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This study presents fibers based on methacrylic acid-methyl methacrylate (Eudragit L100) as Cu(II) adsorbents, resulting in antimicrobial complexes. Eudragit L100, an anionic copolymer synthesized by radical polymerization, was electrospun in dimethylformamide (DMF) and ethanol (EtOH). The electrospinning process was optimized through a 22-factorial design, with independent variables (copolymer concentration and EtOH/DMF volume ratio) and three repetitions at the central point. The smallest average fiber diameter (259 ± 53 nm) was obtained at 14% w/v Eudragit L100 and 80/20 EtOH/DMF volume ratio. The fibers were characterized using scanning electron microscopy (SEM), infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), and differential scanning calorimetry (DSC). The pseudo-second-order mechanism explained the kinetic adsorption toward Cu(II). The fibers exhibited a maximum adsorption capacity (qe) of 43.70 mg/g. The DSC analysis confirmed the Cu(II) absorption, indicating complexation between metallic ions and copolymer networks. The complexed fibers showed a lower degree of swelling than the non-complexed fibers. The complexed fibers exhibited bacteriostatic activity against Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria. This study successfully optimized the electrospinning process to produce thin fibers based on Eudragit L100 for potential applications as adsorbents for Cu(II) ions in aqueous media and for controlling bacterial growth.

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Carboxymethylcellulose (CMC) and keratin nanoparticle (KNP) hydrogels were obtained, characterized, and applied as drug delivery systems (DDSs) for the first time. Lyophilized CMC/KNP mixtures containing 10, 25, and 50 wt% of KNPs were kept at 170 °C for 90 min to crosslink CMC chains through a solid-state reaction with the KNPs. The hydrogels were characterized by infrared spectroscopy, thermal analyses, X-ray diffraction, mechanical measurements, and scanning electron microscopy. The infrared spectra indicated the formation of ester and amide linkages between crosslinked CMC and KNPs. The elastic modulus of the hydrogel containing 10 wt% KNPs was 2-fold higher than that of the hydrogel containing 50 wt% KNPs. The mechanical properties influenced the hydrogel stability and water uptake. The anti-inflammatory prednisolone (PRED) drug was incorporated into the hydrogels, and the release mechanism was investigated. The hydrogels supported PRED release by drug desorption for approximately 360 h. A sustained release mechanism was achieved. The CMC/KNP and CMC/KNP/PRED hydrogels were cytocompatible toward mammalian cells. The CMC/KNP/PRED set imparted the highest cell viability after 7 days of incubation. This study showed a straightforward procedure to create DDSs (chemically crosslinked) based on polysaccharides and proteins for efficient PRED delivery.

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Obtaining CO and H2 from electrochemical CO2 reduction (CO2RR) offers a viable alternative to reduce CO2 emissions and produce chemicals and fuels. Herein, we report a simple strategy for obtaining polycrystalline copper deposited on oxidized graphite felt (Cu-OGF) and its performance on the selective conversion of CO2 and H2O to CO and H2. For the electrode obtaining, graphite felt (GF) was first oxidized (OGF) in order to make the substrate hydrophilic and then copper particles were electrochemically deposited onto OGF. The pH of deposition was investigated, and the CO2RR activity was assessed for the prepared electrodes at each pH (2.0, 4.0, 6.0, 8.0, and 10.0). It was found that pH 2.0 was the most promising for CO2RR due to the presence of hexagonal copper microparticles. Fourier transform infrared analysis of the produced gases showed that this is a low-cost catalyst capable of reducing CO2 and H2O to CO and H2, with Faradaic efficiencies between 0.50 and 5.21% for CO and 50.87 to 98.30% for H2, depending on the experimental conditions. Hence, it is possible for this gas mixture to be used as a fuel gas or to be enriched with CO for use in Fischer-Tropsch processes.

