Boric Acid Derivatives Research Articles

Double cross-linked graphene oxide hydrogel for promoting healing of diabetic ulcers.

This study explores the synthesis and characterization of a novel double cross-linked hydrogel composed of polyvinyl alcohol (PVA), sodium alginate (SA), graphene oxide (GO), and glutathione (GSH), henceforth referred to as PVA/SA/GO/GSH. This innovative hydrogel system incorporates two distinct types of cross-linking networks and is meticulously engineered to exhibit sensitivity to high glucose and/or reactive oxygen species (ROS) environments. A sequential approach was adopted in the hydrogel formation. The initial phase involved the absorption of GSH onto GO, which was subsequently functionalized with boric acid and polyethylene glycol derivatives via a bio-orthogonal click reaction. This stage constituted the formation of the first chemically cross-linked network. Subsequently, freeze-thaw cycles were utilized to induce a secondary cross-linking process involving PVA and SA, thereby forming the second physically cross-linked network. The resultant PVA/SA/GO/GSH hydrogel retained the advantageous hydrogel properties such as superior water retention capacity and elasticity, and additionally exhibited the ability to responsively release GSH under changes in glucose concentration and/or ROS levels. This feature finds particular relevance in the therapeutic management of diabetic ulcers. Preliminary in vitro evaluation affirmed the hydrogel's biocompatibility and its potential to promote cell migration, inhibit apoptosis, and exhibit antibacterial properties. Further in vivo studies demonstrated that the PVA/SA/GO/GSH hydrogel could facilitate the healing of diabetic ulcer sites by mitigating oxidative stress and regulating glucose levels. Thus, the developed PVA/SA/GO/GSH hydrogel emerges as a promising candidate for diabetic ulcer treatment, owing to its specific bio-responsive traits and therapeutic efficacy.

Achieving color-tunable persistent afterglow from ultralong polyacrylamide-based room-temperature phosphorescence materials through phosphorescence Förster resonance energy transfer

Polymer-based pure organic room-temperature phosphorescence (RTP) materials have received widespread attention due to their great application prospects in many fields. However, the reports about polymer-based multicolor RTP materials were still rare. Herein, a series of monochromatic PAM-based RTP materials are constructed by facilely doping boric acid derivatives into polyacrylamide (PAM) matrices. Due to the strong intermolecular hydrogen-bonding interaction, 4-carboxyphenylboronic acid (CPBA) doped system PAM/CPBA achieves an ultralong RTP lifetime of 753 ms with a naked-eye visible blue afterglow up to 12 s. Significantly, PAM/CPBA as energy donor and the commercial fluorescent dye fluorescein (FL) or rhodamine B (RhB) as energy acceptor are used to fabricated ternary doping systems to achieve multicolor afterglow emission through phosphorescence Förster resonance energy transfer (FRET). The afterglow colors of PAM/CPBA/FL and PAM/CPBA/RhB can be easily adjusted from blue to yellow or purple by changing the doping content of FL or RhB. Inspiringly, a nearly white afterglow emission from the quaternary doping system PAM/CPBA/RhB/FL is achieved by varying the amount of FL content. Furthermore, the prepared PAM-based binary and ternary doping RTP materials can be applied in the field of information encryption.

Optimization of guanosine-based hydrogels with boric acid derivatives for enhanced long-term stability and cell survival.

