Cross-linked Porous Gelatin Microparticles with Tunable Shape, Size, and Porosity.

Gelatin particles are relevant to many applications in the biomedical field due to their excellent biocompatibility and versatility. When prepared by double emulsion methods, porous microparticles with different architectures can be obtained. Controlling the shape, size, porosity, swelling, and stability against dissolution is fundamental toward their application under physiological conditions. We prepared porous gelatin microparticles from oil-in-water-in-oil emulsions, modifying the gelatin/surfactant ratio and the stirring speed. The effect on structural properties, including surface and inner porosities, was thoroughly assessed by multiple microscopy techniques (optical, electron, and confocal Raman). Selected samples were cross-linked with glutaraldehyde or glyceraldehyde, and their swelling properties and stability against dissolution were evaluated, while the influence of the cross-linking at the nanoscale was studied by scattering of X-rays. Depending on the preparation protocol, we obtained particles with different shapes (irregular or spherical), radii within ∼40 to 90 µm, and porosities up to 10 µm. The cross-linking extends the stability in water from a few minutes up to several days while the swelling ability and the mesh size at the nanoscale of the gelatin network are preserved. The analysis of the experimental results as a function of the preparation parameters demonstrates that microparticles with tunable features can be designed.

Adsorption of Amino Acids and Glutamic Acid-Based Surfactants on Imogolite Clays.

Aluminum oxide surfaces are of utmost interest in different biotech applications, in particular for their use as adjuvants (i.e., booster of the immune response against infectious agents in vaccines production). In this framework, imogolite clays combine the chemical flexibility of an exposed alumina surface with 1D nanostructure. This work reports on the interaction between amino acids and imogolite, using turbidimetry, ζ-potential measurements, and Fourier transform infrared spectroscopy as main characterization tools. Amino acids with different side chain functional groups were investigated, showing that glutamic acid (Glu) has the strongest affinity for the imogolite surface. This was exploited to prepare a composite material made of a synthetic surfactant bearing a Glu polar head and a hydrophobic C12 alkyl tail, adsorbed onto the surface of imogolite. The adsorption of a model drug (rhodamine B isothiocyanate) by the hybrid was evaluated both in water and in physiological saline conditions. The findings of this paper suggest that the combination between the glutamate headgroup and imogolite represents a promising platform for the fabrication of hybrid nanostructures with tailored functionalities.

A bioinspired and sustainable route for the preparation of Ag-crosslinked alginate fibers decorated with silver nanoparticles.

Functional materials obtained through green and sustainable routes are attracting particular attention due to the need to reduce the environmental impact of the chemical industry. In this work we propose a bioinspired approach for the preparation of alginate fibers containing silver nanoparticles (AgNPs), to be used for antimicrobial purposes. We demonstrate that filiform polymeric structures with length of a few meters can be easily obtained by extruding an alginate solution in an aqueous Ag+-containing bath (i.e. wet spinning) and that treating the fibers with freshly-squeezed lemon juice leads to the formation of AgNPs homogeneously distributed within the polymeric network. Using mixtures of ascorbic and citric acid to mimic lemon juice composition we highlight the influence of the aforementioned molecules on the nanoparticles formation process as well as on the properties of the fibers. Varying the amount of citric and ascorbic acid used for the treatment allows to finely tune the thermal, morphological and water absorption properties of the fibers. This evidence, along with the possibility to easily monitor the preparation through FT-IR spectroscopy, endows the fibers with a high application potential in several fields such as wound healing, water/air purification and agriculture.

Sputtering effects and water formation on an amorphous silicate surface.

We studied the formation of deuterated water on an amorphous silicate surface held at low temperature (10 K < T < 40 K). The surface is first characterized by using Ar(+) ion bombardment, and preferential sputtering of oxygen is found. Sputtering creates oxygen vacancies in the surface region that can be filled by deposition of atomic oxygen. The conditions used in the experiment are meant to make it relevant to the study of the initial stages of water formation on dust grains in interstellar space. By changing the D/O ratio of atomic beams of deuterium and oxygen at thermal energy and the temperature of the sample during deposition, we show that the routes to the formation of D2O2 can be untangled and, under certain circumstances, the net yield of D2O2 can be suppressed. The formation efficiency for water and other molecules is then estimated.

Effect of Atmospheric Pressure Plasma Jet Treatments on Magnesium Phosphate Cements: Performance, Characterization, and Applications.

