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This communication describes the synthesis of an electrochemically active oligonucleotide probe and its application in sensing complementary oligonucleotides sequences using a T7 exonuclease enzyme. Target oligonucleotides are detected by hybridisation with a ferrocene labelled probe oligonucleotide followed by addition of T7 exonuclease. The T7 enzyme is a double strand specific exonuclease that removes the terminal 5′ nucleotide of the probe sequence. The 5′ nucleotide is attached to a ferrocene label, which is subsequently detected at an electrode using differential pulse voltammetry. Time and temperature resolved measurements were performed and an associated study using dual labelled fluorophore–quencher labelled probes was performed to confirm the validity of the electrochemical assay. Keywords: DNA, Electrochemistry, T7 exonuclease

A novel two-photon-fluorescent N,O-heteroatom-rich carbon nanomaterial has been synthesized and characterized. The new carbon nanoparticles were produced by hydro-thermal conversion from a one-photon-fluorescent poly-(4-vinylpyridine) precursor (P4VP). The carbonized particles (cP4VP-dots) with non-uniform particle diameter (ranging from sub-6 nm to 20 nm with some aggregates up to 200 nm) exhibit strong fluorescent properties in different solvents and have also been investigated for applications in cell culture media. The cP4VP-dots retain their intrinsic fluorescence in a cellular environment and exhibit an average excited state lifetime of 2.0 ± 0.9 ns in cell. The cP4VP-dots enter HeLa cells and do not cause significant damage to outer cell membranes. They provide one-photon or two-photon fluorescent synthetic scaffolds for imaging applications and/or drug delivery.

A water-soluble boronate-based fluorescent probe was evaluated for the detection of peroxynitrite (ONOO−) in the presence of a monosaccharide. The enhanced fluorescence of the probe when bound with D-fructose was switched off in the presence of peroxynitrite. In contrast, other reactive oxygen/nitrogen species (ROS/RNS) led to only slight fluorescence decreases due to protection by an internal N–B interaction. The interaction of the probe with D-fructose not only strengthens the fluorescence signal, but also protects the boronic acid from oxidation by other ROS/RNS. Therefore, under conditions generating various ROS/RNS, the boronate-based saccharide complex preferentially reacts with peroxynitrite. The probe was used in cell imaging experiments for the detection of endogenous and exogenous peroxynitrite. The sensor displays good “on–off” responses towards peroxynitrite, both in RAW 264.7 cells and HeLa cells.

Integrated and insulated boronate-based fluorescent probes have been evaluated for the detection of hydrogen peroxide in the presence of saccharides.

Glycated proteins are important biomarkers for age-related disorders, however their analysis is challenging because of the complexity of the protein-carbohydrate adducts. Here we report a method that enables the detection and identification of individual glycated proteins in complex samples using fluorescent boronic acids in gel electrophoresis. Using this method we identified glycated proteins in human serum, insect hemolymph and mouse brain homogenates, confirming this technique as a powerful proteomics tool that can be used for the identification of potential disease biomarkers.