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The pathogenicity of quartz involves lysosomal alteration in alveolar macrophages. This event triggers the inflammatory cascade that may lead to quartz-induced silicosis and eventually lung cancer. Experiments with synthetic quartz crystals recently showed that quartz dust is cytotoxic only when the atomic order of the crystal surfaces is upset by fracturing. Cytotoxicity was not observed when quartz had as-grown, unfractured surfaces. These findings raised questions on the potential impact of quartz surfaces on the phagolysosomal membrane upon internalization of the particles by macrophages. To gain insights on the surface-induced cytotoxicity of quartz, as-grown and fractured quartz particles in respirable size differing only in surface properties related to fracturing were prepared and physico-chemically characterized. Synthetic quartz particles were compared to a well-known toxic commercial quartz dust. Membranolysis was assessed on red blood cells, and quartz uptake, cell viability and effects on lysosomes were assessed on human PMA-differentiated THP-1 macrophages, upon exposing cells to increasing concentrations of quartz particles (10–250 µg/ml). All quartz samples were internalized, but only fractured quartz elicited cytotoxicity and phagolysosomal alterations. These effects were blunted when uptake was suppressed by incubating macrophages with particles at 4 °C. Membranolysis, but not cytotoxicity, was quenched when fractured quartz was incubated with cells in protein-supplemented medium. We propose that, upon internalization, the phagolysosome environment rapidly removes serum proteins from the quartz surface, restoring quartz membranolytic activity in the phagolysosomes. Our findings indicate that the cytotoxic activity of fractured quartz is elicited by promoting phagolysosomal membrane alteration.

Due to their ability to penetrate, deteriorate and discolour stone surfaces, rock-inhabiting black fungi represent a remarkable issue for cultural heritage conservation. Black microcolonial fungi (MCF) can also adapt to different environmental conditions, by converting from yeast-like morphology to a peculiar meristematic development with swollen cells (torulose hyphae, TH), to extremely thin structures (filamentous hyphae, FH). Furthermore, black MCF produce protective pigments: melanin, dark pigment particularly evident on light stone surfaces, and carotenoids. Black fungi produce melanin in critical, oligotrophic conditions as well as constitutively. Melanin function is mostly related to stress resistance and the ability of fungi to generate appressorial turgor to actively penetrate plant cells in pathogenic species. An involvement of melanins in stone surface penetration has been suggested, but not experimentally proved. In this work, we tested the role of hyphal melanisation in penetration mechanisms on the model black fungus Knufia petricola A95 in lab conditions. The wild-type and three mutants with introduced targeted mutations of polyketide-synthases (melanin production) and/or phytoene dehydrogenase (carotenoid synthesis) were inoculated on artificial carbonate pellets (pressed Carrara marble powder) of different porosity. After 5, 10, 17 and 27 weeks, hyphal penetration depth and spread were quantified on periodic acid Schiff-stained cross-sections of the pellets, collecting measurements separately for TH and FH. Droplet assay of the mutants on different media were conducted to determine the role of nutrients in the development of different fungal morphologies. In our in vitro study, the hyphal penetration depth, never exceeding 200 μm, was proven to be consistent with observed penetration patterns on stone heritage carbonate substrates. Pellet porosity affected penetration patterns of TH, which developed in voids of the more porous pellets, instead than actively opening new passageways. Oppositely, the thin diameter of FH allowed their penetration independently of substrate porosity. Instead, the long-hypothesized crucial role of melanin in black MCF hyphal penetration should be rejected. TH were developed within the pellets also by melanin deficient strains, and melanized strains showed an endolithic component of non-melanized TH. FH were non-melanized for all the strains, but deeply penetrated all pellet types, with higher penetration depth probably related to their potential exploratory (nutrient-seeking) role, while TH may be more related to a resistance to surface stress factors. In the melanin deficient strains, the absence of melanin caused an increased penetration rate of FH, hypothetically related to an earlier necessity to search for organic nutrients.

