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Ionic liquids (ILs) and deep eutectic solvents (DESs) are the two most widely used neoteric solvents. Recently, our group described how the simple addition of acetic acid (AcOH) to 1-Ethyl-3-methylimidazolium chloride (EMIMCl) could promote the transition from the original IL to an eutectic mixture of EMIMCl and AcOH. Herein, we studied how cellulose regeneration and EMIMCl recovery from EMIMCl solutions of cellulose could be benefited by the significant differences existing between EMIMCl- and EMIMCl·AcOH-based mixtures and the easy switching from one to the other. Finally, we also demonstrated that the transition could also be accomplished by addition of acetic anhydride and water so that the process could be eventually useful for the achievement of highly acetylated cellulose.
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Due to the wide applications of three-dimensional graphene (3DG) foam in bio-sensors, stretchable electronics, and conductive polymer composites, predicting its mechanical behavior is of paramount importance. In this paper, a novel multiscale finite element model is proposed to predict the compressive modulus of 3DG foams with various densities. It considers the effects of pore size and structure and the thickness of graphene walls on 3DG foams' overall behavior. According to the scanning electron microscope images, a unit cell is selected in the microscale step to represent the incidental arrangement of graphene sheets in 3DG foams. After derivation of equivalent elastic constants of the unit cell by six individual load cases, the whole unit cell is considered an equivalent element. The macroscale model is prepared by defining a representative volume element (RVE), containing a sufficient number of the equivalent elements. Assigning a stochastic local coordinate system for each equivalent element in the macro RVE provides a model that could be utilized for elastic modulus estimation of 3DG foams in macroscale. To investigate the correspondence between the theoretical results and experimental data, 3DG foams were synthesized with four densities, and their compressive behavior were evaluated. The mass densities of the prepared foams were 5.36, 8.50, 9.37, and 11.5 mg cm-3, and the corresponding measured elastic modulus for each were 6.4, 10.7, 16.9, and 29.1 kPa, respectively. The predicted modulus by the proposed model for the synthesized foams were 6.1, 13.1, 15.6 and 21.7 kPa, respectively. The results show that the maximum divergence between estimated values and experimental data is less than 25%, confirming the high capability of the model in the estimation of 3DG foams' properties.
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Deep eutectic solvents (DESs) and dilutions thereof (mainly in H2O but also in many other non-aqueous solvents and co-solvent mixtures) have recently attracted great attention. It is well known that DES dilutions exhibit deviations from ideality. Interestingly, the treatment of DES as a mixture of two components or a pseudo-component is by no means trivial when determining deviations in density and, mainly, in viscosity. Herein, we studied aqueous dilutions of one of the most widely studied DES, this is, that composed of choline chloride and urea in a 1:2 molar ratio (e.g., ChCl2U). Using density and viscosity data reported in previous works, we calculated the excess molar volumes (VE) and excess viscosities (ln ηE) considering ChCl2U as either a mixture of two components or a pseudo-component, that is, taking the DES molecular weight as MChCl2U = fChClMChCl + fUMU = 86.58 g mol-1 (with fChCl = 1/3 and fU = 2/3) or as M* ChCl2U = MChCl + 2 MU = 259.74 g mol-1. We found that neither the sign of VE and VE* nor their evolution with temperature was influenced by the use of either MChCl2U or M* ChCl2U, and only the absolute magnitude of the deviation and the DES content (in wt. %) at which the minimum appears exhibited some differences. However, ln ηE and ln ηE* exhibited opposite signs, negative and positive, respectively. The odd achievement of negative ln ηE in aqueous dilutions of ChCl2U characterized by the formation of HB networks suggest the treatment of ChCl2U as a pseudo-component as more appropriate. Moreover, the role played by the presence of U in the evolution of ln ηE* with temperature was also discussed.
