Multiple international agencies have recently raised environmental and health concerns regarding plastics in nanoforms (nanoplastics), but there is insufficient knowledge of their properties to allow ...for an accurate risk assessment to be conducted and any risks managed. For this reason, research into the toxicity of nanoplastics has focused strongly on documenting their impacts on biological organisms. One scope of this review is to summarise the recent findings on the adverse effects on biological organisms and strategies which can be adopted to advance our understanding of nanoplastic properties and their toxicity. Specifically, a mechanistic approach has already been employed in nanotoxicology, which focuses on the cause-and-effect relationships to establish a tool that predicts the biological impacts based on nanoparticle characteristics. Identifying the chemical and biological bases behind the observed biological effects (such as in vitro cellular response) is a major challenge, due to the intricate nature of nanoparticle-biological molecule complexes and an unawareness of their interaction with other biological targets, particularly at interfacial level. An exemplary case includes protein corona formation and ecological molecule corona (eco-corona) for nanoplastics. Therefore, the second scope of this review is to discuss recent findings and importance of (for both non-plastic and plastic nanoparticles) coronae formation and structure. Finally, we discuss the opportunities provided by model system approaches (model protein corona and lipid bilayer) to deepen the understanding of the above-mentioned perspectives, and corroborate the findings from in vitro experiments.
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•Nanoplastics disrupt the ecological function of biofilms, causing adverse effects in aquatic organisms, and bioaccumulate.•The strategy used in nanotoxicology is critically discussed and considerations specific to nanoplastics are highlighted.•Knowledge gap exists for corona formation around nanoplastics, particularly at interfacial level.•Cellular interactions with nanoplastics at interfacial level are important, and allow corroboration with in vitro effects.
QUOKKA is a 40 m pinhole small‐angle neutron scattering instrument in routine user operation at the OPAL research reactor at the Australian Nuclear Science and Technology Organisation. Operating with ...a neutron velocity selector enabling variable wavelength, QUOKKA has an adjustable collimation system providing source–sample distances of up to 20 m. Following the large‐area sample position, a two‐dimensional 1 m2 position‐sensitive detector measures neutrons scattered from the sample over a secondary flight path of up to 20 m. Also offering incident beam polarization and analysis capability as well as lens focusing optics, QUOKKA has been designed as a general purpose SANS instrument to conduct research across a broad range of scientific disciplines, from structural biology to magnetism. As it has recently generated its first 100 publications through serving the needs of the domestic and international user communities, it is timely to detail a description of its as‐built design, performance and operation as well as its scientific highlights. Scientific examples presented here reflect the Australian context, as do the industrial applications, many combined with innovative and unique sample environments.
The design, performance, operation and scientific highlights from the QUOKKA SANS instrument at the OPAL Research Reactor, Australia, are described.
The electrocatalyst layer (ECL) of the proton-exchange membrane fuel cell (PEMFC) is commonly fabricated from colloidal catalyst ink containing carbon-supported catalyst nanoparticles (NPs), ionomer ...stabilizer, and dispersion medium (DM). The structure, stability, and aggregate size distribution of fuel cell catalyst ink are critically dependent on the quality of DM. However, understanding of the influence of the quality of DM on the hierarchical structure of the ECL is lacking. This work presents a systematic investigation of the effects of reducing alcohol content in isopropyl alcohol/water (IPA/H2O) binary mixtures as DM on the structural evolution of water-rich (green) catalyst ink using contrast-variation small-angle and ultrasmall-angle neutron scattering techniques. Both qualitative and quantitative information are extracted from the data to obtain information about the size, structure, and organization of the catalyst ink using different model functions fit to the experimental data. The catalyst ink prepared using 70% IPA (commonly employed in industry and extensively reported in the literature) is shown to consist of randomly distributed globular carbon aggregates (mean radius of gyration of ∼178.9 nm) stabilized by an ionomer mass fractal shell (thickness of ∼13.0 nm), which is dispersed in the matrix of rodlike (∼1.3 nm radius and ∼35.0 nm length) negatively surface-charged ionomer NPs. These well characterized baseline data are then compared and contrasted with DM formulations of lower IPA content. A sequential reduction in IPA content of DM shows a progressive increase in the ionomer NP radius and electrostatic repulsion, concomitantly with the decrease in the carbon aggregate size and ionomer shell thickness of the catalyst ink. Therefore, the changes in the interfacial structure via adjustments of the DM composition can be used as a controlling parameter to tailor the hierarchical structure of the colloidal fuel cell catalyst ink and to further optimize the performance of the ECL.
