A fully electrical array for voltammetric detection of redox molecules produced by enzyme-labeled affinity binding complexes is shown. The electronic detection is based on ultramicroelectrode arrays manufactured in silicon technology. The 200-microm circular array positions have 800-nm-wide interdigitated gold ultramicroelectrodes embedded in silicon dioxide. Immobilization of oligonucleotide capture probes onto the gold electrodes surfaces is accomplished via thiol-gold self-assembling. Spatial separation of probes at different array positions is controlled by polymeric rings around each array position. The affinity bound complexes are labeled with alkaline phosphatase, which converts the electrochemically inactive substrate 4-aminophenyl phosphate into the active 4-hydroxyaniline (HA). The nanoscaled electrodes are used to perform a sensitive detection of enzyme activity by signal enhancing redox recycling of HA resulting in local and position-specific current signals. Multiplexing and serial readout is realized using a CMOS ASIC module and a computer-controlled multichannel potentiostat. The principle of the silicon-based electrical biochip array is shown for different experimental setups and for the detection of virus DNA in real unpurified multiplex PCR samples. The fast and quantitative electronic multicomponent analysis for all kinds of affinity assays is robust and particle tolerant.

A novel innovative approach towards a marketable lab-on-chip system for point-of-care in vitro diagnostics is reported. In a consortium of seven Fraunhofer Institutes a lab-on-chip system called "Fraunhofer ivD-platform" has been established which opens up the possibility for an on-site analysis at low costs. The system features a high degree of modularity and integration. Modularity allows the adaption of common and established assay types of various formats. Integration lets the system move from the laboratory to the point-of-need. By making use of the microarray format the lab-on-chip system also addresses new trends in biomedicine. Research topics such as personalized medicine or companion diagnostics show that multiparameter analyses are an added value for diagnostics, therapy as well as therapy control. These goals are addressed with a low-cost and self-contained cartridge, since reagents, microfluidic actuators and various sensors are integrated within the cartridge. In combination with a fully automated instrumentation (read-out and processing unit) a diagnostic assay can be performed in about 15 min. Via a user-friendly interface the read-out unit itself performs the assay protocol, data acquisition and data analysis. So far, example assays for nucleic acids (detection of different pathogens) and protein markers (such as CRP and PSA) have been established using an electrochemical read-out based on redoxcycling or an optical read-out based on total internal reflectance fluorescence (TIRF). It could be shown that the assay performance within the cartridge is similar to that found for the same assay in a microtiter plate. Furthermore, recent developments are the integration of sample preparation and polymerase chain reaction (PCR) on-chip. Hence, the instrument is capable of providing heating-and-cooling cycles necessary for DNA-amplification. In addition to scientific aspects also the production of such a lab-on-chip system was part of the development since this heavily affects the success of a later market launch. In summary, the Fraunhofer ivD-platform covers the whole value chain ranging from microfluidics, material and polymer sciences, assay and sensor development to the production and assembly design. In this consortium the gap between diagnostic needs and available technologies can be closed.

Based on electrical biochips made in Si-technology cost effective portable devices have been constructed for field applications and point of care diagnosis. These miniaturized amperometric biosensor devices enable the evaluation of biomolecular interactions by measuring the redox recycling of ELISA products, as well as the electrical monitoring of metabolites. The highly sensitive redox recycling is facilitated by interdigitated ultramicroelectrodes of high spatial resolution. The application of these electrical biochips as DNA microarrays for the molecular diagnosis of viral infections demonstrates the measurement procedure. Self-assembling of capture oligonucleotides via thiol-gold coupling has been used to construct the DNA interface on-chip. Another application for this electrical detection principle is continuous measuring with bead-based biosensors. Here, paramagnetic nanoparticles are used as carriers of the bioanalytical interface in ELISA format. A Si-micromachined glucose sensor for continuous monitoring in interstitial fluid ex vivo shows the flexibility of the electrical platform. Here the novel approach is a pore membrane in micrometer-dimensions acting as a diffusion barrier. The electrochemical detection takes place in a cavity containing glucose oxidase and a Pt-electrode surface. The common hydrogen peroxide detection, together with Si technology, enable precise differential measurements using a second cavity.

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Meat spoilage is a result of an increase in the number of microorganisms and increased levels of biogenic amines (e.g. cadaverine). Destruction of non-spoiled meat products results in substantial waste of resources each year. Currently, the expiration date of meat-products is determined by either subjective sensory and/or expensive and time-consuming microbiological analysis. Cadaverine levels have been demonstrated to be related to the product freshness; however current sensing methods require bulky and expensive chromatography techniques. In this work, the cadaverine binding to a functionalization layer of cyclam (1,4,8,11-tetraazacyclotetradecane) is demonstrated by a systematic study of cyclam/solvent solution influence on morphology and binding. The degradation of the functionalization layer due to storage conditions has also been investigated, and the optimum solvent for the functionalization solution is found to be ethoxyethanol. Functionalized surfaces and cantilevers have been exposed to different types of meat (beef, fish, chicken or pork) and the cadaverine binding has been demonstrated, either by morphology changes (surfaces) or by changes on cantilever resonance frequency due to mass increase (cantilever). The results show a higher cadaverine emission rate for fish, followed by chicken, beef and finally pork.