Tissue defects can lead to serious health problems and often require grafts or transplants to repair damaged soft tissues. However, these procedures can be complex and may not always be feasible due to a lack of available tissue. Hydrogels have shown potential as a replacement for tissue grafts due to their ability to support cell survival and encapsulate biomolecules such as growth factors. In particular, guanosine-based hydrogels have been explored as a potential solution, but they often exhibit limited stability which hampers their use in the biofabrication of complex grafts. To address this issue, we explored the use of borate ester chemistry and more complex boric acid derivatives to improve the stability and properties of guanosine-based hydrogels. We hypothesized that the aromatic rings in these derivatives would enhance the stability and printability of the hydrogels through added π-π stack interactions. After optimization, 13 compositions containing either 2-naphthylboronic acid or boric acid were selected. Morphology studies shows a well-defined nanofibrilar structure with good printable properties (thixotropic behaviour, print fidelity and printability). Moreover, the pH of all tested hydrogels was within the range suitable for cell viability (7.4-8.3). Nevertheless, only the boric acid-based formulations were stable for at least 7days. Thus, our results clearly demonstrated that the presence of additional aromatic rings did actually impair the hydrogel properties. We speculate that this is due to steric hindrance caused by adjacent groups, which disrupt the correct orientation of the aromatic groups required for effective π-π stack interactions of the guanosine building block. Despite this drawback, the developed guanosine-boric acid hydrogel exhibited good thixotropic properties and was able to support cell survival, proliferation, and migration. For instance, SaOS-2 cells planted on these printed structures readily migrated into the hydrogel and showed nearly 100% cell viability after 7days. In conclusion, our findings highlight the potential of guanosine-boric acid hydrogels as tissue engineering scaffolds that can be readily enhanced with living cells and bioactive molecules. Thus, our work represents a significant advancement towards the development of functionalized guanosine-based hydrogels.

The construction of molecularly imprinted electrochemical biosensor for selective glucose sensing based on the synergistic enzyme-enzyme mimic catalytic system.

It is generally accepted that glucose oxidase (GOx) shows unique specificity in β-d-glucose catalysis. However, it has been found that GOx can catalyze diverse monosaccharides. Therefore, the sensing accuracy for glucose biosensors using GOx as probes will be largely compromised by the presence of other monosaccharides. Herein, multifunctional bi-nanospheres (Fe3O4@Au NCs), which show both peroxidase-like and catalase-like catalytic activities in different working conditions, are successfully constructed and served as desirable platform with huge surface area for the immobilization of large amount of GOx probes. In acidic environment, hydroxyl radicals could be generated via the cascaded catalysis of β-d-glucose by Fe3O4@Au-GOx, and then employed to initiate the polymerization of boric acid derivative to prepare molecularly imprinted polymers (MIPs) on the surface of GOx using β-d-glucose as template. Then, the molecularly imprinted GOx are immobilized on the surface of highly oriented pyrolytic graphite (HOPG) electrode and an electrochemical biosensor (Fe3O4@Au-GOx-HOPG) for glucose sensing is successfully obtained. Interestingly, the as-prepared biosensors could selectively detect glucose in the range of 10.0μM - 5.0mM with a LOD=5.0μM with the help of MIPs, which is comparable or better than other glucose sensors reported recently.

A novel PEG-mediated boric acid functionalized magnetic nanomaterials based fluorescence biosensor for the detection of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is one of the pathogens that seriously endanger human health and are widespread in nature. Food poisoning incidents caused by S. aureus frequently break out. Therefore, it is significant that a rapid and accurate method is established for S. aureus detection. In this study, a strategy using magnetic separation combine with fluorescence analysis was proposed for S. aureus detection. Boric acid can selectively enrich compounds with cis-diol groups through a reversible esterification reaction, and has been widely used in the identification of sugars and glycosylated molecules. As a boric acid derivative, 3-aminophenylboronic acid (APBA) has the advantages of stability, low cost, easy synthesis, etc. Therefore, using APBA as a recognition molecule to prepare magnetic nanomaterials can achieve the enrichment of S. aureus. In order to reduce steric hindrance and ensure the dominant orientation of APBA, thus improving the enrichment performance of target bacteria. The polyethylene glycol (PEG) was used as a mediator to prepare PEG-mediated APBA functionalized magnetic nanomaterials (APBA-PEG-MNs). In addition, this study used FITC-pig IgG to label S. aureus because the Fc fragment of IgG to bind protein A on the surface of S. aureus and realized the detection of S. aureus by detecting fluorescence. Under the optimal experimental conditions, the capture efficiency of APBA-PEG-MNs for S. aureus with the concentration of 2.7 × 106 CFU/mL in spinach, juice and pool water spiked samples was 92.6%, 91.6%, 91.6%. The limit of detection of the strategy in spiked samples was 2.7 × 102 CFU/mL within 80 min.

