Synthesis and drug-release properties of biodegradable hydrogels having β-cyclodextrin

A new β-cyclodextrin (β-CD) methacrylated monomer was synthesized from the reaction of β-CD, glycidyl methacrylate. Based on inclusion character of β-CD, a series of hydrogels were prepared by irradiating the mixtures of β-CD methacrylate monomer (β-CD-Met), poly(ethylene glycol) monoacrylate, poly(ethylene glycol)diacrylate, fumaric acid monoethyl ester-functionalized poly(lactic-co-glycolic) acid, 1-vinyl-2-pyrrolidone, N,N′-methylene bisacrylamide, and the photoinitiator. Gel percentages and equilibrium swelling ratios (%) of hydrogels were investigated. It was observed that equilibrium-swelling ratio increased with increasing β-CD-Met content in the hydrogel composition. SEM images demonstrated that β-CD-Met-based hydrogel have lots of voids on the fractured surface. In this study, ibuprofen (IBU) which is capable of forming inclusion complex with β-CD was chosen. For the hydrogel with maximum CD content, the IBU drug loading was found as 9 mg/g dry gel. It can be concluded that the inclusion complex-formation capability of β-CD moiety increases the drug release by improving the aqueous solubility of hydrophilic drugs.     

Synthesis,characterization and As(III) adsorption behavior of β-cyclodextrin modified hydrous ferric oxide

This study investigates the adsorption of As(III) on β-cyclodextrin modified hydrous ferric oxide (HCC). This is characterized by XRD, FESEM, AFM, XPS, BET, surface site concentration and FTIR. The modification of hydrous ferric oxide (HFO) surface by β-cyclodextrin provides ample OH groups which in turn increase As(III) adsorption on HCC compared to HFO. The adsorption remains almost constant in pH range 3–8 which decreases at higher pH (>8) and followed monolayer and pseudo first order kinetics. It is spontaneous at 303 K with increasing entropy and decreasing enthalpy. Thus HCC is found to be more efficient adsorbent than HFO.     

Synthesis of some novel silicone-imide hybrid inorganic–organic polymer and their properties

Synthesis and properties of poly(imide-siloxane) hybrid polymers (PIS), having alternate diimide and disiloxane units, based on 1,3-bis(succinyl anhydride)1,1,3,3-tetraorganodisiloxane (I or II) have been described. Polymers have been synthesized by the precursor synthesis i.e., poly(amic acid), using siloxanes (I or II) and 4,4′-diaminodiphenylmethane (DDM) or 4,4′-diaminodiphenylsulphone (DDS) in N,N-dimethylacetamide (DMAc) followed by thermal imidization. FT-IR, thermal (TGA and TMA), solvent resistant and dielectric properties of the compounds have also been studied. The glass transition, thermal stability and char yields of these hybrid polymers increased appreciably. These materials also showed very good solvent resistant properties in protic and aprotic solvents.     

Synthesis and characterization of curdlan/β-cyclodextrin composite hydrogels for sustained-release

Curdlan/β-cyclodextrin (β-CD) composite hydrogels were prepared by using epichlorohydrin (ECH) and ethylene glycol diglycidyl ether (EGDGE) as cross-linkers respectively. The results showed that a macromolecular network structure was formed. This composite hydrogels showed certain temperature sensitivity, regular swelling ratio and unique mechanical property. The addition of β-CD improved the swelling property of hydrogels in neutral aqueous solution, showing completely opposite results to the cellulose/β-CD hydrogels. This composite hydrogel had certain temperature sensitivity and could sustained-release sodium salicylate for more than 8?hours. The curdlan/β-CD hydrogels, which were cross-linked by natural polymers, had a unique application prospect in the medicine.     

Determination of lisinopril using β-cyclodextrin/graphene oxide-SO3H modified glassy carbon electrode

An electrochemical method has been successfully demonstrated for sensitive determination of lisinopril with β-cyclodextrin-graphene oxide-SO₃H composite modified glassy carbon electrode (β-CD/GO-SO₃H/GCE). Cyclic voltammetry, differential pulse voltammetry, and chronocoulometry were used to investigate the electrochemical behavior of lisinopril at β-CD/GO-SO₃H/GCE. The cyclic voltammetric results indicate that β-CD/GO-SO₃H/GCE can remarkably enhance electroactivity toward the oxidation of lisinopril in buffer solutions. The electrochemical behavior was further exploited as a sensitive detection scheme for the lisinopril determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit were 0.21–190.4 and 0.11 µM (S/N = 3), respectively. The method was successfully applied to assay the drug in human serum.     

