Tuning Local Order in Starch Nanoparticles Exploiting Nonsolvency with "Green" Solvents.

Starch is a renewable biopolymer that can be sourced from agricultural waste and used to produce nanoparticles (SNPs). In particular, amorphous SNPs have potential application in numerous fields, including the consolidation of weakened paintings in the cultural heritage preservation. Starch dissolution followed by nanoprecipitation in nonsolvents is an advantageous synthetic route, but new methodologies are needed to feasibly control the physicochemical properties of the SNPs. Here, we explored nanoprecipitation by nonsolvency using a set of "green" solvents to obtain amorphous SNPs, rather than starch nanocrystals already reported in the literature. The effect of the nonsolvent on the ordering of polymer chains in the obtained SNPs was studied. The recovery of local order (e.g., isolated V-type helices) after dissolution was shown to depend on the type of solvents used in the dissolution and precipitation steps, while long-range order (extended arrays of helices) is lost. Aqueous dispersions of the SNPs provided effective consolidation of powdery painted layers, showing that the selection of particle synthetic routes can be dictated by sustainability and scalability criteria. These "green" formulations are candidates as new consolidants in art preservation, and the possibility of tuning local order in amorphous starch assemblies might also impact fields like food chemistry, pharmaceutics, and nanocomposites, where SNPs with tunable amorphousness are more advantageous than nanocrystals.

Hierarchical Emulsion Structure and Functionality Regulated by Coexisting Bicontinuous Microemulsion and Liquid Crystal Domains.

Since microemulsions are usually low viscosity fluids, enhanced rheological properties while maintaining their structure-derived functionality have long been desired from an industrial application point of view. However, for instance, it is practically difficult to thicken bicontinuous microemulsions (BCMEs) without perturbing their alternating domain structure or to emulsify oils using BCME having ultralow interfacial tension as an external phase. In this study, a methodology called a BCLC emulsification technique has been constructed to obtain oil-in-water emulsions stabilized by coexisting BCME and liquid crystal (LC) phases. The produced emulsions based on polyglyceryl-10 diisostearate, polyglyceryl-6 dicaprate, cetyl ethylhexanoate, and water are structurally scrutinized by means of small- and wide-angle X-ray scattering (SWAXS), freeze fracture transmission electron microscopy (FF-TEM), and scanning electron assisted dielectric microscopy (SE-ADM). The data provide experimental evidence that this methodology enables one to control the bending elasticity of the interfacial membranes and consequent long-range order of the BCME domains. Moreover, closely correlated with the interfacial membrane properties, submicrometer-sized fine oil droplets are supported by the LC networks and agglomerated into spongy or network-like phase-separation patterns. The resulting nonfluidic, jelly emulsions are particularly useful in cosmetics because of combined BCME-derived high cleansing performance and excellent usability owing to the enhanced viscosity. The thickening mechanisms are essentially different from those of common lamellar-gel-stabilized oil-in-water emulsions, which utilize crystalline lamellar gel networks as oil droplet stabilizers.

New sustainable polymers and oligomers for Cultural Heritage conservation.

The development of "green" chemistry materials with enhanced properties is a central topic in numerous applicative fields, including the design of polymeric systems for the conservation of works of art. Traditional approaches in art restoration comprise polymer thickeners and viscous dispersions to partially control solvents in the removal of soil or aged varnishes/coatings from artifacts. Alternatively, polymeric gel networks can be specifically designed to grant full control of the cleaning action, yielding safe, time- and cost-effective restorations. The selection of polymers and oligomers in gel design is crucial to tune solvent upload, retention, and controlled release over the sensitive artistic surfaces. Starting from an overview of traditional polymer formulations and state-of-the-art gel systems for cleaning works of art, we provide here the design of a new class of gels, focusing on the selection of oligomers to achieve gels with tailored hydrophilicity/hydrophobicity. We evaluated the oligomers Hydrophilic-Lipophilic Balance (HLB) by developing, for the first time, a novel methodology combining SEC and DOSY NMR analysis, which was tested on a library of "green" oligoesters synthesized by polycondensation and poorly explored in the literature. Oligomers with moderate polydispersity were chosen to validate the new protocol as a robust tool for designing polymeric gels even on industrial scale. The methodology is more time-effective than traditional methods, and gives additional insights on the oligomers physico-chemical nature, evaluating their compatibility with different solvents. Then, we used the selected oligoesters with castor oil to obtain a new class of organogels able to upload solvents with varying polarity, which effectively removed different types of unwanted layers typically found in painting restoration. These results validate the oligomers screening approach and the new class of gels as promising chemical processes/materials in art preservation. The methodology can potentially allow evaluation of HLB also for small molecules (e.g., surfactants), opening for the formulation of polymers solutions/gels beyond Cultural Heritage conservation, as in pharmaceutics, cosmetics, food industry, tissue engineering, agriculture, and others.

