Multifunctional curcumin-based polymer coating: A promising platform against bacteria, inflammation and coagulation.

The extensive use of polymers in the medical field has facilitated the development of various devices and implants, contributing to the restoration of organ function. However, despite their advantages such as biocompatibility and robustness, these materials often face challenges like bacterial contamination and subsequent inflammation, leading to implant-associated infections (IAI). Integrating implants effectively is crucial to prevent bacterial colonization and reduce inflammatory responses. To overcome these major issues, surface chemical modifications have been extensively explored. Indeed, click chemistry, and particularly, copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has emerged as a promising approach for surface functionalization without affecting material bulk properties. Curcumin, known for its diverse biological activities, suffers from low solubility and stability. To enhance its bioavailability, bioconjugation strategy has garnered attention in recent years. This study represents pioneering work in immobilizing curcumin derivative onto polyethylene terephthalate (PET) surfaces, aiming to combat bacterial adhesion, inflammation and coagulation. Before curcumin derivative bioconjugation, a fluorophore, dansyl derivative, was employed in order to monitor and determine the efficiency of the proposed methodology. Previous surface chemical modifications were required for the immobilization of both dansyl and curcumin derivatives. Ultraviolet-Visible (UV-Vis) demonstrated the amidation functionalization of PET surface. Other surface characterization techniques including X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflectance Fourier Transformed Infrared (ATR-FTIR), Scanning Electron Microscopy (SEM) and contact angle, among others, confirmed also the conjugation of both dansyl and curcumin derivatives. On the other hand, different biological assays corroborated that curcumin derivative immobilized PET surfaces do not exhibit cytotoxicity effect. Additionally, corresponding inflammation test were performed, indicating that these polymeric surfaces do not produce inflammation and, when curcumin derivative is immobilized, they decrease the inflammation marker level (IL-6). Moreover, the bacterial growth of both Gram positive and Gram negative bacteria were measured, demonstrating that the immobilization of curcumin derivative on PET provided antibacterial properties to the material. Finally, hemolysis rate analysis and whole blood clotting assay demonstrated the antithrombogenic effect of PET-Cur surfaces as well as no hemolysis concern in the fabricated functional surfaces.

Improving the Recyclability of an Epoxy Resin through the Addition of New Biobased Vitrimer.

In recent decades, the use of thermoset epoxy resins (ER) has spread to countless applications due to their mechanical properties, heat resistance and stability. However, these ERs are neither biodegradable nor recyclable due to their permanent crosslinked networks and usually, they are synthesized from fossil and toxic precursors. Therefore, reducing its consumption is of vital importance to the environment. On the one hand, the solution to the recyclability problems of epoxy resins can be achieved through the use of vitrimers, which have thermoset properties and can be recycled as thermoplastic materials. On the other hand, vitrimers can be made from natural sources, reducing their toxicity. In this work, a sustainable epoxy vitrimer has been efficiently synthesized, VESOV, by curing epoxidized soybean oil (ESO) with a new vanillin-derived Schiff base (VSB) dynamic hardener, aliphatic diamine (1,4-butanediamine, BDA) and using 1,2-dimethylimidazole (DMI) as an accelerator. Likewise, using the same synthesized VSB agent, a commercial epoxy resin has also been cured and characterized as ESO. Finally, different percentages (30, 50 and 70 wt%) of the same ER have been included in the formulation of VESOV, demonstrating that only including 30 wt% of ER in the formulation is able to improve the thermo-mechanical properties, maintaining the VESOV's inherent reprocessability or recyclability. In short, this is the first approach to achieve a new material that can be postulated in the future as a replacement for current commercial epoxy resins, although it still requires a minimum percentage of RE in the formulation, it makes it possible to recycle the material while maintaining good mechanical properties.

Protective Strategies of Haberlea rhodopensis for Acquisition of Freezing Tolerance: Interaction between Dehydration and Low Temperature.

Resurrection plants are able to deal with complete dehydration of their leaves and then recover normal metabolic activity after rehydration. Only a few resurrection species are exposed to freezing temperatures in their natural environments, making them interesting models to study the key metabolic adjustments of freezing tolerances. Here, we investigate the effect of cold and freezing temperatures on physiological and biochemical changes in the leaves of Haberlea rhodopensis under natural and controlled environmental conditions. Our data shows that leaf water content affects its thermodynamical properties during vitrification under low temperatures. The changes in membrane lipid composition, accumulation of sugars, and synthesis of stress-induced proteins were significantly activated during the adaptation of H. rhodopensis to both cold and freezing temperatures. In particular, the freezing tolerance of H. rhodopensis relies on a sucrose/hexoses ratio in favor of hexoses during cold acclimation, while there is a shift in favor of sucrose upon exposure to freezing temperatures, especially evident when leaf desiccation is relevant. This pattern was paralleled by an elevated ratio of unsaturated/saturated fatty acids and significant quantitative and compositional changes in stress-induced proteins, namely dehydrins and early light-induced proteins (ELIPs). Taken together, our data indicate that common responses of H. rhodopensis plants to low temperature and desiccation involve the accumulation of sugars and upregulation of dehydrins/ELIP protein expression. Further studies on the molecular mechanisms underlying freezing tolerance (genes and genetic regulatory mechanisms) may help breeders to improve the resistance of crop plants.

