Toward chemical recycling of PU foams: study of the main purification options.

The recovery of the polyol component, after glycolysis of polyurethane (PU) foams coming from automotive waste, was investigated. Several separation methods such as simple sedimentation, centrifugation and liquid-liquid extraction, eventually preceded by an acid washing step, were tested. The obtained fractions were characterized by infrared spectroscopy and CHN elemental analysis. Furthermore, multivariate data analysis was carried out on the infrared spectra by principal component analysis to classify the fractions based on purity. IR spectroscopy coupled with principal component analysis was able to estimate the success of the separation and eventual culprits such as contaminations, which were then quantified by CHN elemental analysis. This approach addresses some critical limitations associated with classical analytical techniques such as NMR, TGA, GPC, MALDI-TOF that often require an extremely accurate separation of the depolymerized product fractions. Moreover, IR spectroscopy and CHN elemental analysis techniques are cheap and widespread in standard materials science laboratories. At last, based on the results of the analysis of the regenerated polyol fractions, and on the foaming tests, considerations were made to guide the choice of the purification method according to the application specifications and greenness.

Polystyrene Brush Evolution by Grafting to Reaction on Deglazed and Not-Deglazed Silicon Substrates.

Two model substrates for the grafting to reaction are considered: not-deglazed silicon, whose surface is coated by a thin oxide layer with reactive silanol groups on its surface; and deglazed silicon, where the oxide layer is removed by treatment with hydrofluoric acid. The reactive polymers are hydroxy-terminated polystyrenes with molecular weights ranging from 3.9 to 13.9 kg mol⁻1. The grafting to reaction is carried out at different temperatures and for different periods of time on the two different substrates. The thickness and the thermal stability of the resulting brushes are evaluated. Furthermore, the grafting of a highly dispersed system is simulated by blending two polymers with different molecular weights. Although the brush thickness growth is found to be faster on deglazed silicon, the preferential grafting of short chains occurs with equal chain selection propensity on both substrates.

Structure and stability of 7-mercapto-4-methylcoumarin self-assembled monolayers on gold: an experimental and computational analysis.

Self-assembled monolayers (SAM) of 7-mercapto-4-methylcoumarin (MMC) on a flat gold surface were studied by molecular dynamics (MD) simulations, reference-free grazing incidence X-ray fluorescence (GIXRF) and X-ray photoelectron spectroscopy (XPS), to determine the maximum monolayer density and to investigate the nature of the molecule/surface interface. In particular, the protonation state of the sulfur atom upon adsorption was analyzed, since some recent literature presented evidence for physisorbed thiols (preserving the S-H bond), unlike the common picture of chemisorbed thiyls (losing the hydrogen). MD with a specifically tailored force field was used to simulate either thiol or thiyl monolayers with increasing number of molecules, to determine the maximum dynamically stable densities. This result was refined by computing the monolayer chemical potential as a function of the density with the bennet acceptance ratio method, based again on MD simulations. The monolayer density was also measured with GIXRF, which provided the absolute quantification of the number of sulfur atoms in a dense self-assembled monolayer (SAM) on flat gold surfaces. The sulfur core level binding energies in the same monolayers were measured by XPS, fitting the recorded spectra with the binding energies proposed in the literature for free or adsorbed thiols and thiyls, to get insight on the nature of the molecular species present in the layer. The comparison of theoretical and experimental SAM densities, and the XPS analysis strongly support the picture of a monolayer formed by chemisorbed, dissociated thiyls.

Quantification of molecular weight discrimination in grafting to reactions from ultrathin polymer films by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

In the present study, a reliable and robust method was developed to quantify the molecular weight discrimination that can occur in grafting to reactions via indirect MALDI-TOF quantification of the molecular weights of grafted chains by comparing the characteristics of the polymeric material before the grafting reaction with those of the unreacted material recovered after grafting. Two polystyrene samples with different molecular weights and narrow molecular weight distributions were employed to prepare model blends that were grafted to silicon wafers and an analytical method was developed and validated to assess and quantify the modification of the molecular weight distribution that takes place during the grafting to process. Particular attention was paid to the standardization of the sample treatment and to find the best data collection and calibration methodologies in order to have statistically significant data even in the presence of a very scarce amount of the sample. Furthermore, to evaluate the accuracy of the analytical procedure, the lack of suitable standard and certified materials required a further experiment to be carried out by comparing the new optimized MALDI-TOF method and direct measurements using TGA-GC-MS on a model blend containing deuterated and hydrogenated polystyrene samples with appropriate molecular weights and distributions. The optimized method was applied on samples obtained by a thermally induced grafting to reaction from ultrathin polymer films and, for the first time, to our knowledge, an enrichment effect occurring in the ultrathin grafted layer obtained from a melt was evidenced.

