Noble metal nanoparticles networks stabilized by rod-like organometallic bifunctional thiols

Rod-like organometallic dithiol containing square-planar Pt(II) centers, i. e., trans,trans-[(H3COCS)Pt(PBu3)(2)(C equivalent to C-C6H4-C6H4-C equivalent to C)(PBu3)(2)Pt(SCOCH3)] was used as bifunctional stabilizing agent for the synthesis of Pd-, Au-, and AgNPs (MNPs). All the MNPs showed diameters of about 4 nm, which can be controlled by carefully modulating the synthesis parameters. Covalent MNPs stabilization occurred through a single S bridge between Pt(II) and the noble metal nanocluster surfaces, leading to a network of regularly spaced NPs with the formation of dyads, as supported by SR-XPS data and by TEM imaging analysis. The chemical nature of NPs systems was also confirmed by EDS and NMR. Comparison between SR-XPS data of MNPs and self-assembled monolayers and multilayers of pristine rod-like dithiols deposited onto polycrystalline gold surfaces revealed an electronic interaction between Pt(II) centers and biphenyl moieties of adjacent ligands, stabilizing the organic structure of the network. The possibility to obtain networks of regularly spaced MNPs opens outstanding perspectives in optoelectronics

Noble metal nanoparticles networks stabilized by rod-like organometallic bifunctional thiols

Rod-like organometallic dithiol containing square-planar Pt(II) centers, i. e., trans,trans-[(H3COCS)Pt(PBu3)(2)(C equivalent to C-C6H4-C6H4-C equivalent to C)(PBu3)(2)Pt(SCOCH3)] was used as bifunctional stabilizing agent for the synthesis of Pd-, Au-, and AgNPs (MNPs). All the MNPs showed diameters of about 4 nm, which can be controlled by carefully modulating the synthesis parameters. Covalent MNPs stabilization occurred through a single S bridge between Pt(II) and the noble metal nanocluster surfaces, leading to a network of regularly spaced NPs with the formation of dyads, as supported by SR-XPS data and by TEM imaging analysis. The chemical nature of NPs systems was also confirmed by EDS and NMR. Comparison between SR-XPS data of MNPs and self-assembled monolayers and multilayers of pristine rod-like dithiols deposited onto polycrystalline gold surfaces revealed an electronic interaction between Pt(II) centers and biphenyl moieties of adjacent ligands, stabilizing the organic structure of the network. The possibility to obtain networks of regularly spaced MNPs opens outstanding perspectives in optoelectronics

Effects of simulated microgravity In vitro on human metaphase II oocytes: an electron microscopy-based study

The Gravity Force to which living beings are subjected on Earth rules the functionality of most biological processes in many tissues. It has been reported that a situation of Microgravity (such as that occurring in space) causes negative effects on living beings. Astronauts returning from space shuttle missions or from the International Space Station have been diagnosed with various health problems, such as bone demineralization, muscle atrophy, cardiovascular deconditioning, and vestibular and sensory imbalance, including impaired visual acuity, altered metabolic and nutritional status, and immune system dysregulation. Microgravity has profound effects also on reproductive functions. Female astronauts, in fact, suppress their cycles during space travels, and effects at the cellular level in the early embryo development and on female gamete maturation have also been observed. The opportunities to use space flights to study the effects of gravity variations are limited because of the high costs and lack of repeatability of the experiments. For these reasons, the use of microgravity simulators for studying, at the cellular level, the effects, such as those, obtained during/after a spatial trip, are developed to confirm that these models can be used in the study of body responses under conditions different from those found in a unitary Gravity environment (1 g). In view of this, this study aimed to investigate in vitro the effects of simulated microgravity on the ultrastructural features of human metaphase II oocytes using a Random Positioning Machine (RPM). We demonstrated for the first time, by Transmission Electron Microscopy analysis, that microgravity might compromise oocyte quality by affecting not only the localization of mitochondria and cortical granules due to a possible alteration of the cytoskeleton but also the function of mitochondria and endoplasmic reticulum since in RPM oocytes we observed a switch in the morphology of smooth endoplasmic reticulum (SER) and associated mitochondria from mitochondria-SER aggregates to mitochondria–vesicle complexes. We concluded that microgravity might negatively affect oocyte quality by interfering in vitro with the normal sequence of morphodynamic events essential for acquiring and maintaining a proper competence to fertilization in human oocyte

Current achievements and future research directions in ovarian tissue culture, in vitro follicle development and transplantation: implications for fertility preservation