Synthesis, crystal structure, and DFT study of N-(2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxin-2-yl)phenyl)- 3-methylbutanamide

N-(2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-3-methyl-butanamide is an important boric acid derivative. In this article, the title compound is obtained by a two-step substitution reaction. The structure of the title compound is verified by FTIR, 1H and 13C NMR, and MS. Simultaneously, the single crystal structure of the title compound is gauged by X-ray diffraction and subjected to crystallographic and conformational analyses. Density functional theory (DFT) is applied to further calculate the molecular structure and compare it with X-ray values. The result of the conformational analysis shows that the molecular structure optimized by DFT is identical with the single crystal structure determined by single crystal X-ray diffraction. In addition, DFT is used to further study the molecular electrostatic potential and frontier molecular orbitals of the title compound, revealing the molecular structure characteristics, conformation, and some special physical and chemical properties of the title compound.

Parameterization of Boronates Using VFFDT and Paramfit for Molecular Dynamics Simulation.

Boric acid, borate esters, and hydroxy derivatives are biologically active molecules. Thus, performing molecular dynamics simulations of these molecules is vital in terms of drug design, but it is difficult to find directly generated Amber parameters based on an ab initio method for these kinds of molecules in the literature. In this study, Amber parameters for such molecules containing boron were generated based on ab initio calculations using the paramfit program, which applies a combination of genetic and simplex algorithms, and the Visual Force Field Derivation Toolkit (VFFDT) program containing the Seminario method. The minimized structure, after obtaining novel parameters and using the sander program, was compared with the experimental crystallographic structures, and it was observed that the root-mean-square deviation (RMSD) value between the experimental structure and minimized structure agreed reasonably well. In addition, the molecule was heated, and the molecular dynamics simulation was successfully obtained with the novel parameters.

Smoke Hazard Assessment of Cypress Wood Coated with Boron/Silicon Sol Compounds

In this study, boron/silicon sol compounds were applied to wood for construction and durable materials, and fire risks were investigated in terms of smoke performance index (SPI), smoke growth index (SGI), and smoke intensity (SI). The compound was synthesized by reacting tetraethoxyorthosilicate with boric acid and boronic acid derivatives. Smoke characteristics were investigated using a cone calorimeter (ISO 5660-1) equipment for cypress wood. The fire intensity fixed the external heat flux at 50 kW/m<sup>2</sup>. The smoke performance index measured after the combustion reaction increased between 13.4% and 126.7% compared with cypress wood. The fire risk due to the smoke performance index decreased in the order of cypress, phenylboronic acid/silicon sol (PBA/Si), (2-methylpropyl) boronic acid/silicon sol (IBBA/Si), boric acid/silicon sol (BA/Si). The smoke growth index decreased between 12.0% and 57.5% compared to the base specimen. The risk of fire caused by the smoke growth index decreased in the order of cypress, PBA/Si, IBBA/Si, BA/Si. The fire risk due to smoke intensity decreased between 3.2% and 57.8%, and in the order of cypress, PBA/Si, IBBA/Si, BA/Si. CO<sub>peak</sub> concentrations ranged between 85 and 93 ppm, and decreased between 37% and 43% compared to the base specimen. A comprehensive assessment of the fire risk on smoke hazards decreased in the order of cypress, PBA/Si, IBBA/Si, BA/Si.

