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Bacterial cellulose (BC) represents a promising biomaterial, due to its unique and versatile properties. We report, herein, on purposely-designed structural modifications of BC that enhance its application as a wound dressing material. Chemical modification of the functional groups of BC was performed initially to introduce a hydrophobic/oleophilic character to its surface. Specifically, silanization was carried out in an aqueous medium using methyltrimethoxisilane (MTMS) as the silanizing agent, and aerogels were subsequently prepared by freeze-drying. The BC-MTMS aerogel obtained displayed a highly porous (99 %) and lightweight structure with an oil absorption capacity of up to 52 times its dry weight. The XRD pattern indicated that the characteristic crystallographic planes of the native BC were maintained after the silanization process. Thermal analysis showed that the thermal stability of the BC-MTMS aerogel increased, as compared to the pure BC aerogel (pBC). Moreover, the BC-MTMS aerogel was not cytotoxic to fibroblasts and keratinocytes. In the second step of the study, the incorporation of natural oils into the aerogel's matrix was found to endow antimicrobial and/or healing properties to BC-MTMS. Bourbon geranium (Pelargonium X ssp.) essential oil (GEO) was the only oil that exhibited antimicrobial activity against the tested microorganisms, whereas buriti (Mauritia flexuosa) vegetable oil (BVO) was non-cytotoxic to the cells. This study demonstrates that the characteristics of the BC structure can be modified, while preserving its intrinsic features, offering new possibilities for the development of BC-derived materials for specific applications in the biomedical field.

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Aerogels are highly porous and ultralight three-dimensional materials with great potential for various applications. To obtain highly porous and structurally stable aerogels, a carefully designed synthesis process is required. These materials offer flexibility in manipulating their properties, allowing the incorporation of modifying agents according to specific needs. In this study, compounds were synthesized using graphene oxide (GO) and nanocellulose fibers (NFC) through the hydrothermal reduction methodology. Two drying techniques were employed: lyophilization and oven evaporation, resulting in materials called cryogel and xerogel, respectively. Various parameters that can interfere with the properties of these nanomaterials were evaluated. The results indicated that the cryogel dried by lyophilization provided the best applicability due to its structural flexibility after compressions, whereas the xerogel obtained through the oven evaporation process resulted in a compound with high rigidity and disintegration. Structural characterizations demonstrated the successful development of the precursors and promising characteristics in the synthesized nanomaterials. With its flexibility, approximately 98% porosity, low shrinkage rate, light weight, and electrical conductivity, the developed cryogel showed high potential in various applications, such as pressure sensors, electromagnetic shielding, and other research and development fields.

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The frequent occurrence of oil spills has led to serious environmental pollution and ecological issues. Given the high-viscosity of crude oil, it is essential to develop sorbents with efficient viscosity reduction and sorption capacity in various environmental conditions. Herein, a superhydrophobic carboxymethyl cellulose (CMC) aerogel co-modified by MXene and graphene jointly (M-Mxene/Gr CA) with aligned channels structure was prepared. The aligned channels structure can effectively improve the longitudinal thermal conductivity and reduce the sorption resistance. Through the modification of MXene and graphene, the aerogel realized efficient photo/electro-thermal conversion, thus ensuring its adaption to various working environments. The rapid heat generation can significantly reduce the viscosity of crude oil, achieving rapid recovery. Under one sun illumination (1.0 kW/m2), the surface temperature of M-Mxene/Gr CA can reach 72.6 °C and its sorption capability for high-viscous crude oil reaches 18 g/g. Combining photo-thermal and electro-thermal (0.5 kW/m2 and 23 V), the average sorption rate of crude oil can reach 1.3 × 107 g m-3 s-1. Finally, we present a continuous sorption system to recover offshore oil spills under the assistance of a pump. This work provides a new option for tackling high-viscous offshore oil spills due to its environmental friendliness and fast sorption capacity.