Bioactive glasses are the materials of choice in the field of bone regeneration. Antioxidant properties of interest to limit inflammation and foreign body reactions have been conferred to bioactive glasses by the addition of appropriate ions (such as Ce or Sr). On the other hand, the antioxidant activity of bioactive glasses without specific ion/molecular doping has been occasionally cited in the literature but never investigated in depth. In the present study, three silica-based bioactive glasses have been developed and characterized for their surface properties (wettability, zeta potential, chemical composition, and reactivity) and radical scavenging activity in the presence/absence of cells. For the first time, the antioxidant activity of simple silica-based (SiO2–CaO–Na2O) bioactive glasses has been demonstrated.

Background Li-ion batteries (LIB) are used in most portable electronics. Among a wide variety of materials, LiCoO2 (LCO) is one of the most used for the cathode of LIB. LCO particles induce oxidative stress in mouse lungs due to their Co content, and have a strong inflammatory potential. In this study, we assessed the mutagenic potential of LCO particles in lung cells in comparison to another particulate material used in LIB, LTO (Li4Ti5O12), which has a low inflammatory potential compared to LCO particles. Results We assessed the mutagenic potential of LCO and LTO particles in vitro by performing a cytokinesis-block micronucleus (MN) assay with rat lung epithelial cells (RLE), as well as in vivo in alveolar type II epithelial (AT-II) cells. LCO particles induced MN in vitro at non-cytotoxic concentrations and in vivo at non-inflammatory doses, indicating a primary genotoxic mechanism. LTO particles did not induce MN. Electron paramagnetic resonance and terephthalate assays showed that LCO particles produce hydroxyl radicals (•OH). Catalase inhibits this •OH production. In an alkaline comet assay with the oxidative DNA damage repair enzyme human 8-oxoguanine DNA glycosylase 1, LCO particles induced DNA strand breaks and oxidative lesions. The addition of catalase reduced the frequency of MN induced by LCO particles in vitro. Conclusions We report the mutagenic activity of LCO particles used in LIB in vitro and in vivo. Our data support the role of Co(II) ions released from these particles in their primary genotoxic activity which includes the formation of •OH by a Fenton-like reaction, oxidative DNA lesions and strand breaks, thus leading to chromosomal breaks and the formation of MN. Documenting the genotoxic potential of the other LIB particles, especially those containing Co and/or Ni, is therefore needed to guarantee a safe and sustainable development of LIB.

Significance Silica particles with a population of nearly free silanols damage cellular membranes and initiate inflammatory reactions. Nearly free silanols are found on the surface of both fractured quartz and amorphous silica particles, and their occurrence initiates the toxicity of silica, thus revisiting the ancient paradigm whereby crystallinity is critical for silica toxicity. This finding resolves the lingering questions about the origin and the variability of the toxicity of silica particles. The discovery of the biological activity of nearly free silanols opens perspectives for the prevention of silicosis through a safer-by-design approach, and will have an impact on other fields that involve interfacial phenomena, including biomaterial design, nanofabrication, and catalysis., Inhalation of silica particles can induce inflammatory lung reactions that lead to silicosis and/or lung cancer when the particles are biopersistent. This toxic activity of silica dusts is extremely variable depending on their source and preparation methods. The exact molecular moiety that explains and predicts this variable toxicity of silica remains elusive. Here, we have identified a unique subfamily of silanols as the major determinant of silica particle toxicity. This population of “nearly free silanols” (NFS) appears on the surface of quartz particles upon fracture and can be modulated by thermal treatments. Density functional theory calculations indicates that NFS locate at an intersilanol distance of 4.00 to 6.00 Å and form weak mutual interactions. Thus, NFS could act as an energetically favorable moiety at the surface of silica for establishing interactions with cell membrane components to initiate toxicity. With ad hoc prepared model quartz particles enriched or depleted in NFS, we demonstrate that NFS drive toxicity, including membranolysis, in vitro proinflammatory activity, and lung inflammation. The toxic activity of NFS is confirmed with pyrogenic and vitreous amorphous silica particles, and industrial quartz samples with noncontrolled surfaces. Our results identify the missing key molecular moieties of the silica surface that initiate interactions with cell membranes, leading to pathological outcomes. NFS may explain other important interfacial processes involving silica particles.