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In the present contribution, we report how through the use of metal-organic frameworks (MOFs) composed of addressable combinations of up to four different metal elements it is possible to program the composition of multimetal oxides, which are not attainable by other synthetic methodologies. Thus, due to the ability to distribute multiple metal cations at specific locations in the MOF secondary building units it is possible to code and transfer selected metal ratios to multimetal oxides with novel, desired compositions through a simple calcination process. The demonstration of an enhancement in the electrocatalytic activity of new oxides by preadjusting the metal ratios is here reported for the oxygen reduction reaction, for which activity values comparable to commercial Pt/C catalysts are reached, while showing long stability and methanol tolerance.
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PURPOSE: Advanced maternal age (AMA) is a known risk factor for pregnancy-related venous thromboembolism. However, it is unclear if underlying differences exist in the maternal coagulation profiles of AMA vs non-AMA women. The aim of this prospective observational study was to compare peripartum thromboelastography parameters of AMA and non-AMA women undergoing elective Cesarean delivery (CD). METHODS: We compared the peripartum thromboelastographic profiles of healthy AMA women (age > 35 yr) and non-AMA women (age ≤ 35 yr) undergoing elective CD under neuraxial anesthesia. Blood samples were drawn prior to CD and at 24 hr and 72 hr post-CD. At each time point, we assessed thromboelastographic and other standard laboratory coagulation indices. We used a linear mixed-effects regression model (SAS(®) PROC MIXED) to assess between-group differences for individual thromboelastographic and laboratory coagulation parameters. RESULTS: The median [interquartile range] ages of women were 38 [37-41] yr and 29 [25-34] yr in the AMA and non-AMA groups, respectively (P < 0.001). We observed no statistically significant effect of study group on any thromboelastographic or laboratory coagulation parameters. No statistically significant correlations were found between any thromboelastographic parameter and maternal age. Peripartum thromboelastography and coagulation profiles of healthy AMA and healthy non-AMA women up to 72 hr post-CD were also similar. CONCLUSION: These data suggest that maternal thromboelastographic profiles of healthy AMA and non-AMA women undergoing elective CD are similar. The study was registered at ClinicalTrials.gov (identifier: NCT01416454).
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Coagulação Sanguínea/fisiologia , Idade Materna , Tromboelastografia , Adulto , Fatores Etários , Cesárea , Feminino , Humanos , Modelos Lineares , Período Periparto , Gravidez , Estudos Prospectivos , Fatores de RiscoRESUMO
Chitosan is the N-deacetylated derivative of chitin, a naturally abundant mucopolysaccharide that consists of 2-acetamido-2-deoxy-ß-d-glucose through a ß (1â4) linkage and is found in nature as the supporting material of crustaceans, insects, etc. Chitosan has been strongly recommended as a suitable functional material because of its excellent biocompatibility, biodegradability, non-toxicity, and adsorption properties. Boosting all these excellent properties to obtain unprecedented performances requires the core competences of materials chemists to design and develop novel processing strategies that ultimately allow tailoring the structure and/or the composition of the resulting chitosan-based materials. For instance, the preparation of macroporous materials is challenging in catalysis, biocatalysis and biomedicine, because the resulting materials will offer a desirable combination of high internal reactive surface area and straightforward molecular transport through broad "highways" leading to such a surface. Moreover, chitosan-based composites made of two or more distinct components will produce structural or functional properties not present in materials composed of one single component. Our group has been working lately on cryogenic processes based on the unidirectional freezing of water slurries and/or hydrogels, the subsequent freeze-drying of which produce macroporous materials with a well-patterned structure. We have applied this process to different gels and colloidal suspensions of inorganic, organic, and hybrid materials. In this review, we will describe the application of the process to chitosan solutions and gels typically containing a second component (e.g., metal and ceramic nanoparticles, or carbon nanotubes) for the formation of chitosan nanocomposites with a macroporous structure. We will also discuss the role played by this tailored composition and structure in the ultimate performance of these materials.
