Writing and Functionalisation of Suspended DNA Nanowires on Superhydrophobic Pillar Arrays

Nanowire arrays and networks with precisely controlled patterns are very interesting for innovative device concepts in mesoscopic physics. In particular, DNA templates have proven to be versatile for the fabrication of complex structures that obtained functionality via combinations with other materials, for example by functionalisation with molecules or nanoparticles, or by coating with metals. Here, the controlled motion of the a three‐phase contact line (TCL) of DNA‐loaded drops on superhydrophobic substrates is used to fabricate suspended nanowire arrays. In particular, the deposition of DNA wires is imaged in situ, and different patterns are obtained on hexagonal pillar arrays by controlling the TCL velocity and direction. Robust conductive wires and networks are achieved by coating the wires with a thin layer of gold, and as proof of concept conductivity measurements are performed on single suspended wires. The plastic material of the superhydrophobic pillars ensures electrical isolation from the substrate. The more general versatility of these suspended nanowire networks as functional templates is outlined by fabricating hybrid organic–metal–semiconductor nanowires by growing ZnO nanocrystals onto the metal‐coated nanowires.     

Ultrasmall Nanoplatforms as Calcium‐Responsive Contrast Agents for Magnetic Resonance Imaging

The preparation of ultrasmall and rigid platforms (USRPs) that are covalently coupled to macrocycle‐based, calcium‐responsive/smart contrast agents (SCAs), and the initial in vitro and in vivo validation of the resulting nanosized probes (SCA‐USRPs) by means of magnetic resonance imaging (MRI) is reported. The synthetic procedure is robust, allowing preparation of the SCA‐USRPs on a multigram scale. The resulting platforms display the desired MRI activity—i.e., longitudinal relaxivity increases almost twice at 7 T magnetic field strength upon saturation with Ca²⁺. Cell viability is probed with the MTT assay using HEK‐293 cells, which show good tolerance for lower contrast agent concentrations over longer periods of time. On intravenous administration of SCA‐USRPs in living mice, MRI studies indicate their rapid accumulation in the renal pelvis and parenchyma. Importantly, the MRI signal increases in both kidney compartments when CaCl₂ is also administrated. Laser‐induced breakdown spectroscopy experiments confirm accumulation of SCA‐USRPs in the renal cortex. To the best of our knowledge, these are the first studies which demonstrate calcium‐sensitive MRI signal changes in vivo. Continuing contrast agent and MRI protocol optimizations should lead to wider application of these responsive probes and development of superior functional methods for monitoring calcium‐dependent physiological and pathological processes in a dynamic manner.     

绿茶胶囊对黑巧克力中表儿茶素和儿茶素在人体内生物利用率的影响

以志愿者体内实验方式考察绿茶胶囊对黑巧克力中表儿茶素和儿茶素在人体内生物利用率的影响.六位志愿者在实验前一天严格执行低黄酮类饮食,空腹过夜并留下尿样作为空白样本.试验第一阶段:志愿者摄入50g黑巧克力(含表儿茶素152mg,儿茶素33mg).一周之后的第二阶段,志愿者摄入50g黑巧克力和一片绿茶胶囊(绿茶胶囊含表儿茶素207mg,儿茶素39mg).服用后每间隔一定时间,收集志愿者尿样,测定表儿茶素和儿茶素的生物利用率.结果显示,虽然第二阶段的表儿茶素和儿茶素摄入总量均高于第一阶段,但两者在第一阶段人体中的生物利用率均高于第二阶段.因此和单独摄入黑巧克力相比,绿茶胶囊和黑巧克力同时服用可能会导致减少或者延迟人体对表儿茶素和儿茶素的吸收.     

Tuning light emission of PbS nanocrystals from infrared to visible range by cation exchange

Colloidal semiconductor nanocrystals, with intense and sharp-line emission between red and near-infrared spectral regions, are of great interest for optoelectronic and bio-imaging applications. The growth of an inorganic passivation layer on nanocrystal surfaces is a common strategy to improve their chemical and optical stability and their photoluminescence quantum yield. In particular, cation exchange is a suitable approach for shell growth at the expense of the nanocrystal core size. Here, the cation exchange process is used to promote the formation of a CdS passivation layer on the surface of very small PbS nanocrystals (2.3 nm in diameter), blue shifting their optical spectra and yielding luminescent and stable nanostructures emitting in the range of 700–850 nm. Structural, morphological and compositional investigation confirms the nanocrystal size contraction after the cation-exchange process, while the PbS rock-salt crystalline phase is retained. Absorption and photoluminescence spectroscopy demonstrate the growth of a passivation layer with a decrease of the PbS core size, as inferred by the blue-shift of the excitonic peaks. The surface passivation strongly increases the photoluminescence intensity and the excited state lifetime. In addition, the nanocrystals reveal increased stability against oxidation over time. Thanks to their absorption and emission spectral range and the slow recombination dynamics, such highly luminescent nano-objects can find interesting applications in sensitized photovoltaic cells and light-emitting devices.     

Measuring institutional research productivity for the life sciences: the importance of accounting for the order of authors in the byline

Accurate measurement of institutional research productivity should account for the real contribution of the research staff to the output produced in collaboration with other organizations. In the framework of bibliometric measurement, this implies accounting for both the number of co-authors and each individual’s real contribution to scientific publications. Common practice in the life sciences is to indicate such contribution through the order of author names in the byline. In this work, we measure the distortion introduced to university-level bibliometric productivity rankings when the number of co-authors or their position in the byline is ignored. The field of observation consists of all Italian universities active in the life sciences (Biology and Medicine). The analysis is based on the research output of the university staff over the period 2004–2008. Based on the results, we recommend against the use of bibliometric indicators that ignore co-authorship and real contribution of each author to research outputs.     

Chronic fondaparinux use in a hemodialysis patient with heparin‐induced thrombocytopenia type II and extracorporeal circuit thrombosis—A case report and review of the literature

Heparin‐induced thrombocytopenia (HIT) is a potentially life‐threatening condition that can develop after exposure to unfractionated or low–molecular‐weight heparins. Treatment options appear to be limited in patients on concurrent intermittent hemodialysis. We report the case of an 88‐year‐old man newly initiated on high‐flux hemodialysis who developed HIT and extracorporeal circuit thrombosis after 3 weeks of exposure to unfractionated heparin. Our patient was successfully treated with fondaparinux 2.5 mg subcutaneously three times per week and citrate during dialysis sessions. Antifactor Xa levels were measured on several occasions while receiving fondaparinux.