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This review reports recent advances in polysaccharide-based magnetic hydrogels as smart platforms for different biomedical applications. These hydrogels have proved to be excellent, viable, eco-friendly alternative materials for the biomedical field due to their biocompatibility, biodegradability, and possibility of controlling delivery processes via modulation of the remote magnetic field. We first present their main synthesis methods and compare their advantages and disadvantages. Next, the synergic properties of hydrogels prepared with polysaccharides and magnetic nanoparticles (MNPs) are discussed. Finally, we describe the main contributions of polysaccharide-based magnetic hydrogels in the targeted drug delivery, tissue regeneration, and hyperthermia therapy fields. Overall, this review aims to motivate the synthesis of novel composite biomaterials, based on the combination of magnetic nanoparticles and natural polysaccharides, to overcome challenges that still exist in the treatment of several diseases.

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In this work, we describe the synthesis, the characterization, and the potential application of a pH-responsive guar gum-based hydrogel. The polysaccharide produced permanent hydrogels with improved biocompatibility. In this work, we report the chemical modification of guar gum (with glycidyl methacrylate) and its use, as the main constituent, in obtaining chemically cross-linked hydrogels. The morphology, swelling properties, and cytotoxicity of the resulting materials were studied in-depth. The hydrogels showed to be pH-responsive, and non-toxic being safe to use it as a biomaterial. In addition, we tested the potential of this one as a drug carrier. Herein, we have chosen hydrocortisone (HCS) as a drug model. The mechanism of HCS release changed as a function of pH, owing to different responses in each medium. Our results indicate that the guar gum hydrogels have great potential to be used, with safety, as a drug carrier.

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Hydrogels based on pectin and cellulose nanocrystals (CNC) were used in our study to nucleation and growth of hydroxyapatite (HAp) by the biomimetic method. In this study, we evaluated the direct impact of the different percentages of CNC on pectin hydrogel and the influence of HAp obtained through two methods. CNC were obtained from HCl hydrolysis following chemical functionalization through vinyl groups. The percentage of CNC positively induces thermal stability, mechanical properties and HAp mineralization from biomimetic using simulated body fluid (1.5 SBF). Hydrogels with 5% of CNC showed a higher amount of HAp immersed for 14 days, about 28% of HAp. The obtained hydrogels were compared with hydrogels containing 20% of HAp nanoparticles obtained by chemical precipitation. Biocompatibility of the hydrogels was evaluated by cell viability using fibroblasts (L929). In general, the hydrogels obtained through the biomimetic method show slightly larger biocompatibility compared to the hybrid hydrogels obtained from chemical precipitation.

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This study compared the controlled release of two drugs: vitamin-B12, and l-dopa from hydrogels based on 50% of casein (CAS, a protein), 50% of chondroitin sulfate (CS, a polysaccharide) and different amounts of SiO2. The results indicated that the incorporation of 5% of SiO2 to the materials, allowed the best organization, distribution, and diameter of the pores, which are responsible for ensuring a more controlled release. Also, the matrices were not efficient in releasing vitamin-B12, but it successfully released l-dopa. It happened because vitamin-B12 is highly hydrophilic, interacting more with the medium than with the CAS/CS matrix, while l-dopa is less polar than vitamin-B12, interacting more with the CAS/CS matrix. It is worth mentioning that all synthesized hydrogels were non-toxic to the cells as showed by the in vitro assay. This work also demonstrated the importance of evaluating drug delivery devices using drugs of different polarities before stating if they are efficient or not.

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In this study, the materials were synthesized by chemically crosslinking chondroitin sulfate (CS), casein (CAS), and silica nanospheres (SiO2), creating a highly crosslinked network. The hydrogel release profile was adaptable (that is, it could be faster or slower as needed) simply by changing the polymeric proportion. The incorporation of 5% of silica nanospheres, in mass, for all CAS/CS matrices promoted a better-controlled and sustained release of l-dopa, focusing on the matrix based on 70% of CAS, 30% of CS and 5% of silica, whose l-dopa release lasted for 87 h. Besides, hydrogels are cytocompatible. These new hydrogels can be considered highly attractive materials to be used for controlled and sustained drug release purposes, as well as scaffolds and wound dressing systems.