Synthesis and properties of PDMS modified waterborne polyurethane–acrylic hybrid emulsion by solvent-free method

A new type of polysiloxane modified polyurethane–acrylic hybrid emulsion was synthesized by solvent-free method and the polysiloxane was introduced into the soft segment of polyurethane chains using dihydroxybutyl-terminated polydimethylsiloxane (PDMS). The formed film from the hybrid emulsion could provide obviously higher water-resistance property. The preparation technologies such as the content of carboxy group and acrylic monomer, the rate and the time of emulsification were discussed systematically. The chain structure and the particle size were confirmed by the analysis of Fourier transform infrared spectroscopy and transmission electron microscopy, respectively. The effect of PDMS content on the water resistance and the mechanical property were investigated by absorbed water ratio, water contact angle and dynamic mechanical measurement.     

Chiral adsorption of phenylalanine by α-, β-cyclodextrin modified layered double hydroxides

The chiral adsorption of racemic phenylalanine (Phe) by carboxymethyl-α/β-cyclodextrin-intercalated Zn-Al layered double hydroxides (CM-α/β-CD-LDHs) has been studied. The adsorption isotherms of chiral excess adsorption and the total adsorption of Phe by these CM-α/β-CD-LDHs have been investigated. CM—CD-LDHs were found to be more suitable for chiral recognition of Phe than CM—CD-LDHs. Furthermore, the intraparticle diffusion model is successfully validated in this work. Intraparticle effective diffusivities (D _eff ) of Phe in these CM-α/β-CD-LDHs macroparticles were determined from the homogeneous Fickian diffusion model at various temperatures.     

Selective adsorption of L-TA/D-TA by β-cyclodextrin derivative modified with l-tryptophan: Isotherm,kinetic and thermodynamics studies

β-Cyclodextrin derivative modified with l-tryptophan (L-Trp-CD) was prepared for recognitive chiral separation of tartaric acid enantiomers from ethanol solution. Kinetic properties were successfully investigated by pseudo-first-order model and pseudo-second-order model. Equilibrium data were described by the Langmuir and Freundlich isotherm models. The thermodynamics parameters (positive values of ΔH° and ΔS°, negative values of ΔG°) indicated that binding system for L-Trp-CD was endothermic, entropy gained and spontaneous. Selective adsorption result of l-tartaric acid (L-TA)/d-tartaric acid (D-TA) by L-Trp-CD indicated that L-Trp-CD has significantly higher adsorption capacity for L-TA compared with D-TA, and the selectivity coefficient is 3.36.     

Synthesis and properties of hybrid alkyd–acrylic dispersions and their use in VOC-free waterborne coatings

Hybrid waterborne alkyd–acrylic dispersions with solid content of 40%, free from any surfactant and exempt of any organic solvent, were successfully synthesized by a melt co-condensation reaction between an acrylic prepolymer bearing carboxylic groups and a long-oil alkyd resin. Spontaneous emulsification of the ensuing hybrid resin was achieved by the addition of an aqueous ammonia solution that neutralized the carboxylic functions. The key role of the carboxylic groups on the stabilization process and on the storage stability of the dispersion was assessed and it was shown that the insertion of anhydride moieties within the acrylic prepolymer ensured the efficient coupling between the acrylic and the alkyd resin and prevented the phase separation. These dispersions are easy to implement and might be used to prepare high quality zero VOC coatings in terms of drying time, stability and gloss. The most stable dispersion was also used in the formulation of air-drying waterborne lacquers and their coating properties were evaluated.     