Reversible First-Order Single Crystal to Single Crystal Thermal Phase Transition in [(CH3)3CNH3]4[V4O12].

The well-known compound tetrakis(tert-butylammonium)-cyclo-tetrametavanadate (V), [(CH3)3CNH3]4[V4O12] (1h_RT), which crystallizes in the tetragonal I4/m space group, undergoes an irreversible solid state transformation upon heating, constituting one of the few examples in which the initial and the final stages are structurally characterized by sc-XRD. Now, we observed the ability of the same compound to undergo an additional single-crystal-to-single-crystal (SCSC) transformation upon thermal stimuli, but this time at low temperatures (153 K). Compound 1h_RT contains a discrete unprotonated [V4O12]4- tetrahedral anion in which V and O bridging atoms are coplanar. In both phases, these tetrameric anions are linked through tert-butylammonium cations in an extensive network of hydrogen bonds, but at low temperatures, this phase loses its characteristic O-V-O coplanarity, with the resulting rearrangement of the crystal packing and hydrogen-bond network which provide its reversibility at low temperatures. Again, the initial and final stages have been characterized structurally by sc-XRD.

Frozen in the dark: interplay of night-time activity of xanthophyll cycle, xylem attributes, and desiccation tolerance in fern resistance to winter.

While most ferns avoid freezing as they have a tropical distribution or shed their fronds, wintergreen species in temperate and boreoalpine ecosystems have to deal with sub-zero temperatures. Increasing evidence has revealed overlapping mechanisms of desiccation and freezing tolerance in angiosperms, but the physiological mechanisms behind freezing tolerance in ferns are far from clear. We evaluated photochemical and hydraulic parameters in five wintergreen fern species differing in their ability to tolerate desiccation. We assessed frond freezing tolerance, ice nucleation temperature and propagation pattern, and xylem anatomical traits. Dynamics of photochemical performance and xanthophyll cycle were evaluated during freeze-thaw events under controlled conditions and, in selected species, in the field. Only desiccation-tolerant species, which possessed a greater fraction of narrow tracheids (<18 µm) than sensitive species, tolerated freezing. Frond freezing occurred in the field at -3.4 ± 0.9 °C (SD) irrespective of freezing tolerance, freezable water content, or tracheid properties. Even in complete darkness, maximal photochemical efficiency of photosystem II was down-regulated concomitantly with zeaxanthin accumulation in response to freezing. This was reversible upon re-warming only in tolerant species. Our results suggest that adaptation for freezing tolerance is associated with desiccation tolerance through complementary xylem properties (which may prevent risk of irreversible cavitation) and effective photoprotection mechanisms. The latter includes de-epoxidation of xanthophylls in darkness, a process evidenced for the first time directly in the field.

How dry is dry? Molecular mobility in relation to thallus water content in a lichen.

Lichens can withstand extreme desiccation to water contents of ≤ 0.1 g H2O g-1 DW, and in the desiccated state are among the most extremotolerant organisms known. Desiccation-tolerant life-forms such as seeds, mosses and lichens survive 'vitrification', that is the transition of their cytoplasm to a 'glassy' state, which causes metabolism to cease. However, our understanding of the mechanisms of desiccation tolerance is hindered by poor knowledge of what reactions occur in the desiccated state. Using Flavoparmelia caperata as a model lichen, we determined at what water contents vitrification occurred upon desiccation. Molecular mobility was assessed by dynamic mechanical thermal analysis, and the de- and re-epoxidation of the xanthophyll cycle pigments (measured by HPLC) was used as a proxy to assess enzyme activity. At 20 °C vitrification occurred between 0.12-0.08 g H2O g-1 DW and enzymes were active in a 'rubbery' state (0.17 g H2O g-1 DW) but not in a glassy state (0.03 g H2O g-1 DW). Therefore, desiccated tissues may appear to be 'dry' in the conventional sense, but subtle differences in water content will have substantial consequences on the types of (bio)chemical reactions that can occur, with downstream effects on longevity in the desiccated state.

