Stable dispersions of azide functionalized ferromagnetic metal nanoparticles.

Ferromagnetic nanoparticles are covalently modified in order to enhance the dispersion stability as well as the antifouling properties. Insertion of an azide moiety allows "click"-reaction of a relevant tag molecule. This and the high saturation magnetization of the presented nanocomposite offer a promising platform for magnetic biosensors.

Silica particles with encapsulated DNA as trophic tracers.

Ecological networks such as food webs are extremely complex and can provide important information about the robustness and productivity of an ecosystem. In most cases, it is not feasible to observe trophic interactions between predators and prey directly and with the available methods, it is difficult to quantify the connections between them. Here, we show that submicron-sized silica particles (100-150 nm) with encapsulated DNA (SPED) enable accurate food and organism labelling and quantification of specific animal-to-animal transfer over more than one trophic level. We found that SPED were readily transferable and quantifiable from the bottom to the top of a two-level food chain of arthropods. SPED were taken up in the gut system and remained persistent in an animal over several days. When uniquely labelled SPED were applied at predefined ratios, we found that information about their relative abundance was reliably conserved after trophic level transfer and over time. SPED were also applied to investigate the flower preference of fly pollinators and proved to be a fast and accurate analysis method. SPED combine attributes of DNA barcoding and stable isotope analysis such as unique labelling, quantification via real-time PCR and exact backtracking to the tracer source. This improves and simplifies the analysis and monitoring of ecological networks.

DNA protection against ultraviolet irradiation by encapsulation in a multilayered SiO2/TiO2 assembly.

DNA is protected against UV-induced damage by encapsulation in a core-shell-shell particulate construct. The DNA is hermetically sealed in SiO2 particles coated with TiO2. The TiO2 coating acts as a physical sunscreen and prevents high energy photons from damaging the nucleic acids. DNA can be recovered unharmed from the protection system with fluoride comprising buffers, and then directly analyzed using biochemical standard techniques (quantitative PCR, gel electrophoresis and Sanger sequencing). The coatings increase the DNA UV resistance by 42 times, which is equivalent to the increase in UV resistance obtained by bacteria during sporulation. The attenuation coefficient of the 20 nm titania layer is 1.8 106 cm-1 at 254 nm UV irradiation and optical attenuation is largely attributed to light scattering on the titania surface.