Development of an enrichment method for endogenous phosphopeptide characterization in human serum.

The work describes the development of an enrichment method for the analysis of endogenous phosphopeptides in serum. Endogenous peptides can play significant biological roles, and some of them could be exploited as future biomarkers. In this context, blood is one of the most useful biofluids for screening, but a systematic investigation of the endogenous peptides, especially phosphorylated ones, is still lacking, mainly due to the lack of suitable analytical methods. Thus, in this paper, different phosphopeptide enrichment strategies were pursued, based either on metal oxide affinity chromatography (MOAC, in the form of commercial TiO2 spin columns or magnetic graphitized carbon black-TiO2 composite), or on immobilized metal ion affinity chromatography (IMAC, in the form of Ti4+-IMAC magnetic material or commercial Fe3+-IMAC spin columns). While MOAC strategies proved completely unsuccessful, probably due to interfering phospholipids displacing phosphopeptides, the IMAC materials performed very well. Different sample preparation strategies were tested, comprising direct dilution with the loading buffer, organic solvent precipitation, and lipid removal from the matrix, as well as the addition of phosphatase inhibitors during sample handling for maximized endogenous phosphopeptide enrichment. All data were acquired by a shotgun peptidomics approach, in which peptide samples were separated by reversed-phase nanoHPLC hyphenated with high-resolution tandem mass spectrometry. The devised method allowed the identification of 176 endogenous phosphopeptides in fresh serum added with inhibitors by the direct dilution protocol and the Ti4+-IMAC magnetic material enrichment, but good results could also be obtained from the commercial Fe3+-IMAC spin column adapted to the batch enrichment protocol.

Composition of ultrathin binary polymer brushes by thermogravimetry-gas chromatography-mass spectrometry.

In the present paper, a reliable and rugged thermogravimetry-gas chromatography-mass spectrometry (TGA-GC-MS) method was developed to determine the composition of ultrathin films consisting of binary blends of functional polystyrene (PS) and polymethylmethacrylate (PMMA) grafted to a silicon wafer. A general methodology will be given to address the composition determination problem for binary or even multicomponent polymer brush systems using the PS/PMMA-based samples as a paradigmatic example. In this respect, several distinct tailor-made materials were developed to ensure reliable calibration and validation stages. The analytical method was tested on unknown samples to follow the composition evolution in PS/PMMA brushes during the grafting reaction. A preferential grafting of the PMMA was revealed in full agreement with its preferential interaction with the SiO2 polar surface.

Bessel-like photonic nanojets from core-shell sub-wavelength spheres.

It is accepted so far that the formation of photonic nanojets requires the use of large dielectric spheres (several wavelengths in diameter). Here we show both numerically and experimentally that similar effects can be obtained with properly engineered sub-wavelength core-shell colloids. The design of the spheres is strongly inspired by a far-field approach for the generation of Bessel beams.

Evolution of lateral ordering in symmetric block copolymer thin films upon rapid thermal processing.

This work reports experimental findings about the evolution of lateral ordering of lamellar microdomains in symmetric PS-b-PMMA thin films on featureless substrates. Phase separation and microdomain evolution are explored in a rather wide range of temperatures (190-340 °C) using a rapid thermal processing (RTP) system. The maximum processing temperature that enables the ordering of block copolymers without introducing any significant degradation of macromolecules is identified. The reported results clearly indicate that the range of accessible temperatures in the processing of these self-assembling materials is mainly limited by the thermal instability of the grafted random copolymer layer, which starts to degrade at T > 300 °C, inducing detachment of the block copolymer thin film. For T ⩽ 290 °C, clear dependence of correlation length (ξ) values on temperature is observed. The highest level of lateral order achievable in the current system in a quasi-equilibrium condition was obtained at the upper processing temperature limit after an annealing time as short as 60 s.

Thermally induced self-assembly of cylindrical nanodomains in low molecular weight PS-b-PMMA thin films.

The phase behaviour in thin films of an asymmetric polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymer with a molecular weight of 39 kg mol(-1) was assessed at a wide range of temperatures and times. Cylindrical PMMA structures featuring a diameter close to 10 nm and perpendicularly oriented with respect to the substrate were obtained at 180 °C in relatively short annealing times (t ≤ 30 min) by means of a simple thermal treatment performed in a standard rapid thermal processing machine.

Periodic Arrays of Dopants in Silicon by Ultralow Energy Implantation of Phosphorus Ions through a Block Copolymer Thin Film.

