3D-Ensembles of gold nanowires: preparation, characterization and electroanalytical prospects

Nanoelectrode ensembles (NEEs) of gold nanodisks, prepared by electroless template deposition of gold within the pores of track-etched polycarbonate membranes, are treated with oxygen plasma or with solvent mixtures in order to achieve controlled etching of part of the polycarbonate of the template. This causes the structure of the final ensemble to change from a 2-D flat structure into a 3-D one. The cyclic voltammetric (CV) behavior of redox probes at the 3DNEEs is examined and compared with the behavior observed at 2D-NEEs. Finally, 3D-NEEs are examined in order to test possible applications for the development of mediated sensors

Nanoelectrode ensembles as recognition platform for electrochemical immunosensors

In this study we demonstrate the possibility to prepare highly sensitive nanostructured electrochemical immunosensors by immobilizing biorecognition elements on nanoelectrode ensembles (NEEs) prepared in track-etch polycarbonate membranes. The gold nanodisk electrodes act as electrochemical transducers while the surrounding polycarbonate binds the antibody-based biorecognition layer. The interaction between target protein and antibody is detected by suitable secondary antibodies labelled with a redox enzyme. A redox mediator, added to the sample solution, shuttles electrons from the nanoelectrodes to the biorecognition layer, so generating an electrocatalytic signal. This allows one to fully exploit the highly improved signal-to-background current ratio, typical of NEEs. In particular, the receptor protein HER2was studied as the target analyte. HER2 detection allows the identification of breast cancer that can be treated with the monoclonal antibody trastuzumab. NEEs were functionalized with trastuzumab which interacts specifically with HER2. The biorecognition process was completed by adding a primary antibody and a secondary antibody labelled with horseradish peroxidase. Hydrogen peroxide was added to modulate the label electroactivity; methylene blue was the redox mediator generating voltammetric signals. NEEs functionalized with trastuzumab were tested to detect small amounts of HER2 in diluted cell lysates and tumour lysates

Functionalized ensembles of nanoelectrodes as affinity biosensors for DNA hybridization detection

A novel electrochemical biosensor for DNA hybridization detection based on nanoelectrode ensembles (NEEs) is presented. NEEs are prepared by electroless deposition of gold into the pores of a templating track-etched polycarbonate (PC) membrane. The wide surface of the templating membrane surrounding the nanoelectrodes is exploited to bind the capture DNA probes via amide coupling with the carboxylic groups present on the PC surface. The probes are then hybridized with the complementary target labelled with glucose oxidase (GO). The occurrence of the hybridization event is detected by adding, to the supporting electrolyte, excess glucose as the substrate and the (ferrocenylmethyl) trimethylammonium cation (FA) as suitable redox mediator. In the case of positive hybridization, an electrocatalytic current is detected. In the proposed sensor, the biorecognition event and signal transduction occur in different but neighbouring sites, i.e., the PC surface and the nanoelectrodes, respectively; these sites are separated albeit in close proximity on a nanometer scale. Finally, the possibility to activate the PC surface by treatment with permanganate is demonstrated and the analytical performances of biosensors prepared with KMnO4-treated NEEs and native NEEs are compared and critically evaluated. The proposed biosensor displays high selectivity and sensitivity, with the capability to detect few picomoles of target DNA

Genomewide Association Scan of Suicidal Thoughts and Behaviour in Major Depression

Background Suicidal behaviour can be conceptualised as a continuum from suicidal ideation, to suicidal attempts to completed suicide. In this study we identify genes contributing to suicidal behaviour in the depression study RADIANT. Methodology/Principal Findings A quantitative suicidality score was composed of two items from the SCAN interview. In addition, the 251 depression cases with a history of serious suicide attempts were classified to form a discrete trait. The quantitative trait was correlated with younger onset of depression and number of episodes of depression, but not with gender. A genome-wide association study of 2,023 depression cases was performed to identify genes that may contribute to suicidal behaviour. Two Munich depression studies were used as replication cohorts to test the most strongly associated SNPs. No SNP was associated at genome-wide significance level. For the quantitative trait, evidence of association was detected at GFRA1, a receptor for the neurotrophin GDRA (p = 2e-06). For the discrete trait of suicide attempt, SNPs in KIAA1244 and RGS18 attained p-values of <5e-6. None of these SNPs showed evidence for replication in the additional cohorts tested. Candidate gene analysis provided some support for a polymorphism in NTRK2, which was previously associated with suicidality. Conclusions/Significance This study provides a genome-wide assessment of possible genetic contribution to suicidal behaviour in depression but indicates a genetic architecture of multiple genes with small effects. Large cohorts will be required to dissect this further