New horizons on advanced nanoscale materials for Cultural Heritage conservation.

Nanomaterials have permeated numerous scientific and technological fields, and have gained growing importance over the past decades also in the preservation of Cultural Heritage. After a critical overview of the main nanomaterials adopted in art preservation, we provide new insights into some highly relevant gels, which constitute valuable tools to selectively remove dirt or other unwanted layers from the surface of works of art. In particular, the recent "twin-chain" gels, obtained by phase separation of two different PVAs and freeze-thawing, were considered as the most performing gel systems for the cleaning of Cultural Heritage. Three factors are crucial in determining the final gel properties, i.e., pore size, pore connectivity, and surface roughness, which belong to the micro/nanodomain. The pore size is affected by the molecular weight of the phase-separating PVA polymer, while pore connectivity and tortuosity likely depend on interconnections formed during gelation. Tortuosity greatly impacts on cleaning capability, as the removal of matter at the gel-target interface increases with the uploaded fluid's residence time at the interface (higher tortuosity produces longer residence). The gels' surface roughness, adaptability and stickiness can also be controlled by modulating the porogen amount or adding different polymers to PVA. Finally, PVA can be partially replaced with different biopolymers yielding gels with enhanced sustainability and effective cleaning capability, where the selection of the biopolymer affects the gel porosity and effectiveness. These results shed new light on the effect of micro/nanoscale features on the cleaning performances of "twin-chain" and composite gels, opening new horizons for advanced and "green"/sustainable gel materials that can impact on fields even beyond art preservation, like drug-delivery, detergency, food industry, cosmetics and tissue engineering.

Highly biocidal poly(vinyl alcohol)-hydantoin/starch hybrid gels: A "Trojan Horse" for Bacillus subtilis.

HYPOTHESIS: Poly (vinyl alcohol) (PVA) cryogels can be functionalized with n-Halamines to confer biocidal features useful for their application as wound-dressing tools. Their efficacy can be boosted by stably embedding a polymeric bacterial food source (e.g., starch) in the gel matrix. The bioavailability of the food source lures bacteria inside the gel network via chemotactic mechanisms, promoting their contact with the biocidal functionalities and their consequent inactivation. EXPERIMENTS: The synthesis of a novel hydantoin-functionalized PVA (H-PVA-hyd) is proposed. The newly synthesized H-PVA-hyd polymer was introduced in the formulation of H-PVA-based cryogels. To promote the cryogelation of the systems we exploited phase-separation mechanisms employing either a PVA carrying residual acetate groups (L-PVA) or starch as phase-segregating components. The permanence of the biocidal functionality after swelling was investigated via proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FT-IR) microscopy. The activated H-PVA-hyd cryogels have been tested against bacteria with amylolytic activity (Bacillus subtilis) and the outcomes were analyzed by direct observation via confocal laser scanning microscopy (CLSM). FINDINGS: The cryogels containing starch resulted in being the most effective (up to 90% bacterial killing), despite carrying a lower amount of hydantoin groups than their starch-free counterparts, suggesting that their improved efficacy relies on a "Trojan Horse" type of mechanism.

Tailoring the properties of poly(vinyl alcohol) "twin-chain" gels via sebacic acid decoration.

