Mesoporous (H(I)-ePt) platinum microelectrodes electrodeposited from the hexagonal (H(I)) lyotropic liquid crystalline phase are shown to be excellent amperometric sensors for the detection of hydrogen peroxide over a wide range of concentrations. Good reproducibility, high precision, and accuracy of measurements are demonstrated. Mesoporous microelectrodes retain the high rates of mass transport typical of conventional microelectrodes, and their high real surface area greatly enhances their catalytic activity. This unique combination of properties overcomes the limitations of previous amperometric hydrogen peroxide sensors and yields outstanding qualitative and quantitative results.

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We present a new type of DNA switch, based on the Holliday junction, that uses a combination of binding and conformational switching to enable specific label-free detection of DNA and RNA. We show that a single RNA oligonucleotide species can be detected in a complex mixture of extracted cellular RNA and demonstrate that by exploiting different aspects of the switch characteristics we can achieve 30-fold discrimination between single-nucleotide mismatches in a DNA oligonucleotide.

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Conformational transitions in a 4-way DNA junction when titrated with ionic solutions are studied using time-resolved fluorescence resonance energy transfer. Parameters characterising the transition in terms of critical ion concentration (c1/2) and the Hill coefficient for ion binding are obtained by fitting a simple two-state model using steady-state spectra. Data obtained from a fluorescence lifetime plate reader and analysed by fitting a single exponential to donor fluorescence lifetime decays are shown to be in good agreement with the parameters obtained from steady-state measurements. Fluorescence lifetimes, however, offer advantages, particularly in being independent of fluorophore concentration, output intensity, inhomogeneity in the excitation source and output wavelength. We demonstrate preliminary FRET-FLIM images of DNA junction solutions obtained using a picosecond gated CCD which are in agreement with results from a fluorescence lifetime plate reader. The results suggest that time-resolved FRET-FLIM is sensitive to subtle structural changes and may be useful in assays based on 4-way DNA junctions.

This work reports how the use of a standard integrated circuit (IC) fabrication process can improve the potential of silicon nitride layers as substrates for microarray technology. It has been shown that chemical mechanical polishing (CMP) substantially improves the fluorescent intensity of positive control gene and test gene microarray spots on both low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films, while maintaining a low fluorescent background. This results in the improved discrimination of low expressing genes. The results for the PECVD silicon nitride, which has been previously reported as unsuitable for microarray spotting, are particularly significant for future devices that hope to incorporate microelectronic control and analysis circuitry, due to the film's use as a final passivating layer.