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The aerial parts of plants, including the leaves, fruits and non-lignified stems, are covered with a protective cuticle, largely composed of the polyester cutin. Two mechanisms of cutin deposition have been identified in tomato (Solanum lycopersicum) fruit. The contribution of each mechanism to cutin synthesis and deposition has shown a temporal and coordinated sequence that correlates with the two periods of organ growth, cell division and cell expansion. Cutinsomes, self-assembled particles composed of esterified cutin monomers, are involved in the synthesis of the procuticle during cell division and provide a template for further cutin deposition. CUTIN SYNTHASE1 (CUS1), an acyl transferase enzyme that links cutin monomers, contributes to massive cuticle deposition during the early stages of the cell expansion period by incorporating additional cutin to the procuticle template. However, cutin deposition and polymerization appear to be part of a more complex biological scenario, which is yet not fully understood. CUS1 is also associated with the coordinated growth of the cutinized and non-cutinized domains of the outer epidermal wall, and affects cell size. A dynamic and complex interplay linking cutin synthesis with cell wall development and epidermal cell size has been identified. [ABSTRACT FROM AUTHOR]

Superhydrophobic and wear abrasion resistant high impact polystyrene (HIPS)/silica nanocomposite coatings for metal surfaces have been produced by spray. An environmentally friendly perfluorinated acrylic copolymer (PFAC) primer coating layer was applied first, in order to enhance adhesion with the substrate and prolong abrasion resistance. The best nanocomposite composition was found to be 50% silica nanoparticles with respect to HIPS by weight. This coating displayed the lowest friction coefficient compared to other nanocomposites with lower or higher silica concentrations. Tribological experiments on the best performing nanocomposites indicated that wear tracks or marks had no debris, cracks or complete material removal. Furthermore, Taber® abrasion tests confirmed tribological findings and showed that the best nanocomposites resisted superhydrophobic degradation up to 35 continuous linear abrasion cycles (15 kPa). Nanocomposites made with general purpose polystyrene instead of HIPS could only resist up to 15 Taber® abrasion cycles. The reason was attributed to the mechanical energy dissipation capability of rubber domains in HIPS. Thermal annealing of the coatings had a deterministic effect on the durability of the coatings against wear induced loss of superhydrophobicity. Annealed and non-annealed coatings were characterized by Fourier transform infrared and X-ray photoelectron spectroscopy. Due to ease of fabrication, resultant mechanical robustness, use of non-toxic materials, and low-cost industrial scale availability of HIPS, nanoparticles and the primer polymer, these coatings can be effortlessly transformed into larger scale non-wettable protective treatments for metals. [ABSTRACT FROM AUTHOR]

Microcrystalline cellulose (MCC) and polyamide 66 (PA66) have been separately dissolved in solutions containing trifluoroacetic acid (TFA) as a common solvent, mixed after their dissolution and cast. After solvent evaporation, self-organized membranes have been formed with three dimensional (3D) porous, interconnected morphology, the porosity of which depends on the relative ratio of cellulose and PA66, and is lost when the initial MCC content exceeds 50% by weight. Thermal and chemical analysis and X-ray diffraction results indicate that the addition of cellulose induces the amorphisation of PA66, while possible chemical interaction exists between the amorphous parts of PA66 and the cellulose. The various membranes produced with different 3D porosities have been characterized in terms of dielectric constant and salt permeability and their relation to cellulose-PA66 ratio has been determined. [ABSTRACT FROM AUTHOR]

Fatty polyhydroxyesters (C≥16) are present in nature as barrier polymers like cutin in some protective tissues of higher plants. The mimicry of these biopolymers is regarded as a strategy to design nontoxic and fully biodegradable food packaging films and coatings. To obtain cutin inspired materials we have used a natural occurring polyhydroxylated monomer like aleuritic (9,10,16-trihydroxypalmitic) acid and a direct and scalable synthesis route consisting in the noncatalyzed melt-condensation polymerization in air. To reduce the number of hydroxyl groups and to increase hydrophobicity, palmitic acid has been used as a capping agent. Aleuritic-palmitic polyhydroxyesteres films have been obtained and characterized. [ABSTRACT FROM PUBLISHER]