Glasses are among the most widely used of everyday materials, yet the process by which a liquid’s viscosity increases by 14 decades to become a glass remains unclear, as often contradictory theories provide equally good descriptions of the available data. Knowledge of emergent lengthscales and higher-order structure could help resolve this, but this requires time-resolved measurements of dense particle coordinates—previously only obtained over a limited time interval. Here we present an experimental study of a model colloidal system over a dynamic window significantly larger than previous measurements, revealing structural ordering more strongly linked to dynamics than previously found. Furthermore we find that immobile regions and domains of local structure grow concurrently with density, and that these regions have low configurational entropy. We thus show that local structure plays an important role at deep supercooling, consistent with a thermodynamic interpretation of the glass transition rather than a principally dynamic description., The glass transition remains an unsolved problem due to the scarcity of particle-resolved data over a large dynamic range. Hallett et al. probe an unprecedented time window and show a strong correlation between local structure and slow dynamics in a deeply supercooled liquid of colloids.

Among the physico-chemical features responsible for the so-called “variability of quartz hazard”, a key role has been assigned to the silica surface charge, evaluated by means of ζ potential measurement. The ζ potential of silica describes the protonation state of silanols which, in turn, determine interactions with cell membranes. To gain a molecular understanding of the role of silanols in silica pathogenicity, we conducted a systematic investigation of the variation of the ζ potential as a function of pH (ζ plot titration curve) on a large set of respirable quartz particles with different levels of metal contaminants. The membranolytic activity of the particles on red blood cells, used as a readout of pathogenic activity, was assessed in parallel. Pure quartz surfaces showed sigmoid-shaped ζ plots suggesting the presence of silanol families with similar acidity, whereas contaminated dusts exhibited convex-shaped ζ plots, indicating a higher silanol heterogeneity on contaminated surfaces with respect to the pure ones. The quartz particles with a higher surface heterogeneity related to metal contamination showed a higher membranolytic activity. By removing structural defects and chemical heterogeneity, the ζ plot shifted towards the typical shape of pure quartz and the membranolytic activity was reduced. We conclude that the ζ plot is a useful readout to measure the acid-base behavior of quartz surfaces and to describe the chemical heterogeneity of quartz silanols. Surface heterogeneity, here induced by metal contamination, is proposed as the main cause of quartz membranolytic activity, further supporting the hypothesis that surface silanol disorganization determines silica pathogenicity.

Starting from an ideal crystalline state, we numerically study a nonequilibrium dynamical order- disorder transition promoted by the application of a periodic shearing protocol at low temperatures in model systems in two and three dimensions. We observe a continuous (2D) and discontinuous (3D) dynamical transition from an ordered to a disordered steady state. Through the analysis of large-scale simulations, we show that the amorphization mechanism around the discontinuous transition is reminiscent of spinodal decomposition.

Thermo-gravimetric analysis coupled to time/temperature-resolved FTIR spectroscopy of evolved gases was used to measure the vinyl alcohol units content in EVOH copolymer. Pure homopolymers were used as references. The quantitative analysis here proposed is based on the calculation of integral profiles relative to FTIR signals of water molecules evolved during the thermal degradation (pyrolysis) of vinyl alcohol units.

Magnetite-containing glass-ceramics are promising bio-materials for replacing bone tissue after tumour resection. Thanks to their ferrimagnetic properties, they generate heat when subjected to an alternated magnetic field. In virtue of this they can be employed for the hyperthermic treatment of cancer. Moreover, grafting anti-cancer drugs onto their surface produces specific anti-neoplastic activity in these biomaterials. Gallic acid (GA) exhibits antiproliferative activity which renders it a promising candidate for anticancer applications. In the present paper, the reactivity of ferrimagnetic glass-ceramic SC-45 grafted with GA (SC-45+GA) was studied in terms of ROS release, rupture of the C–H bond of the formate molecule and Fenton reactivity by EPR/spin trapping in acellular systems. The ability of these materials to cause lipid peroxidation was assessed by UV–vis/TBA assay employing linoleic acid as a model of membrane lipid. The results, compared to those obtained with SC-45, showed that GA grafting (i) significantly enhanced the Fenton reactivity and (ii) restored the former reactivity of SC-45 towards both the C–H bond and linoleic acid which had been completely suppressed by prolonged contact with water. Fe 2+ centres at the surface are probably implicated. GA, acting as a pro-oxidant, reduces Fe 3+ to Fe 2+ by maintaining a supply of Fe 2+ at the surface of SC-45+GA.