Synthesis and characterisation of silica–carbon nanotube hybrid microparticles and their effect on the electrical properties of poly(vinyl alcohol) composites

Hybrid silica–carbon nanotube (CNT) particles with a radial symmetry were produced by the growth of nanotubes onto spherical, mesoporous silica gel particles using the floating catalyst chemical vapour deposition (FC-CVD) method. Characterisation of the hybrid particles, using electron microscopy, Raman spectroscopy and thermogravimetry showed the geometry and porosity of the silica particles to influence the alignment and density of the CNTs produced. CNT growth initiated in the pores of the gel particles and three hours of CVD growth were required to get extensive surface coverage. In the early stages of growth, the reactants diffused inside the mesoporous silica and consequently the CNTs grew mainly within the silica gel rather than on the surface. Some indication of catalyst templating was observed within the smaller (<10 nm) pores, but this templating did not result in aligned CNTs. Composite films of hybrid silica–CNT particles in poly(vinyl alcohol) were cast and their impedance measured. An electrical percolation threshold of 0.62 wt.% was found for the hybrid particles, of which 0.20 wt.% were CNTs.     

Synthesis and Characterization of the Inclusion Complex of β-cyclodextrin and Azomethine

A β-cyclodextrin (β-Cyd) inclusion complex containing azomethine as a guest was prepared by kneading method with aliquot addition of ethanol. The product was characterized by Fourier Transform Infrared (FTIR) spectrometer, ¹H Nuclear Magnetic Resonance (¹H NMR) and Thermogravimetric Analyzer (TGA), which proves the formation of the inclusion complex where the benzyl part of azomethine has been encapsulated by the hydrophobic cavity of β-Cyd. The interaction of β-Cyd and azomethine was also analyzed by means of spectrometry by UV-Vis spectrophotometer to determine the formation constant. The formation constant was calculated by using a modified Benesi-Hildebrand equation at 25 °C. The apparent formation constant obtained was 1.29 × 10⁴ L/mol. Besides that, the stoichiometry ratio was also determined to be 1:1 for the inclusion complex of β-Cyd with azomethine.     

Electrochemical study of isopoly- and heteropoly-oxometallates film modified microelectrodes —vi. preparation and redox properties of 12-molybdophosphoric acid and 12-molybdosilicic acid modified carbon fiber microelectrodes

The redox behaviours of 12-molybdophosphoric acid (12-MPA) and 12-molybdosilicic acid (12-MSA) in aqueous acid media are characterized at the carbon fiber (CF) microelectrode. The preparation of CF microelectrode modified with 12-MPA or 12-MSA monolayer and the oxidation-reduction properties of the modified electrode in aqueous acid media or 50% (v/v) water-organic media containing some inorganic acids are studied by cyclic voltammetry. 12-MPA or 12-MSA monolayer modified CF microelectrode with high stability and redox reversibility in aqueous acidic media can be prepared by simple dip coating. The cyclic voltammograms of 12-MPA and 12-MSA and their modified CF microelectrodes in aqueous acid solution exhibit three two-electron reversible waves with the same half-wave potentials, which defines that the species adsorbed on the CF electrode surface are 12-MPA and 12-MSA themselves. The acidity of electrolyte solution, the organic solvents in the electrolyte solution, and the scanning potential range strongly influence on the redox behaviours and stability of 12-MPA or 12-MSA monolayer modified electrodes. On the other hand, the catalytic effects of the 12-MPA and 12-MSA and chlorate anions in aqueous acidic solution on the electrode reaction processes of 12-MPA or 12-MSA are described.     

Fluorescence and β-cyclodextrin inclusion properties of three carbazole-based dyes

Fluorescence behavior of three carbazole-based dyes, 2-(9H-carbazol-9-yl) butanoic acid, 2-(1,4-dimethyl-9H-carbazol-9-yl)acetic acid and 3-(1,4-dimethyl-9H-carbazol-9-yl)propanoic acid were examined. General solvent effects of the butanoic and acetic acid derivatives in 23 different solvents was not well-described by the Lippert–Mataga equation, indicating a specific solvent effect due to intermolecular hydrogen bonding dominated fluorescence spectra. The emission wavelengths and fluorescence intensities were relatively stable in aqueous acetonitrile and aqueous methanol solutions. Their fluorescence intensities increased from low to high pH and also from high to low temperature. The acid dissociation constants of the three carbazole derivatives in their ground state were estimated to be in the range 3.2–4.8. The fluorescence intensities were also enhanced in the presence of β-cyclodextrin. The average stability constant of the inclusion complexes was 21.2 ± 13.4 at pH3 and 54.0 ± 7.0 at pH8. A molecular dynamics simulation indicated that the carbazole moiety was partially included into the β-cyclodextrin cavity leaving the carboxylic acid group exposed.     