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The incorporation of polymeric components into aerogels based on clay produces a significant improvement in the physical and thermal properties of the aerogels. In this study, clay-based aerogels were produced from a ball clay by incorporation of angico gum and sodium alginate using a simple, ecologically acceptable mixing method and freeze-drying. The compression test showed a low density of spongy material. In addition, both the compressive strength and the Young's modulus of elasticity of the aerogels showed a progression associated to the decrease in pH. The microstructural characteristics of the aerogels were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The chemical structure was studied by infrared spectroscopy with Fourier transform (FTIR). The TGA curves from a non-oxidizing atmosphere indicated that the clay had a mass loss of 9% above 500 °C and that due to the presence of polysaccharides, the aerogels presented a decomposition of 20% at temperatures above 260 °C. The DSC curves of the aerogels demonstrated a displacement in higher temperatures. In conclusion, the results showed that aerogels of ball clay with the incorporation of polysaccharides, which are still minimally studied, have potential application as thermal insulation considering the mechanical and thermal results obtained.

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This study explores the use of silica-coated bacterial nanocellulose (BC) scaffolds with bulk macroscopic yet nanometric internal pores/structures as functional supports for high surface area titania aerogel photocatalysts to design flexible, self-standing, porous, and recyclable BC@SiO2-TiO2 hybrid organic-inorganic aerogel membranes for effective in-flow photo-assisted removal of organic pollutants. The hybrid aerogels were prepared by sequential sol-gel deposition of the SiO2 layer over BC, followed by coating of the resulting BC@SiO2 membranes with a porous titania aerogel overlayer of high surface area using epoxide-driven gelation, hydrothermal crystallization, and subsequent supercritical drying. The silica interlayer between the nanocellulose biopolymer scaffold and the titania photocatalyst was found to greatly influence the structure and composition, particularly the TiO2 loading, of the prepared hybrid aerogel membranes, allowing the development of photochemically stable aerogel materials with increased surface area/pore volume and higher photocatalytic activity. The optimized BC@SiO2-TiO2 hybrid aerogel showed up to 12 times faster in-flow photocatalytic removal of methylene blue dye from aqueous solution in comparison with bare BC/TiO2 aerogels and outperformed most of the supported-titania materials reported earlier. Moreover, the developed hybrid aerogels were successfully employed to remove sertraline drug, a model emergent contaminant, from aqueous solution, thus further demonstrating their potential for water purification.

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In this paper, a model for Cr (VI) removal and optimization was made using a novel aerogel material, chitosan-resole CS/R aerogel, where a freeze-drying and final thermal treatment was employed to fabricate the aerogel. This processing ensures a network structure and stability for the CS, despite the non-uniform ice growth promoted by this process. Morphological analysis indicated a successful aerogel elaboration process., FTIR spectroscopy corroborated the aerogel precursor's identity and ascertained chemical bonding after adsorption. Owing to the variability of formulations, the adsorption capacity was modeled and optimized using computational techniques. The response surface methodology (RSM), based on the Box-Behnken design using three levels, was used to calculate the best control parameters for the CS/R aerogel: the concentration at %vol (50-90%), the initial concentration of Cr (VI) (25-100 mg/L), and adsorption time (0.3-4 h). Analysis of variance (ANOVA) and 3D graphs reveal that the CS/R aerogel concentration and adsorption time are the main parameters that influence the initial concentration of CS/R aerogel metal-ion uptake. The developed model successfully describes the process with a correlation coefficient of R2 = 0.96 for the RSM. The model obtained was optimized to find the best material design proposal for Cr (VI) removal. Numerical optimization was used and showed superior Cr (VI) removal (94.4%) under conditions of a CS/R aerogel concentration of 87/13 %vol, with an initial concentration of Cr (VI) of 31 mg/L, and an adsorption time of 3.02 h. These results suggest that the proposed computational model can obtain an effective and viable model for CS material processing and for optimization of the uptake of this metal.