Spectroscopic insight into supramolecular assemblies of boric acid derivatives and β-cyclodextrin

Interactions of select boric acid derivatives with β-cyclodextrin were investigated. All products were obtained employing the grinding-induced mechanochemical approach. It was found that phenylboronic acid, benzoxaborole and boric acid form non-covalent, hydrogen bonding-based systems with β-cyclodextrin, whereas catechol and pinacol esters of phenylboronic acid as well as ferroceneboronic acid form host-guest inclusion complexes. The interactions were probed using spectroscopic methods: 1H NMR, 1H-1H ROESY NMR, 1H DOSY NMR, FT-IR. Association constant values were evaluated by 1H DOSY NMR. The highest association constant was found for boric acid (117.5 ± 2.5 M−1), whilst the lowest for benzoxaborole (14.8 ± 0.3 M−1). The study shows the influence of boron compound structure on the nature of the assembly formed with β-cyclodextrin, laying up the basis for future work with such supramolecular systems.

Modeling Multiple Chemical Equilibrium in Single-Stage Extraction of Atenolol Enantiomers with Tartrate and Boric Acid as Chiral Selector

Enantioselective liquid–liquid extraction (ELLE) was adopted to separate atenolol (AT) enantiomers, where tartrate and boric acid (BA) were used as the chiral selector. Influence of process variables on extraction efficiency were studied, including type of tartaric acid derivatives, type of the organic solvent, pH of aqueous phase, molality of BA and tartaric acid derivatives, as well as temperature. A theoretical model was developed based on the mechanism research on reactive extraction of AT enantiomers by n-hexyl (L)-tartrate (LT) and BA. Important parameters of this model were determined. By modeling and experiment, the optimal conditions identified involve the LT molality of 0.0796 mol·kg–1, BA molality of 0.1 mol·kg–1, AT molality of 1.592 mmol·kg–1, and pH value of 9.00 at 278 K, where the obtained enantioselectivity (α) is 1.8951 and performance factor (pf) is 0.0608.

A novel near-infrared fluorescent probe for H2O2 in alkaline environment and the application for H2O2 imaging in vitro and in vivo

H2O2 as one of the most important ROS (Reactive Oxygen Species) has more attack activity to biomolecules such as DNA, RNA, protein and enzyme in alkaline environment and leads to a series of disease. However, no attention has been paid to the fluorescent detection of H2O2 in alkaline environment in the past. Herein, we reported the first ratiometric near-infrared fluorescent probe based on a boric acid derivative of Changsha near-infrared dye (CSBOH) for H2O2 detection in alkaline condition and the application for H2O2 imaging in vivo. ICT (intra-molecular charge transfer) mechanism was used in CSBOH to modulate the fluorescence change. The photophysical change of CSBOH was investigated by comparison with a phenol derivative of Changsha near-infrared dye (CSOH), a structural analogue bearing phenol group. In the presence of H2O2, CSBOH exhibited remarkably different fluorescence change at 650 nm and 720 nm when excited by 560 nm and 670 nm light respectively in alkaline buffer and showed high selectivity toward H2O2. Cellular experiments demonstrate that CSBOH can image endogenously generated H2O2 in macrophages and A431 cells. In vivo experiment demonstrates that both CSOH and CSBOH can be used for bio-imaging, and CSBOH can image H2O2 in living animal successfully.

New polyol for production of rigid polyurethane‐polyisocyanurate foams, Part 2: Preparation of rigid polyurethane‐polyisocyanurate foams with the new polyol

AbstractThe method of preparation, determination of foaming parameters, and methods for the determination of physicochemical properties of polyurethane‐polyisocyanurate (PUR‐PIR) foams prepared with the use of N,N′‐di(methyleneoxy‐2‐hydroxyethyl)urea and boric acid derivatives are presented in this paper. It was found that application of the borate as a polyol component and simultaneously as a flame retardant in the recipe for production of PUR‐PIR foams was very favorable. The foams prepared were characterized by reduced brittleness, higher compressive strength and content of closed cells, as well as considerably lower flammability in comparison with standard foam. The results show that the new polyol prepared on the basis of N,N′‐di(methyleneoxy‐2‐hydroxyethyl)urea and boric acid can be applied for production of rigid PUR‐PIR foams, and it improves their physicochemical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

