Graphene oxide as inhibitor on the hydrolysis of fats under simulated in vitro duodenal conditions.

Obesity is a global pandemic, thus novel developments that reduce the absorption of fats is of interest. We have evaluated the effect of graphene oxide (GO) on the lipase catalyzed hydrolysis of fats (tributyrin, sunflower and olive oil) under simulated duodenal conditions. Results indicate that the presence of GO in the digestion mixture can inhibit lipase activity up to a 90% of the initial reaction rate, and this inhibition lasts even during 2 h of digestion. The inhibition mechanism seems non competitive and could be opposite to the effect of bile salts, although the direct interaction between GO and the enzyme cannot be discarded. The inhibition is found also in alimentary fats suggesting that GO could be a strong inhibitor for fat hydrolysis.

Synthesis and Catalytic Activity for 2, 3, and 4-Nitrophenol Reduction of Green Catalysts Based on Cu, Ag and Au Nanoparticles Deposited on Polydopamine-Magnetite Porous Supports.

This work reports on the synthesis of nine materials containing Cu, Ag, Au, and Ag/Cu nanoparticles (NPs) deposited on magnetite particles coated with polydopamine (PDA). Ag NPs were deposited on two PDA@Fe3O4 supports differing in the thickness of the PDA film. The film thickness was adjusted to impart a textural porosity to the material. During synthesis, Ag(I) was reduced with ascorbic acid (HA), photochemically, or with NaBH4, whereas Au(III), with HA, with the PDA cathecol groups, or NaBH4. For the material characterization, TGA, XRD, SEM, EDX, TEM, STEM-HAADF, and DLS were used. The catalytic activity towards reduction of 4-, 3- and 2-nitrophenol was tested and correlated with the synthesis method, film thickness, metal particle size and NO2 group position. An evaluation of the recyclability of the materials was carried out. In general, the catalysts prepared by using soft reducing agents and/or thin PDA films were the most active, while the materials reduced with NaBH4 remained unchanged longer in the reactor. The activity varied in the direction Au > Ag > Cu. However, the Ag-based materials showed a higher recyclability than those based on gold. It is worth noting that the Cu-containing catalyst, the most environmentally friendly, was as active as the best Ag-based catalyst.

Novel Microwave-Assisted Synthesis of COFs: 2020-2022.

Covalent organic frameworks (COFs) have emerged as a new type of crystalline porous polymers of great interest. However, their preparation requires long reaction times. Microwave-assisted synthesis (MAS) offers an interesting approach to increasing the reaction rate of chemical processes. Thus, microwaves can be a key tool for the fast and scalable synthesis of COFs. Since our previous review on the topic, the preparation of COFs with microwaves has been evolving. Herein, we present a compilation of COFs studies and experiments published in the last three years on the synthesis of COFs using microwave-assisted synthesis as a source of energy. The articles include imine, triazine, and other 2D COFs synthesized using MAS. The 3D COFs have also been compiled. The chemical structure of the monomers and the COFs and their main parameters of synthesis and application are summarized for each article.

Fast Microwave-Assisted Synthesis, Calcination and Functionalization of a Silica Mesoporous Nanomaterial: UVM-7.

We report here, for the first time, the use of a solid state microwave source for the synthesis, calcination and functionalization of a UVM-7 based hybrid mesoporous silica material. The synthesis of the UVM-7 material is obtained in 2 min at low power (50 W) by the combination of a microwave irradiation and the atrane route. Moreover, it has been successfully calcined and functionalized in just 13 and 4 min respectively with microwave assisted procedures. A total synthesis comprising each individually optimized step, can be executed in only 4 h including work-up, by contrast to a typical synthesis that comprises several days. Savings higher than one order or magnitude are obtained in time and energy. Our example is a proof of concept of the potential use of solid state microwave generators for the ultrafast on-command preparation of hybrid nanomaterials due to their accurate control and accelerating properties.

Metal-organic frameworks as promising solid-phase sorbents for the isolation of third-generation synthetic cannabinoids in biological samples.

In this work, metal-organic frameworks (MOFs) were used for the first time as solid-phase extraction (SPE) sorbents for the isolation of synthetic cannabinoids (SCs) from oral fluids and subsequently quantified by LC-fluorescence detection (FLD). In this context, different MOF families were synthesized and tested under SPE mode. UiO-66 was the family selected, being the amino functionalized (NH2-UiO-66) the best candidate in terms of extraction performance. After the method optimization, several analytical parameters of interest were obtained, reaching limits of detection (LODs) as low as 0.6-0.8 µg L-1 and precision values (expressed as RSD) lower than 10.6%. The developed method was successfully applied to the determination of 8 SCs in different oral fluids at three spiked levels with recoveries between 67 and 114%. This method claims to be a real alternative for screening purposes, being a cost-effective procedure due to the price of the sorbent (<0.5 €/cartridge) and its recyclability (up to 12 uses), among others good features.