Many experimental studies about the harmful effects of crystalline silica on human health are present in the literature. However, the relationship between toxicological properties and surface functionalities of quartz is not yet fully explained because of the large intrinsic variability of natural samples. Specific surface properties are related to the surface structure: this implies that a reliable constraint on the crystal growth morphologies is necessary in order to control the behavior variability. With a view to understanding this relationship, a consistent, clean, and easy way to crystallize quartz is proposed. In this paper, α-quartz crystals with controlled morphology and properties were prepared by an unusual and accurate approach under mild hydrothermal conditions (200 °C, autogenic pressure) starting from silica gels prepared with different polymerizing agents. Gels and synthetic crystals were characterized using a wide range of experimental techniques: elemental analysis by ICP-OES, X-ray powd...

Colloidal suspensions have long been studied as a model for atomic and molecular systems, due to the ability to fluorescently label and individually track each particle, yielding particle-resolved structural information. This allows various local order parameters to be probed that are otherwise inaccessible for a comparable molecular system. For phase transitions such as crystallisation, appropriate order parameters which emphasise 6-fold symmetry are a natural choice, but for vitrification the choice of order parameter is less clear cut. Previous work has highlighted the importance of icosahedral local structure as the glass transition is approached. However, counting icosahedra or related motifs is not a continuous order parameter in the same way as, for example, the bond-orientational order parameters $Q_{6}$ and $W_6$. In this work we investigate the suitability of using pentagonal bipyramid membership, a structure which can be assembled into larger, five-fold symmetric structures, as a finer order parameter to investigate the glass transition. We explore various structural and dynamic properties and show that this new approach produces many of the same findings as simple icosahedral membership, but we also find that large instantaneous displacements are often correlated with significant changes in pentagonal bipyramid membership, and unlike the population of defective icosahedra, the pentagonal bypyramid membership and spindle number do not saturate for any measured volume fraction, but continues to increase., Comment: accepted by JStat Mech: Theory and Experiment 2019

Fe-based materials are considered for the manufacture of temporary implants that degrade through the corrosion of Fe by oxygen. Here we document the generation of hydroxyl radicals (HO˙) during this corrosion process, and their deleterious impacts on human endothelial (ECs) and smooth muscle cells (SMCs) in vitro. The generation of HO˙ was documented by two independent acellular assays, terephtalic acid hydroxylation (fluorescence) and spin trapping technique coupled with electron paramagnetic resonance spectroscopy. All Fe-based materials tested exhibited a strong potential to generate HO˙. The addition of catalase prevented the formation of HO˙. Cellular responses were assessed in two ECs and SMCs lines using different cytotoxicity assays (WST-1 and CellTiter-Glo). Cells were exposed directly to Fe powder in the presence/absence of catalase, or to extracts obtained from the corrosion of Fe. Cell viability was dose-dependently affected by the direct contact with Fe materials, but not in the presence of catalase or after indirect exposure to cell extracts. The deleterious effect of HO˙ on ECs and SMCs was confirmed by the dose-dependent increase of the transcripts of the oxidative stress gene heme oxygenase-1 4 h or 6 h after direct exposure to the particles, but not in presence of catalase or after indirect exposure. The demonstration of HO˙production during corrosion and consequent oxidative stress on human ECs and SMCs newly reveals a deleterious consequence of Fe-corrosion that should be integrated in the assessment of the biocompatibility of Fe-based alloys.