Synthesis and characterization of V–C60/TiO2 photocatalysts designed for degradation of methylene blue

C₆₀/TiO₂ and V–C₆₀/TiO₂ composite photocatalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol–gel method. Fullerene had absorptive and semiconducting properties, and vanadium could enhance the photogenerated electron transfer. The V–C₆₀/TiO₂ composite shows a good photo-degradation activity. XRD patterns of the composites showed that the C₆₀/TiO₂ composite contained a mixture of anatase and rutile phase forms while the V–C₆₀/TiO₂ composite contained a typical single and clear anatase phase. The surface properties seen by SEM and FE-SEM present a characterization of the texture on C₆₀/TiO₂ and V–C₆₀/TiO₂ composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong V peaks for the V–C₆₀/TiO₂ composite. From the photocatalytic results, the excellent activity of the C₆₀/TiO₂ and V–C₆₀/TiO₂ composites for degradation of methylene blue under UV irradiation could be attributed to both the effects between photocatalysis of the supported TiO₂ and charge transfer of the fullerene, and the introduction of vanadium to enhance the photogenerated electrons transfer.     

Synthesis and dissolution behavior of β-TCP and HA/β-TCP composite powders

Calcium phosphate powders, β-TCP and biphasic HA/β-TCP, were synthesized by calcining the powders obtained from the co-precipitation method using Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄. The effects of the initial Ca/P ratio and pH of the solution on the phase evolution and in vitro dissolution behavior of the powders in a Ringer's solution were investigated. The Ca/P ratio of the resulting powders was strongly dependent on the pH of the solution and weakly dependent on the initial Ca/P ratio. Single phase TCP powder was obtained at pH=7.4 and the initial Ca/P ratio had a little effect on the resulting Ca/P ratio. Biphasic composite powders were prepared at pH=8.0 and the Ca/P ratio of resulting powder was controllable by adjusting the initial Ca/P ratio. TCP powder showed the highest dissolution rate in the Ringer's solution and biphasic composite powder exhibited an intermediate dissolution behavior between that of HA and TCP.     

Effects of ultrasound on adsorption and desorption of chromium(Ⅵ) on activated carbon

研究了超声波对活性炭吸附/脱附Cr(Ⅵ)的影响,结果表明：有无超声波作用下,活性炭对Cr(Ⅵ)的吸附率均随pH值的升高而减小,相对于无超声作用体系,超声作用下的相平衡向吸附量减小的方向移动,且pH值越大,其减小的幅度越大;当Cr(Ⅵ)初始浓度由20 mg·L^-1增至110 mg·L^-1时,超声波作用下的Cr(Ⅵ)去除率由99.9%降至79.8%,平衡吸附量则由3.3 mg·g^-1增至15.0 mg·g^-1,与无超声波作用下的效果接近,但无超声波作用时的吸附率持续上升至平衡,而超声波作用下的吸附率先快速增加至近平衡,再出现小幅下降后又缓慢增至平衡。脱附实验发现,无论有无超声作用,活性炭表面Cr(Ⅵ)在蒸馏水中的脱附率均很小;添加NaOH可显著改善脱附效果,脱附率随NaOH用量的增加而增加,且超声场中NaOH对脱附的促进作用显著高于非超声场中的效果。     

Synthesis of water dispersible reduced graphene oxide via supramolecular complexation with modified β-cyclodextrin

A noncovalent functionalization of the edges of reduced graphene oxide (RGO) with β-cyclodextrin-graft-hyperbranched polyglycerol (β-CD-g-HPG) was successfully performed via a host-guest interaction. The results showed that β-CD-g-HPG disperses the graphene sheets better than pure β-CD or HPG. The resulted supramolecular structure is stable in neutral water medium more than one week. However, in acidic medium the host-guest interaction is collapsed and graphene nanosheets precipitate.     