Bioactive compounds and enzymatic browning inhibition in cloudy apple juice by a new magnetic UVM-7-SH mesoporous material.

Fruits and vegetables juices present a high supply of polyphenols, making them highly exposed to enzymatic browning. In this work, we report a novel magnetized mesoporous silica material (Fe3O4NPs-UVM-7) functionalised with thiol and amine groups and evaluate their effect on the enzymatic browning as well as the physicochemical properties (pH and °Brix), bioactive compounds (ascorbic acid, total phenolics, flavonoids, and flavonols) and the antioxidant capacity of cloudy apple juice. From the obtained results, the mesoporous silica material magnetized by 11 % (w/w) with magnetite and functionalized with thiol groups reduce by 70 % the enzymatic browning in apple juice. It did not affect the physicochemical parameters such as pH or total soluble solids with respect to freshly squeezed juice. In addition, the content of flavonoids, vitamin C, and the antioxidant capacity measured by ABTS are also not affected by oxidation. However, the total content of polyphenols in the treated juice drops by 15 % compared to freshly squeezed juice, nonetheless, the loss is 20 % less than the control untreated. Thus, the material mitigates the loss of total polyphenols and also the antioxidant capacity.

One-Pot Synthesis of MnOx-SiO2 Porous Composites as Nanozymes with ROS-Scavenging Properties.

The development of nanomaterials that mimic the activity of enzymes is a topic of interest, for the decomposition of reactive oxygen species (ROS). We report the preparation of a novel nanocomposite of MnOx needles covered with SiO2 porous material. The material was prepared in one pot with a two-step procedure. The material was characterized by EDX, SEM, TEM, XRD, nitrogen adsorption-desorption isotherms, and XPS. The synthesis protocol took advantage of the atrane method, favoring the nucleation and initial growth of manganese oxide needles that remained embedded and homogeneously dispersed in a mesoporous silica matrix. The final composite had a high concentration of Mn (Si/Mn molar ratio of ca. 1). The nanozyme presented bimodal porosity: intraparticle and interparticle association with the surfactant micelles and the gaps between silica particles and MnOx needles, respectively. The porosity favored the migration of the reagent to the surface of the catalytic MnOx. The nanozyme showed very efficient SOD and catalase activities, thus improving other materials previously described. The kinetics were studied in detail, and the reaction mechanisms were proposed. It was shown that silica does not play an innocent role in the case of catalase activity, increasing the reaction rate.

Batch and Flow Synthesis of CeO2 Nanomaterials Using Solid-State Microwave Generators.

Microwave-assisted synthesis in combination with flow synthesis offers an interesting approach to develop faster and more sustainable procedures for the preparation of homogeneous nanomaterials. Recently, solid-state generators of microwaves appeared as a tool with improved control over power and frequency. Cerium oxide, despite its excellent catalytic activity, has not been prepared before using solid-state generators or microwave-assisted flow chemistry. We report a procedure for the preparation of nanoparticulated CeO2 (around 4 nm) under 2.45 GHz microwaves in only 30 s. The materials are further calcined at 800 °C to increase particle size, with a better defined particle size and crystallinity. The procedure was tested in batch at pH 11 and 12 and diverse potencies, and the products were characterized by TEM, XRD, DLS, and N2 adsorption-desorption isotherms. The materials were similar at the diverse pH values and potencies. XRD confirms the crystallinity of the CeO2 material with a fluorite-like structure. They are composed of particles around 40 nm that aggregate as structures of around 100 nm. The procedure was successfully adapted to flow synthesis, obtaining materials with structure and properties equivalent to batch synthesis. The batch and flow materials offer peroxidase properties, opening the door for their use as ROS scavengers.

Iron-Doped Bimodal Mesoporous Silica Nanomaterials as Sorbents for Solid-Phase Extraction of Perfluoroalkyl Substances in Environmental Water Samples.

