A versatile-deployable bacterial detection system for food and environmental safety based on LabTube-automated DNA purification, LabReader-integrated amplification, readout and analysis.

Contamination of foods is a public health hazard that episodically causes thousands of deaths and sickens millions worldwide. To ensure food safety and quality, rapid, low-cost and easy-to-use detection methods are desirable. Here, the LabSystem is introduced for integrated, automated DNA purification, amplification and detection. It consists of a disposable, centrifugally driven DNA purification platform (LabTube) and a low-cost UV/vis-reader (LabReader). For demonstration of the LabSystem in the context of food safety, purification of Escherichia coli (non-pathogenic E. coli and pathogenic verotoxin-producing E. coli (VTEC)) in water and milk and the product-spoiler Alicyclobacillus acidoterrestris (A. acidoterrestris) in apple juice was integrated and optimized in the LabTube. Inside the LabReader, the purified DNA was amplified, readout and analyzed using both qualitative isothermal loop-mediated DNA amplification (LAMP) and quantitative real-time PCR. For the LAMP-LabSystem, the combined detection limits for purification and amplification of externally lysed VTEC and A. acidoterrestris are 10(2)-10(3) cell-equivalents. In the PCR-LabSystem for E. coli cells, the quantification limit is 10(2) cell-equivalents including LabTube-integrated lysis. The demonstrated LabSystem only requires a laboratory centrifuge (to operate the disposable, fully closed LabTube) and a low-cost LabReader for DNA amplification, readout and analysis. Compared with commercial DNA amplification devices, the LabReader improves sensitivity and specificity by the simultaneous readout of four wavelengths and the continuous readout during temperature cycling. The use of a detachable eluate tube as an interface affords semi-automation of the LabSystem, which does not require specialized training. It reduces the hands-on time from about 50 to 3 min with only two handling steps: sample input and transfer of the detachable detection tube.

Cyclic electrodeposition of PtCu alloy: facile fabrication of highly porous platinum electrodes.

Cyclic electrodeposition of platinum and copper enables the fabrication of high surface area electrodes (roughness factors of >3000) by multiple alternation of alloy co-deposition and dealloying of copper from the just-fabricated alloy layers. The underlying processes, resulting electrode structures, and their applicability to potentially implantable glucose fuel cells are discussed.

Strategies for the fabrication of porous platinum electrodes.

Porous platinum is of high technological importance due to its various applications in fuel cells, sensors, stimulation electrodes, mechanical actuators and catalysis in general. Based on a discussion of the general principles behind the reduction of platinum salts and corresponding deposition processes this article discusses techniques available for platinum electrode fabrication. The numerous, different strategies available to fabricate platinum electrodes are reviewed and discussed in the context of their tuning parameters, strengths and weaknesses. These strategies comprise bottom-up approaches as well as top-down approaches. In bottom-up approaches nanoparticles are synthesized in a fi rst step by chemical, photochemical or sonochemical means followed by an electrode formation step by e.g. thin fi lm technology or network formation to create a contiguous and conducting solid electrode structure. In top-down approaches fabrication starts with an already conductive electrode substrate. Corresponding strategies enable the fabrication of substrate-based electrodes by e.g. electrodeposition or the fabrication of self-supporting electrodes by dealloying. As a further top-down strategy, this review describes methods to decorate porous metals other than platinum with a surface layer of platinum. This way, fabrication methods not performable with platinum can be applied to the fabrication of platinum electrodes with the special benefit of low platinum consumption.

Carbon electrodes for direct electron transfer type laccase cathodes investigated by current density-cathode potential behavior.

Direct electron transfer from carbon electrodes to adsorbed laccase (EC 1.10.3.2) from Trametes versicolor is widely used to enable mediatorless enzymatic biofuel cell cathodes. However, data published so far are poorly comparable in terms of oxygen reduction performance. We thus present a comparative characterization of carbon-based electrode materials as cathode in half-cell configuration, employing adsorbed laccase as oxygen reduction catalyst. Open circuit potentials and performances were significantly increased by laccase adsorption, indicating the occurrence of direct electron transfer. At a potential of 0.5 V vs. SCE volume-normalized current densities of approximately 10, 37, 40, 70, and 77 µA cm(-3) were measured for cathodes nanotubes, carbon nanofibers and multi-walled carbon nanotubes, respectively. In addition, we could show that both, carbon nanotubes and porous carbon tubes exhibit dramatically lower current densities compared to graphite felt and carbon nanofibers when normalized to BET surface instead of electrode volume. Further work will be required to clarify whether this stems from material-dependent interaction of enzyme and electrode surface or constricted enzyme adsorption due to agglomeration of the nanotubes. In case of the latter, an improved dispersion of the nanotubes upon electrode fabrication may greatly enhance their performance.