Atmospheric pressure plasma treatments are nowadays gaining importance to improve the performance of biomaterials in the orthopedic field. Among those, magnesium phosphate-based cements (MPCs) have recently shown attractive features as bone repair materials. The effect of plasma treatments on such cements, which has not been investigated so far, could represent an innovative strategy to modify MPCs' physicochemical properties and to tune their interaction with cells. MPCs were prepared and treated for 5, 7.5, and 10 min with a cold atmospheric pressure plasma jet. The reactive nitrogen and oxygen species formed during the treatment were characterized. The surfaces of MPCs were studied in terms of the phase composition, morphology, and topography. After a preliminary test in simulated body fluid, the proliferation, adhesion, and osteogenic differentiation of human mesenchymal cells on MPCs were assessed. Plasma treatments induce modifications in the relative amounts of struvite, newberyite, and farringtonite on the surfaces on MPCs in a time-dependent fashion. Nonetheless, all investigated scaffolds show a good biocompatibility and cell adhesion, also supporting osteogenic differentiation of mesenchymal cells.

A quaterthiophene-based rotaxane: synthesis, spectroscopy, and self-assembly at surfaces.

Threaded molecular wires are shown to feature tunable properties. A new rotaxane based on a quaterthiophene threaded through a single ß-cyclodextrin exhibits delocalization of the aromatic system that is also extended onto the central phenyl rings of the m-terphenylene end-groups. The rotaxane can undergo self-assembly that is better than the analogous bithiophene derivative, due to the increased π-π interactions.

Analysis of oxidative degradation and calcification behavior of a silicone polycarbonate polyurethane-polydimethylsiloxane material.

The biocompatibility and chemical stability of implantable devices are crucial for their long-term success. CarboSil® is a silicon polycarbonate polyurethane copolymer with good biocompatibility and biostability properties. Here, we explored the possibility to improve these characteristics by introducing 30% of extra-chain cross-linkable poly(dimethyl siloxane) (PDMS). Patches made of CarboSil and CarboSil-30% PDMS were manufactured by spray, phase-inversion technique and subjected to a heating-pressure treatment. Both materials showed good biocompatibility, either in viability and proliferation of cell-based experiments both with mouse fibroblasts and subcutaneous implant in rats. Fourier-transform infrared spectroscopy showed a significant decrease in soft segment loss in CarboSil-30% PDMS samples with respect to CarboSil in in vitro accelerated oxidative treatments with CoCl2 and 20% H2 O2 at 37°C up to 36 days. Same results were observed in subcutaneous implants up to 90 days. Field-emission scanning electron microscopy on samples exposed to calcification solutions during 80 days highlighted the presence of a homogeneous distribution of calcium deposition over the entire surface of CarboSil samples, while no calcium deposits were observed in CarboSil-30% PDMS samples. Patches subjected to subcutaneous experiments showed no sign of calcification after 90 days, irrespectively of their composition. Thanks to the improved characteristics in terms of degradation and calcification the modified materials described in this work hold great promise for their use in the manufacture of cardiovascular devices.

N-Doped Carbon Dot Hydrogels from Brewing Waste for Photocatalytic Wastewater Treatment.

The brewery industry annually produces huge amounts of byproducts that represent an underutilized, yet valuable, source of biobased compounds. In this contribution, the two major beer wastes, that is, spent grains and spent yeasts, have been transformed into carbon dots (CDs) by a simple, scalable, and ecofriendly hydrothermal approach. The prepared CDs have been characterized from the chemical, morphological, and optical points of view, highlighting a high level of N-doping, because of the chemical composition of the starting material rich in proteins, photoluminescence emission centered at 420 nm, and lifetime in the range of 5.5-7.5 ns. With the aim of producing a reusable catalytic system for wastewater treatment, CDs have been entrapped into a polyvinyl alcohol matrix and tested for their dye removal ability. The results demonstrate that methylene blue can be efficiently adsorbed from water solutions into the composite hydrogel and subsequently fully degraded by UV irradiation.

New frontiers in materials science for art conservation: responsive gels and beyond.