HYPOTHESIS: The development of gels capable to adapt and act at the interface of rough surfaces is a central topic in modern science for Cultural Heritage preservation. To overcome the limitations of solvents or polymer solutions, commonly used in the restoration practice, poly(vinyl alcohol) (PVA) "twin-chain" polymer networks (TC-PNs) have been recently proposed. The properties of this new class of gels, that are the most performing gels available for Cultural Heritage preservation, are mostly unexplored. This paper investigates how chemical modifications affect gels' structure and their rheological behavior, producing new gelled systems with enhanced and tunable properties for challenging applications, not restricted to Cultural Heritage preservation. EXPERIMENTS: In this study, the PVA-TC-PNs structural and functional properties were changed by functionalization with sebacic acid into a new class of TC-PNs. Functionalization affects the porosity and nanostructure of the network, changing its uptake/release of fluids and favoring the uptake of organic solvents with various polarity, a crucial feature to boost the versatility of TC-PNs in practical applications. FINDINGS: The functionalized gels exhibited unprecedented performances during the cleaning of contemporary paintings from the Peggy Gugghenheim collection (Venice), whose restoration with traditional solvents and swabs would be difficult to avoid possible disfigurements to the painted layers. These results candidate the functionalized TC-PNs as a new, highly promising class of gels in art preservation.

Direct observation of the effects of chemical fixation in MNT-1 cells: A SE-ADM and Raman study.

Aldehydes fixation was accidentally discovered in the early 20th century and soon became a widely adopted practice in the histological field, due to an excellent staining enhancement in tissues imaging. However, the fixation process itself entails cell proteins denaturation and crosslinking. The possible presence of artifacts, that depends on the specific system under observation, must therefore be considered to avoid data misinterpretation. This contribution takes advantage of scanning electron assisted-dielectric microscopy (SE-ADM) and Raman 2D imaging to reveal the possible presence and the nature of artifacts in unstained, and paraformldehyde, PFA, fixed MNT-1 cells. The high resolution of the innovative SE-ADM technique allowed the identification of globular protein clusters in the cell cytoplasm, formed after protein denaturation and crosslinking. Concurrently, SE-ADM images showed a preferential melanosome adsorption on the cluster's outer surface. The micron-sized aggregates were discernible in Raman 2D images, as the melanosomes signal, extracted through 2D principal component analysis, unequivocally mapped their location and distribution within the cells, appearing randomly distributed in the cytoplasm. Protein clusters were not observed in living MNT-1 cells. In this case, mature melanosomes accumulate preferentially at the cell periphery and are more closely packed than in fixed cells. Our results show that, although PFA does not affect the melanin structure, it disrupts melanosome distribution within the cells. Proteins secondary structure, conversely, is partially lost, as shown by the Raman signals related to α-helix, ß-sheets, and specific amino acids that significantly decrease after the PFA treatment.

Reproducing bronze archaeological patinas through intentional burial: A comparison between short- and long-term interactions with soil.

The reproduction of archaeological corrosion patinas is a key issue for the reliable validation of conservation materials before their use on cultural objects. In this study, bronze disks were intentionally buried for 15 years in the soil of the archaeological site of Tharros, both in laboratory and in situ, with the aim of reproducing corrosion patinas typical of archaeological artifacts to be used as representative surfaces for testing novel cleaning gels. The microstructural, microchemical and mineralogical features of the patinas were analyzed by a multianalytical approach, based on optical microscopy (OM), field emission scanning electron microscopy coupled with energy dispersive spectrometry (FE-SEM-EDS) and X-ray diffraction (XRD). The patinas developed in 15 years were compared with an archaeological bronze recovered from the same site after about two thousand years of burial (referred as short-term and long-term interaction, respectively). Results revealed a similar corrosion behavior, especially in terms of chemical composition and corrosion mechanisms. XRD detected the ubiquitous presence of cuprite, copper hydroxychlorides and terrigenous minerals, while OM and FE-SEM-EDS analyses of cross-sections evidenced similar patinas' stratigraphy, identifying decuprification as driving corrosion mechanism. However, some differences related to the type of local environment and to the time spent in soil were evidenced. In particular, patinas developed in situ are more heterogeneous and rougher, while the archaeological one is thicker and presents a major amount of cuprite, terrigenous deposits and uncommon corrosion compounds. Based on our findings, the disks buried in situ were selected and used as disposable substrates to study the cleaning effect of a novel polyvinyl alcohol (PVA)-based gel loaded with a chelating agent (Na2EDTA · 2H2O). Results show that the gel is effective in removing disfiguring degradation compounds and preserving the stable and protective patina. Based on the conservation needs, the time of application can be properly tuned. It is worth noticing that after a few minutes the green corrosion products can be selectively removed. The EDS analysis performed on the gels after cleaning reveals that they are highly selective for the removal of copper(II) compounds rather than Cu(I) oxide or Cu(0) from bronze substrates.

