Chiral plasmonic films have been prepared by incorporating gold nanorods (NRs) in a macroscopic cholesteric film formed by self-assembled cellulose nanocrystals (CNCs). Composite NR-CNC films ...revealed strong plasmonic chiroptical activity, dependent on the photonic properties of the CNC host and plasmonic properties of the NRs. The plasmonic chiroptical properties of the composite films were tuned by changing the conditions of film preparation. The strategy presented herein paves the way for the scalable and cost-efficient preparation of plasmonic chiral materials.
In the search for induced chiral plasmonic activity, cholesteric films formed by cellulose nanocrystals have attracted great interest as potential hosts for plasmonic nanoparticles. Circular ...dichroism (CD) spectra of the composite films exhibit two peaks, one of which is ascribed to the cholesteric host and the other one to plasmonic chiroptical activity of the plasmonic nanoparticles. Here we report the results of comprehensive studies of extinction and CD properties of composite films formed by different types of cellulose nanocrystals and different types of plasmonic nanoparticles. We show that the second peak in the CD spectra acquired using CD spectrometers appears as the result of the local reduction of the CD signal of the host material, due to excessive absorption by the nanoparticles, and thus it cannot be interpreted as induced plasmonic chiroptical activity. Instead, we propose an alternative way to measure CD spectra of plasmonic cholesteric films by using Mueller matrix transmission ellipsometry. The results of this study are important for ongoing research in the field of chiral plasmonics and for the optical characterization of a broad range of chiral nematic nanostructured materials.
Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest. Surface-patterned particles act as colloidal analogues ...of atoms and molecules, serve as model systems in studies of phase transitions in liquid systems, behave as 'colloidal surfactants' and function as templates for the synthesis of hybrid particles. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient, but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties. At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles, and nanoparticles with surface ripples or a 'raspberry' surface morphology. Here we demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. These patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization.
Chemically and topographically patterned nanoparticles (NPs) with dimensions on the order of tens of nanometers have a diverse range of applications and are a valuable system for fundamental ...research. Recently, thermodynamically controlled segregation of a smooth layer of polymer ligands into pinned micelles (patches) offered an approach to nanopatterning of polymer-functionalized NPs. Control of the patch number, size, and spatial distribution on the surface of spherical NPs has been achieved, however, the role of NP shape remained elusive. In the present work, we report the role of NP shape, namely, the effect of the local surface curvature, on polymer segregation into surface patches. For polymer-functionalized metal nanocubes, we show experimentally and theoretically that the patches form preferentially on the high-curvature regions such as vertices and edges. An in situ transformation of the nanocubes into nanospheres leads to the change in the number and distribution of patches; a process that is dominated by the balance between the surface energy and the stretching energy of the polymer ligands. The experimental and theoretical results presented in this work are applicable to surface patterning of polymer-capped NPs with different shapes, thus enabling the exploration of patch-directed self-assembly, as colloidal surfactants, and as templates for the synthesis of hybrid nanomaterials.
Coassembly of nanoparticles with different size-, shape-, and composition-dependent properties is a promising approach to the design and fabrication of functional materials and devices. This paper ...reports the results of a detailed investigation of the formation and properties of free-stranding composite films formed by the coassembly of cellulose nanocrystals and shape-isotropic plasmonic gold nanoparticles. The effect of gold nanoparticle size, surface charge, and concentration on the structural and optical properties of the composite films has been studied. The composite films retained photonic crystal and chiroptical activity properties. The size and surface charge of gold nanoparticles had a minor effect on the structure and properties of the composite films, while the concentration of gold nanoparticles in the composite material played a more significant role and can be used to fine-tune the optical properties of materials derived from cellulose nanocrystals. These findings significantly broaden the range of nanoparticles that can be used for producing nanocomposite materials based on cellulose nanocrystals. The simplicity of film preparation, the abundance of cellulose nanocrystals, and the robust, free-standing nature of the composite films offer highly advantageous features and pave the way for the generation of functional materials with coupled optical properties.
An easy, inexpensive urea-melt assisted route was designed for the synthesis of ∼10 nm-sized Ni/NiO nanoparticles (NPs). The method consists of the thermal decomposition of a urea-melted medium ...containing a Ni2+-salt and involves the olygomerization and self-combustion of the organic matrix and the formation of the Ni/NiO NPs within it in a two stepped process of Ni2+ reduction yielding Ni crystallization and subsequent inward oxidation. Control over the microstructural features of the NPs within three typical regimes was accomplished by means of the initial urea quantity. Type A samples (0.2 g urea/0.2908 g nickel nitrate) consists of NiO nanostructures which might contain dispersed Ni nuclei of a few atoms; B NPs (2 g urea/0.2908 g nickel nitrate) are made of proper small Ni cores, in the limit of the coherence length of XRD, surrounded by thick NiO shells, while C (20 g urea/0.2908 g nickel nitrate) NPs correspond to relative big Ni cores and thin NiO shells. Further control over the thickness of the NiO shell was achieved within each regime by means of the calcination time of the organic matrix, painting a whole palette of Nicore−NiOshell NPs. Magnetic characterization revealed large (for A and B) and common (C) shifts of the hysteresis loops, which were ascribed to the high disorder of the (A, B and C) NPs obtained by quenching as well as to exchange bias (EB) effects (B and C). A thorough characterization of the reaction pathway is reported.