The outer surfaces of epidermal cell walls are impregnated with an extracellular matrix called the cuticle. This composite matrix provides several functions at the interface level that enable plants to thrive in different habitats and withstand adverse environmental conditions. The lipid polymer cutin, which is the main constituent of the plant cuticle, has some unique biophysical properties resulting from its composition and structure. This review summarizes the progress made towards understanding the biophysical significance of this biopolymer with special focus on its structural, thermal, biomechanical, and hydric properties and relationships. The physiological relevance of such biophysical properties is discussed in light of existing knowledge on the plant cuticle. [ABSTRACT FROM AUTHOR]

Bio‐inspired and biodegradable quantum optics scenarios constitute a pathway toward environmentally friendly front‐end technologies. Such an inspiring perspective necessitates the replacement of classic gain materials with a biological counterpart like photoluminescent bacteria. It is easy to imagine that, in this case, a planar and cell‐viable substitute of classic bulk solid‐states resonators can be highly beneficial. In this paper a micro‐ and nano‐photonic structuration of both a standard and a functionalized version of a typical bacterial growth medium (Luria‐Bertani Agar – LBA) is successfully realized. Three structures belonging to the categories of photonic crystals are replicated, such as quasi‐crystals and meta‐surfaces, demonstrating how the proposed media can be used as templates for high‐end photonic applications. The optical quality of the replicated structures is confirmed by far‐field diffraction measurements. The structured growth media allow for a broad control of the surface wettability by accessing a so‐called Wenzel state, in which the original hydrophilicity of a material is increased due to the photonic structuration. Finally, the suitability of the nano‐structured LBA as a plasmonic platform is evidenced. The proposed micro‐and nano‐structured photonic growth media constitute the first, fundamental step toward quantum optical frameworks from biological media. [ABSTRACT FROM AUTHOR]

In this study, active biocomposite films of low-density polyethylene (LDPE) containing 5% wt. of curcumin, a natural chemical produced by some plants, are developed by melt extrusion and hot pressing. The detailed study of the physicochemical properties of the formed films demonstrates that the curcumin molecules, homogeneously dispersed in the whole volume of the LDPE matrix, cause a notable increase in the thermal stability of the LDPE polymer, without altering its thermal processability. At the same time the LDPE's water vapor barrier properties are significantly improved, while an effective antioxidant scavenging activity is observed against the 2,2-diphenyl-1-picrylhydrazyl free radicals (DPPH•). These results indicate that the developed active films based on the combination of LDPE and curcumin, following industrially applied preparation methods, are ideal candidates for active food packaging applications. Image 1 • Highly antioxidant food packaging films from low-density polyethylene (LDPE) and curcumin. • Excellent water vapor barrier properties. • High thermal stability without altering thermal processability. • Fabrication through industrially applicable methods. [ABSTRACT FROM AUTHOR]

In this study, biofilaments based on cocoa shell waste, a by-product of the chocolate industry, and biodegradable poly(ε-caprolactone), PCL, have been prepared using a single-screw extruder. Micronized cocoa shell waste is compounded in the polymer up to 50% by weight without significant alteration of its crystalline structure. Resultant elastic (Young's) modulus of biofilaments remains close to that of pure PCL. Scanning electron microscopy results indicate that micronized cocoa shell waste is homogeneously dispersed in the polymer during the extrusion process. Detailed thermal characterization measurements on the extruded filaments allow tuning of the fused deposition modeling 3D printing parameters. 3D printed items display a well-defined structure with good adhesion between deposition layers and fine resolution. Hence, with this simple and solvent-free fabrication technique, uniformly structured cocoa shell waste biofilaments can be produced in a very reproducible manner and can be used in 3D printing of diverse objects with potential household and biomedical applications. [ABSTRACT FROM AUTHOR]