From Nanoparticles to Gels: A Breakthrough in Art Conservation Science.

Cultural heritage is a crucial resource to increase our society's resilience. However, degradation processes, enhanced by environmental and anthropic risks, inevitably affect works of art, hindering their accessibility and socioeconomic value. In response, interfacial and colloidal chemistry has proposed valuable solutions over the past decades, overcoming the limitations of traditional restoration materials and granting cost- and time-effective remedial conservation of the endangered artifacts. Ranging from inorganic nanoparticles to hybrid composites and soft condensed matter (gels, microemulsions), a wide palette of colloidal systems has been made available to conservators worldwide, targeting the consolidation, cleaning, and protection of works of art. The effectiveness and versatility of the proposed solutions allow the safe and effective treatment of masterpieces belonging to different cultural and artistic productions, spanning from classic ages to the Renaissance and modern/contemporary art. Despite these advancements, the formulation of materials for the preservation of cultural heritage is still an open, exciting field, where recent requirements include coping with the imperatives of the Green Deal to foster the production of sustainable, low-toxicity, and environmentally friendly systems. This review gives a critical overview starting from pioneering works up to the latest advancements in colloidal systems for art conservation, a challenging topic where effective solutions can be transversal to multiple sectors even beyond cultural heritage preservation, from the pharmaceutical and food industry, to cosmetics, tissue engineering, and detergency.

Sponge-like Cryogels from Liquid-Liquid Phase Separation: Structure, Porosity, and Diffusional Gel Properties.

Macroporous gels find application in several scientific fields, ranging from art restoration to wastewater filtration or cell entrapment. In this work, two-component sponge-like cryogels are challenged to assess their cleaning performances and to investigate how pores size and connectivity affect physico-chemical properties. The gels were obtained through a freeze-thaw process, exploiting a spontaneous polymer-polymer phase-separation occurring in the pre-gel solution. During the freezing step, a highly hydrolyzed polyvinyl alcohol (H-PVA) forms the hydrogel walls. The secondary components, namely a partially hydrolyzed polyvinyl alcohol (L-PVA) or polyvinyl pyrrolidone (PVP), act as modular porogens, being partially extracted during gel washing. H-PVA/L-PVA and H-PVA/PVP mixtures were studied by confocal laser scanning microscopy to unveil sols and gels morphology at the micron-scale, while small angle X-ray scattering was used to get insights about characteristic dimensions at the nanoscale. The gelation mechanism was investigated through rheology measurements, and the characteristic exponents were compared to De Gennes' scaling laws gathered from percolation. In the field of art conservation, these sponge-like gels are ideal systems for the cleaning of artistic painted surfaces. Their interconnected pores allow the diffusion of cleaning fluids at the painted interface, facilitating dirt uptake and/or detachment. This study uncovered a direct relationship linking a gel's cleaning performance to its apparent tortuosity. These findings can pave the way to fine-tuning systems with enhanced cleaning abilities, not restricted to the restoration of irreplaceable priceless works of art, but with possible application in diverse research fields.

Ultrasound and Microwave-Assisted Synthesis of Hexagonally Ordered Ce-Promoted Mesoporous Silica as Ni Supports for Ethanol Steam Reforming.

Solvothermal synthesis of mesoporous materials based on amphiphilic molecules as structure-directing agents can be enhanced using non-conventional technologies for stirring and thermal activation. Here, we disclose a green synthesis approach for the preparation of cerium-modified hexagonally ordered silica sieves. Ultrasound micromixing enabled us to obtain well-dispersed Ce in the self-assembled silica network and yielded ordered materials with high cerium content (Ce/Si molar ratio = 0.08). Microwave dielectric heating, applied by an innovative open-end coaxial antenna, was used to reduce the overall hydrothermal synthesis time and to improve the surface area and textural properties. These mesoporous materials were used as a Ni catalyst support (10 wt.% metal loading) for the ethanol steam reforming reaction. The new catalysts featured complete ethanol conversion, high H2 selectivity (65%) and better stability, compared to the same catalyst prepared with magnetic stirring and conventional heating. The Ce-promoted silica sieves offered a suitable support for the controlled growth of nanocarbon that does not result in catalyst deactivation or poisoning after 6 h on stream.