The works of art and artifacts that constitute our cultural heritage are subject to deterioration, both from internal and from external factors. Surfaces that interact with the environment are the most prone to aging and decay; accordingly, soiling is a prime factor in the degradation of surfaces and the attendant disfigurement of a piece. Coatings that were originally intended to protect or contribute aesthetically to an artwork should be removed if they begin to have a destructive impact on its appearance or surface chemistry. Since the mid-19th century, organic solvents have been the method of choice for cleaning painted surfaces and removing degraded coatings. Care must be taken to choose a solvent mixture that minimizes swelling of or leaching from the original paint films, which would damage and compromise the physical integrity of all the layers of paint. The use of gels and poultices, first advocated in the 1980s, helps by localizing the solvent and, in some cases, by reducing solvent permeation into underlying paint layers. Unfortunately, it is not always easy to remove gels and their residues from a paint surface. In this Account, we address the removal problem by examining the properties of three classes of innovative gels for use on artwork--rheoreversible gels, magnetic gels, and "peelable" gels. Their rheological properties and efficacies for treating the surfaces of works have been studied, demonstrating uniquely useful characteristics in each class: (1) Rheoreversible gels become free-flowing on application of a chemical or thermal "switch". For art conservation, a chemical trigger is preferred. Stable gels formed by bubbling CO(2) through solutions of polyallylamine or polyethylenimines (thereby producing ammonium carbamates, which act as chain cross-links) can be prepared with a wide range of solvent mixtures. After solubilization of varnish and dirt, addition of a weak acid (mineral or organic) displaces the CO(2), and the resulting free-flowing liquid can be removed gently. (2) Incorporation of magnetic, coated-ferrite nanoparticles into polyacrylamide gels adds functionality to a versatile system comprising oil-in-water microemulsions, aqueous micellar solutions, or xerogels that act as sponges. The ferrite particles allow the use of magnets both to place the gels precisely on a surface and to lift them from it after cleaning. (3) Novel formulations of poly(vinyl alcohol)-borate gels, which accept a range of organic cosolvents, show promise for swelling and dissolving organic coatings. This family of gels can be quite stiff but can be spread. They are non-sticky and have sufficient strength to be removed by peeling or lifting them from a sensitive surface. These three classes of gels are potentially very important soft materials to augment and improve the range of options available for conserving cultural heritage, and their interesting chemical-physical properties open a rich area for future scientific investigation.

Physico-Chemical Challenges in 3D Printing of Polymeric Nanocomposites and Hydrogels for Biomedical Applications.

Additive manufacturing techniques (i.e., 3D printing) are rapidly becoming one of the most popular methods for the preparation of materials to be employed in many different fields, including biomedical applications. The main reason is the unique flexibility resulting from both the method itself and the variety of starting materials, requiring the combination of multidisciplinary competencies for the optimization of the process. In particular, this is the case of additive manufacturing processes based on the extrusion or jetting of nanocomposite materials, where the unique properties of nanomaterials are combined with those of a flowing matrix. This contribution focuses on the physico-chemical challenges typically faced in the 3D printing of polymeric nanocomposites and polymeric hydrogels intended for biomedical applications. The strategies to overcome those challenges are outlined, together with the characterization approaches that could help the advance of the field.

Dynamics of Water and Other Molecular Liquids Confined Within Voids and on Surface of Lignin Aggregates in Aging Bio Crude Oils.

Neutron scattering methods were employed to study the microscopic structure and dynamics of Bio Crude Oils (BCOs) and their lignin fractions. The structure of the carbonaceous aggregates was investigated using Small Angle Neutron Scattering to reveal a fractal hierarchy as well as a growth of the aggregates as the aging of the BCO proceeds. Elastic Neutron Scattering measurements indicate that BCO liquid phase, comprised of water and other hydrogenated molecular liquids, is in a state of extreme confinement. Quasi-Elastic Neutron Scattering yields information on the molecular motions, indicating that long range translational diffusion is suppressed and only localized dynamics take place on the tens of picosecond time range. The obtained results provide quantitative information on the molecular activity, as aging proceed, in these reactive materials of relevance as potential renewable energy sources.

3D printable magnesium-based cements towards the preparation of bioceramics.

HYPOTHESIS: Among all the materials used so far to replace and repair damaged bone tissues, magnesium silicate bioceramics are one of the most promising, thanks to their biocompatibility, osteoinductive properties and good mechanical stability. EXPERIMENTS: Magnesium silicate cement pastes were prepared by hydration of MgO mixed with different SiO2 batches at different Mg/Si molar ratios. Pastes were either moulded or 3D printed to obtain set cements that were then calcined at 1000 °C to produce biologically relevant ceramic materials. Both cements and ceramics were characterized by means of X-ray diffraction, while two selected formulations were thoroughly characterized by means of injectability tests, Raman confocal microscopy, scanning electron microscopy, atomic force microscopy, gas porosimetry, X-ray microtomography and compressive tests. FINDINGS: The results show that bioceramic scaffolds, namely forsterite and clinoenstatite, can be effectively obtained by 3D printing MgO/SiO2 cement pastes, paving the way towards important advances in the field of bone tissue engineering.

Photopolymerizable pullulan: Synthesis, self-assembly and inkjet printing.