In this work, block copolymer lithography and ultralow energy ion implantation are combined to obtain nanovolumes with high concentrations of phosphorus atoms periodically disposed over a macroscopic area in a p-type silicon substrate. The high dose of implanted dopants grants a local amorphization of the silicon substrate. In this condition, phosphorus is activated by solid phase epitaxial regrowth (SPER) of the implanted region with a relatively low temperature thermal treatment preventing diffusion of phosphorus atoms and preserving their spatial localization. Surface morphology of the sample (AFM, SEM), crystallinity of the silicon substrate (UV Raman), and position of the phosphorus atoms (STEM- EDX, ToF-SIMS) are monitored during the process. Electrostatic potential (KPFM) and the conductivity (C-AFM) maps of the sample surface upon dopant activation are compatible with simulated I-V characteristics, suggesting the presence of an array of not ideal but working p-n nanojunctions. The proposed approach paves the way for further investigations on the possibility to modulate the dopant distribution within a silicon substrate at the nanoscale by changing the characteristic dimension of the self-assembled BCP film.

Persistent dystrophin protein restoration 90 days after a course of intraperitoneally administered naked 2'OMePS AON and ZM2 NP-AON complexes in mdx mice.

In Duchenne muscular dystrophy, the exon-skipping approach has obtained proof of concept in animal models, myogenic cell cultures, and following local and systemic administration in Duchenne patients. Indeed, we have previously demonstrated that low doses (7.5 mg/Kg/week) of 2'-O-methyl-phosphorothioate antisense oligoribonucleotides (AONs) adsorbed onto ZM2 nanoparticles provoke widespread dystrophin restoration 7 days after intraperitoneal treatment in mdx mice. In this study, we went on to test whether this dystrophin restoration was still measurable 90 days from the end of the same treatment. Interestingly, we found that both western blot and immunohistochemical analysis (up to 7% positive fibres) were still able to detect dystrophin protein in the skeletal muscles of ZM2-AON-treated mice at this time, and the level of exon-23 skipping could still be assessed by RT real-time PCR (up to 10% of skipping percentage). In contrast, the protein was undetectable by western blot analysis in the skeletal muscles of mdx mice treated with an identical dose of naked AON, and the percentage of dystrophin-positive fibres and exon-23 skipping were reminiscent of those of untreated mdx mice. Our data therefore demonstrate the long-term residual efficacy of this systemic low-dose treatment and confirm the protective effect nanoparticles exert on AON molecules.

Sulfonates-PMMA nanoparticles conjugates: a versatile system for multimodal application.

We report herein the viability of a novel nanoparticles (NPs) conjugated system, namely the attachment, based on ionic and hydrophobic interactions, of different sulfonated organic salts to positively charged poly(methylmethacrylate) (PMMA)-based core-shell nanoparticles (EA0) having an high density of ammonium groups on their shells. In this context three different applications of the sulfonates@EA0 systems have been described. In detail, their ability as cytotoxic drugs and pro-drugs carriers was evaluated in vitro on NCI-H460 cell line and in vivo against human ovarian carcinoma IGROV-1 cells. Besides, 8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt (HPTS) was chosen for NPs loading, and its internalization as bioimaging probe was evaluated on Hep G2 cells. Overall, the available data support the interest for these PMMA NPs@sulfonates systems as a promising formulation for theranostic applications. In vivo biological data strongly support the potential value of these core-shell NPs as delivery system for negatively charged drugs or biologically active molecules. Additionally, we have demonstrated the ability of these PMMA core-shell nanoparticles to act as efficient carriers of fluorophores. In principle, thanks to the high PMMA NPs external charge density, sequential and very easy post-loading of different sulfonates is achievable, thus allowing the preparation of nanocarriers either with bi-modal drug delivery behaviour or as theranostic systems.

Following the fate of microplastic in four abiotic and biotic matrices along the Ticino River (North Italy).