New Polyol for Production of Rigid Potyurethane-polyisocyanurate Foams Part 2: Preparation of Rigid Polyurethane-polyisocyanurate Foams with the New Polyol

Method of preparation, the determination of foaming parameters and methods for the determination of physicochemical properties of PUR-PIR foams prepared with the use of N,N'-di(methyleneoxy-2-hydroxyethyl)urea and boric acid derivative has been presented in this paper. It was found that application of the borate as a polyol component and simultaneously as a flame retardant in the recipe for production of polyurethane-polyisocyanurate foams (PUR-PIR) was very favourable. The foams prepared were characterized by reduced brittleness, higher compressive strength and content of closed cells as well as considerably lower flammability in comparison with standard foam. The results show that the new polyol prepared on the basis of N,N'-di(methyleneoxy-2-hydroxyethyl)urea and boric acid can be applied for production of rigid polyurethane-polyisocyanurate foams and it improves their physicochemical properties.

The dehydrogenation of ammonia–borane catalysed by dicarbonylruthenacyclic(ii) complexes

The reactivity of ruthenacyclic compounds towards ammonia-borane's dehydrogenation was investigated by considering both hydrolytic and anhydrous conditions. The study shows that the highly soluble μ-chlorido dicarbonylruthenium(II) dimeric complex derived from 4-tert-butyl,2-(p-tolyl)pyridine promotes, with an activation energy E(a) of 22.8 kcal mol(-1), the complete hydrolytic dehydrogenation of NH(3)BH(3) within minutes at ca. 40 °C. The release of 3 eq. of H(2) entails the formation of boric acid derivatives and the partly reversible protonolysis of the catalyst, which produces free 2-arylpyridine ligand and a series of isomers of "Ru(CO)(2)(H)(Cl)". Under anhydrous conditions, hydrogen gas release was found to be slower and the dehydrogenation of NH(3)BH(3) results in the formation of conventional amino-borane derivatives with concomitant protonolysis of the catalyst and release of isomers of "Ru(CO)(2)(H)(Cl)". The mechanism of the protonolysis of the ruthenacycle was investigated with state-of-the-art DFT-D methods. It was found to proceed by the concerted direct attack of the catalyst by NH(3)BH(3) leading either to the formation of a coordinatively unsaturated "Ru(CO)(2)(H)(Cl)" species. The key role of "Ru(CO)(2)(H)(Cl)" species in the dehydrogenation of ammonia-borane was established by trapping and quenching experiments and inferred from a comparison of the catalytic activity of a series of dicarbonylruthenium(II) complexes.

Studies on the boronation of methyl-β-d-cellobioside—a cellulose model

The conversion of phenylboronic acid (PBA) with methyl-β-d-cellobioside (Me-β-d-clb) and cellodextrins (DPw 12) was investigated to gain a basic understanding of the interactions of boric acid derivatives with oligo- and polyglucans. By means of MS and NMR experiments, it was possible to show a first stage formation of a six-membered ring at C-4 and C-6 of the non-reducing glucose occurs as in the case of monosaccharides. If the amount of reagent is increased the formation of seven-membered rings at the secondary OH moieties is observed. Even the existence of two of these large ring-systems in the direct neighborhood was found. Application of an excess of boronation reagent led to dimerization reactions of Me-β-d-clb via the primary reducing glucose residue as confirmed by DOSY NMR studies. Preliminary 13C NMR studies for the interaction of cellodextrins with PBA in DMSO solution confirmed a functionalization at the trans-1,2-diol moieties of these oligomers. The amount of reagent applied may either was shown to lead to soluble products or to insoluble cross-linked material.