Conformational changes and location of BSA upon immobilization on zeolitic imidazolate frameworks.

The location and the conformational changes of proteins/enzymes immobilized within Metal Organic Frameworks (MOFs) are still poorly investigated and understood. Bovine serum albumin (BSA), used as a model protein, was immobilized within two different zeolitic imidazolate frameworks (ZIF-zni and ZIF-8). Pristine ZIFs and BSA@ZIFs were characterized by X-ray diffraction, small-angle X-ray scattering, scanning electron microscopy, confocal laser scanning microscopy, thermogravimetric analysis, micro-FTIR and confocal Raman spectroscopy to characterize MOFs structure and the protein location in the materials. Moreover, the secondary structure and conformation changes of BSA after immobilization on both ZIFs were studied with FTIR. BSA is located both in the inner and on the outer surface of MOFs, forming domains that span from the micro- to the nanoscale. BSA crystallinity (ß-sheets + α-helices) increases up to 25 % and 40 % due to immobilization within ZIF-zni and ZIF-8, respectively, with a consequent reduction of ß-turns.

Nanostructured bio-based castor oil organogels for the cleaning of artworks.

HYPOTHESIS: Organic solvents are often used for cleaning highly water-sensitive artifacts in modern/contemporary art. Due to the toxicity of most solvents, confining systems must be formulated to use these fluids in a safe and controlled way. We propose here castor oil (CO) organogels, obtained thorough cost-effective sustainable polyurethane crosslinking. This methodology is complementary to previously demonstrated hydrogels, when conservators opt for organic solvents over aqueous formulations. EXPERIMENTS: The gels were characterized via Small-angle Neutron Scattering and rheology before and after swelling in two organic solvents commonly adopted in cleaning paintings. The removal of a photo-aged acrylic-ketonic varnish was evaluated under visible and ultraviolet light, and with FTIR 2D imaging. FINDINGS: The new gels are dry systems that can be easily stored and loaded with solvents before use. Their nanoscale organization, viscoelasticity and cleaning action are controlled changing the amount of crosslinking, the polymeric backbone, and the loaded solvents. The fluids are confined in the nanosized polymeric mesh of the gels, which are highly retentive, granting controlled release over delicate paint layers, and transparent, allowing monitoring of the cleaning process. These features, along with their sustainable synthesis, candidate the CO organogels as feasible solutions for cultural heritage preservation, expanding the palette of advanced tools for conservators over traditional thickeners.

Adsorption kinetics of acetic acid into ZnO/castor oil-derived polyurethanes.

HYPOTHESIS: Materials and colloids science can provide significant contributions to the conservation of Cultural Heritage. Hybrid systems made of a castor oil-derived polymeric network and a disperse phase of zinc oxide particles (ZnO/COPs) can be more effective absorbers of acetic acid (AcOH, a major pollutant harmful to artifacts in museums and art collections) than state-of-the-art materials, provided the acid uptake mechanism by the hybrids is elucidated and optimized. The starting hypothesis was that the polymer matrix might act as transporter, while acid adsorption would take place at the ZnO particles surface. The effect of particles size was expected to play a significant role. EXPERIMENTS: The adsorption kinetics of the hybrids were studied in the 23-45˚C range, in comparison with activated charcoal, the benchmark employed by conservators. Morphological and fractal dimension of ZnO micro- and nano-particles in the hybrid networks were investigated and correlated to the adsorption kinetics. FINDINGS: The presence of a two-steps mechanism for AcOH uptake by the hybrids was demonstrated for the first time: a combination of Fickian diffusion and Case-II transport occurs in the COP matrix, and adsorption dominates acid uptake (followed by neutralization) at the particles surface. This mechanism is likely key to explain the enhanced performances of the hybrids vs activated charcoal and state-of-the-art tools to remove AcOH. The hybrids have high uptake capacity, and lower activation energies for the removal process than materials where the uptake of acid relies solely on adsorption. The size of the ZnO particles contributes to the process, i.e. nanoparticles form smaller and ramified fractal clusters that are able to adsorb AcOH more effectively than microparticles. These insights demonstrated the efficacy of the novel hybrids in art conservation, where the control of minimal concentrations of VOCs is crucial for the preventive conservation of masterpieces, and can be useful to other fields where efficient capture of acetic acid is critical (food industry, textile dyeing/printing, etc.).