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Quitosana/química , Sistemas de Liberação de Medicamentos , Nanocompostos , Animais , Liofilização , Congelamento , Géis , Humanos , Porosidade , SoluçõesRESUMO
Carbon nanotubes and graphene are some of the most intensively explored carbon allotropes in materials science. This interest mainly resides in their unique properties with electrical conductivities as high as 10(4) S cm(-1), thermal conductivities as high as 5000 W m(-1) K and superior mechanical properties with elastic moduli on the order of 1 TPa for both of them. The possibility to translate the individual properties of these monodimensional (e.g. carbon nanotubes) and bidimensional (e.g. graphene) building units into two-dimensional free-standing thick and thin films has paved the way for using these allotropes in a number of applications (including photocatalysis, electrochemistry, electronics and optoelectronics, among others) as well as for the preparation of biological and chemical sensors. More recently and while recognizing the tremendous interest of these two-dimensional structures, researchers are noticing that the performance of certain devices can experience a significant enhancement by the use of three-dimensional architectures and/or aerogels because of the increase of active material per projected area. This is obviously the case as long as the nanometre-sized building units remain accessible so that the concept of hierarchical three-dimensional organization is critical to guarantee the mass transport and, as consequence, performance enhancement. Thus, this review aims to describe the different synthetic processes used for preparation of these three-dimensional architectures and/or aerogels containing either any or both allotropes, and the different fields of application in which the particular structure of these materials provided a significant enhancement in the efficacy as compared to their two-dimensional analogues or even opened the path to novel applications. The unprecedented compilation of information from both CNT- and graphene-based three-dimensional architectures and/or aerogels in a single revision is also of interest because it allows a straightforward comparison between the particular features provided by each allotrope.
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Géis/química , Grafite/química , Nanotubos de Carbono/química , Géis/síntese química , Grafite/síntese química , Modelos Moleculares , Nanotubos de Carbono/ultraestrutura , PorosidadeRESUMO
Clinical evidence suggests that early malnutrition promotes symptoms related to psychiatric disorders later in life. Nevertheless, the molecular mechanisms underpinning nutritional injury induce depression remains unknown. The purpose of the present study was to evaluate whether perinatal protein restriction increases vulnerability to developing depressive-like behavior in adulthood by focusing on anhedonia, a core symptom of depression. To this, male adult Wistar rats submitted to a protein restriction schedule at perinatal age (PR-rats), were subjected to the sucrose preference test (SPT), the novel object recognition test (NORT), the forced swim test (FST), and the elevated plus maze (EPM), and compared to animals fed with a normoprotein diet. To investigate neurobiological substrates linked to early protein undernutrition-facilitated depressive-like behavior, we assessed the levels of brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the nucleus accumbens (NAc), and evaluated the reversal of anhedonic-like behavior by infusing ANA-12. We found that early malnutrition decreased sucrose preference, impaired performance in the NORT and increased immobility time in the FST. Furthermore, perinatal protein-restriction-induced anhedonia correlated with increased BDNF and p-TrkB protein levels in the NAc, a core structure in the reward circuit linked with anhedonia. Finally, bilateral infusion of the TrkB antagonist ANA-12 into the NAc shell ameliorated a reduced sucrose preference in the PR-rats. Altogether, these findings revealed that protein restriction during pregnancy and lactation facilitates depressive-like behavior later in life and may increase the risk of developing anhedonia by altering BDNF-TrkB in the NAc shell.