Kinetic analysis of the thermal degradation of an epoxy-based intumescent coating

The aim of this work is to analyse and to simulate the kinetics of pyrolysis of an intumescent formulation designed to protect steel in the case of hydrocarbon and jet fires. The coating is based on a thermoset epoxy-amine resin system into which two fire retardant agents, boric acid and ammonium polyphosphate derivative have been incorporated. Industrial tests (jet fire tests) are usually used to evaluate the degradation mode of an intumescent coating. But these tests are quite expensive, and as the heating rates are extremely high (between 500 and 800 °C/min), it is not possible to evaluate the thermal degradation behaviour of the intumescent coating directly by thermogravimetric analyses. That is why it is necessary to develop predictive models of kinetics of degradation of these intumescent coatings. In this work, the coating has been pyrolyzed at different heating rates and a predictive model of its kinetics of degradation has been developed.

Characterization of the performance of an intumescent fire protective coating

The aim of this work is to study the efficiency of different intumescent formulations designed to protect steel in the case of hydrocarbon fire. The coating is based on a thermoset epoxy–amine resin system into which fire retardant agents, boric acid and ammonium polyphosphate derivative have been incorporated. The first part of the study evaluates, using large scale industrial furnace tests, the behavior of the thermoset resin containing alone or in combination with additives. It is revealed that in this epoxy resin, the combination between ammonium polyphosphate and boric acid leads to the best protective results. The second part of the study attempts to investigate more precisely the effect and the mode of action of the additives in terms of thermal stability, mechanical resistance and rheological properties using small scale lab tests, to explain why this combination works better than using the two fire retardants used separately. The experiments show that this combination leads to the smallest decrease of viscosity when the resin degrades, the highest mechanical resistance and the highest expansion.

Synthesis and x-ray structural examination of intracomplex boroxadiazolidines

The reaction between acetone monoalkylhydrazones and aldehydes in the presence of boric acid derivatives has given five-membered boron-nitrogen heterocycles, the stability of which is to a large extent dependent on the substituents in the ring. An x-ray structural examination of the boroxadiazolidine (VI) has been carried out.

Organoboron antioxidants, 2 boric acid derivatives as secondary antioxidants

AbstractBoric acid esters and arylboronic esters and amides are known to be good primary antioxidants, but they are also capable of destroying hydroperoxides effectively. We have found three principal ways of hydroperoxide decomposition. At first, simple alkyl, but also other esters catalytically destroy hydroperoxides, e. g. cumyl and tert‐butyl hydroperoxide, after an induction period. In a second route, reduction of the hydroperoxides takes place under transformation of oxidizable parts of the organoboron compound. Boric acid catechol esters, for example, reduce tert‐butyl hydroperoxide giving a black precipitate, a reaction product of the instable o‐benzoquinone. Catechol and hydroperoxide in the absence of boron compound do not react. Finally, p‐phenylboronic acid esters reduce hydroperoxides to give alcohol and the corresponding boric acid ester. Many boron derivatives can react in two or all three ways, e. g. 2‐phenyl‐1, 3, 2‐benzodioxaborole. 1 mol of this compound destroys 2 mol of cumyl hydroperoxide giving cumyl alcohol, and more than 10 mol to give acetone and phenol. In side reactions, cumyl hydroperoxide is converted into dicumyl peroxide and acetophenone. The last compound indicates a reaction passing via radicals; but in all cases, this reaction is not important.

Organoboron antioxidants: Part 1—Boric acid derivatives as primary antioxidants

Organoboron compounds, particularly boric acid esters and arylboronic acid derivatives, are known to be good antioxidants. In this paper, the inhibiting activities of various boron compounds are compared with those of phenolic antioxidants and phosphites. Whereas in the autoxidation of polypropylene, aryl borates give rise to approximately the same induction periods as the constituent phenols, aryl phenylboronates are, to some extent, considerably better. For the calculation of kinetic data, particularly the rate constants ( k 7) of the reaction with peroxyl radicals and the stoichiometric factor ( f), investigations into the inhibiting activity of boron compounds in the initiated oxidation of cumene at low temperatures are used. The rate constant k 7 of aryl phenylboronates is approximately ten times greater than that for structurally analogous phosphites, whereas aryl borates can be regarded as ‘depots’ for phenols.