Stability of the interface between indium-tinoxide and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) in polymer light-emitting diodes. Applied

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Healthcare is in demand of technologies for real-time sensing in order to continuously guard the state of patients. Here we present biomarker-monitoring based on the sensing of particle mobility, a concept wherein particles are coupled to a substrate via a flexible molecular tether, with both the particles and substrate provided with affinity molecules for effectuating specific and reversible interactions. Single-molecular binding and unbinding events modulate the Brownian particle motion and the state changes are recorded using optical scattering microscopy. The technology is demonstrated with DNA and protein as model biomarkers, in buffer and in blood plasma, showing sensitivity to picomolar and nanomolar concentrations. The sensing principle is direct and self-contained, without consuming or producing any reactants. With its basis in reversible interactions and single-molecule resolution, we envisage that the presented technology will enable biosensors for continuous biomarker monitoring with high sensitivity, specificity, and accuracy.

Assay technologies capable of detecting low biomarker concentrations in complex biological samples are fundamental for biological research and for applications in medical diagnostics. In this paper we address the challenge to perform protein biomarker detection homogeneously in one single step, applying a minute amount of reagent directly into whole human blood plasma, avoiding any sample dilution, separation, amplification, or fluid manipulation steps. We describe a one-step homogeneous assay technology based on antibody-coated magnetic nanoparticles that are spiked in very small amount directly into blood plasma. Pulsed magnetic fields and a double-linker molecular architecture are used to generate high biomarker-induced binding and low nonspecific binding between the nanoparticles. We demonstrate dose-response curves for prostate specific antigen (PSA) measured in undiluted human blood plasma with a detection limit of 400-500 femtomol/L, in a total assay time of 14 min and an optically probed volume of only 1 nL. We explain the dose-response curves with a model based on discrete binding of biomarker molecules onto the nanoparticles, which allows us to extract reaction parameters for the binding of biomarker molecules onto the nanoparticles and for the biomarker-induced binding between nanoparticles. The demonstrated analytical performance and understanding of the nanoparticle assay technology render it of interest for a wide range of applications in quantitative biology and medical diagnostics.

The sulfidation of disk-shaped MOO, particles with a thickness of 5-10 nm supported on a 5-nm-thick layer of Si02 on Si(100) in a mixture of 10% H2S in H2 at atmospheric pressure has been studied as a function of temperature. XPS and SIMS indicate the formation of Mo4+OS, at the surface and Mo(1V) oxides (probably H1.6Mo03 or MOO?) in the interior of the particles at temperatures between 20 and 100 OC, whereas MoS2 forms at temperatures of 125 OC and higher. Sulfur is present in two forms, as S2-and in a second form which is most probably Sz2-or SH-, but not elemental sulfur. The additional sulfur species disappear at temperatures between 150 and 200 OC. Rutherford backscattering analysis indicates S:Moatomicratios of 1-1.5 at sulfidation temperatures below 100 OC and of 2-2.5 above 100 OC. It is concluded that the sulfidation of Moo3 to MoS2 proceeds through a Mo(1V) oxysulfide, formed initially at the outside of the particle, and Mo(1V) oxide in the interior of the particle. Sulfidic species are believed to facilitate the reduction of Moo3 to Mo(1V) species at low temperatures.