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A procedure of direct magnetic sorbent sampling in flame atomic absorption spectrometry (DMSS-FAAS) was developed in this work. Metal-loaded magnetic sorbents were directly inserted in the flame of the FAAS for direct metal desorption/atomization. Magnetic graphene oxide aerogel (M-GOA) particles were synthesized, characterized, and used as a proof-of-concept in the magnetic dispersive solid phase extraction of Pb2+ ions from water samples. M-GOA was selected because is a light and porous sorbent, with high adsorption capacity, that is quickly burned by the flame. Magnetic particles were directly inserted in the flame by using a metallic magnetic probe, thereby avoiding the need for a chemical elution step. As all the extracted Pb2+ ions arrive to the flame without passing through the nebulization system, a drastic increase in the analytical signal was achieved. The improvement in the sensitivity of the proposed method (DMSS-FAAS) for Pb2+ determination was at least 40 times higher than the conventional procedure in which the Pb2+ is extracted, eluted, and analyzed by conventional flame atomic absorption spectrometry (FAAS) via the nebulization system. The analytical curve was linear from 5.0 to 180.0 µg L-1 and the limit of detection was found to be 1.30 µg L-1. Background measurements were insignificant, and the atomic absorption peaks were narrow and reproducible. Precision assessed as a percentage of the relative standard deviation %RSD was found to be 17.4, 7.1, and 7.8% for 10, 70, and 180 µg L-1 levels, respectively. The method showed satisfactory results even in the presence of other ions (Al3+, Cr3+, Co2+, Cu2+, Fe3+, Mn2+, Ba2+, Mg2+, and Li+). The performance of the new system was also evaluated for Cd2+ ions, as well as by using other magnetic particles available in our lab: magnetic carbon nanotubes (M-CNTs), magnetic restricted access carbon nanotubes (M-RACNT), magnetic poly (methacrylic acid-co-ethylene glycol dimethacrylate) (M-PMA), magnetic nanoparticles coated with orange powder peel (M-OPP), and magnetic nanoparticles covered with SiO2 (M - SiO2). Analytical signals increased for both analytes in all sorbents (increases of about 4-37 times), attesting the high potential and applicability of the proposed method. Simplicity, high analytical frequency, high detectability and reproducibility, low cost, and possibility of being totally mechanized are the most relevant advantages.

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Hydrophobic chitosan aerogels are promising adsorbents for immiscible contaminants such as oils and organic solvents. However, few studies have reported the application of hydrophobic aerogels as adsorbent for organic contaminants dissolved in water. Herein, novel highly hydrophobic chitosan (CS) beads containing cellulose nanocrystals (CNC) and hydrophobized tannic acid (HTA) composite were prepared with different CS and CNC-HTA content to achieve an optimized adsorbent to remove emerging contaminants from water in batch and fixed-bed assays. The CS@CNC-HTA beads properties were assessed by FTIR, XRD, SEM, XPS, Micro-CT, WCA, and zeta potential. Supramolecular interactions and physical interlacements between CS and CNC-HTA enabled the formation of CS@CNC-HTA beads with high porosity (98.6%), great volume of open pore space (10.16 mm3) and hydrophobicity (121.8°). The 1:1 CS@CNC-HTA beads showed the best performance for removing the pharmaceutical sildenafil citrate, the basic blue 26 dye, and the surfactant cetylpyridinium chloride, reaching adsorption capacities of 86 (73%), 375 (84%), and 390 (90%) mg.g-1, respectively. The 1:1 CS@CNC-HTA beads efficiently removed sildenafil citrate, basic blue 26 and cetylpyridinium chloride in fixed-bed experiments with exhaustion times of 890, 300, and 470 min, respectively. Theoretical calculations and adsorption assays indicate that the main attractive interactions are pyridinium-π, π-π, electrostatic and hydrophobic.

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This paper evaluates corn starch aerogels, studying different crosslinking agent (trisodium citrate) concentrations (1:1, 1:1.5, and 1:2) and sorption conditions (contact time, adsorbent weight, and initial concentration) regarding the potentially toxic elements (PTEs) [Cd(II) or Zn(II)] adsorption of the aqueous systems. Besides, other properties of aerogels, such as structural properties, specific surface area, and mechanical performance, were evaluated. For adsorption results, better values were observed in adsorption capacity and efficiency for the initial concentration of 100 ppm. In addition, an adsorption time of 12 h and an adsorbent weight of 3.0 g obtained better results due to the possible balance in this time and the high specific surface area available for Cd(II) adsorption. As for the type of adsorbent, the Aero 1:1.5 sample (intermediate crosslinking agent concentration) obtained better results, possibly due to the high porosity, smaller pore sizes, high pore density, and high specific surface area (198 m2·g-1). In addition, hydroxyl groups in the starch aerogel removed Cd(II) ions with 30 % adsorption efficiency. Lastly, Aero 1:1.5 obtained a high mechanical strength at compression and a satisfactory compressive modulus. In contrast, starch aerogels did not absorb the Zn(II) ion.