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Anedonia , Fator Neurotrófico Derivado do Encéfalo , Núcleo Accumbens , Ratos Wistar , Receptor trkB , Transdução de Sinais , Animais , Núcleo Accumbens/metabolismo , Núcleo Accumbens/efeitos dos fármacos , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Masculino , Anedonia/fisiologia , Ratos , Receptor trkB/metabolismo , Feminino , Transdução de Sinais/fisiologia , Transdução de Sinais/efeitos dos fármacos , Gravidez , Dieta com Restrição de Proteínas , Efeitos Tardios da Exposição Pré-Natal/metabolismo , Depressão/metabolismo , Depressão/psicologia , Azepinas , BenzamidasRESUMO
Biodegradable polyesters with interconnected macroporosity, such as poly(l-lactide) (PLLA) and poly(ε-caprolactone) (PCL), have gained significant importance in the fields of tissue engineering and separation. This study introduces functional macroinitiators, specifically polycaprolactone triol (PCLT) and polyethylene glycol (PEG), both OH-terminated, in the solventless ring-opening polymerization (ROP) of a liquid deep eutectic system monomer (DESm) composed of LLA and CL at a 30 : 70 molar ratio, respectively. The macroinitiators selectively initiate the organocatalyzed ROP of LLA in the DESm during the first polymerization stage, thereby modifying the PLLA architecture. This results in the formation of either branched or linear PLLA copolymers depending on the macroinitiator, PCLT and PEG, respectively. In the second stage, the ROP of the CL, which is a counterpart of the DESm, produces PCL that blends with the previously formed PLLA. The insights gained into the PLLA architectures during the first stage of the DESm ROP, along with the overall molecular weight and hydrophobicity of the resulting PLLA/PCL blend in bulk, were advantageously used to design polymerizable high internal phase emulsions (HIPEs) oil-in-DESm. By incorporating a liquid mixture of DESm and macroinitiators (PCLT or PEG), stable HIPE formulations were achieved. These emulsions sustained the efficient organocatalyzed ROP of the continuous phase at 37 °C with high conversions. The resulting polymer replicas of the HIPEs, characterized by macroporous and interconnected structures, were subjected to a degradation assay in PBS at pH 7.4 and 37 °C and remained mechanically stable for at least 30 days. Notably, they exhibited the capability to sorb crude oil in a proof-of-concept test, with a rate of 2 g g-1. The macroporous and interconnected features of the polyHIPEs, combined with their inherent degradation properties, position them as promising degradable polymeric sorbents for efficient separation of hydrophobic fluids from water.
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The autoimmune/inflammatory syndrome induced by adjuvants (ASIA) encompasses various autoimmune conditions triggered by exposure to substances with adjuvant activity. Despite its potential relevance to public health, global scientific production on ASIA syndrome is significantly limited. This knowledge gap underscores the need for a comprehensive bibliometric assessment to understand global research in this field. Therefore, this article aims to conduct a bibliometric analysis to identify and evaluate research trends related to ASIA syndrome worldwide. A Scopus search identified scientific documents published between 2010 and 2022. A total of 2,133 articles meeting inclusion criteria were selected and analyzed for scientific production, authors, and institutions. Two-hundred fifty six documents were analyzed, mostly journal articles with multiple authors. The year with the highest publications was 2023, marking a notable increase since 2021. Italy and Israel had the most documents and citations, correlating with authors Yehuda Shoenfeld (Israel) and Carlo Perricone (Italy). Standout journals are "The Journal of Immunologic Research" and "Lupus." Relevant affiliations include Tel-Aviv University and the National Autonomous University of Mexico. This article identifies and analyzes scientific trends associated with ASIA syndrome. Despite increased publications, this field remains controversial and lacks full acceptance within the medical and scientific community, as evidenced by limited scientific production compared to other pathologies. These findings may motivate researchers to generate impactful publications, contributing to the global knowledge expansion on this syndrome.