In this work, sorbets based on UVM-7 mesoporous silica doped with Fe were synthesized and applied to solid-phase extraction of perfluoroalkyl substances from environmental water samples. These emerging pollutants were then determined by liquid chromatography coupled with a mass spectrometry detector. Thus, Fe-UVM-7 mesoporous silica materials with different contents of iron, as well as different pore sizes (by using alkyltrimethilamonium bromide surfactants with different organic tail lengths) were synthesized, and their structure was confirmed for the first time by transmission electron microscopy, nitrogen adsorption-desorption, X-ray diffraction, and Raman spectroscopy. After comparison, Fe50-UVM-7-C12 was selected as the best material for analyte retention, and several extraction parameters were optimized regarding the loading and elution step. Once the method was developed and applied to real matrices, extraction efficiencies in the range of 61-110% were obtained for analytes with C8-C14 chain length, both perfluoroalkyl carboxylates, and perfluoroalkyl sulfonates. Likewise, limits of detection in the range of 3.0-8.1 ng L-1 were obtained for all target analytes. In the analysis of real well-water samples, no target compounds were detected. Spiked samples were analyzed in comparison to Oasis WAX cartridges, and statistically comparable results were achieved.

A ß-cyclodextrin sorbent based on hierarchical mesoporous silica for the determination of endocrine-disrupting chemicals in urine samples.

In the present work, a method for the determination of parabens and bisphenol A in urine samples has been developed. For this purpose, a novel hierarchical mesoporous silica doped with ß-cyclodextrin was developed and used as a sorbent for preconcentration and clean-up step, before analyte determination by liquid chromatography coupled to mass spectrometry detector. Disordered silica materials were also synthesized for comparison purposes. All materials were characterized by electron microscopy, X-ray diffraction, porosimetry, nuclear magnetic resonance, thermogravimetric analysis, elemental CNH analysis, and confocal microscopy, and the attachment of cyclodextrins has been proved as well as their uniform distribution in the resulting material. After the optimization of several protocol parameters, good analytical features were achieved, including recoveries in the range of 96-109% for all analytes, as well as relative standard deviations between 8 and 24%. Also, limits of quantification in the range of 0.003-0.19 µg L-1 were obtained in all cases. The developed method was applied to the determination of parabens and bisphenol A in real urine samples in comparison with a reference method using C18 cartridges, including the correction with creatinine content. Target analytes were detected in all analysed samples, with being BPA the most detected compound.

Mesoporous silica sorbent with gold nanoparticles for solid-phase extraction of organochlorine pesticides in water samples.

In this work, a novel sorbent, based on UVM-7 mesoporous silica doped with Au, has been proposed for organochlorine pesticides extraction. Cartridges containing this material have been applied to the preconcentration of 20 pesticides from water samples, through a solid-phase extraction (SPE) protocol, with their later determination by gas chromatography with an electron capture detector. First, UVM-7 materials were properly characterized by X-ray diffraction, N2 adsorption-desorption, electron microscopy techniques, and UV-Vis spectroscopy, thus confirming their structure and Au incorporation. After optimization of main extraction parameters, recoveries in the range of 80-110% were obtained for most of the analytes, with enrichment factors comprised between 275 and 430. The obtained sensitivity was comparable with other reported methods, with limits of quantification in the range of 0.3-20 ng L-1, thus allowing the determination of these compounds according to European legislation. The developed method has been successfully applied to the analysis of real spiked samples in comparison with a reference method, thus being this sorbent an alternative for organochlorine pesticide enrichment, through a simple, reusable, cheap, and environmentally friendly SPE procedure.

Assessment of migrating endocrine-disrupting chemicals in bottled acidic juice using type UVM-7 mesoporous silica modified with cyclodextrin.

An innovative material based in type UVM-7 mesoporous silica containing analyte-accessible cyclodextrin units is described and assessed as a selectivity-enhancing sorbent for extracting endocrine-disrupting chemicals from bottled apple juice to subsequently quantify them. The synthesis procedure has been carried out using both ß- and γ-cyclodextrin for their later comparison. Then, a complete analytical method for the isolation and determination of the above analytes has been validated. Following the optimized procedure, recoveries between 94% and 100% have been achieved and good repeatability is obtained with deviations under 6.8% for intra-day and inter-day experiments. The detection limits of the method have been established in the ng L-1 level, which demonstrates the ability to quantify the trace concentrations established by sanitary restrictions. A low matrix effect is found when working with real samples. To end, a comparison with an alternative extraction method using C18 extraction cartridges has been carried out and the results obtained with both procedures are comparable.

Targeted-lung delivery of dexamethasone using gated mesoporous silica nanoparticles. A new therapeutic approach for acute lung injury treatment.

