Kinetic and mechanistic studies on the formation of bis(dicarboxylato)carbonatochromate(III) complexes

The reaction of the Cr(xx)₂(H₂O)₂ ⁻ (xx = oxalate, malonate and methylmalonate) complexes with dissolved CO₂ was studied by stopped-flow spectrophotometry in the 7 < pH < 9 range and between 20 to 30°C at an ionic strength of 0.5 mol dm⁻³ (NaCl). Under the experimental conditions the aqua complex ion consists of a pH-dependent mixture of Cr(xx)₂(H₂O)₂ ⁻, Cr(xx)₂(OH) (H₂O)²⁻ and Cr(xx)₂(OH)₂ ³⁻. The monohydroxo and dihydroxo species undergo CO₂ uptake and subsequent intramolecular carbonate ligand chelation independently, at rates which are readily distinguishable and are governed by the uptake rate constants k ₁ and k ₂ and chelation rate constants k ₃ and k ₄, respectively. Only the k ₁ values for oxalato, malonato and methylmalonato complexes could be calculated; k ₁ = 1084 and 1333 and 1650 mol⁻¹ dm³ s⁻¹, respectively. The results obtained were compared with those obtained from other systems that have either cobalt(III), iridium(III) or rhodium(III) as central atoms. This revised version was published online in June 2006 with corrections to the Cover Date.     

Demonstration of a plasmonic thermocycler for the amplification of human androgen receptor DNA

A plasmonic heating method for the polymerase chain reaction is demonstrated by the amplification of a section of the human androgen receptor gene. The thermocycler has a simple low-cost design, demonstrates excellent temperature stability and represents the first practical demonstration of plasmonic thermocycling.     

Algal fluorescence sensor integrated into a microfluidic chip for water pollutant detection

We report the first miniaturized fluorescent sensor based on algae, with an organic light emitting diode (OLED) and an organic photodetector (OPD) integrated into a microfluidic chip. The blue emission OLED was used as the excitation source, while a blend of PTB3/PC(61)BM was used for the fabrication of the organic photodetector. Excitation and emission color filters based on acid/base dyes and a metal complex were developed and assembled with the organic optoelectronic components in order to complete the fluorescent detection system. The detection system was then integrated in a microfluidic chip made from (poly)dimethylsiloxane (PDMS). The complete sensor is designed to detect algal fluorescence in the microfluidic chamber. Algal chlorophyll fluorescence enables evaluation of the toxicity of pollutants like herbicides and metals-ions from agricultural run-offs. The entirely organic bioassay here presented allowed detection of the toxic effects of the herbicide Diuron on Chlamydomonas reinhardtii green algae that gave 50% inhibition of the algae photochemistry (EC(50)) with a concentration as low as 11 nM.     

Tuning the adhesion of layer-by-layer films to the physicochemical properties of inner limiting membranes using nanoparticles

Retinal trauma is a serious concern for patients undergoing inner limiting membrane (ILM) peeling to correct for various vitreoretinal interface conditions. This mechanical trauma can be prevented by modifying the surface of surgical instruments to increase adhesion to the ILM. To this effect, we have studied the effects of roughness and surface charge on the adhesive properties of ILMs by utilizing layer-by-layer (LbL) films with embedded gold nanoparticles (LbL-AuNP films). LbL films were assembled on atomic force microscopy (AFM) tipless cantilevers. Topographical analysis of these films, with and without nanoparticles, showed that LbL films with nanoparticles had a higher rms roughness compared to films alone or unmodified cantilevers. Nanoparticle-modified LbL films significantly increased the adhesion forces at the cantilever-ILM interface, compared to LbL films without particles. Surprisingly, adsorption of gold nanoparticles onto the AFM cantilevers caused increases in adhesion forces greater than those measured with LbL-AuNP films. These results have important implications for the design of surface modifications for vitreoretinal surgical instruments.