Amorphous cellulose and poly(methyl methacrylate) (PMMA) blends in the form of free standing transparent hybrid films were prepared by dissolving both polymers in trifluoroacetic acid (TFA). Ultraviolet–visible (UV–vis) measurements indicated that the transparency of the films was always maintained regardless of cellulose-PMMA proportions. In addition, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements were carried out in order to characterize the chemical composition, intermolecular interactions and the crystallinity of the hybrid films. Thermo-gravimetric analysis (TGA), differential scanning calorimeter (DSC) and tensile test measurements demonstrated that amorphous cellulose improved the thermal and mechanical properties of PMMA considerably. Scanning electron microscope (SEM) and atomic force microscopy (AFM) measurements showed that hybrid films had no micron scale phase separation or segregation, resulting in highly uniform and homogenous miscibility between amorphous cellulose and PMMA. The wetting characteristics of the hybrid films were also studied by water contact angle measurements. Hybrid films showed better water barrier properties in comparison to commercial paper packaging. Furthermore, the hybrid films exhibited relative high dissolution resistance to common organic solvents, which dissolve PMMA completely. Considering the recent interest in polymer blends based on natural and synthetic macromolecules, these new transparent hybrids can have various potential applications particularly in general packaging and biomedical technologies. [ABSTRACT FROM AUTHOR]

Bioplasticswith a wide range of mechanical properties were directlyobtained from industrially processed edible vegetable and cereal wastes.As model systems, we present bioplastics synthesized from wastes ofparsley and spinach stems, rice hulls, and cocoa pod husks by digestingin trifluoroacetic acid (TFA), casting, and evaporation. In this way,amorphous cellulose-based plastics are formed. Moreover, many othernatural elements present in these plants are carried over into thebioplastics rendering them with many exceptional thermo-physical properties.Here, we show that, due to their broad compatibility with cellulose,amorphous cellulose can be naturally plasticized with these bioplasticsby simply mixing during processing. Comparison of their mechanicalproperties with that of various petroleum based synthetic polymersindicates that these bioplastics have equivalent mechanical propertiesto the nondegrading ones. This opens up possibilities for replacingsome of the nondegrading polymers with the present bioplastics obtainedfrom agro-waste. [ABSTRACT FROM AUTHOR]

• Graphene has a stimulatory effect on neuronal differentiation of N2a cells. • The adhesion factor polylysine enhances the stimulatory effect. • The physicochemical features of polylysine on graphene act as cues for N2a cells. • Polylysine–coated graphene is promising for regenerative medicine. We compared the proliferation and differentiation of mouse neuroblastoma Neuro 2A cell line on single layer graphene and glass substrates. Quantitative and qualitative analysis of the cell proliferation and differentiation were performed, considering also the effect of a common adhesion factor, namely polylysine. We observed that on graphene substrates the cells proliferate faster with respect to glass; additionally, the presence of the adhesion factor enhances the difference and, remarkably, boosts the cell differentiation on the graphene-based interface. To understand the mechanism underlying a different cell behavior on the same adhesion coating, we carried out a physicochemical investigation of the studied interfaces (glass and graphene, bare and polylysine coated) by several techniques. In particular, we employed infrared spectroscopy to gain information on polylysine conformation, and atomic force microscopy force-distance curves to study adhesion properties at the surface. The results indicate that polylysine has an enhanced binding affinity for graphene, as well as a different molecular arrangement on graphene with respect to glass. These properties act as surface cues to trigger the cell response. [ABSTRACT FROM AUTHOR]