Structural Characterization of Mono and Dihydroxylated Umbelliferone Derivatives.

Coumarin derivatives are a class of compounds with a pronounced wide range of applications, especially in biological activities, in the medicine, pharmacology, cosmetics, coatings and food industry. Their potential applications are highly dependent on the nature of the substituents attached to their nucleus. These substituents modulate their photochemical and photophysical properties, as well as their interactions in their crystalline form, which largely determines the final field of application. Therefore, in this work a series of mono and dihydroxylated coumarin derivatives with different chemical substituents were synthesized and characterized by UV-Visible spectroscopy, thermal analysis (differential scanning calorimetry (DSC) and TGA), 1H NMR and X-Ray Diffraction to identify limitations and possibilities as a function of the molecular structure for expanding their applications in polymer science.

Desiccation Tolerance in Chlorophyllous Fern Spores: Are Ecophysiological Features Related to Environmental Conditions?

Fern spores of most species are desiccation tolerant (DT) and, in some cases, are photosynthetic at maturation, the so-called chlorophyllous spores (CS). The lifespan of CS in the dry state is very variable among species. The physiological, biochemical, and biophysical mechanisms underpinning this variability remain understudied and their interpretation from an ecophysiological approach virtually unexplored. In this study, we aimed at fulfilling this gap by assessing photochemical, hydric, and biophysical properties of CS from three temperate species with contrasting biological strategies and longevity in the dry state: Equisetum telmateia (spore maturation and release in spring, ultrashort lifespan), Osmunda regalis (spore maturation and release in summer, medium lifespan), Matteuccia struthiopteris (spore maturation and release in winter, medium-long lifespan). After subjection of CS to controlled drying treatments, results showed that the three species displayed different extents of DT. CS of E. telmateia rapidly lost viability after desiccation, while the other two withstood several dehydration-rehydration cycles without compromising viability. The extent of DT was in concordance with water availability in the sporulation season of each species. CS of O. regalis and M. struthiopteris carried out the characteristic quenching of chlorophyll fluorescence, widely displayed by other DT cryptogams during drying, and had higher tocopherol and proline contents. The turgor loss point of CS is also related to the extent of DT and to the sporulation season: lowest values were found in CS of M. struthiopteris and O. regalis. The hydrophobicity of spores in these two species was higher and probably related to the prevention of water absorption under unfavorable conditions. Molecular mobility, estimated by dynamic mechanical thermal analysis, confirmed an unstable glassy state in the spores of E. telmateia, directly related to the low DT, while the DT species entered in a stable glassy state when dried. Overall, our data revealed a DT syndrome related to the season of sporulation that was characterized by higher photoprotective potential, specific hydric properties, and lower molecular mobility in the dry state. Being unicellular haploid structures, CS represent not only a challenge for germplasm preservation (e.g., as these spores are prone to photooxidation) but also an excellent opportunity for studying mechanisms of DT in photosynthetic cells.

Novel Antibacterial and Toughened Carbon-Fibre/Epoxy Composites by the Incorporation of TiO2 Nanoparticles Modified Electrospun Nanofibre Veils.

The inclusion of electrospun nanofiber veils was revealed as an effective method for enhancing the mechanical properties of fiber-reinforced epoxy resin composites. These veils will eventually allow the incorporation of nanomaterials not only for mechanical reinforcement but also in multifunctional applications. Therefore, this paper investigates the effect of electrospun nanofibrous veils made of polyamide 6 modified with TiO2 nanoparticles on the mechanical properties of a carbon-fiber/epoxy composite. The nanofibers were included in the carbon-fiber/epoxy composite as a single structure. The effect of positioning these veils in different composite positions was investigated. Compared to the reference, the use of unmodified and TiO2 modified veils increased the flexural stress at failure and the fracture toughness of composites. When TiO2 modified veils were incorporated, new antibacterial properties were achieved due to the photocatalytic properties of the veils, widening the application area of these composites.

Effect of Different Types of Electrospun Polyamide 6 Nanofibres on the Mechanical Properties of Carbon Fibre/Epoxy Composites.

Delamination and brittle matrix fracture have long since been the biggest problems in fibre-reinforced composites. Recently, the incorporation of electrospun nanofibre veils has been shown to be an effective method for improving the mechanical properties of these composites, without causing process problems and negatively affecting other mechanical properties. Thus, these nanofibres have the potential to be used as thickness-reinforcing materials in composites. This paper investigates the effect of incorporating standalone electrospun nanofibre veils made of two different types of polyamide 6 (PA6) on the mechanical properties of carbon fibre/epoxy composites. The influence of positioning the electrospun veils at different interlaminar positions of the laminate has also been investigated.