Advances in stretchable electronics concern engineering of materials with strain-accommodating architectures and fabrication of nanocomposites by embedding a conductive component into an elastomer. ...The development of organic conductors that can intrinsically stretch and repair themselves after mechanical damage is only in the early stages yet opens unprecedented opportunities for stretchable electronics. Such functional materials would allow extended lifetimes of electronics as well as simpler processing methods for fabricating stretchable electronics. Herein, we present a unique molecular approach to intrinsically stretchable and healable conjugated polymers. The simple yet versatile synthetic procedure enables one to fine-tune the electrical and mechanical properties without disrupting the electronic properties of the conjugated polymer. The designed material is comprised of a hydrogen-bonding graft copolymer with a conjugated backbone. The morphological changes, which are affected by the composition of functional side chains, and the solvent quality of the casting solution play a crucial role in the synthesis of highly stretchable and room-temperature healable conductive electronic materials.
The nano- and micron scale morphology of poly(3-hexylthiophene) (P3HT) and polystyrene- block -polyisoprene- block -polystyrene (PS–PI–PS) elastomeric blends is investigated through the use of ...ultra-small and small angle X-ray and neutron scattering (USAXS, SAXS, SANS). It is demonstrated that loading P3HT into elastomer matrices is possible with little distortion of the elastomeric structure up to a loading of ∼5 wt%. Increased loadings of conjugated polymer is found to significantly distort the matrix structure. Changes in processing conditions are also found to affect the blend morphology with especially strong dependence on processing temperature. Processing temperatures above the glass transition temperature ( T g ) of polystyrene and the melting temperature ( T m ) of the conjugated polymer additive (P3HT) creates significantly more organized mesophase domains. P3HT blends with PS–PI–PS can also be flow-aligned through processing, which results in an anisotropic structure that could be useful for the generation of anisotropic properties ( e.g. conductivity). Moreover, the extent of flow alignment is significantly affected by the P3HT loading in the PS–PI–PS matrix. The work adds insight to the morphological understanding of a complex P3HT and PS–PI–PS polymer blend as conjugated polymer is added to the system. We also provide studies isolating the effect of processing changes aiding in the understanding of the structural changes in this elastomeric conjugated polymer blend.
Upon contact with biological fluids, the surface of nanoparticles is surrounded by many types of proteins, forming a so-called “protein corona”. The physicochemical properties of the ...nanoparticle/corona complex depend predominantly on the nature of the protein corona. An understanding of the structure of the corona and the resulting complex provides insight into the structure–activity relationship. Here, we structurally evaluate the soft and hard components of the protein corona, formed from polystyrene (PS) nanoplastics and human serum albumin (HSA). Using circular dichroism spectroscopy to elucidate the structure of HSA within the complex, we establish the effect of nanoparticle size and pH on the nature of the protein corona formed- whether hard or soft. Despite the weak interaction between PS and the HSA corona, small angle neutron scattering revealed the formation of a complex structure that enhanced the intermolecular interactions between HSA proteins, PS particles, and the HS/PSA complexes. Fractal formation occurred under conditions where the interaction between PS and HSA was strong, and increasing HSA concentrations suppressed the degree of aggregation. The size of the nanoparticles directly influenced the nature of the protein corona, with larger particles favoring the formation of a soft corona, due to the decreased PS–HSA attraction.
The development of protein-based 3D printable hydrogel systems with tunable structure and properties is a critical challenge in contemporary biomedicine. Particularly, 3D printing of modular ...hydrogels comprising different types of protein tertiary structure, such as globular and fibrous, has not yet been achieved. Here we report the extrusion-based 3D printing of hybrid hydrogels photochemically co-cross-linked between globular soy protein isolate (SPI) and fibrous silk fibroin (SF) for the first time. The hierarchical structure and organization of pristine SPI and SF, and 1:3 (SPI/SF) hybrid inks under various shear stress were investigated using in situ rheology combined with small-/ultra-small-angle neutron scattering (Rheo-SANS/USANS). The hybrid ink exhibited an isotropic mass fractal structure that was stable between tested shear rates of 0.1 and 100 s–1 (near printing shear). The kinetics of sol–gel transition during the photo-cross-linking reaction and the micromechanical properties of fabricated hydrogels were investigated using photorheology and atomic force microscopy, where the hybrid hydrogels exhibited tunable storage and Young’s moduli in the range of 13–29 and 214–811 kPa, respectively. The cross-link density and printing accuracy of hybrid hydrogels and inks were observed to increase with the increase in SF content. The 3D printed hybrid hydrogels exhibited a micropore size larger than that of solution casted hydrogels; where the 3D printed 1:3 (SPI/SF) hybrid hydrogel showed a pore size about 7.6 times higher than that of the casted hydrogel. Moreover, the fabricated hybrid hydrogels exhibit good mouse fibroblast cell attachment, viability, and proliferation, demonstrating their potential for tissue engineering applications.
Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) experiments have been carried out to study the competitive effects of NaCl and sodium dodecyl sulfate (SDS) surfactant on the ...evolution of the structure and interactions in a silica nanoparticle-Bovine serum albumin (BSA) protein system. The unique advantage of contrast-matching SANS has been utilized to particularly probe the structure of nanoparticles in the multi-component system. Silica nanoparticles and BSA protein both being anionic remain largely individual in the solution without significant adsorption. The non-adsorbing nature of protein is known to cause depletion attraction between nanoparticles at higher protein concentrations. The nanoparticles undergo immediate aggregation in the nanoparticle-BSA system on the addition of a small amount of salt referred as the critical salt concentration (CSC), much less than that required to induce aggregation in a pure nanoparticle dispersion. The salt ions screen the electrostatic repulsion between the nanoparticles, whereby the BSA-induced depletion attraction dominates the system and contributes to the nanoparticle aggregation of a mass fractal kind of morphology. Further, the addition of SDS in this system interestingly suppresses nanoparticle aggregation for salt concentrations lower than the CSC. The presence of SDS gives rise to additional electrostatic repulsion in the system by binding with the BSA protein
via
electrostatic and hydrophobic interactions. For salt concentrations higher than the CSC, the formation of clusters of nanoparticles is inevitable even in the presence of protein-surfactant complexes, but the mass fractal kind of branched aggregates transform to surface fractals. This has been attributed to the BSA-SDS complex induced depletion attraction along with salt-driven screening of electrostatic repulsion. Thus, the interplay of depletion and electrostatic and hydrophobic interactions has been utilized to tune the structures formed in a multicomponent silica nanoparticle-BSA-SDS/NaCl system.
Structure formation of the binary system of silica nanoparticle-BSA protein in presence of salt (below and above the critical salt concentration (CSC)) as a function of SDS concentration.
The evolving structure of protein-based foods during the digestion process is critical to the release of nutrients. However, traditional in vitro monitoring of the gel micro- and nano-structure ...during digestion involves analysing sample aliquots taken at different digestion time periods. This can pose issues for some gels, such as casein-based gels, as they are sensitive to sample manipulation and environmental changes. Herein, a newly developed flow setup was utilised to monitor (at the micro- and nano-length scales) the gel protein network of rennet-induced (RG) and transglutaminase-induced acid gels (TG) in situ and in real-time during simulated gastric digestion using ultra-small and small-angle neutron scattering (USANS and SANS). The proteolysis kinetics of the gels were investigated at two different pepsin enzyme concentrations (2000 and 8000 U mL-1) and in two different solvent environments (H2O and D2O). Results indicate that the flowing in situ system had a greater effect on the microstructural breakdown of TG relative to the acid-sensitive RG, compared to the traditional static method. This is the first in situ digestion study observing the structural changes of large protein gel particles with USANS or SANS in real-time. Our findings advance the understanding of the kinetics of casein gel disintegration under simulated conditions of gastric digestion relating to pepsin enzyme concentration and solvent environment, and critically, the utilisation of a new in situ and real-time setup for neutron studies.
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•A recirculated flow setup was built for in situ USANS/SANS measures of protein gels.•Structural changes were measured for gels digested with 2000 & 8000 U mL−1 pepsin.•Increased pepsin concentration will increase digestion rates for fragile gels only.•An optimum enzyme-substrate concentration should be determined for each setup.
Ancient Indian iron artefacts have always fascinated researchers due to their excellent corrosion resistance, but the scientific explanation of this feature remains to be elucidated. We have ...investigated corrosion resistance of iron manufactured according to traditional metallurgical processes by the Indian tribes called 'Agaria'. Iron samples were recovered from central India (Aamadandh, Korba district, Chhattisgarh). Iron artefacts are investigated using a range of correlative microscopic, spectroscopic, diffraction and tomographic techniques to postulate the hidden mechanisms of superlative corrosion resistance. The importance of manufacturing steps, ingredients involved in Agaria's iron making process, and post-metal treatment using metal-working operation called hot hammering (forging) is highlighted. This study also hypothesizes the probable protective mechanisms of corrosion resistance of iron. Findings are expected to have a broad impact across multiple disciplines such as archaeology, metallurgy and materials science.
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