Acute lung injury (ALI) is a critical inflammatory syndrome, characterized by increased diffuse inflammation and severe lung damage, which represents a clinical concern due to the high morbidity and mortality in critical patients. In last years, there has been a need to develop more effective treatments for ALI, and targeted drug delivery to inflamed lungs has become an attractive research field. Here, we present a nanodevice based on mesoporous silica nanoparticles loaded with dexamethasone (a glucocorticoid extensively used for ALI treatment) and capped with a peptide that targets the TNFR1 receptor expressed in pro-inflammatory macrophages (TNFR-Dex-MSNs) and avoids cargo leakage. TNFR-Dex-MSNs nanoparticles are preferentially internalized by pro-inflammatory macrophages, which overexpressed the TNFR1 receptor, with the subsequent cargo release upon the enzymatic hydrolysis of the capping peptide in lysosomes. Moreover, TNFR-Dex-MSNs are able to reduce the levels of TNF-α and IL-1ß cytokines in activated pro-inflammatory M1 macrophages. The anti-inflammatory effect of TNFR-Dex-MSNs is also tested in an in vivo ALI mice model. The administered nanodevice (intravenously by tail vein injection) accumulated in the injured lungs and the controlled dexamethasone release reduces markedly the inflammatory response (TNF-α IL-6 and IL-1ß levels). The attenuation in lung damage, after treatment with TNFR-Dex-MSNs, is also confirmed by histopathological studies. Besides, the targeted-lung dexamethasone delivery results in a decrease of dexamethasone derived side-effects, suggesting that targeted nanoparticles can be used for therapy in ALI and could help to overcome the clinical limitations of current treatments.

Host-guest interactions for extracting antibiotics with a γ-cyclodextrin poly(glycidyl-co-ethylene dimethacrylate) hybrid sorbent.

A procedure for the solid-phase extraction of antibiotics (enoxacin, ofloxacin, norfloxacin, ciprofloxacin, and sparfloxacin) in water has been developed. The sorbent used is based on a poly(glycidyl-co-ethylene dimethacrylate) network, whose previously modified surface has been functionalized with γ-cyclodextrin through a click-chemistry reaction. The architecture of the material has been characterized by thermogravimetric analysis, N2 adsorption-desorption, Raman spectroscopy, confocal microscopy, and scanning electron microscopy, showing good capability to be used as a filler for extraction cartridges. The optimization of the extraction methodology shows good intra-day and inter-day repeatability of the extraction procedure, with coefficients of variation between 2.5 and 5.1% and the possibility of reusing the material at least five times. The detection limits of the method have been established at the µg L-1 level, confirming the possibility of quantifying trace levels. To end, real groundwater samples have been analyzed and the results are comparable with those obtained with a reference method. The proposed material can be used for assessing the presence of antibiotics in aqueous environments through an extraction procedure taking advantage of the presence of γ-cyclodextrin on its structure.

Chromogenic Chemodosimeter Based on Capped Silica Particles to Detect Spermine and Spermidine.

A new hybrid organic-inorganic material for sensing spermine (Spm) and spermidine (Spd) has been prepared and characterized. The material is based on MCM-41 particles functionalized with an N-hydroxysuccinimide derivative and loaded with Rhodamine 6G. The cargo is kept inside the porous material due to the formation of a double layer of organic matter. The inner layer is covalently bound to the silica particles, while the external layer is formed through hydrogen and hydrophobic interactions. The limits of detection determined by fluorimetric titration are 27 µM and 45 µM for Spm and Spd, respectively. The sensor remains silent in the presence of other biologically important amines and is able to detect Spm and Spd in both aqueous solution and cells.

Enhancing extraction performance of organophosphorus flame retardants in water samples using titanium hierarchical porous silica materials as sorbents.

A sorbent for the extraction of organophosphorus flame retardants has been proposed, based on UVM-7 (University of Valencia Materials) mesoporous silica doped with titanium. Designed cartridges have been applied to the extraction and preconcentration of flame retardants in water samples, followed by gas chromatography coupled to a mass spectrometry detector. Firstly, UVM-7 materials with different contents of titanium were synthesized and characterized by several techniques, thus confirming the proper mesoporous architecture. The potential of these materials was assessed in comparison with their morphological properties, resulting Ti50-UVM-7 the best solid phase. Several extraction parameters were also optimized. Analytical parameters were also evaluated, and limits of detection from 0.019 to 0.21 ng mL-1 were obtained, as well as intra-day relative standard deviation below 11% for all analytes. Extraction efficiencies above 80% in water samples were achieved. The reusability of the material was also proved. Finally, the designed protocol was applied for the analysis of real water samples, and quantifiable concentrations of tris(2-chloroisopropyl) phosphate (TCIPP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and triphenyl phosphate (TPhP) were obtained in some samples. The method was compared with a United States Environmental Protection Agency general method with C18 cartridges.