Role of amylose and amylopectin in PVA-starch hybrid cryo-gels networks formation from liquid-liquid phase separation.

HYPOTHESIS: The role of amylose and amylopectin in the formation of cryogels based on Poly(vinyl alcohol) (PVA) and starch is poorly understood. A systematic investigation of simplified systems containing PVA, amylose, and/or amylopectin constitutes the basis to predict the final features of PVA/starch cryogels by knowing their composition, and the amylose content of the employed raw starches. EXPERIMENTS: Pre-gel solutions and cryogels containing PVA/amylose, PVA/amylopectin, and PVA/amylose/amylopectin in variable ratios were investigated employing small-angle X-ray scattering (SAXS), confocal laser scanning microscopy (CLSM), differential scanning calorimetry (DSC), and rheological measurements. The gel fraction (G%) of 23 samples with variable compositions was calculated and plotted to predict the G% (the gel fraction) of any PVA/amylose/amylopectin mixing ratio. FINDINGS: We report on how the PVA, amylose, and amylopectin composition affect the properties of the final polymer blend and cryogel formation. In particular, PVA/amylose and PVA/amylopectin show different behaviors with respect to cryogel formation. We show that is possible to predict cryogel formation by using the simple G% parameter for any PVA/amylose/amylopectin mixing ratio, ruling out the starch botanical origin in the gel formation. The results reported in this work represent a simple tool, able to predict the formation of high-quality biobased materials that can replace fully synthetic materials with a significantly positive impact on our ecosystem.

Synthesis, Characterization, and Soil Burial Degradation of Biobased Polyurethanes.

There is an urgent need for developing degradable polymeric systems based on bio-derived and sustainable materials. In recent years, polyurethanes derived from castor oil have emerged due to the large availability and sustainable characteristics of castor oil. However, these polymers are normally prepared through tedious and/or energy-intensive procedures or using high volatile and/or toxic reagents such as volatile isocyanates or epoxides. Furthermore, poor investigation has been carried out to design castor oil derived polyurethanes with degradable characteristics or thorough specifically sustainable synthetic procedures. Herein, castor oil-derived polyurethane with more than 90% biomass-derived carbon content and enhanced degradable features was prepared through a simple, eco-friendly (E-factor: 0.2), and scalable procedure, employing a recently developed commercially available biomass-derived (61% bio-based carbon content) low-volatile polymeric isocyanate. The novel material was compared with a castor oil derived-polyurethane prepared with a commercially available fossil-based isocyanate counterpart. The different castor oil-derived polyurethanes were investigated by means of water uptake, soil burial degradation, and disintegration tests in compost. Characterization analyses, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM), were carried out both prior to and after degradation tests. The results suggest potential applications of the degradable castor oil-derived polyurethane in different fields, such as mulch films for agricultural purposes.

A study on biorelevant calciprotein particles: Effect of stabilizing agents on the formation and crystallization mechanisms.

HYPOTHESIS: Calciprotein particles (CPPs) are endogenous nanoparticles consisting of hybrid mineral-organic colloidal complexes made of calcium phosphates and Fetuin-A (Fet-A), a protein that in physiological conditions binds to amorphous calcium phosphate forming primary CPP (CPP1). CPP1 can crystallize resulting in hydroxyapatite-based secondary CPP (CPP2) that can eventually precipitate leading to vascular calcifications. The treatment of patients with molecules and ions that delay the amorphous-to-crystalline transition has shown promising results from a clinical perspective, but the study of their mechanism of action has not been thoroughly examined so far. EXPERIMENTS: This work describes the formation and crystallization mechanism of synthetic analogs of endogenous CPPs. The effect of different concentrations of Fet-A and of stabilizing agents (Mg2+, citrate and pyrophosphate) on the features and stability of CPPs was addressed by combining different characterization techniques such as turbidimetry, dynamic light scattering, infrared spectroscopy, and scanning electron microscopy. FINDINGS: The results show that the stabilizing agents display different action mechanisms and are effective to a different extent in preventing the formation of CPPs or delaying their crystallization. Such findings could be of interest to develop effective therapies for vascular calcifications and to deepen the understanding of amorphous calcium phosphate stabilization and its interaction with proteins.