Female cancer patients are offered 'banking' of gametes before starting fertility-threatening cancer therapy. Transplants of fresh and frozen ovarian tissue between healthy fertile and infertile women have demonstrated the utility of the tissue banked for restoration of endocrine and fertility function. Additional methods, like follicle culture and isolated follicle transplantation, are in development. Specialist reproductive medicine scientists and clinicians with complementary expertise in ovarian tissue culture and transplantation presented relevant published literature in their field of expertise and also unpublished promising data for discussion. As the major aims were to identify the current gaps prohibiting advancement, to share technical experience and to orient new research, contributors were allowed to provide their opinioned expert views on future research. Normal healthy children have been born in cancer survivors after orthotopic transplantation of their cryopreserved ovarian tissue. Longevity of the graft might be optimized by using new vitrification techniques and by promoting rapid revascularization of the graft. For the in vitro culture of follicles, a successive battery of culture methods including the use of defined media, growth factors and three-dimensional extracellular matrix support might overcome growth arrest of the follicles. Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation. Large animals, including non-human primates, are essential working models. Experiments on ovarian tissue from non-human primate models and from consenting fertile and infertile patients benefit from a multidisciplinary approach. The new discipline of oncofertility requires professionalization, multidisciplinarity and mobilization of funding for basic and translational research

Silicon photonics comb demultiplexer for elastic optical networks

An integrated reconfigurable optical comb demultiplexer for flexible-grid optical networks is demonstrated using high-order distributed feedback resonators realized in silicon-on-insulator technology. Low-loss tone isolation of nearly 30dB for a comb spacing of 12.5GHz is experimentally demonstrated in an ultra-compact layout, with potentials for operation with finer grids

Integrated Silicon-on-Insulator Optical Comb Demultiplexer for Elastic Optical Networks

Practical deployment of elastic optical networks requires key enabling technologies supporting the miniaturization of flexible optical transponders for provisioning large-bandwidth services at low-cost per users. A silicon photonics (SiP) reconfigurable optical frequency comb (OFC) demultiplexer based on passive optical filtering exhibiting a minimum spurious tone rejection (STR) of nearly 30dB at 12.5GHz tone spacing is here reported. Low power penalty due to inter-channel crosstalk (IXT) originated by finite STR is observed. Improved filter designs for reduced IXT and/or operation at 6.25GHz comb spacing are experimentally and numerically verified. By monolithic integration with SiP OFC sources and I-Q modulators the scheme has potentials for realizing ultra-compact multiple-flow optical transmitters with adaptive bandwidth and channel spacing

Wideband Single-Sideband Suppressed-Carrier Modulation with Silicon Photonics Optical Filters

Optical single-sideband suppressed-carrier (SSBSC) modulation based on advanced silicon photonics (SiP) optical filter is experimentally demonstrated. Wideband frequency shift of 2 Gb/s modulated data over a 30 GHz range spanning from the X to the Ka bands with large side-mode suppression ratio up to more than 30 dB is reported. The scheme can potentially be updated for operation up to the mm-wave band and broadband signal modulation. The impact of the filter phase response is assessed by transmission over 60 km of standard single mode fiber of the generated SSB-SC signal which resulted in moderate power penalty of ~0.5 dB in respect to SSB-CS data obtained using commercial I-Q modulator. The scheme is simple and stable and suitable for realizing a photonic integrated circuit with minimized footprint by monolithic integration of the filter with phase/amplitude modulators and other functional elements in silicon-on-insulator technology

Type of protein supplement in cryopreservation solutions impacts on the degree of ultrastructural damage in frozen-thawed human oocytes

Abstract Protein sources used as supplements of IVF culture media are known to have several implications for the function and stability of embryo culture environment. In fact, they i) transport biologically active molecules ii) chelate heavy metals, iii) regulate media pH, iii) scavenge reactive oxygen species (ROS) and iv) attenuate osmotic stress to which cells are exposed in sub-optimal culture conditions. Instead, their specific relevance to the formulation of cryopreservation solutions used for gamete and embryo cryopreservation remains uncertain. In the present work, we tested the hypothesis that different protein supplements present in cryopreservation solutions, serum or plasma protein solution (PPS), or different concentrations of the same supplement (serum), are associated with different types and/or magnitude of cryopreservation-derived cell damage. To this end, using cryopreservation solutions containing serum or PPS, donated supernumerary human mature oocytes were frozen-thawed by slow freezing and compared with fresh controls. Ultrastructural markers of oocyte quality were adopted as objective measure to assess possible damage from cryopreservation. The study results indicate that the adoption of serum minimises cell damage induced by cryopreservation. Indeed, typical hallmarks of cryodamage in human oocytes, i.e. loss of cortical granules, zona pellucida hardening and above all vacuolization, were largely reduced in oocytes cryopreserved with solutions containing serum, especially if used a higher concentration. This suggest that oocyte cryopreservation still has significant margins of improvement that may derive also from composition of cryopreservation media