Effects of Graphene Oxide and Chemically-Reduced Graphene Oxide on the Dynamic Mechanical Properties of Epoxy Amine Composites.

Composites based on epoxy/graphene oxide (GO) and epoxy/reduced graphene oxide (rGO) were investigated for thermal-mechanical performance focusing on the effects of the chemical groups present on nanoadditive-enhanced surfaces. GO and rGO obtained in the present study have been characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD) demonstrating that materials with different oxidation degrees have been obtained. Thereafter, GO/epoxy and rGO/epoxy nanocomposites were successfully prepared and thoroughly characterized by dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM). A significant increase in the glass transition temperature was found in comparison with the neat epoxy. The presence of functional groups on the graphene surface leads to chemical interactions between these functional groups on GO and rGO surfaces with the epoxy, contributing to the possible formation of covalent bonds between GO and rGO with the matrix. The presence of oxidation groups on GO also contributes to an improved exfoliation, intercalation, and distribution of the GO sheets in the composites with respect to the rGO based composites.

Construction of antibacterial poly(ethylene terephthalate) films via layer by layer assembly of chitosan and hyaluronic acid.

Polyelectrolytic multilayers (PEMs) with enhanced antibacterial properties were built up onto commercial poly(ethylene terephthalate) (PET) films based on the layer by layer assembling of bacterial contact killing chitosan and bacterial repelling highly hydrated hyaluronic acid. The optimization of the aminolysis modification reaction of PET was carried out by the study of the mechanical properties and the surface characterization of the modified polymers. The layer by layer assembly was successfully monitored by TEM microscopy, surface zeta-potential, contact angle measurements and, after labeling with fluorescein isothiocyanate (FTIC) by absorption spectroscopy and confocal fluorescent microscopy. Beside, the stability of the PEMs was studied at physiological conditions in absence and in the presence of lysozyme and hyaluronidase enzymes. Antibacterial properties of the obtained PEMs against Escherichia coli were compared with original commercial PET.

Covalently and Ionically Crosslinked Chitosan Nanogels for Drug Delivery.

Chitosan nanogels present a very interesting combination of valuable characteristics for drug delivery; those derived from their nanometric size, such as, large surface area, rapid stimuli-response, and easy functionalization; and those emerged especially from their biocompatibility, biodegradability and mucoadhesive nature. Due to this, chitosan nanogels have reached a prominent position as nanocarriers and have originated accelerated research worldwide. Diverse methods to prepare chitosan nanogels have been reported, showing a dependence on final swelling, drug encapsulation capability and release properties with different synthesis variables, in such a way that they can be exploited to be modulated. The present review describes the properties of chitosan nanogels, along with the different methods of crosslinking and confining chitosan in nanosized particles, and the various fields of drug delivery where they have been applied. This work aims to emphasize the connection between the characteristics of chitosan and the synthetic variables with the final properties of chitosan nanogels in order to enhance controlled drug loading and a sustained release.

Evidence for the absence of enzymatic reactions in the glassy state. A case study of xanthophyll cycle pigments in the desiccation-tolerant moss Syntrichia ruralis.

Desiccation-tolerant plants are able to withstand dehydration and resume normal metabolic functions upon rehydration. These plants can be dehydrated until their cytoplasm enters a 'glassy state' in which molecular mobility is severely reduced. In desiccation-tolerant seeds, longevity can be enhanced by drying and lowering storage temperature. In these conditions, they still deteriorate slowly, but it is not known if deteriorative processes include enzyme activity. The storage stability of photosynthetic organisms is less studied, and no reports are available on the glassy state in photosynthetic tissues. Here, the desiccation-tolerant moss Syntrichia ruralis was dehydrated at either 75% or <5% relative humidity, resulting in slow (SD) or rapid desiccation (RD), respectively, and different residual water content of the desiccated tissues. The molecular mobility within dry mosses was assessed through dynamic mechanical thermal analysis, showing that at room temperature only rapidly desiccated samples entered the glassy state, whereas slowly desiccated samples were in a 'rubbery' state. Violaxanthin cycle activity, accumulation of plastoglobules, and reorganization of thylakoids were observed upon SD, but not upon RD. Violaxanthin cycle activity critically depends on the activity of violaxanthin de-epoxidase (VDE). Hence, it is proposed that enzymatic activity occurred in the rubbery state (after SD), and that in the glassy state (after RD) no VDE activity was possible. Furthermore, evidence is provided that zeaxanthin has some role in recovery apparently independent of its role in non-photochemical quenching of chlorophyll fluorescence.