Self-Assembly of Soluplus in Aqueous Solutions: Characterization and Prospectives on Perfume Encapsulation.

Soluplus is an amphiphilic graft copolymer intensively studied as a micellar solubilizer for drugs. An extensive characterization of the nanostructure of its colloidal aggregates is still lacking. Here, we provide insights into the polymer's self-assembly in water, and we assess its use as an encapsulating agent for fragrances. The self-assembly properties of Soluplus aqueous solutions were studied over a wide concentration range (1-70% w/w) by means of small-angle neutron scattering (SANS), differential scanning calorimetry, NMR, and rheometry. SANS analyses revealed the presence of polymeric micelles with a fuzzy surface interacting via a 2-Yukawa potential, up to 15% w/w polymer. Increasing the polymer concentration up to 55% w/w led to tightly packed micelles described according to the Teubner-Strey model. The ability of Soluplus to encapsulate seven perfume molecules, 2-phenyl ethanol, l-carvone, linalool, florhydral, ß-citronellol, α-pinene, and R-limonene, was then examined. We showed that the fragrance's octanol/water partition coefficient (log Kow), widely used to characterize the solubilization capacity, is not sufficient to characterize such systems and the presence of specific functional groups or molecular conformation needs to be considered. In fact, the combination of SANS, NMR, confocal laser scanning microscopy, and confocal Raman microscopy showed that the perfumes, interacting with different regions of the polymer aggregates, are able to tune the systems' structures resulting in micelles, matrix-type capsules, core-shell capsules, or oil-in-water emulsions.

pH-Controlled assembly of polyelectrolyte layers on silica nanoparticles in concentrated suspension.

HYPOTHESIS: Preparation of suspensions of nanoparticles (>1 wt%) coated with a polyelectrolyte multilayers is a challenging task because of the risk of flocculation when a polyelectrolyte is added to a suspension of oppositely charged nanoparticles. This situation can be avoided if the charge density of the polymers and particles is controlled during mixing so as to separate mixing and adsorption events. EXPERIMENTS: The cationic polyethylenimine (PEI) and the anionic carboxymethylcellulose (CMC) were used as weak polyelectrolytes. Polyelectrolyte multilayers build-up was conducted by reducing the charge of one of the components during the addition of the next component. Charge density was controlled by tuning pH. Analysis of the suspension of coated nanoparticles was done by means of dynamic light scattering, electrophoresis and small angle x-ray scattering measurements, while quartz crystal microbalance was used to study the build-up process on flat silica surfaces. FINDINGS: Charge density, controlled through pH, can be used as a tool to avoid flocculation during layer-by-layer deposition of polyelectrolytes on 20 nm silica particles at high concentration (∼40 wt%). When added to silica at pH 3, PEI did not induce flocculation. Adsorption was triggered by raising the pH to 11, pH at which CMC could be added. The pH was then lowered to 3. The process was repeated, and up to five polyelectrolyte layers were deposited on concentrated silica nanoparticles while inducing minimal aggregation.

Environmentally friendly ZnO/Castor oil polyurethane composites for the gas-phase adsorption of acetic acid.

HYPOTHESIS: Acetic acid, a common pollutant present in museums and art galleries, can irreversibly damage works of art. Herein, a sustainable and scalable synthesis of zinc oxide-castor oil polyurethane hybrids (ZnO/COPs), to be used as acetic acid removers in the preventive conservation of Cultural Heritage, is reported. EXPERIMENTS: The adsorption capacities of ZnO/COPs were studied in saturated acetic acid atmosphere, at low acetic acid gas concentration, and inside a wooden crate (naturally emitting acetic acid) representative of those used in the storage deposits of museums and art collections. FINDINGS: Upon exposure, acetic acid interacts with the castor oil polyurethane and diffuses to the surface of ZnO particles where is stably fixed as zinc acetate crystals. Zinc acetate domains form homogeneously on the surface and are distributed evenly within the ZnO/COPs, thanks to weak interactions between the polyurethane matrix and acetic acid that favour the transport of the acid up to reach the zinc oxide surfaces, resulting in a synergistic effect. The ZnO/COPs composites showed significantly enhanced adsorption capacities of acetic acid surpassing those of the activated carbon benchmark, with the advantage of being easily handled and movable, without the health issues and risks associated to the use of non-confined micro/nano-powders.