Key to resolving the scientific challenge of the glass transition is to understand the origin of the massive increase in viscosity of liquids cooled below their melting temperature (avoiding crystallisation). A number of competing and often mutually exclusive theoretical approaches have been advanced to describe this phenomenon. Some posit a bona fide thermodynamic phase to an "ideal glass", an amorphous state with exceptionally low entropy. Other approaches are built around the concept of the glass transition as a primarily dynamic phenomenon. These fundamentally different interpretations give equally good descriptions of the data available, so it is hard to determine which -- if any -- is correct. Recently however this situation has begun to change. A consensus has emerged that one powerful means to resolve this longstanding question is to approach the putative thermodynamic transition sufficiently closely, and a number of techniques have emerged to meet this challenge. Here we review the results of some of these new techniques and discuss the implications for the existence -- or otherwise -- of the thermodynamic transition to an ideal glass., Comment: 42 pages

We study the joint variability of structural information in a hard sphere fluid biased to avoid crystallisation and form five-fold symmetric geometric motifs. We show that the structural covariance matrix approach, originally proposed for on-lattice liquids [P. Ronceray and P. Harrowell, J. Stat. Mech.: Theory Exp. 2016(8), 084002], can be meaningfully employed to understand structural relationships between different motifs and can predict, within the linear-response regime, structural changes related to motifs distinct from that used to bias the system.

In trajectory space, dynamical heterogeneities in glass-forming liquids correspond to the emergence of a dynamical phase transition between an active phase poor in local structure and an inactive phase which is rich in local structure. We support this scenario with the study of a model additive mixture of Lennard-Jones particles, quantifying how the choice of the relevant structural and dynamical observable affects the transition in trajectory space. We find that the low mobility, structure-rich phase is dominated by icosahedral order. Applying a non-equilibrium rheological protocol, we connect local order to the emergence of mechanical rigidity.

A quasi two-dimensional colloidal suspension is studied under the influence of immobilisation (pinning) of a random fraction of its particles. We introduce a novel experimental method to perform random pinning and, with the support of numerical simulation, we find that increasing the pinning concentration smoothly arrests the system, with a cross-over from a regime of high mobility and high entropy to a regime of low mobility and low entropy. At the local level, we study fluctuations in area fraction and concentration of pins and map them to entropic structural signatures and local mobility, obtaining a measure for the local entropic fluctuations of the experimental system.

The discrepancy in nucleation rate densities between simulated and experimental hard spheres remains staggering and unexplained. Suggestively, more strongly sedimenting colloidal suspensions of hard spheres nucleate much faster than weakly sedimenting systems. In this work we consider firstly the effect of sedimentation on the structure of colloidal hard spheres, by tuning the density mismatch between solvent and colloidal particles. In particular we investigate the effect on the degree of five fold symmetry present. Secondly we study the size of density fluctuations in these experimental systems in comparison to simulations. The density fluctuations are measured by assigning each particle a local density, which is related to the number of particles within a distance of 3.25 particle diameters. The standard deviation of these local densities gives an indication of the fluctuations present in the system. Five fold symmetry is suppressed by a factor of two when sedimentation is induced in our system. Density fluctuations are also increased by a factor of two in experiments compared to simulations. The change in five fold symmetry makes a difference to the expected nucleation rates, but we demonstrate that it is ultimately too small to resolve the discrepancy between experiment and simulation, while the fluctuations are shown to be an artefact of 3d particle tracking., Comment: 8 pages

Supercooled liquids are kinetically trapped materials in which the transition to a thermodynamically more stable state with long-range order is strongly suppressed. To assess the glass-forming abilities of a liquid empirical rules exist, but a comprehensive microscopic picture of devitrification is still missing. Here we study the crystallization of a popular model glass former, the binary Kob-Andersen mixture, in small systems. We perform trajectory sampling employing the population of the locally favored structure as order parameter. While for large population a dynamical phase transition has been reported, here we show that biasing towards a small population of locally favored structures induces crystallization, and we estimate the free energy difference. This result sheds new light on the competition between local and global structure in glass-forming liquids and its implications for crystallization.