Microplastics (MPs) are emerging contaminants in freshwater systems that have already attracted much scientific interest, but little attention has been paid to a multi-matrix analysis of MP occurrences along the length of a river. The present research provides the first record of MP contamination of four abiotic and biotic matrices from a river ecosystem simultaneously analysed. MPs were isolated and identified by micro-Fourier Transform Infrared (µ-FTIR) spectroscopy from samples collected along the Ticino River in North Italy during spring 2019. Abiotic samples were surface water (n = 18, 33 MPs m-3) and sediment (n = 18, 11 MPs kg-1), while biological samples consisted of stomach and gut content of fish (n = 18, wels catfish, Silurus glanis, 0.032 MPs g-1) and macroinvertebrates (n = 90, caddisfly larvae, Hydropsychidae, 0.03 MPs mg-1). MPs were found in biota from all stations; 44% of fish and 61% of macroinvertebrate samples contained MPs. The calculated unit-consistent concentration ratios indicate that both S. glanis and Hydropsychidae larvae had a consistent higher amount of MPs than their respective medium (sediment and water), strongly suggesting an efficient uptake pathway into organisms. MP levels in surface water, sediment, fish and macroinvertebrates were not correlated and did not increase with the river's length. From our mass balance calculations, the Ticino River transports a consistent amount of MP (yearly load of 3.40 × 1011 ± 1.1 × 1011 MPs) to the Po River. This MP load was almost half than an estimated MP load from wastewater treatment plants (WWTPs). On that basis and supported by the finding that MP concentration in sediment was mostly opposed to that in surface water but was on average 750-fold higher compared to the water matrix, we surmise that the complex hydrological network of the Ticino River retains a consistent amount of MPs which might build up over time.

A Biological Study of Composites Based on the Blends of Nanohydroxyapatite, Silk Fibroin and Chitosan.

In this work, the biological properties of three-dimensional scaffolds based on a blend of nanohydroxyapatite (nHA), silk fibroin (SF), and chitosan (CTS), were prepared using a lyophilization technique with various weight ratios: 10:45:45, 15:15:70, 15:70:15, 20:40:40, 40:30:30, and 70:15:15 nHA:SF:CTS, respectively. The basic 3D scaffolds were obtained from 5% (w/w) chitosan and 5% silk fibroin solutions and then nHA was added. The morphology and physicochemical properties of scaffolds were studied and compared. A biological test was performed to study the growth and osteogenic differentiation of human bone marrow mesenchymal stem cells (hMSCs). It was found that the addition of chitosan increases the resistance properties and extends the degradation time of materials. In vitro studies with human mesenchymal stem cells found a high degree of biotolerance for the materials produced, especially for the 20:40:40 and 15:70:15 (nHa:SF:CTS) ratios. The presence of silk fibroin and the elongated shape of the pores positively influenced the differentiation of cells into osteogenic cells. By taking advantage of the differentiation/proliferation cues offered by individual components, the composites based on the nanohydroxyapatite, silk fibroin, and chitosan scaffold may be suitable for bone tissue engineering, and possibly offer an alternative to the widespread use of collagen materials.

Microplastic contamination of supraglacial debris differs among glaciers with different anthropic pressures.

Microplastic (MP) contamination is ubiquitous and widespread in terrestrial and aquatic ecosystems, including remote areas. However, information on the presence and distribution of MPs in high-mountain ecosystems, including glaciers, is still limited. The present study aimed at investigating presence, spatial distribution, and patterns of contamination of MPs on three glaciers of the Ortles-Cevedale massif (Central Alps, Northern Italy) with different anthropic pressures, i.e., the Forni, Cedec and Ebenferner-Vedretta Piana glaciers. Samples of supraglacial debris were randomly collected from the glaciers and MPs were isolated. The mean amount (±SE) of MPs measured in debris from Forni, Cedec and Ebenferner-Vedretta Piana glaciers was 0.033 ± 0.007, 0.025 ± 0.009, and 0.265 ± 0.027 MPs g-1 dry weight, respectively. The level and pattern of MP contamination from the Ebenferner-Vedretta Piana glacier were significantly different from those of the other glaciers. No significant spatial gradient in MP distribution along the ablation areas of the glaciers was observed, suggesting that MPs do not accumulate toward the glacier snout. Our results confirmed that local contamination can represent a relevant source of MPs in glacier ecosystems experiencing high anthropic pressure, while long-range transport can be the main source on other glaciers.

Microplastic Contamination in Snow from Western Italian Alps.

Recent studies have documented the presence of microplastics (MPs) in remote areas, including soils or sediments collected in mountain and glacier environments, but information on their presence in snow is scant. The present study aimed at exploring the presence of MPs in residual snow collected in four locations of the Aosta Valley (Western Italian Alps), with different accessibility and human presence. Overall, the µ-FTIR analyses confirmed the presence of 18 MPs in snow, 7 (39%) items were fibres, while 11 (61%) were fragments. Polyethylene (PE; 7 MPs) was the main polymer, followed by polyethylene terephthalate (PET; 3 MPs), high density PE (HDPE; 3 MPs), polyester (2 MPs), while only 1 MP made by low density PE, polypropylene and polyurethane were found. The mean (± SE) concentration of MPs in snow ranged between 0.39 ± 0.39 MPs/L and 4.91 ± 2.48 MPs/L, with a mean of 2.32 ± 0.96 MPs/L for the sampling locations. The concentration of MPs did not statistically differ among locations. Our results suggest that MPs presence in high-mountain ecosystems might depend on deposition through atmospheric precipitations or local sources due to human activities. For these reasons, policies aiming at reducing plastic use and dispersal in mountain areas may be effective in preventing local MP contamination.