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As an alternative to eliminating cancer cells with minimal impacts on the nearby tissues, biocompatible nanoparticles based on silica-coated carbon nano-onions, with outstanding photothermal efficiency, are presented. Metal-doped carbon nano-onion@SiO2 materials are produced using flame synthesis. Metal complexes are injected in the flame to tune the carbon organization levels, which results in materials with excellent photostability and total photothermal conversion efficiency, regarding the incident light input, as higher as 48% for 785 nm laser. It was found that the metal dopant, even at a very low content, plays an interesting role in photothermal efficiency. We tested the effect of thin silica layers on the carbon nanosphere, first as a way to improve biocompatibility and provide a more reactive surface toward the modifications process to add vectorizing agents. Despite the primary goal of the silica shell, a notable increase in photothermal efficiency was observed. In vivo studies of the biological response to the materials as probed by the zebrafish model found that the as-prepared carbon nanospheres and the SiO2-coated particles are highly biocompatible. The SiO2-coated samples were found to be more suitable for photothermal application, due to the higher colloidal stability and higher photothermal efficiency.

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Yeast cell wall particles isolated from Saccharomyces cerevisiae (scYCWPs) have a rich constitution of ß-glucan derived from the cell wall. After removing intracellular contents, ß-glucan molecules are readily recognized by dectin-1 receptors, present on the cytoplasmic membrane surface of the mononuclear phagocytic cells and internalized. Leishmania spp. are obligate intracellular parasites; macrophages are its primary host cells. An experimental murine model of visceral leishmaniasis caused by L. infantum was used to evaluate the antileishmanial activity of oral administration of these particles. A low-water soluble thiophene previously studied in vitro against L. infantum was entrapped into scYCWPs to direct it into the host cell, in order to circumvent the typical pharmacokinetic problems of water-insoluble compounds. We found that scYCWPs + T6 reduced the parasitic burden in the liver and spleen. There was an increase in IFN-γ levels related to nitric oxide production, explaining the reduction of the L. infantum burden in the tissue. Histological analysis did not show signals of tissue inflammation and biochemical analysis from plasma did not indicate signals of cytotoxicity after scYCWPs + T6 treatment. These findings suggested that scYCWPs + T6 administered through oral route reduced the parasitic burden without causing toxic effects, satisfying requirements for development of new strategies to treat leishmaniasis.

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In recent years, electrochemical energy devices, i.e. batteries, fuel cells, solar cells, and supercapacitors, have attracted considerable attention of scientific community. The architecture of active materials plays a crucial role for improving supercapacitors performance. Herein, titanium dioxide (TiO2) nanofibers (1D) have been synthesized by electrospinning process and used as a backbone to manganese dioxide (MnO2) nanosheets (2D) growth through hydrothermal method. This strategy allows the obtaining of 1D/2D heterostructure architecture, which has demonstrated superior electrochemical performance in relation to pristine MnO2. The highest electrochemical performance is due to the synergic effect between the metal oxides, where TiO2 nanofibers provide electrochemical stability for active MnO2 phase. Thus, the designed TiO2@MnO2 structure can reach maximum specific capacitance of 525 F·g-1 at a current density of 0.25 A·g-1, and it demonstrates an excellent stability by retaining 81% of the initial capacitance with coulombic efficiency of 91%. Therefore, the novel architecture of TiO2@MnO2 based on nanofibers and nanosheets exhibits superior electrochemical properties to be used in supercapacitor applications.

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Alginate/chitosan (ALG/CHT) and alginate/N,N-dimethyl chitosan (ALG/DMC) polyelectrolyte complex (PEC)-based adsorbents with high capacities for removing Pb(II) from aqueous systems are produced in [1-hydrogen-3-methylimidazolium hydrogen sulfate ionic liquid ([Hmim][HSO4-]). The [Hmim][HSO4-] is recovered, characterized by 1H NMR and reused to yield novel polysaccharide-based adsorbents. As-obtained PEC materials are characterized through infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and Zeta potential measurements. Kinetic and equilibrium adsorption studies reveal that the pseudo-second-order Kinetic, as well as the Redlich-Peterson isotherm, provide the best fits for the experimental data, respectively. CHT/ALG and DMC/ALG adsorbents promoted maximum adsorption capacities (qm) of 529.4 mg g-1 and 560.2 mg g-1, respectively. After adsorption, the materials are characterized by infrared spectroscopy and X-ray photoelectron spectroscopy, confirming that the chemisorption prevails upon Pb(II) removal. Also, PECs produced in the recovered [Hmim][HSO4-] have good capacities for removing Pb(II) ions from aqueous systems as well. This study showed that the [Hmim][HSO4-] is an alternative solvent to prepare novel and eco-friendly PEC-based adsorbents.