HYPOTHESIS: Pullulan, an exopolysaccharide consisting of maltotriose repeating units, has recently found many applications in different fields, such as food, packaging, cosmetics and pharmaceuticals. The introduction of photo-crosslinkable methacrylic units potentially allows to use pullulan derivative in inkjet 3D printing. EXPERIMENTS: Pullulan was functionalized with methacrylic groups and the derivative was characterized by NMR, FT-IR and Raman spectroscopy. Water dispersions were thoroughly investigated by optical microscopy, SAXS and rheology to evaluate the self-assembly properties and they were used as photo-crosslinkable inks in a 3D printer, also in comparison with pristine pullulan. The structural and mechanical properties of the obtained films were studied by Atomic Force Microscopy and tensile strength tests. FINDINGS: The introduction of methacrylic groups moderately affects the self-assembly of the polymer in water, resulting in a slight increase of the gyration radius of the polymer coils and in a small decrease of the viscosity, retaining the typical shear-thinning behavior of concentrated polysaccharides in water. The structural and mechanical properties of the 3D printed films are much more affected, showing the presence of sub-micrometric phase segregated domains which are further separated by the cross-linking. As a result, the deformability of the materials is improved, with a lower tensile strength.

Modifying the crystallization of amorphous magnesium-calcium phosphate nanoparticles with proteins from Moringa oleifera seeds.

HYPOTHESIS: Endogenous Amorphous Magnesium-Calcium Phosphates (AMCPs) form in the human body and, besides their biomedical implications, the development of effective stabilization strategies is an open challenge. An interesting approach consists of stabilizing amorphous phosphates with macromolecules that have beneficial effects from a nutritional/medical point of view, for a potential application of the hybrid particles in nutraceutics or drug delivery. EXPERIMENTAL: We investigated the effect of proteins extracted from Moringa oleifera seeds (MO) on the features of synthetic analogs of AMCPs and on their crystallization pathway. The stability of the amorphous phase was studied using infrared spectroscopy and X-ray diffraction. To unravel the effect of the protein on the nano-scale structure of the inorganic particles, we also studied how MO affects the features of the amorphous phase using thermal analysis, small angle X-ray scattering and confocal Raman microscopy. FINDINGS: We observed that MO markedly delays the transition from amorphous to crystalline phosphate in a concentration-dependent fashion. Interestingly, MO not only enhances the lifetime of the amorphous phase, but also influences the type and amount of crystalline material formed. The results are relevant from both a fundamental and an applied perspective, paving the way for the use of these hybrids in the field of nutraceutics and drug delivery.

A conjugated thiophene-based rotaxane: synthesis, spectroscopy, and modeling.

A dithiophene rotaxane 1 subsetbeta-CD and its shape-persistent corresponding dumbbell 1 were synthesized and fully characterized. 2D NOESY experiments, supported by molecular dynamics calculations, revealed a very mobile macrocycle (beta-CD). Steady-state and time-resolved photoluminescence experiments in solution were employed to elucidate the excited-state dynamics for both systems and to explore the effect of cyclodextrin encapsulation. The photoluminescence (PL) spectrum of 1 subsetbeta-CD was found to be blueshifted with respect to the dumbbell 1 (2.81 and 2.78 eV, respectively). Additionally, in contrast to previous observations, neither PL spectra nor the decay kinetics of both threaded and unthreaded systems showed changes upon increasing the concentration or changing the polarity of the solutions, thereby providing evidence for a lack of tendency toward aggregation of the unthreaded backbone.

Sustainable Strategies in the Synthesis of Lignin Nanoparticles for the Release of Active Compounds: A Comparison.

The preparation of nanoparticles represents a powerful tool for lignin valorization, as it combines easy methodologies with high application potential. Different synthetic strategies and various lignin sources have been employed in the process. However, the great variability in the lignin structure prevents a direct comparison of the so far reported lignin nanoparticles (LNPs), especially as regards their physicochemical and functional properties. To this purpose, two green protocols, that is, solvent-antisolvent and hydrotropic, were optimized and used to generate LNPs from the same softwood kraft lignin. The nanomaterials were fully characterized to extrapolate structure/property relationships and reveal any differences in the mechanism of self-assembly. Furthermore, tests on methylene blue entrapment capacity and release behavior at two different pH values (2.0 and 7.4) evidenced a clear dependence on the LNPs characteristics and thus on the strategy adopted for their production.

Tailoring bicomponent supramolecular nanoporous networks: phase segregation, polymorphism, and glasses at the solid-liquid interface.