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OBJECTIVE: Our objective was to evaluate the effect of glucocorticoid regimens on renal response, infections, and mortality among patients with lupus nephritis (LN). METHODS: We performed a systematic review and meta-analysis of the control arms of randomized clinical trials (RCTs). We included RCTs of biopsy-proven LN that used a protocolized regimen of glucocorticoids in combination with mycophenolic acid analogs or cyclophosphamide and reported the outcomes of complete response (CR), serious infections, and death. The starting dosage of glucocorticoids, tapering method, and administration of glucocorticoid pulses were abstracted. Meta-analysis of proportions, meta-regression, and subgroup meta-analysis were performed at 6 and 12 months for all outcomes. RESULTS: Fifty RCT arms (3,231 patients with LN) were included. The predicted rates of CR, serious infections, and death when starting on oral prednisone at 25 mg/day without pulses were 19.5% (95% confidence interval [CI] 7.3-31.5), 3.2% (95% CI 2.4-4.0), and 0.2% (95% CI 0.0-0.4), respectively. Starting on prednisone at 60 mg/day (without pulses) increased the rates to 34.6% (95% CI 16.9-52.3), 12.1% (95% CI 9.3-14.9), and 2.7% (95% CI 0.0-5.3), respectively. Adding glucocorticoid pulses increased the rates of CR and death but not serious infections. We observed a dose-response gradient between the initial glucocorticoid dosage and all the outcomes at six months after accounting for the administration of glucocorticoid pulses, underlying immunosuppressant, and baseline proteinuria. CONCLUSION: A higher exposure to glucocorticoids during the initial therapy of LN was associated with better renal outcomes at the cost of increased infections and death.
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Ciclofosfamida , Glucocorticoides , Imunossupressores , Nefrite Lúpica , Ácido Micofenólico , Prednisona , Ensaios Clínicos Controlados Aleatórios como Assunto , Nefrite Lúpica/tratamento farmacológico , Nefrite Lúpica/mortalidade , Humanos , Glucocorticoides/uso terapêutico , Glucocorticoides/administração & dosagem , Ciclofosfamida/uso terapêutico , Ciclofosfamida/administração & dosagem , Imunossupressores/uso terapêutico , Imunossupressores/administração & dosagem , Ácido Micofenólico/uso terapêutico , Ácido Micofenólico/administração & dosagem , Prednisona/uso terapêutico , Prednisona/administração & dosagem , Infecções , Resultado do Tratamento , Quimioterapia Combinada , Relação Dose-Resposta a DrogaRESUMO
Bacterial infection related to the implantation of medical devices represents a serious clinical complication, with dramatic consequences for many patients. In past decades, numerous attempts have been made to develop materials with antibacterial and/or antifouling properties by the incorporation of antibiotic and/or antiseptic compounds. In this context, deep eutectic solvents (DESs) are acquiring increasing interest not only as efficient carriers of active principle ingredients (APIs) but also as assistant platforms for the synthesis of a wide repertoire of polymer-related materials. Herein, we have successfully prepared biodegradable poly(octanediol-co-citrate) polyesters with acquired antibacterial properties by the DES-assisted incorporation of quaternary ammonium or phosphonium salts into the polymer network. In the resulting polymers, the presence of these salts (i.e., choline chloride, tetraethylammonium bromide, hexadecyltrimethylammonium bromide, and methyltriphenylphosphonium bromide) inhibits bacterial growth in the early postimplantation steps, as tested in cultures of Escherichia coli on solid agar plates. Later, positive polymer cytocompatibility is expected to support cell colonization, as anticipated from in vitro preliminary studies with L929 fibroblasts. Finally, the attractive elastic properties of these polyesters permit matching those of soft tissues such as skin. For all of these reasons, we envisage the utility of some of these antibacterial, biocompatible, and biodegradable polyesters as potential candidates for the preparation of antimicrobial wound dressings. These results further emphasize the enormous versatility of DES-assisted synthesis for the incorporation, in the synthesis step, of a wide palette of APIs into polymeric networks suitable for biomedical applications.