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An infinite number of possibilities can emerge from the combination of phases in hybrid systems. Interfacing phases is a strategy to obtain a set of properties in one system that are beyond the abilities of single phases. Herein, the progress in materials science exploring hybrid systems are discussed from the point of view of three important applications: wound dressing; electrocatalysis; and chemical separation. These three unrelated applications exemplify the broad impact of hybrid materials, which can be coherently designed to achieve outstanding performance. Many inspiring works have been published in the last few years, remodeling the edges of human knowledge on hybrid materials. However, the challenges in the coherent design seem to rely on the development of synthetic processes to achieve stronger integration among the phases in a hybrid material.

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Photocatalytic activity of TiO2 nanoparticles is highly dependent on their phase composition. The coexistence of anatase and rutile phases in a single nanoparticle eases the electron transfer process between the phases, and favors the separation of photogenerated pairs. In this work, highly photoactive mixed-phase TiO2 nanostructures were prepared by supercritical antisolvent precipitation (SAS), an environmentally friendly technology. It is shown here that this methodology has the remarkable ability to produce highly porous (515 m2/g) and crystalline TiO2 nanoparticles. The phase composition of as-prepared TiO2 samples can be tailored through annealing process. Several mixed-phase TiO2 samples were tested to assess the correlation between photocatalytic activity and phase composition. The photocatalytic performance is strongly affected by the anatase-rutile ratio, since the synergism between phases enhances the charge separation, reducing the recombination effect of the photogenerated pairs (e-/h+). It was found that the nanocatalyst composed by 7.0 wt% of rutile phase and 93.0 wt% of anatase phase, named as TiO2_650, presented the highest photodegradation for both methyl orange (MO) and methylene blue (MB) dyes. Interestingly, TiO2 samples prepared by SAS have superior photoactivity than the benchmark photocatalyst names as P25, which is a widely used TiO2 material composed of anatase and rutile phases.

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Gold nano "breath figure" films are for the first time reported and their function as ideal systems for plasmonics demonstrated. Metal nano-breath figure substrates are metal thin films containing nanohole arrays supported on a solid substrate. Au nanohole arrays are prepared from the dynamic breath figure phenomenon, in which the pore formation is controlled to provide holes smaller than 100 nm. Au layer is deposited on polymer substrates containing breath figure topology. The breath figure topology can be fully translated to the Au layer. The nanofabrication process is completed within few minutes. A simplified preparation process but very impressive light trapping and surface electromagnetic field enhancement are related to the Au breath figure films obtained in this work. The porous films demonstrated higher absorbance in the region of 500-1100 nm than nonporous Au films. In the case of 10 nm Au film, the plasmon absorbance becomes more intense than the electronic band absorbance. The electromagnetic enhancement is proved by surface enhanced Raman spectroscopy effect, which is found to be very close to the maximum possible value predicted for nonresonant species.

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Antimicrobial films based on distinct polymer matrices, poly (vinyl alcohol) (PVA) or poly (N-isopropylacrylamide) (PNIPAAm), and silver nanoparticles (AgNPs) immobilized onto cellulose nanowhiskers (CWs) were successfully prepared by either casting or electrospinning. CWs were first functionalized with carboxylate groups (labeled as CWSAc) and later they were immersed in a silver nitrate solution (AgNO3). After Ag+ ions anchored in the COO- groups are chemically reduced to produce AgNPs. The CWSAc/AgNPs biological activity was evaluated against Staphylococcus aureus (S. aureus), Bacillus Subtilis (B. subtilis), Escherichia coli (E. coli), and Candida albicans (C. albicans). The materials were more effective against C. albicans that showed a MIC of 15.6 µg/mL. In the process of AgNPs synthesis, the activity of the stabilizing agent (gelatin) and concentration of precursor and reducing agents were evaluated. The synthesized polymeric films displayed good antimicrobial activity against S. aureus, E. coli, and Pseudomonas aeruginosa (P. aeruginosa) bacteria. The PVA films with CWSAc/AgNPs showed diameter of the inhibition halo of up to 11 mm. The results obtained displayed that the films obtained have a potential application to be used in different fields such as packaging, membrane filtration, wound dressing, clothing and in different biomedical applications.