Nanoparticles, named cutinsomes, have been prepared from aleuritic (9,10,16-trihidroxipalmitic) acid and tomato fruit cutin monomers (a mixture of mainly 9(10),16-dihydroxypalmitic acid (85%, w/w) and 16-hydroxyhexadecanoic acid (7.5%, w/w)) with pectin in aqueous solution. The process of formation of the nanoparticles of aleuritic acid plus pectin has been monitored by UV-Vis spectrophotometry, while their chemical and morphological characterization was analyzed by ATR-FTIR, TEM, and non-contact AFM. The structure of these nanoparticles can be described as a lipid core with a pectin shell. Pectin facilitated the formation of nanoparticles, by inducing their aggregation in branched chains and favoring the condensation between lipid monomers. Also, pectin determined the self-assembly of cutinsomes on highly ordered pyrolytic graphite (HOPG) surfaces, causing their opening and forming interconnected structures. In the case of cutin monomers, the nanoparticles are fused, and the condensation of the hydroxy fatty acids is strongly affected by the presence of the polysaccharide. The interaction of pectin with polyhydroxylated fatty acids could be related to an initial step in the formation of the plant biopolyester cutin. [ABSTRACT FROM AUTHOR]

Plant trichomes play important protective functions and may have a major influence on leaf surface wettability. With the aim of gaining insight into trichome structure, composition, and function in relation to water-plant surface interactions, we analyzed the adaxial and abaxial leaf surface of holm oak (Quercus ilex) as a model. By measuring the leaf water potential 24 h after the deposition of water drops onto abaxial and adaxial surfaces, evidence for water penetration through the upper leaf side was gained in young and mature leaves. The structure and chemical composition of the abaxial (always present) and adaxial (occurring only in young leaves) trichomes were analyzed by various microscopic and analytical procedures. The adaxial surfaces were wettable and had a high degree of water drop adhesion in contrast to the highly unwettable and water-repellent abaxial holm oak leaf sides. The surface free energy and solubility parameter decreased with leaf age, with higher values determined for the adaxial sides. All holm oak leaf trichomes were covered with a cuticle. The abaxial trichomes were composed of 8% soluble waxes, 49% cutin, and 43% polysaccharides. For the adaxial side, it is concluded that trichomes and the scars after trichome shedding contribute to water uptake, while the abaxial leaf side is highly hydrophobic due to its high degree of pubescence and different trichome structure, composition, and density. Results are interpreted in terms of water-plant surface interactions, plant surface physical chemistry, and plant ecophysiology. [ABSTRACT FROM AUTHOR]

The surface of peach (Prunus persica 'Calrico') is covered by a dense indumentum, which may serve various protective purposes. With the aim of relating structure to function, the chemical composition, morphology, and hydrophobicity of the peach skin was assessed as a model for a pubescent plant surface. Distinct physicochemical features were observed for trichomes versus isolated cuticles. Peach cuticles were composed of 53% cutan, 27% waxes, 23%, cutin, and 1% hydroxycinnamic acid derivatives (mainly ferulic and p-coumaric acids). Trichomes were covered by a thin cuticular layer containing 15% waxes and 19% cutin and were filled by polysaccharide material (63%) containing hydroxycinnamic acid derivatives and flavonoids. The surface free energy, polarity, and work of adhesion of intact and shaved peach surfaces were calculated from contact angle measurements of water, glycerol, and diiodomethane. The removal of the trichomes from the surface increased polarity from 3.8% (intact surface) to 23.6% and decreased the total surface free energy chiefly due to a decrease on its nonpolar component. The extraction of waxes and the removal of trichomes led to higher fruit dehydration rates. However, trichomes were found to have a higher water sorption capacity as compared with isolated cuticles. The results show that the peach surface is composed of two different materials that establish a polarity gradient: the trichome network, which has a higher surface free energy and a higher dispersive component, and the cuticle underneath, which has a lower surface free energy and higher surface polarity. The significance of the data concerning water-plant surface interactions is discussed within a physiological context. [ABSTRACT FROM AUTHOR]