The use of nanotechnology is growing enormously and occupational physicians have an increasing interest in evaluating potential hazards and finding biomarkers of effect in workers exposed to nanoparticles.A study was carried out with 36 workers exposed to (nano)TiO2 pigment and 45 controls. Condensate (EBC) titanium and markers of oxidation of nucleic acids (including 8-hydroxy-2-deoxyguanosine (8-OHdG), 8-hydroxyguanosine (8-OHG), 5-hydroxymethyl uracil (5-OHMeU)) and proteins (such as o-tyrosine (o-Tyr), 3-chlorotyrosine (3-ClTyr) and 3-nitrotyrosine (3-NOTyr)) were analysed from samples of their exhaled breath.In the production workshops, the median total mass 2012 and 2013 TiO2 concentrations were 0.65 and 0.40 mg/m(3), respectively. The median numbers of concentrations measured by the scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) were 1.98 × 10(4) and 2.32 × 10(4) particles/cm(3), respectively; and about 80% of those particles were smaller than 100 nm in diameter. In the research workspace, lower aerosol concentrations (0.16 mg/m(3) and 1.32 × 10(4) particles/cm(3)) were found. Titanium in the EBC was significantly higher in production workers (p0.001) than in research workers and unexposed controls. Accordingly, most EBC oxidative stress markers, including in the preshift samples, were higher in production workers than in the two other groups. Multiple regression analysis confirmed an association between the production of TiO2 and the levels of studied biomarkers.The concentration of titanium in EBC may serve as a direct exposure marker in workers producing TiO2 pigment; the markers of oxidative stress reflect the local biological effect of (nano)TiO2 in the respiratory tract of the exposed workers.

Ageing phenomena are investigated from a structural perspective in two binary Lennard-Jones glassformers, the Kob-Andersen and Wahnström mixtures. In both, the geometric motif assumed by the glassformer upon supercooling, the locally favoured structure (LFS), has been established. The Kob-Andersen mixture forms bicapped square antiprisms; the Wahnström model forms icosahedra. Upon ageing, we find that the structural relaxation time has a time-dependence consistent with a power law. However, the LFS population and potential energy increase and decrease, respectively, in a logarithmic fashion. Remarkably, over the time scales investigated, which correspond to a factor of 104 change in relaxation times, the rate at which these quantities age appears almost independent of temperature. Only at temperatures far below the Vogel-Fulcher-Tamman temperature do the ageing dynamics slow.

Geometric frustration describes the inability of a local molecular arrangement, such as icosahedra found in metallic glasses and in model atomic glass-formers, to tile space. Local icosahedral order however is strongly frustrated in Euclidean space, which obscures any causal relationship with the observed dynamical slowdown. Here we relieve frustration in a model glass-forming liquid by curving 3-dimensional space onto the surface of a 4-dimensional hypersphere. For sufficient curvature, frustration vanishes and the liquid freezes in a fully icosahedral structure via a sharp `transition'. Frustration increases upon reducing the curvature, and the transition to the icosahedral state smoothens while glassy dynamics emerges. Decreasing the curvature leads to decoupling between dynamical and structural length scales and the decrease of kinetic fragility. This sheds light on the observed glass-forming behavior in the Euclidean space., Comment: 5 pages + supplementary material

We consider the sedimentation of a colloidal gel under confinement in the direction of gravity. The confinement allows us to compare directly experiments and computer simulations, for the same system size in the vertical direction. The confinement also leads to qualitatively different behaviour compared to bulk systems: in large systems gelation suppresses sedimentation, but for small systems sedimentation is enhanced relative to non-gelling suspensions , although the rate of sedimentation is reduced when the strength of the attraction between the colloids is strong. We map interaction parameters between a model experimental system (observed in real space) and computer simulations. Remarkably, we find that when simulating the system using Brownian dynamics in which hydrodynamic interactions between the particles are neglected, we find that sedimentation occurs on the same timescale as the experiments, however the thickness of the “arms” of the gel is rather larger in the experiments, compared with the simulations. An analysis of local structure in the simulations showed similar behaviour to gelation in the absence of gravity.

The formation of colloidal gels is strongly dependent on the volume fraction of the system and the strength of the interactions between the colloids. Here we explore very dilute solutions by the means of numerical simulations, and show that, in the absence of hydrodynamic interactions and for sufficiently strong interactions, percolating colloidal gels can be realised at very low values of the volume fraction. Characterising the structure of the network of the arrested material we find that, when reducing the volume fraction, the gels are dominated by low-energy local structures, analogous to the isolated clusters of the interaction potential. Changing the strength of the interaction allows us to tune the compactness of the gel as characterised by the fractal dimension, with low interaction strength favouring more chain-like structures.

