on gold and mediates the specific recognition of hybridised target DNA amplified with uniplex or multiplex PCR. In here we show the potential of the designed electrical microarray to function as an advanced screening method for the parallel detection of a panel of the four pathogens Bacillus anthracis, Yersinia pestis, Francisella tularensis and ortho pox viruses (genus), which are among the most relevant biowarfare agents. PCR products, generated from 10 to 50 gene equivalents, have been detected reproducibly. The experiments with varying pathogen amounts showed the good reliability and the high sensitivity of the method, equivalent to optical real-time PCR detection systems. Without PCR the total assay time amounts to 27 min. The advantage of the combination of multiplex-PCR with electrical microarray detection avoiding intensive PCR probe labelling strategies is illustrated.

Rapid detection of viruses using electrical biochips and anti-virion sera.

Aims:  Rapid detection and quantification of viruses is crucial in clinical practice, veterinary medicine, agriculture, basic research as well as in biotechnological factories. However, although various techniques were described and are currently used, development of more rapid, more sensitive and quantitative methods seems to be still important.

Functionalizing micro-cantilevers for meat degradation measurements

This paper presents an investigation of the functionalization of micro-cantilevers in order to bind to specific biogenic amines related to meat degradation, as for example cadaverine. The micro-cantilevers were functionalized with the compost 1,4,8,11 - tetraazacyclotetradecane (cyclam), which is binding to cadaverine molecules on gas phase. Different functionalization conditions were investigated, by immersing gold coated AFM cantilevers in cyclam solutions at different concentrations, for different functionalization times, and for different post-annealing treatments. The results show different morphologies for different conditions, and specific binding properties for different morphologies. The samples were exposed to gas phase cadaverine at different concentrations and to meat sample. Changes in resonance frequency of the cantilevers (due to mass increase by cadaverine binding) were measured using an atomic force microscope (AFM) and were in the range of few kHz, corresponding to a mass change of about 600 femtogram (for 4 seconds exposure to cadaverine).

rapid detection of different human anti-hcV immunoglobulins on electrical biochips

The detection of hepatitis C virus (HCV) in the blood of patients is currently based on immunological assays (enzyme-linked immunosorbent assay (ELISA) and recombinant immunoblot assay) that use different HCV epitopes to detect anti-HCV antibodies, and these tests usually require laboratories and trained personnel. The ELISA-based systems are also time consuming. Portable diagnostic devices offering rapid test results would therefore be advanta- geous in the field of medical care. To facilitate the fast and reliable diagnosis of HCV, we used a miniaturized automated system based on a cartridge with an integrated electrical biochip for the decentralized detection of anti-HCV antibodies against the Core, NS3, and NS4A proteins. This system allows the detection of virus-specific antibodies in 2 µL of serum or whole blood within 15 minutes using an ELISA directly on a gold electrode array containing HCV proteins as the capture antigen. The sensitivity of this system is comparable with standard microtiter plate ELISAs, but the duration of the novel assay is 5%-6% that of standard ELISAs.