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The advances in the field of biomaterials have led to several studies on alternative biocompatible devices and to their development focusing on their properties, benefits, limitations, and utilization of alternative resources. Due to their advantages like biocompatibility, biodegradability, and low cost, polysaccharides have been widely used in the development of hydrogels. Among the polysaccharides studied on hydrogels preparation, chitosan (pure or combined with natural/synthetic polymers) have been widely investigated for use in biomedical field. In view of potential applications of chitosan-based hydrogels, this review focuses on the most recent progress made with respect to preparation, properties, and their salient accomplishments for drug delivery and tissue engineering.

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Cellulose nanowhiskers (CWs) extracted from cotton fibers were successfully modified with distinct anhydrides structures and used as additives in poly(vinyl alcohol) (PVA) nanocomposite films. The surface modification of CWs was performed with maleic, succinic, acetic or phthalic anhydride to compare the interaction and action the carboxylic groups into PVA films and how these groups influence in mechanical properties of the nanocomposites. CWs presented a high degree of crystallinity and good dispersion in water, with average length at the nanoscale. The addition of specific amounts (3, 6 and 9 wt.%) of modified-CWs increased up to 4.4 times the storage modulus (PVA88-CWSA 9 wt.%), as observed from dynamic mechanical analysis (DMA), compared to the bare PVA films. A significant increase in mechanical properties such as tensile strength, elastic modulus, and elongation at break showed a close relationship to the amount and chemical surface characteristics of CWs added, suggesting that these modified-CWs could be explored as reinforcement additives in PVA films.

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Magnetic microgels with pH- and thermo-responsive properties were developed from the pectin maleate, N-isopropyl acrylamide, and Fe3O4 nanoparticles. The hybrid materials were characterized by infrared spectroscopy, scanning electron microscope coupled with X-ray energy dispersive spectroscopy, wide angle X-ray scattering, Zeta potential, and magnetization hysteresis measurements. Curcumin (CUR) was loaded into the microgels, and release assays were carried out in simulated environments (SGF and SIF) at different conditions of temperature (25 or 37°C). A slow and sustainability CUR release was achieved under external magnetic field influence. Loaded CUR displayed stability, bioavailability and greater solubility regarding free CUR. Besides, the cytotoxicity assays showed that magnetic microgels without CUR could suppress the Caco-2 cells growth. So, the pectin maleate, N-isopropyl acrylamide, and Fe3O4 could be tailored to elicit hybrid-based materials with satisfactory application in the medical arena.

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Cellulose nanowhiskers (CNWs) with different surface composition were used to generate the biomimetic growth hydroxyapatite (HAp). Hybrids materials primarily consist of CNWs with HAp content below 24%. CNWs were produced by different inorganic acid hydrolyses to generate cellulose particles with surface groups to induce HAp mineralization. In the present study, we evaluate the use of CNWs prepared from hydrochloric acid, sulfuric acid and phosphoric acid. HAp growth was obtained from the biomimetic method using a simulated body fluid concentration of 1.5M (SBF). The sulfonate and phosphonate groups on the CNW surface have a direct impact on the nucleation and growth of HAp. HAp/CNW were also compared with the physical mixture method using HAp nanoparticles prepared by chemical precipitation. The bioactivity and biocompatibility of the hybrid materials were assessed by cell viability studies using fibroblast cells (L929). The materials obtained from the biomimetic method have superior biocompatibility/bioactivity compared to the material synthesized by the wet chemical precipitation method with an incubation period of 24h.

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