Nanoscale titanium dioxide (nanoTiO2) is a commercially important nanomaterial. Animal studies have documented lung injury and inflammation, oxidative stress, cytotoxicity and genotoxicity. Yet, human health data are scarce and quantitative risk assessments and biomonitoring of exposure are lacking. NanoTiO2 is classified by IARC as a group 2B, possible human carcinogen. In our earlier studies we documented an increase in markers of inflammation, as well as DNA and protein oxidative damage, in exhaled breath condensate (EBC) of workers exposed nanoTiO2. This study focuses on biomarkers of lipid oxidation. Several established lipid oxidative markers (malondialdehyde, 4-hydroxy-trans-hexenal, 4-hydroxy-trans-nonenal, 8-isoProstaglandin F2α and aldehydes C6–C12) were studied in EBC and urine of 34 workers and 45 comparable controls. The median particle number concentration in the production line ranged from 1.98 × 104 to 2.32 × 104 particles/cm3 with ∼80% of the particles

We perform particle resolved experimental studies on the heterogeneous crystallisation process of two compo- nent mixtures of hard spheres. The components have a size ratio of 0.39. We compared these with molecular dynamics simulations of homogenous nucleation. We find for both experiments and simulations that the final assemblies are interstitial solid solutions, where the large particles form crystalline close-packed lattices, whereas the small particles occupy random interstitial sites. This interstitial solution resembles that found at equilibrium when the size ratios are 0.3 [Filion et al., Phys. Rev. Lett. 107, 168302 (2011)] and 0.4 [Filion, PhD Thesis, Utrecht University (2011)]. However, unlike these previous studies, for our system sim- ulations showed that the small particles are trapped in the octahedral holes of the ordered structure formed by the large particles, leading to long-lived non-equilibrium structures in the time scales studied and not the equilibrium interstitial solutions found earlier. Interestingly, the percentage of small particles in the crystal formed by the large ones rapidly reaches a maximum of around 14% for most of the packing fractions tested, unlike previous predictions where the occupancy of the interstitial sites increases with the system concentration. Finally, no further hopping of the small particles was observed.

In this study, bio-based substances (BBS) obtained from composted urban biowaste are used as stabilizers for the synthesis of magnet-sensitive nanoparticles (NPs). The BBS-stabilized NPs are characterized by means of different techniques (FTIR, XRD, SEM, BET analysis, magnetization curves). Additionally, TGA coupled on-line with FTIR and GC/MS analysis of the exhausted gas are performed in order to simultaneously identify all the degradation products and evaluate the exact composition of such BBS-stabilized materials. Moreover, Fenton-like or photo-Fenton-like experiments carried out at circumneutral pH are performed in order to evaluate the BBS-functionalized NPs photo-activity towards the degradation of caffeine (taken as model emerging pollutant). The obtained promising results encourage the use of BBS as a green alternative tool for the preparation of smart materials with enhanced magnet-sensitive properties, also suitable for applications in wastewater purification treatments., Facultad de Ciencias Exactas, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas

Ferrimagnetic bioactive glass ceramics are promising biomaterials in the field of bone substitution and cancer treatment for their ability to bond to bone (bioactive behavior) and to be heated by the application of an external magnetic field (hyperthermia). Surface functionalization of these materials with polyphenols is a challenging and innovative strategy in order to impart them additional functional and specific properties (e.g. antioxidant, anticancer and antibacterial). Gallic acid (GA) is a phenolic acid which can be considered a good model molecule for polyphenols due to its simple structure and representative properties. In the present paper GA has been grafted to a ferrimagnetic glass ceramic (SC-45), in bulk and powder forms, in view of its potential clinical applications (such as hyperthermic treatment of cancer combined with the anticancer action of GA). The grafting process has been optimized in order to preserve GA activity. The effectiveness of the functionalization procedure has been demonstrated by means of Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric analysis-gas evolved analysis (TGA-EGA) and Folin&Ciocalteu tests (F&C). Release tests have been performed in double distilled water at 37 °C and 43 °C to verify the stability of the material.