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Antibacterianos/síntese química , Antibacterianos/farmacologia , Materiais Biocompatíveis/síntese química , Materiais Biocompatíveis/farmacologia , Poliésteres/síntese química , Poliésteres/farmacologia , Solventes/química , Animais , Antibacterianos/toxicidade , Materiais Biocompatíveis/toxicidade , Linhagem Celular , Técnicas de Química Sintética , Escherichia coli/efeitos dos fármacos , Camundongos , Testes de Sensibilidade Microbiana , Compostos Organofosforados/química , Poliésteres/toxicidade , Compostos de Amônio Quaternário/químicaRESUMO
OBJECTIVE: Opioids (except for tramadol) have not been shown to be effective in patients with fibromyalgia, but they can increase the risk of adverse drug reactions. The aim was to determine the treatment patterns of a group of patients with fibromyalgia and to identify the factors associated with the use of opioids in Colombia. METHODS: This was a cross-sectional study of a group of patients with fibromyalgia from a pain clinic in Colombia. Sociodemographic, clinical and pharmacological variables were identified. Descriptive, bivariate, and multivariate analyses were performed. RESULTS: A total of 559 patients were analysed, 88.6% of whom were women, and the mean age was 53.4 ± 12.6 years. A total of 40.6% received nonpharmacological management, and the majority were treated with acetaminophen (96.1%) and pregabalin (62.8%). A total of 69.6% received opioids, the most common of which was hydrocodone (36.3%). The average morphine equivalent milligrammes was 36.9 ± 91.2 (range: 2.3-750 mg), and 43.8% had intermediate/high doses. Being male (OR: 3.12; 95% CI: 1.40-6.91), having arterial hypertension (OR: 1.67; 95% CI: 1.04-2.69), obesity (OR: 2.23; 95% CI: 1.18-4.24), degenerative disease of vertebral discs (OR: 2.32; 95% CI: 1.10-4.88) and comedication with gabapentinoids (OR: 1.75; 95% CI: 1,15-2.65) were associated with a higher probability of receiving opioids, while patients treated with muscle relaxants had a lower risk of opioid treatment (OR: 0.64; 95% CI: 0.41-0.98). CONCLUSIONS: A significant proportion of patients were treated with opioids, the most common of which was hydrocodone, which goes against the recommendations of clinical practice guidelines.
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Analgésicos Opioides , Fibromialgia , Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Analgésicos Opioides/efeitos adversos , Hidrocodona/uso terapêutico , Estudos Transversais , Acetaminofen/uso terapêutico , Padrões de Prática MédicaRESUMO
The immobilization of more than one single substance within the structure of a biocompatible polymer provides multifunctional biomaterials with attractive and enhanced properties. In the context of bone tissue engineering, it could be of great interest to synthesize a biomaterial that simultaneously contains amorphous calcium phosphate (ACP), to favor calcium and phosphate precipitation and promote osteogenesis, and an antibiotic such as ciprofloxacin (CFX) that can, eventually, avoid infections resulting after surgical scaffold implantation. However, the co-immobilization of multiple substances is by no means a trivial issue because of the enhanced number of interactions that can take place. One of the main issues is controlling not only the diverse solid forms that individual substances can eventually adopt, but also the forces responsible for the self-organization of the individual components. The latter determines whether phase-separated structures or conjugated architectures are obtained and, consequently, may dramatically affect their functionality. Herein, we have observed-by SEM, TEM, and solid-state NMR-that enzymatically-assisted coprecipitation of ACP and CFX resulted in phase-separated structures. Thus, CFX crystals showed identical morphology to that obtained in the absence of ACP, but the size was smaller. Neither the size nor the morphology of ACP exhibited significant differences whether precipitated with or without CFX, but, in the former case, ACP was stabilized over a wider range of pH and temperature. Finally, by using this methodology and the ice segregation induced self-assembly process (ISISA), we have successfully co-immobilized ACP and CFX in chitosan-based scaffolds. Interestingly, the presence of ACP exerted significant control on the CFX release from these materials.
