Label-free electrochemical impedance biosensor to detect human interleukin-8 in serum with sub-pg/ml sensitivity

Biosensors with high sensitivity and short time-to-result that are capable of detecting biomarkers in body fluids such as serum are an important prerequisite for early diagnostics in modern healthcare provision. Here, we report the development of an electrochemical impedance-based sensor for the detection in serum of human interleukin-8 (IL-8), a pro-angiogenic chemokine implicated in a wide range of inflammatory diseases. The sensor employs a small and robust synthetic non-antibody capture protein based on a cystatin scaffold that displays high affinity for human IL-8 with a KD of 35 ± 10 nM and excellent ligand specificity. The change in the phase of the electrochemical impedance from the serum baseline, ∆θ(ƒ), measured at 0.1 Hz, was used as the measure for quantifying IL-8 concentration in the fluid. Optimal sensor signal was observed after 15 min incubation, and the sensor exhibited a linear response versus logarithm of IL-8 concentration from 900 fg/ml to 900 ng/ml. A detection limit of around 90 fg/ml, which is significantly lower than the basal clinical levels of 5-10 pg/ml, was observed. Our results are significant for the development of point-of-care and early diagnostics where high sensitivity and short time-to-results are essential

Competitive interactions among three ectomycorrhizal fungi and their relation to host plant performance

1. Competition strongly influences many species assemblages, but its role in mycorrhizal fungal interactions is not well understood. We examined interactions among three ectomycorrhizal (ECM) species to determine if the structure of competition could be characterized by either competitive networks (where no clear hierarchy exists in the outcome of competition between various species pairs) or competitive hierarchies (where one species out competes all other species). 2. Using a bioassay experiment, we inoculated Pinus muricata seedlings with three Rhizopogon species (R. occidentalis, R. salebrosus, and R. vulgaris) in single-, two-, and three-species treatments. After 7 months, we assessed the relative abundance of each species in each treatment using real-time PCR of internal transcribed spacer rDNA. 3. We found that R. occidentalis was strongly inhibited by R. vulgaris and R. salebrosus in all competition treatments. In contrast, R. vulgaris and R. salebrosus had similar ECM biomasses in the two-species treatment, but R. vulgaris had significantly higher biomass than R. salebrosus in the three-species treatment. 4. In the single-species treatments, seedlings colonized by the competitive dominants had higher shoot biomass and total leaf nitrogen, but also higher percentage ECM biomass. In the multi-species treatments, seedlings had either equivalent or somewhat lower shoot biomass and total leaf nitrogen than their respective single-species treatments. 5. Synthesis. Our results indicate that ECM competition does not appear to be characterized by strict networks or hierarchies. Instead, the outcome is dependent on the conditions of the local environment in which it occurs. There also does not seem to be a clear relationship between ECM competitive ability and plant performance, but competition does appear to negatively affect the ability of ECM fungi to provide benefits to their hosts

Multi-scale assessment of macroinvertebrate richness and composition in Mediterranean-climate rivers

1. Similar constraints in distant, but climatically comparable, regions may be expected to yield biotic assemblages with similar attributes. Environmental factors that constrain communities at smaller scales, however, may be different between climatically similar regions. Thus, patterns observed at large scales may differ from those detected at small scales, and international comparisons should be focussed at multiple scales. 2. Mediterranean-climate regions (MCRs) are characterized by remarkable seasonal variability in precipitation and temperature. Accordingly, rivers in these regions have seasonal and predictable floods and droughts, and temporary reaches are frequent. Present in six geographical regions of the world, MCRs have similar environmental constraints and are ideal for testing intercontinental similarities between macroinvertebrate communities. 3. We examined aquatic macroinvertebrate taxon richness and composition in MCRs at three scales: regional, reach and macrohabitat. At the regional scale, the Mediterranean Basin had the highest taxon richness at family level, and southwestern Australia the lowest. Taxonomic composition showed c. 85% similarity between the northern hemisphere MCRs of California and the Mediterranean Basin, which were followed in similarity by South Africa. The two Australian MCRs (South west and South) showed a similarity to each other of about 70% whereas the Chilean fauna was the most distinct. 4. At the reach scale, taxon richness was not significantly different between permanent and temporary reaches in any MCR, whereas taxonomic composition was significantly different among northern hemisphere MCRs. At the macrohabitat scale, taxon richness was not significantly different between lotic and lentic macrohabitats within any of the MCRs, but differences in macroinvertebrate communities were found between macrohabitats when considering regions. 5. Our results show that the strength of similarity between distant but climatically similar regions is scale-dependent, being highest at the macrohabitat scale. Although the similarities in richness and composition at the macrohabitat scale are presumed to be universal, the seasonal predictability of drought in MCRs is expected to result in characteristic macroinvertebrate responses at the reach scale. We suggest, however, that regional evolutionary history and environmental characteristics may override this general pattern of a similar response of MCRs at different scales. The Mediterranean Basin and California, having similar historical and environmental condition, thus appeared as the most similar MCRs at all scales