We study the formation of four supramolecular bicomponent networks based on four linear modules (linkers) bridging melamine via triple hydrogen-bonds. We explore at the nanoscale level the phenomena of polymorphism and phase segregation which rule the generation of highly crystalline nanoporous patterns self-assembled at the solid-liquid interface. The investigated linkers include two systems exposing diuracil groups in the alpha and omega position, naphthalene tetracarboxylic diimide and pyromellitic diimide. In situ scanning tunneling microscopy (STM) investigations revealed that, when blended with melamine, out of the four systems, three are able to form two-dimensional (2D) porous architectures, two of which exhibit highly ordered hexagonal structures, while pyromellitic diimide assembles only into one-dimensional (1D) supramolecular arrays. These bicomponent self-assembled monolayers are used as a test bed to gain detailed insight into phase segregation and polymorphism in 2D supramolecular systems by exploring the contribution of hydrogen-bond energy and periodicity, molecular flexibility, concentration and ratio of the components in solution as well as the effect of annealing via time-dependent and temperature-modulated experiments. These comparative studies, obtained through a joint experimental and computational analysis, offer new insights into strategies toward the bottom-up fabrication of highly ordered tunable nanopatterning at interfaces mediated by hydrogen bonds.

Molecule-Graphene Hybrid Materials with Tunable Mechanoresponse: Highly Sensitive Pressure Sensors for Health Monitoring.

The development of pressure sensors is crucial for the implementation of electronic skins and for health monitoring integrated into novel wearable devices. Tremendous effort is devoted toward improving their sensitivity, e.g., by employing microstructured electrodes or active materials through cumbersome processes. Here, a radically new type of piezoresistive pressure sensor based on a millefeuille-like architecture of reduced graphene oxide (rGO) intercalated by covalently tethered molecular pillars holding on-demand mechanical properties are fabricated. By applying a tiny pressure to the multilayer structure, the electron tunnelling ruling the charge transport between successive rGO sheets yields a colossal decrease in the material's electrical resistance. Significantly, the intrinsic rigidity of the molecular pillars employed enables the fine-tuning of the sensor's sensitivity, reaching sensitivities as high as 0.82 kPa-1 in the low pressure region (0-0.6 kPa), with short response times (≈24 ms) and detection limit (7 Pa). The pressure sensors enable efficient heartbeat monitoring and can be easily transformed into a matrix capable of providing a 3D map of the pressure exerted by different objects.

Liquid Crystal-Induced Myoblast Alignment.

The ability to control cell alignment represents a fundamental requirement toward the production of tissue in vitro but also to create biohybrid materials presenting the functional properties of human organs. However, cell cultures on standard commercial supports do not provide a selective control on the cell organization morphology, and different techniques, such as the use of patterned or stimulated substrates, are developed to induce cellular alignment. In this work, a new approach toward in vitro muscular tissue morphogenesis is presented exploiting liquid crystalline networks. By using smooth polymeric films with planar homogeneous alignment, a certain degree of cellular order is observed in myoblast cultures with direction of higher cell alignment corresponding to the nematic director. The molecular organization inside the polymer determines such effects since no cell organization is observed using homeotropic or isotropic samples. These findings represent the first example of cellular alignment induced by the interaction with a nematic polymeric scaffold, setting the stage for new applications of liquid crystal polymers as active matter to control tissue growth.

Thermodynamic and kinetic characterization of host-guest association between bolaform surfactants and alpha- and beta-cyclodextrins.

The thermodynamics and kinetics of formation of host-guest complexes between a series of bolaform surfactants of type C n Me 6 (2+)2Br (-) ( n = 8, 10, and 12) and alpha-cyclodextrin and beta-cyclodextrin were studied with the aid of isothermal titration calorimetry (ITC) at 298.15 and 308.20 K. The association constant, the enthalpy, and the entropy of formation were determined. The obtained thermodynamic parameters are compared with parameters for the micelle formation of a related cationic surfactant. The difference in magnitude and sign between the parameters of the alpha-CD and beta-CD complexes is discussed based on the curvature of the cavity of the CD. We suggest that the water molecules inside the alpha-CD cavity are not able to maintain their hydrogen bond network. Upon complex formation these water molecules are expelled and reform their hydrogen bond network. The situation is different in the larger beta-CD cavity where water has the possibility of a more extensive hydrogen bonding. The kinetics for alpha-CD is slow, associated with high activation energies for both association and dissociation of the complex. The rates increased with a decrease in the number of methylene groups in the hydrocarbon chain. The slow kinetics is argued to originate from the fact that the charged headgroup needs to be pushed through a relative nonpolar cavity. A comparison is made with the Born energy.