Preparation and investigation of acid–base composite membranes with modified graphitic carbon nanosheets for direct methanol fuel cells

The ethylenediamine-modified graphite oxide (EGO)-doped sulfonated poly (arylene ether ketone) (SPEEK) composite membranes have been prepared and developed for fuel cell applications in the present work. The base-modified EGO improves the dispersion of inorganic nanosheet in the polymer matrix and enhances proton conductivity by creating continuous conduction pathways. Furthermore, the methanol barrier property also be enhanced due to the nanosheet block the methanol-transport channels. EGO-filled membranes display improved dimensional stability, proton conductivity, and ethanol permeability than those using SPEEK control and graphite oxide (GO)-filled membranes. In the direct methanol fuel cells (DMFCs), the SPEEK/EGO-1.5 membrane displays the highest current density of 395.9 mA/cm² at 60°C, which is 1.6- and 1.4-fold higher than that of SPEEK (254.0 mA/cm²) and SPEEK/GO membrane (292.6 mA/cm²).     

Synthesis of magnetically modified palygorskite composite for immobilization of Candida sp. 99–125 lipase via adsorption

Magnetically modified palygorskite composites were synthesized withγ-Fe2O3 dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffrac-tion, transmission electron microscopy, and vibrating sample magnetometer. Candida sp. 99–125 lipase was immobilized on magnetic palygorskite composites by physical adsorption with enzyme loading of 41.5 mg·g-1 support and enzyme activity of 2631.6 U·(g support)-1. The immobilized lipase exhibit better thermal and broader pH stability and excellent reusability compared with free lipase.     

Synthesis of 3-oxalinolenic acid and β-oxidation-resistant 3-oxa-oxylipins

3-Oxalinolenic acid (3-oxa-9(Z), 12(Z), 15(Z)-octadecatrienoic acid or (6(Z), 9(Z), 12(Z)-pentadecatrienyloxy)acetic acid) was synthesized from 5(Z), 8(Z), 11(Z), 14(Z), 17(Z)-eicosapentaenoic acid by a sequence involving the C15 aldehyde 3(Z), 6(Z), 9(Z), 12(Z)-pentadecatetraenal as a key intermediate. Conversion of the aldehyde by isomerization and two steps of reduction afforded 6(Z), 9(Z), 12(Z)-pentadecatrienol, which was coupled to bromoacetate to afford after purification by HPLC >99%-pure 3-oxalinolenic acid in 10–15% overall yield. 3-Oxalinolenic acid was efficiently oxygenated by soybean lipoxygenase-1 into 3-oxa-13(S)-hydroperoxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid, and this hydroperoxide could be further converted chemically into 3-oxa-13(S)-hydroxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid and 3-oxa-13-oxo-9(Z), 11(E), 15(Z)-octadecatrienoic acid. The 3-oxa-hydroperoxide also served as the substrate for the plant enzymes allene oxide synthase, divinyl ether synthase, and hydroperoxide lyase to produce 3-oxa-12-oxo-10, 15(Z)-phytodienoic acid and other 3-oxa-oxylipins that were characterized by MS, 3-Oxalinolenic acid was not oxygenated by 9-lipoxygenase from tomato but was converted at a slow rate into 3-oxa-9(S)-hydroperoxy-10(E), 12(Z), 15(Z)-octadecatrienoic acid by recombinant maize 9-lipoxygenase. Recombinant α-dioxygenase-1 from Arabidopsis thaliana catalyzed the conversion of 3-oxalinolenic acid into a 2-hydroperoxide, which underwent spontaneous degradation into a mixture of 6,9,12-pentadecatrienol and 6,9,12-pentadecatrienyl formate. A novel α-dioxygenase from the moss Physcomitrella patens was cloned and expressed and was found to display the same activity with 3-oxalinolenic acid as Arabidopsis thaliana α-dioxygenase-1. Lipoxygenase-generated 3-oxa-oxylipins are resistant toward β-oxidation and have the potential for displaying enhanced biological activity in situations where activity is limited by metabolic degradation.