Zona pellucida (ZP), the extracellular matrix sheltering mammalian oocytes and embryos, is composed by 3 to 4 proteins. The roles of the three proteins present in mice have been elucidated by KO ...models, but the function of the fourth component (ZP4), present in all other eutherian mammals studied so far, has remained elusive. Herein, we report that
ablation impairs fertility in female rabbits. Ovulation, fertilization and in vitro development to blastocyst were not affected by
ablation. However, in vivo development is severely impaired in embryos covered by a ZP4-devoided zona, suggesting a defective ZP protective capacity in the absence of ZP4. ZP4-null ZP was significantly thinner, more permeable, and exhibited a more disorganized and fenestrated structure. The evolutionary conservation of ZP4 in other mammals, including humans, suggests that the structural properties conferred by this protein are required to ensure proper embryo sheltering during in vivo preimplantation development.
A lot of interesting and sophisticated examples of nanoparticle (NP) self-assembly (SA) are known. From both fundamental and technological standpoints, this field requires advancements in three ...principle directions: (a) understanding the mechanism and driving forces of three-dimensional (3D) SA with both nano- and microlevels of organization; (b) understanding disassembly/deconstruction processes; and (c) finding synthetic methods of assembly into continuous superstructures without insulating barriers. From this perspective, we investigated the formation of well-known star-like PbS superstructures and found a number of previously unknown or overlooked aspects that can advance the knowledge of NP self-assembly in these three directions. The primary one is that the formation of large seemingly monocrystalline PbS superstructures with multiple levels of octahedral symmetry can be explained only by SA of small octahedral NPs. We found five distinct periods in the formation PbS hyperbranched stars: (1) nucleation of early PbS NPs with an average diameter of 31 nm; (2) assembly into 100–500 nm octahedral mesocrystals; (3) assembly into 1000–2500 nm hyperbranched stars; (4) assembly and ionic recrystallization into six-arm rods accompanied by disappearance of fine nanoscale structure; (5) deconstruction into rods and cuboctahedral NPs. The switches in assembly patterns between the periods occur due to variable dominance of pattern-determining forces that include van der Waals and electrostatic (charge–charge, dipole–dipole, and polarization) interactions. The superstructure deconstruction is triggered by chemical changes in the deep eutectic solvent (DES) used as the media. PbS superstructures can be excellent models for fundamental studies of nanoscale organization and SA manufacturing of (opto)electronics and energy-harvesting devices which require organization of PbS components at multiple scales.
Nanoparticles (NPs) exhibit strong tendency to self-assemble. It is important to understand how the presence of other macromolecular compounds, affects this ability. The interaction between standard ...thiol-capped cadmium telluride (CdTe) NPs and streptavidin (STAV)the essential component of many NP applicationswas examined at different molar ratios and pH values. The central observation of this study is that STAV strongly inhibits the self-assembly of CdTe NPs into nanowires. The underlying mechanism of inhibition was attributed to the formation of a STAV corona and surface layer that precludes attachment of NPs to each other. Instead of nanowires, we observed a spectrum of agglomerates containing both CdTe and STAV of different geometries depending on the molar ratios of the reagents in NP synthesis and pH values of the media.
Abstract
STUDY QUESTION
Is the abundance of certain biochemical compounds in human cumulus cells (CCs) related to oocyte quality?
SUMMARY ANSWER
Malonate, 5-oxyproline, and erythronate were ...positively associated with pregnancy potential.
WHAT IS KNOWN ALREADY
CCs are removed and discarded prior to ICSI, thereby constituting an interesting biological material on which to perform molecular analysis aimed to predict oocyte developmental competence. Mitochondrial DNA content and transcriptional analyses in CC have been shown to provide a poor predictive value of oocyte competence, but the untargeted analysis of biochemical compounds (metabolomics) has been unexplored.
STUDY DESIGN, SIZE, DURATION
CCs were obtained from three groups of cumulus–oocyte complexes (COCs) of known developmental potential: oocytes not developing to blastocyst following ICSI (Bl−); oocytes developing to blastocyst but failing to establish pregnancy following embryo transfer (P−); and oocytes developing to blastocyst able to establish a pregnancy (P+). Metabolomics analyses were performed on 12 samples per group, each sample comprising the CC recovered from a single COC.
PARTICIPANTS/MATERIALS, SETTING, METHODS
Human CC samples were obtained from IVF treatments. Only unfrozen oocytes and embryos not submitted to preimplantation genetic testing were included in the analysis. Metabolomics analysis was performed by ultra-high performance liquid chromatography-tandem mass spectroscopy.
MAIN RESULTS AND THE ROLE OF CHANCE
The analysis identified 98 compounds, five of which were differentially abundant (P < 0.05) between groups: asparagine, proline, and malonate were less abundant in P− compared to Bl−, malonate and 5-oxoproline were less abundant in P− group compared to P+, and erythronate was less abundant in Bl− group compared to P+. No significant association between the abundance of the compounds identified and donor age or BMI was noted.
LIMITATIONS, REASONS FOR CAUTION
Data dispersion and the lack of coherence between developmental groups preclude the direct use of metabolic markers in clinical practice, where the uterine environment plays a major role in pregnancy outcome. The abundance of other compounds not detected by the analysis may be associated with oocyte competence. As donors were lean (only two with BMI > 30 kg/m2) and young (<34 years old), a possible effect of obesity or advanced age on the CC metabolome could not be determined.
WIDER IMPLICATIONS OF THE FINDINGS
The abundance of malonate, 5-oxyproline, and erythronate in CC was significantly higher in COCs ultimately establishing pregnancy, providing clues on the pathways required for oocyte competence. The untargeted analysis uncovered the presence of compounds that were not expected in CC, such as β-citrylglutamate and the neurotransmitter N-acetyl-aspartyl-glutamate, which may play roles in chromatin remodeling and signaling, respectively.
STUDY FUNDING/COMPETING INTEREST(S)
Research was supported by the Industrial Doctorate Project IND2017/BIO-7748 funded by Madrid Region Government. The authors declare no competing interest.
TRIAL REGISTRATION NUMBER
N/A.
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