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Fosfatos de Cálcio/química , Quitosana/síntese química , Ciprofloxacina/química , Sistemas de Liberação de Medicamentos , Hidrogéis/síntese química , Quitosana/química , Cristalização , Hidrogéis/química , Tamanho da Partícula , Reologia , Propriedades de SuperfícieRESUMO
Deep eutectic solvents promoted the stabilization of the collapsed state of elastin-like recombinamers - and the subsequent formation of aggregates - upon the loss of the structural water molecules involved in hydrophobic hydration. Cryo-etch scanning electron microscopy allowed the observation of these aggregates in neat deep eutectic solvents. The suppression of the lower critical solution temperature transition, observed by differential scanning calorimetry and dynamic light scattering, confirmed the presence of the elastin-like recombinamers in their collapsed state. Actually, the transition from the collapsed to the expanded state was suppressed even after moderate aqueous dilution - for water contents ranging from nil to ca. 45 wt % - and it was only recovered upon further addition of water - above 50 wt %. These features revealed the preferred stabilization of the collapsed state in not only neat deep eutectic solvents but also partially hydrated deep eutectic solvents. We consider that the capability to trigger the lower critical solution temperature transition by partial hydration of deep eutectic solvent may open interesting perspectives for nano(bio)technological applications of elastin-like recombinamers.
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Colina/química , Peptídeos/química , Solventes/química , Ureia/química , Água/química , Sequência de Aminoácidos , Microscopia Crioeletrônica , Elastina , Microscopia Eletrônica de Varredura , Tamanho da Partícula , Transição de Fase , Estrutura Quaternária de Proteína , Proteínas Recombinantes/química , Temperatura de TransiçãoRESUMO
Resistance to ß-lactam antibiotics, including the "last-resort" carbapenems, has emerged as a major threat to global health. A major resistance mechanism employed by pathogens involves the use of metallo-ß-lactamases (MBLs), zinc-dependent enzymes that inactivate most of the ß-lactam antibiotics used to treat infections. Variants of MBLs are frequently discovered in clinical environments. However, an increasing number of such enzymes have been identified in microorganisms that are less impacted by human activities. Here, an MBL from Lysobacter antibioticus, isolated from the rhizosphere, has been shown to be highly active toward numerous ß-lactam antibiotics. Its activity is higher than that of some of the most effective MBLs linked to hospital-acquired antibiotic resistance and thus poses an interesting system to investigate evolutionary pressures that drive the emergence of such biocatalysts.
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Antibacterianos/química , Lysobacter/enzimologia , Zinco/química , beta-Lactamases/química , beta-Lactamas/químicaRESUMO
This work describes a simple synthetic route to induce chitosan (CHI) gelation by the in situ formation of gold nanoparticles (AuNPs). AuNPs were obtained by thermal treatment (e.g., 40 and 80 °C) of CHI aqueous solutions containing HAuCl(4) and in the absence of further reducing agents. The CHI hydrogels resulting after AuNP formation were submitted to unidirectional freezing and subsequent freeze-drying via ISISA (ice-segregation-induced self-assembly) process for the preparation of CHI scaffolds. The study of AuNP-CHI scaffolds by SEM and confocal fluorescence microscopy revealed a morphological structure characteristic of the hydrogel nature of the samples subjected to the ISISA process. Interestingly, not only the morphology but also the dissolution and swelling degree of the resulting CHI scaffolds were strongly influenced by the strength of the hydrogels obtained by the in situ formation of AuNP. We have also studied the catalytic activity AuNP-CHI scaffolds in the reduction of p-nitrophenol. The negligible dissolution and low swelling degree obtained in certain AuNP-CHI scaffolds allowed them to be used for more than four cycles with full preservation of the reaction kinetics.