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In this study, graphene oxide (GO)-based aerogels cross-linked with chitosan (CS), gelatin (GEL), and polyvinyl alcohol (PVA) were characterized and their hemostatic efficiencies both in vitro and in vivo were investigated and compared to commercial materials (ChitoGauze®XR and Spongostan™). All aerogels exhibited highly porous structures and a negative surface charge density favorable to their interaction with blood cells. The in vitro studies showed that all aerogels coagulated >60 % of the blood contained in their structures after 240 s of the whole-blood clotting assay, the GO-CS aerogel being the one with the highest blood clotting. All aerogels showed high hemocompatibility, with hemolytic rates <5 %, indicating their use as biomaterials. Among them, the GO-GEL aerogel exhibited the lowest hemolytic activity, due possibly to its high GEL content compared to the GO amount. According to their blood clotting activity, aerogels did not promote coagulation through extrinsic and intrinsic pathways. However, their surfaces are suitable for accelerating hemostasis by promoting alternative routes. All aerogels adhered platelets and gathered RBCs on their surfaces, and in addition the GO-CS aerogel surface also promoted the formation of filamentous fibrin networks adhered on its structure. Furthermore, in vivo evaluations revealed that all aerogels significantly shortened the hemostatic times and reduced the blood loss amounts compared both to the Spongostan™ and ChitoGauze®XR commercial materials and to the gauze sponge (control group). The hemostatic performance in vitro and in vivo of these aerogels suggests that they could be used as hemostats for controlling profuse bleedings.

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The effective integration of multiple thermal functions into one material is highly attractive in personal thermal management, taking the complex application environment into consideration. Herein, a multifunctional Janus cellulosic composite encompassing superior electrical heating, energy storage, thermal insulation, and infrared camouflage performance was firstly developed by integrating Janus cellulose nanofibers (CNF) aerogel, polypyrrole (PPy), and polyethylene glycol (PEG). In practice, the active heating-thermal regulation layer (PPy@CNFphilic-PEG) of multifunctional Janus cellulosic composite is faced inward to provide heating on-demand through the joint action of the electrically conductive PPy and thermally regulative PEG. The outward-facing hydrophobic aerogel layer (CNFphobic) serves as the thermal insulator, which simultaneously enables infrared camouflage by reducing heat loss to the environment via infrared radiation. This work presents an effective and facile strategy toward multifunctional Janus materials for efficient personal thermal management, showing great promise for potential applications, such as thermal comfort, infrared camouflage, and security protection.

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In this work, unsupported Pd aerogel catalysts were synthesized for the very first time by using microwaves as a heating source followed by a lyophilization drying process and used towards formic acid electro-oxidation in a microfluidic fuel cell. Aerogels were also made by heating in a conventional oven to evaluate the microwave effect during the synthesis process of the unsupported Pd aerogels. The performance of the catalysts obtained by means of microwave heating favored the formic acid electro-oxidation with H2SO4 as the electrolyte. The aerogels' performance as anodic catalysts was carried out in a microfluidic fuel cell, giving power densities of up to 14 mW cm-2 when using mass loads of only 0.1 mg on a 0.019 cm2 electrode surface. The power densities of the aerogels obtained by microwave heating gave a performance superior to the resultant aerogel prepared using conventional heating and even better than a commercial Pd/C catalyst.

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A new alternative aerogel was prepared from low-cost chitin and psyllium biopolymers to adsorb crystal violet (CV) dye from liquid media and possibly treat effluents containing other dyes. The aerogel was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), which demonstrated that aerogel has a typical structure of amorphous materials and presented a randomly interconnected porous structure that resembles an open pore network. 2.5 g L-1 of aerogel was able to remove 86.00% of CV from solutions, and the natural pH of the CV solution was considered the more adequate for adsorption. The pseudo-second-order (PSO) model satisfactorily described the adsorption kinetics, and the Freundlich model was suitable to represent the adsorption equilibrium. The maximum experimental capacity achieved was 227.11 mg g-1, which indicates that aerogel is very efficient and competitive with several adsorbents. Tests using a simulated effluent showed that aerogel has excellent potential to treat real colored effluents.