We consider a model of self-propelled dynamics for athermal active particles, where the non-equilibrium active forces are modelled by a Ornstein-Uhlenbeck process. In the limit of no-driving force, the model reduces to the passive, Brownian dynamics of an atomistic glass forming fluid, the Wahnstr\"om binary mixture. The Wahnstr\"om mixture is known to show strong correlations between the emergence of slow dynamics and the formation of locally favoured structures based on icosahedra. Here, we study how the non-equilibrium forces affect the local structure of the system, and find that these strongly promote icosahedral order. The phases rich in local icosahedral order correspond to configurations of very low potential energy, suggesting that the non-equilibrium dynamics in the self propelled model can be effectively exploited to explore the potential energy surface of the binary mixture and have access to states that are difficult to attain using passive dynamics.

Background Exposure to some - but not all - quartz particles is associated to silicosis, lung cancer and autoimmune diseases. What imparts pathogenicity to any single quartz source is however still unclear. Crystallinity and various surface features are implied in toxicity. Quartz dusts used so far in particle toxicology have been obtained by grinding rocks containing natural quartz, a process which affects crystallinity and yields dusts with variable surface states. To clarify the role of crystallinity in quartz pathogenicity we have grown intact quartz crystals in respirable size. Methods Quartz crystals were grown and compared with a fractured specimen obtained by grinding the largest synthetic crystals and a mineral quartz (positive control). The key physico-chemical features relevant to particle toxicity - particle size distribution, micromorphology, crystallinity, surface charge, cell-free oxidative potential - were evaluated. Membranolysis was assessed on biological and artificial membranes. Endpoints of cellular stress were evaluated on RAW 264.7 murine macrophages by High Content Analysis after ascertaining cellular uptake by bio-TEM imaging of quartz-exposed cells. Results Quartz crystals were grown in the submicron (n-Qz-syn) or micron (μ-Qz-syn) range by modulating the synthetic procedure. Independently from size as-grown quartz crystals with regular intact faces did not elicit cellular toxicity and lysosomal stress on RAW 264.7 macrophages, and were non-membranolytic on liposome and red blood cells. When fractured, synthetic quartz (μ-Qz-syn-f) attained particle morphology and size close to the mineral quartz dust (Qz-f, positive control) and similarly induced cellular toxicity and membranolysis. Fracturing imparted a higher heterogeneity of silanol acidic sites and radical species at the quartz surface. Conclusions Our data support the hypothesis that the biological activity of quartz dust is not due to crystallinity but to crystal fragmentation, when conchoidal fractures are formed. Besides radical generation, fracturing upsets the expected long-range order of non-radical surface moieties - silanols, silanolates, siloxanes - which disrupt membranes and induce cellular toxicity, both outcomes associated to the inflammatory response to quartz. Electronic supplementary material The online version of this article (doi:10.1186/s12989-016-0136-6) contains supplementary material, which is available to authorized users.

This work describes the design of a modified porphyrin that bears four furan rings linked by 1,2-bis-(2-aminoethoxy)ethane spacers. This unit is a well-suited scaffold for a Diels-Alder reaction with commercial reduced-graphene oxide, which is also described in this paper. A new hybrid material is obtained, thanks to efficient grafting under microwave irradiation, and fully characterized in terms of structure (UV, TGA, Raman) and morphology (HR-TEM and AFM). Potential applications in photo- and sonodynamic therapy are envisaged.

We investigate the effects of the reversal of the gravitational field onto a sedimented and partially crystallised suspension of nearly-hard sphere colloids. We analyse the structural changes that take place during the melting of the crystalline regions and the reorganisation and assembly of the sedimenting particles. Through a comparison with numerical simulation, we access the single-particle kinetics and identify the key structural mechanism in the competition between five-fold symmetric and cubic crystalline structures. With the use of a coarse-grained, discrete model, we reproduce the kinetic network of reactions underpinning crystallisation and highlight the main microscopic transitions.