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Quitosana/química , Ouro/química , Nanopartículas Metálicas/química , Nitrofenóis/química , Catálise , Temperatura Alta , Hidrogéis , Oxirredução , PorosidadeRESUMO
Water-in-salt (WIS) electrolytes are gaining increased interest as an alternative to conventional aqueous or organic ones. WIS electrolytes offer an interesting combination of safety, thanks to their aqueous character, and extended electrochemical stability window, thanks to the strong coordination between water molecules and ion salt. Nonetheless, cost, the tendency of salt precipitation, and sluggish ionic transfer leading to poor rate performance of devices are some intrinsic drawbacks of WIS electrolytes that yet need to be addressed for their technological implementation. It is worth noting that the absence of "free'' water molecules could also be achieved via the addition of a certain cosolvent capable of coordinating with water. This is the case of the eutectic mixture formed between DMSO and H2O with a molar ratio of 1:2 and a melting point as low as -140 °C. Interestingly, addition of salts at near-saturation conditions also resulted in an increase of the boiling point of the resulting solution. Herein, we used a eutectic mixture of DMSO and H2O for dissolution of LiTFSI in the 1.1-8.8 molality range. The resulting electrolyte (e.g., the so-called aqueous-eutectic-in-salt) exhibited excellent energy and power densities when operating in a supercapacitor cell over a wide range of extreme ambient temperatures, from as low as -35 °C to as high as +65 °C.
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Deep eutectic solvents (DESs) resulting from the right combination between a hydrogen-bond donor (HBD) and a hydrogen-bond acceptor (HBA) are becoming quite popular in number of applications. More recently, natural DESs (NADESs) containing sugars, natural organic acids, and amino acids as HBDs and ChCl as HBA have received great attention because of their further environmental sustainability as compared to regular DESs. Within this context, mixing water in controlled amounts has been widely accepted as a simple and practical way of altering DES chemical and thermodynamic properties, with viscosity and conductivity experiencing the most significant changes. However, the number of papers describing eutectic mixtures with water as the only HBD is scarce and basically none has been done in fundamental terms. Herein, we investigated mixtures composed of water as the only HBD and ChCl as the HBA using differential scanning calorimetry (DSC) as well as 1H nuclear magnetic resonance (NMR) and Brillouin spectroscopies. We found the aqueous dilution of ChCl/2H2O with a ChCl/2H2O content of ca. 80 wt % was an eutectic. Interestingly, this mixture could be considered a NADES according to its eutectic distance (ΔTme), in range to eutectics obtained in aqueous dilutions of salt hydrates.
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High-performance energy-storage devices are receiving great interest in sustainable terms as a required complement to renewable energy sources to level out the imbalances between supply and demand. Besides electrode optimization, a primary objective is also the judicious design of high-performance electrolytes combining novel ionic liquids (ILs) and mixtures of aqueous solvents capable of offering "à la carte" properties. Herein, it is described the stoichiometric addition of a zwitterion such as betaine (BET) to protic ILs (PILs) such as those formed between methane sulfonic acid (MSAH) or p-toluenesulfonic acid (PTSAH) with ethanolamine (EOA). This addition resulted in the formation of zwitterionic-based PILs (ZPILs) containing the original anion and cation as well as the zwitterion. The ZPILs prepared in this work ([EOAH]+ [BET][MSA]- and [EOAH]+ [BET][PTSA]- ) were liquid at room temperature even though the original PILs ([EOAH]+ [MSA]- and [EOAH]+ [PTSA]- ) were not. Moreover, ZPILs exhibited a wide electrochemical stability window, up to 3.7â V vs. Ag wire for [EOAH]+ [BET][MSA]- and 4.0â V vs. Ag wire for [EOAH]+ [BET][PTSA]- at room temperature, and a high miscibility with both water and aqueous co-solvent (WcS) mixtures. In particular, "WcS-in-ZPIL" mixtures of [EOAH]+ [BET][MSA]- in 2 H2 O/ACN/DMSO provided specific capacitances of approximately 83â F g-1 at current densities of 1â A g-1 , and capacity retentions of approximately 90 % after 6000â cycles when operating at a voltage of 2.0â V and a current density of 4â A g-1 .