Cell instructive Liquid Crystalline Networks for myotube formation.

Development of biological tissues in vitro is not a trivial task and requires the correct maturation of the selected cell line. To this aim, many attempts were done mainly by mimicking the biological environment using micro/nanopatterned or stimulated scaffolds. However, the obtainment of functional tissues in vitro is still far from being achieved. In contrast with the standard methods, we here present an easy approach for the maturation of myotubes toward the reproduction of muscular tissue. By using liquid crystalline networks with different stiffness and molecular alignment, we demonstrate how the material itself can give favorable interactions with myoblasts helping a correct differentiation. Electrophysiological studies demonstrate that myotubes obtained on these polymers have more adult-like morphology and better functional features with respect to those cultured on standard supports. The study opens to a platform for the differentiation of other cell lines in a simple and scalable way.

Cationic PMMA nanoparticles bind and deliver antisense oligoribonucleotides allowing restoration of dystrophin expression in the mdx mouse.

For subsets of Duchenne muscular dystrophy (DMD) mutations, antisense oligoribonucleotide (AON)-mediated exon skipping has proven to be efficacious in restoring the expression of dystrophin protein. In the mdx murine model systemic delivery of AON, recognizing the splice donor of dystrophin exon 23, has shown proof of concept. Here, we show that using cationic polymethylmethacrylate (PMMA) (marked as T1) nanoparticles loaded with a low dose of 2'-O-methyl-phosphorothioate (2'OMePS) AON delivered by weekly intraperitoneal (IP) injection (0.9 mg/kg/week), could restore dystrophin expression in body-wide striated muscles. Delivery of an identical dose of naked AON did not result in detectable dystrophin expression. Transcription, western, and immunohistochemical analysis showed increased levels of dystrophin transcript and protein, and correct localization at the sarcolemma. This study shows that T1 nanoparticles have the capacity to bind and convoy AONs in body-wide muscle tissues and to reduce the dose required for dystrophin rescue. By immunofluorescence and electron microscopy studies, we highlighted the diffusion pathways of this compound. This nonviral approach may valuably improve the therapeutic usage of AONs in DMD as well as the delivery of RNA molecules with many implications in both basic research and medicine.

Occurrence of microplastics in pellets from the common kingfisher (Alcedo atthis) along the Ticino River, North Italy.

Previous research has reported avian plastic ingestion in marine bird species. Yet, while research attention on plastic pollution is shifting from marine to freshwater ecosystems, very few information on plastic ingestion is available for freshwater birds. Here, we examined the presence of microplastic in regurgitated pellets of the common kingfisher (Alcedo atthis) collected along the Ticino River (North Italy). In total, 133 kingfisher's pellets were examined between March and October 2019 from 54 transects along the river. Plastic elements were detected and identified by visual inspection followed by µ-FTIR and SEM-EDS. Overall, we found 12 (micro)plastics from at least three different polymers in 7.5% of the pellets. This study provides the first report of plastic uptake of this bird species. It highlights the importance of spectroscopic techniques in plastic monitoring studies in order to avoid misidentification of items found. Documenting the presence of plastic ingestion by top carnivores such as fish-eating birds is necessary to understand the pervasiveness and impact of (micro)plastic pollution in food webs of freshwater ecosystems.

Core-shell silica-rhodamine B nanosphere for synthetic opals: from fluorescence spectral redistribution to sensing.

Photonic crystals are a unique tool to modify the photoluminescence of light-emitting materials. A variety of optical effects have been demonstrated by infiltrating opaline structures with photoactive media. On the other hand, the fabrication of such structures includes complex infiltration steps, that often affect the opal lattice and decrease the efficiency of light emission control. In this work, silica nanospheres were directly functionalized with rhodamine B to create an emitting shell around the dielectric core. Simple tuning of the microsphere preparation conditions allows selecting the appropriate sphere diameter and polydispersity index approaching 5%. These characteristics allow facile self-assembling of the nanospheres into three-dimensional photonic crystals whose peculiar density of photonic states at the band-gap edges induces spectral redistribution of the rhodamine B photoluminescence. The possibility to employ the new stable structure as sensor is also investigated. As a proof of principle, we report the variation of light emission obtained by exposure of the opal to vapor of chlorobenzene.