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Sol-gel technique aiming enzymatic immobilization in situ with ionic liquids as additives is poorly studied. In this process, the addition of the enzyme is carried out in the synthesis of the support. The characteristics of ionic liquids, such as low vapor pressure, thermal stability, and non-flammability, make them strong candidates for use as immobilization additives. The objective of the present study was to immobilize the Candida antarctica B lipase by the sol-gel technique using ionic liquids as additives. The optimum points determined for ionic liquids 1-butyl-3-methylimidazolium chloride, 1-octyl-3-methylimidazolium bromide, and 1 hexadecyl-3-methylimimidazolium were 0.30, 0.27, and 0.22 g/mL of enzyme and 1.60, 1.52, and 1.52% of additive, respectively. The amount of enzyme and ionic liquids used in aerogel immobilization was the same as the optimized values in the xerogel immobilization process (for each ionic liquid). Ionic liquids proved to be good additives in the enzymatic immobilization process. Xerogel, regardless of the ionic liquid, presented a greater number of use cycles and better thermal stability compared to aerogel.

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Biodegradable aerogels may help to develop eco-friendly technological pathways to increase the efficiency of chemical processes. In the present work, we describe the preparation of a novel bacterial cellulose aerogel oxidized by TEMPO, nanofibrillated in a blender, and silanized with methyltrimethoxysilane, resulting in four different types of aerogel. The aerogels produced from the double-functionalized cellulose suspension (BCOXNS) were compared to other non-oxidized (BCN and BCNS) and non-silanized (BCOXN) aerogels All aerogels were very light (density 10-14 kg.m-3) and very porous (porosity >99 %). The aerogels of BCOXNS showed better mechanical properties (tension of 13.0 kPa, modulus of elasticity of 39.4 kPa) and hydrophobicity, and could absorb organic solvents of different polarities. The BCOXNS could be recycled at least 7 times after absorbing organic solvents while retaining an absorption capacity of 83 %. This material can be used as a standard for the further development of aerogels based on bacterial biopolymers.

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To address the problems associated with the use of unsupported nanomaterials, in general, and molybdenum disulfide (MoS2), in particular, we report the preparation of self-supported hybrid aerogel membranes that combine the mechanical stability and excellent textural properties of bacterial nanocellulose (BC)-based organic macro/mesoporous scaffolds with the excellent adsorption-cum-photocatalytic properties and high contaminant removal performance of MoS2 nanostructures. A controlled hydrothermal growth and precise tuning of the synthetic parameters allowed us to obtain BC/MoS2-based porous, self-supported, and stable hybrid aerogels with a unique morphology resulting from a molecular precision in the coating of quantum-confined photocatalytic MoS2 nanostructures (2-4 nm crystallite size) on BC nanofibrils. These BC/MoS2 samples exhibit high surface area (97-137 m2·g-1) and pore volume (0.28-0.36 cm3·g-1) and controlled interlayer distances (0.62-1.05 nm) in the MoS2 nanostructures. Modification of BC with nanostructured MoS2 led to an enhanced pollutants removal efficiency of the hybrid aerogels both by adsorptive and photocatalytic mechanisms, as indicated by a detailed study using a specifically designed membrane photoreactor containing the developed photoactive/adsorptive BC/MoS2 hybrid membranes. Most importantly, the prepared BC/MoS2 aerogel membranes showed high performance in the photoassisted in-flow removal of both organic dye (methylene blue (MB)) molecules (96% removal within 120 min, Kobs = 0.0267 min-1) and heavy metal ions (88% Cr(VI) removal within 120 min, Kobs = 0.0012 min-1), separately and/or simultaneously, under UV-visible light illumination as well as excellent recyclability and photostability. Samples with interlayer expanded MoS2 nanostructures were particularly more efficient in the removal of smaller species (CrO42-) as compared to larger (MB) dye molecules. The prepared hybrid aerogel membranes show promising behavior for application in in-flow water purification, representing a significant advancement in the use of self-supported aerogel membranes for photocatalytic applications in liquid media.