• Electrospun fibrous hydrogels loaded with hydroxycinnamic acids have been designed. • The fibrous hydrogels were able to control the release of PCA and FA. • PVP-based hydrogels have shown biocompatibility and hemocompatibility in-vitro. • The dressings have shown strong antioxidant activity in-vitro and in - vivo. • PCA and FA have displayed anti-inflammatory efficacy in ex-vivo human skin model. Polyvinylpyrrolidone (commonly known as povidone or PVP) rapidly dissolves in water. This significantly hinders its use in sustained release formulations developed for the biomedical field. Electrospun fibers of PVP dissolve even faster due to larger surface to volume ratio. In this work, we propose a way to circumvent this problem by developing and using functional fibrous materials in hydrogel form. In particular, we demonstrate that ethanolic solutions of PVP containing two hydroxycinnamic acid derivatives, namely p -coumaric and ferulic acids could be electrospun into functional hydrogel fiber mats. After electrospinning, the formed composite mats were first thermally treated at 130 °C for 20 h and subsequently were immersed in aqueous media, where they turned into hydrogels. Thermal annealing did not degrade hydroxycinnamic acid derivatives, preserving their functionality. We propose these hydrogel fiber mats as potential wound dressings and to that end, in vitro tests showed up to 8 days of antioxidants' release, and consequent protection of A549 epithelial cells against oxidative stresses. Biocompatibility tests using human red blood cells, A549 and HaCaT cell lines indicated no adverse effects. Model studies of mice skin burns induced by UV-B radiation showed that the hydrogel fiber dressings significantly reduced the levels of matrix metallopeptidase, (MMP-9), and glutathione peroxidase 1 (GPX-1), which are usually upregulated by reactive oxidative species on burnt skin. Finally, ex-vivo human skin investigations demonstrated skin regeneration and control of the inflammatory phase as indicated by low levels of pro-inflammatory cytokines (IL-6 and IL-8). Therefore, our outcomes indicate that the developed PVP-based fiber hydrogels, produced using a simple protocol, are promising candidates for active wound dressings. [ABSTRACT FROM AUTHOR]

All -PLA blends have been fabricated by an easily scalable and green melt-blending of linear-PLLA and 3-armed star-shaped PDLLA at different proportions (100:0, 95:5, 90:10, 80:20, and 50:50, w:w). The fabrication process, carried out in a hot-press, consisted of three steps: an initial heating of the thoroughly blended polymer mixtures at 170 °C for 5 min, a second heating at 170 °C for 5 min with a pressure of 200 Pa, and a final cooling at room temperature during 20 min keeping the same pressure. This methodology resulted in very homogenous amorphous samples, as revealed by XRD and DSC. The incorporation of star-PDLLA toughened the polylactide matrix by a clear ductilization, opening opportunities for the expanded use of the developed blends in different applications, due to their increased processability. DSC analysis revealed indeed that by increasing star-PDLLA content it is possible to gradually reduce the T g , as well as the capability of crystallization of the linear-PLLA component. Such properties determine a plasticizing effect on the final blends. The increased content of the star component turned the films from transparent to translucent and decreases the thermal decomposition temperatures, which remain in any case very well above room temperature. The water vapor transmission rates varied with the star-PDLLA content between values characteristic for isolating to breathable films, thus allowing the use of these blends in different applications such as food packaging and biomedical devices. Finally, no important changes of water contact angle and water uptake were observed between the different blends. Despite the negligible effect of seawater on the biodegradation of commercial PLA, star-PDLLA-containing blends showed high biodegradation rates at short-times in marine environments, reinforcing the environmentally friendly character of polylactide. Image 1 • All -PLA blends have been fabricated by melt-blending of linear and star PLA. • The incorporation of star PLA toughened the polylactide matrix. • These blends showed high biodegradation rates at short-times in marine environments. [ABSTRACT FROM AUTHOR]