Microwave-Assisted Synthesis of Covalent Organic Frameworks: A Review.

Covalent organic frameworks (COFs) are relatively recent materials. They have received great attention due to their interesting properties. However, the application of microwaves in their synthesis, despite its advantages such as faster and more reproducible processes, is a minority. Herein, a comprehensive compilation of the research results published in the microwave-assisted synthesis (MAS) of COFs is presented. This review includes articles of 2D and 3D COFs prepared using microwaves as source of energy. The articles have been classified depending on the functional groups including boronate ester, imines, enamines, azines, and triazines, among others. It compiles the main parameters of synthesis and characteristics of the materials together with some general issues related with COFs and microwaves. Additionally, current and future perspectives of the topic have been discussed.

Cyclodextrins as a Key Piece in Nanostructured Materials: Quantitation and Remediation of Pollutants.

Separation and pre-concentration of trace pollutants from their matrix by reversible formation of inclusion complexes has turned into a widely studied field, especially for the benefits provided to different areas. Cyclodextrins are non-toxic oligosaccharides that are well known for their host-guest chemistry, low prices, and negligible environmental impact. Therefore, they have been widely used as chiral selectors and delivery systems in the pharmaceutical and food industry over time. However, their use for extraction purposes is hampered by their high solubility in water. This difficulty is being overcome with a variety of investigations in materials science. The setting-up of novel solid sorbents with improved properties thanks to the presence of cyclodextrins at their structure is still an open research area. Some properties they can offer, such as an increased selectivity or a good distribution along the surface of a solid support, which provides better accessibility for guest molecules, are characteristics of great interest. This systematic review reports the most significant uses of cyclodextrins for the adsorption of pollutants in different-origin samples based on the works reported in the literature in the last years. The study has been carried out indistinctly for quantitation and remediation purposes.

Use of Silica Based Materials as Modulators of the Lipase Catalyzed Hydrolysis of Fats under Simulated Duodenal Conditions.

The effect of silica materials and their functionalization in the lipase catalyzed fat hydrolysis has been scarcely studied. Fifteen silica materials were prepared and their effect on the fat hydrolysis was measured, under simulated duodenal conditions, using the pH-stat method. The materials are composed of the combination of three supports (Stöber massive silica nanoparticles, Stöber mesoporous nanoparticles and UVM-7) and four surface functionalizations (methyl, trimethyl, propyl and octyl). In addition, the non-functionalized materials were tested. The functional groups were selected to offer a hydrophobic character to the material improving the interaction with the fat globules and the lipase. The materials are able to modulate the lipase activity and their effect depending on the support topology and the organic covering, being able to increase or reduce the fat hydrolysis. Depending of the material, relative fat hydrolysis rates of 75 to 140% in comparison with absence of the material were obtained. The results were analyzed by Partial Least Square Regression and suggest that the alkyl modified mesopores are able to improve the fat hydrolysis, by contrast the non-porous nanoparticles and the textural pores tend to induce inhibition. The effects are more pronounced for materials containing long alkyl chains and/or in absence of taurodeoxycholate.

Bimodal porous silica nanomaterials as sorbents for an efficient and inexpensive determination of aflatoxin M1 in milk and dairy products.

An extraction procedure was developed for the determination of aflatoxin M1 in milk and dairy products. A sorbent based on UVM-7 mesoporous silica was used as solid phase for the sample clean-up, and the analyte determination was carried out by HPLC coupled to a fluorescence detector. The material architecture was characterized by transmission electronic microscopy, X-ray diffraction, 29Si NMR and nitrogen adsorption-desorption. After the optimization of extraction parameters, the influence of the matrix has been evaluated, obtaining recoveries in the range 78-105% for whole and skimmed milk and yogurt matrix. The reusability of the material was also proved. The sensitivity of the method was also evaluated, and a LOQ (0.015 µg kg-1) below the European legislation limit was obtained. The procedure was successfully applied for the determination of aflatoxin M1 in real samples. The results were compared with those obtained with a reference method, being the results statistically comparable.