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The procedures to obtain two types of acemannan (AC) physical gels and their respective aerogels are reported. The gelation was induced by the diffusion of an alkali or a non-solvent, then supercritical CO2 drying technology was used to remove the solvent out and generate the AC aerogels. Fourier-transform infrared spectroscopic analysis indicated that alkali diffusion produced extensive AC deacetylation. Conversely, the non-solvent treatment did not affect the chemical structure of AC. Both types of gels showed syneresis and the drying process induced further volume reduction. Both aerogels were mesoporous nanostructured materials with pore sizes up to 6.4 nm and specific surface areas over 370 m²/g. The AC physical gels and aerogels enable numerous possibilities of applications, joining the unique features of these materials with the functional and bioactive properties of the AC.

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This study describes the valorization of rice and oat husks by obtaining cellulose nanocrystals for the production of aerogels for food packaging applications. Commercial cellulose was used as a control sample. Nanocrystals from cellulose were obtained by enzymatic hydrolysis and mechanical treatment at high pressure. The morphology, particle size, functional groups, crystallinity, and thermal properties of the cellulose nanocrystals were analyzed. The morphology, functional groups, crystallinity, water absorption capability, and zeta potential of aerogels were also analyzed. Cellulose nanocrystals show different structural properties and crystallinity depending on the source of the cellulose. The average diameter of the nanocrystals varied from 16.0 to 28.8 nm. The aerogels prepared with cellulose nanocrystals showed a porous and uniform structure with a water absorption capacity between 264.2% and 402.8% at 25 °C. The aerogel of oat cellulose nanocrystals showed a larger pore size than that of eucalyptus cellulose nanocrystals, and this may have influenced the lowest water absorption capacity of the aerogels of eucalyptus cellulose nanocrystals. These results show that agroindustrial residues have promising applications in various industrial fields and could be used as aerogel absorbers of water in food packaging.

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Smart electroactive biomaterials are sought to allow the direct delivery of electrical, electrochemical and electromechanical signals to biological tissues. Specifically, poly-(3,4-ethylenedioxythiophene) (PEDOT) is a polymer of special interest attending to its biocompatibility, tuneable electrical conductivity and processing versatility. In this work, nanostructured PEDOT was synthesized using starch/κ-carrageenan aerogels as templates. κ-carrageenan biopolymer acted as doping agent of the conductive polymer to enhance the biocompatibility and the electrical response. The physicochemical, morphological, mechanical and electrical properties of the nanostructured PEDOT and templates were characterized. The incorporation of κ-carrageenan to the nanostructured materials resulted in an increase in the compressive strength of ca. 40% and a decrease in the electrical impedance of one order-of-magnitude. The synergistic combination of the inherent electrical properties of the PEDOT, the advantageous features of κ-carrageenan as doping agent and the porous morphology of the aerogel template resulted in electroactive PEDOT nanostructures with relevant properties for biomedical applications.

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The graphene aerogels' potential for use as both a hemostatic agent and dermal delivery system has scarcely been investigated. In this study, we used a sol-gel process for generating dry and stable composite aerogels based on graphene oxide (GO) and poly(vinyl alcohol) (PVA). Furthermore, we incorporated natural extract of País grape seed (SD) and skin (SK), rich in proanthocyanidins (PAs or condensed tannins). The effect of the incorporation of the grape extracts was investigated in relation to the aerogels' structure, coagulation performance and the release of the extracts. The results demonstrated that they have a porous structure and low density, capable of absorbing water and blood. The incorporation of 12% (w/w) of PA extracts into the aerogel increased the negative zeta potential of the material by 33% (-18.3 ± 1.3 mV), and the coagulation time was reduced by 37% and 28% during the first 30 and 60 s of contact between the aerogel and whole blood, respectively. The release of extracts from the GO-PVA-SD and GO-PVA-SK aerogels was prolonged to 3 h with 20%, probably due to the existence of strong binding between PAs andGO-PVA, both characterized by the presence of aromatic and hydroxyl groups that can form noncovalent bonds but are strong and stable enough to avoid a greater release into the medium. This study provides a new GO-based aerogel, which has a great potential use in the field of dermal delivery, wound healing and/or the treatment of trauma bleeding.

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