Preparation and electrochemical behavior of water-soluble inclusion complex of ferrocene with β-cyclodextrin polymer

A new water-soluble inclusion complex of ferrocene (Fc) with β-cyclodextrin polymer (β-CDP) was prepared by a facile strategy and characterized by ¹H NMR spectroscopy, elemental analysis, powder X-ray diffractometry, thermogravimetry, UV–vis spectroscopy and cyclic voltammetry. Compared with Fc and the inclusion complex of Fc with β-cyclodextrin (Fc-β-CD), the solubility of ferrocene-β-cyclodextrin polymer (Fc-β-CDP) was greatly enhanced due to the water-soluble β-CDP host. The ratio of β-cyclodextrin (β-CD) unit in β-CDP to Fc was determined as 1:1. At 25 °C, the dissociated constant of Fc-β-CDP was measured as 3.65 mM by UV–vis spectroscopy and cyclic voltammetry. The electrochemical properties of Fc-β-CDP in water were studied. The diffusion coefficients of oxidation state and reduction state were calculated as 3.52 × 10⁻⁷ cm² s⁻¹ and 3.93 × 10⁻⁷ cm² s⁻¹. The resulting value of standard rate constant was measured as 1.95 × 10⁻³ cm s⁻¹. The diffusion activation energy was calculated as 21.8 kJ mol⁻¹.     

Synthesis of poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) and its inclusion compound of β-cyclodextrin

Well-defined amphiphilic poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) (PNIPAM-b-PCL) block copolymers have been successfully prepared in two steps. PNIPAMOH is firstly prepared by using 4,4′-azobis(4-cyano-1-pentanol) as bifunctional initiator, and then PNIPAM-b-PCL copolymer is synthesized via a ring-opening polymerization of CL using PNIPAMOH as a macro-initiator in the presence of stannous octoate as a catalyst. The PNIPAM-b-PCL copolymers self-assemble to form spherical micelles of 50–130 nm in diameter, which can be modulated by the chain length of PCL block. The inclusion complexes are fabricated by treating PNIPAM-b-PCL with β-cyclodextrin and they are characterized by infrared and ¹H NMR spectroscopies, X-ray powder diffraction, thermogravimetric analysis, and differential scanning calorimetry.     

A novel bridged organocobaloxime/ β-cyclodextrin inclusion complex produced by a β-cyclodextrin induced reaction

A cobalt-to-oxime carbon bridged organocobaloxime/β-cyclodextrin inclusion complex has been formed in a β-cyclodextrin induced reaction, which was confirmed by X-ray structure analysis and FAB-MS.     

Characterization,stability, and pharmacokinetics of sibutramine/β-cyclodextrin inclusion complex

β-Cyclodextrin (β-CD) is widely used to increase the stability, solubility, and bioavailability of poorly soluble drugs because of the appropriate size of its cavity. Sibutramine is a neurotransmitter reuptake inhibitor that has been investigated as an oral anorexiant. Here we report the complexation of sibutramine base with β-CD and the stability, dissolution, and pharmacokinetic properties of the sibutramine/CD complex. The formation of sibutramine/β-CD inclusion complexes is confirmed using differential scanning calorimetry, X-ray diffractometry, and ¹H nuclear magnetic resonance. The thermal and photochemical stability of sibutramine is significantly improved by the complexation with β-CD, and the pharmacokinetic parameters (e.g., the plasma concentration, area under the curve, and maximum concentration of two active metabolites) for humans are comparable with those of the commercialized standard product (Reductil^®). Our study suggests that sibutramine/β-CD complexation can be of great use to increase the stability and biological efficacy of sibutramine base.     

Synthesis and controlled release of curcumin-β-cyclodextrin inclusion complex from nanocomposite poly(N-isopropylacrylamide/sodium alginate) hydrogels

Inclusion complex of curcumin with β-cyclodextrin (Cur-β-CD) was prepared using coprecipitation method. Stoichiometric ratio between curcumin and β-cyclodextrin was found to be 1:2 with an association constant of 3.80 × 10⁸ M⁻² using Benesi–Hildebrand method. Inclusion complex formation was confirmed by FTIR and DSC analyses. Water solubility of curcumin increased from 0.00122 to 0.721 mg mL⁻¹ with the inclusion complex formation. Release of the inclusion complex from the nanocomposite and conventional poly(N-isopropylacrylamide/sodium alginate hydrogels crosslinked by nanoclay and N,N′-methylenebis(acrylamide) (BIS), respectively, were investigated in simulated gastrointestinal conditions. Swelling ratio and cumulative release were dependent on the hydrogel composition and pH. At pH = 1.2, hydrogels showed the lowest release ratio, but at pH = 6.8 highest swelling ratios were attained. The swelling ratio and cumulative release decreased with increasing the nanoclay content in nanocomposite hydrogels. On the contrary, as the ratio of BIS in the conventional hydrogels increased, the swelling ratio and cumulative release increased. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47554.     

Preparation and characterization of thermo-sensitive microspheres with β-cyclodextrin groups

采用沉淀聚合机理,由一步法和两步法制备聚（N-异丙基丙烯酰胺-甲基丙烯酸缩水甘油酯） [P(NIPAM-co-GMA)]温敏性微球。其中一步法是同时加入所有反应物反应成微球,而两步法是先加NIPAM成微球,再加入GMA,最终均生成P(NIPAM-co-GMA)微球;再将改性的乙二胺代环糊精（EDA-β-CD）通过化学反应引入到P(NIPAM-co-GMA)微球结构中,制备得到聚（N-异丙基丙烯酰胺-甲基丙烯酸-2-羟丙基乙二胺基环糊精） [P(NIPAM-co-GMA/β-CD)]共聚高分子微球。分别用扫描电镜、红外光谱、控温激光粒度仪及光学显微镜对产物的形貌、结构和温敏特性进行了表征。结果表明,两种方法制备的微球均具有良好的单分散性和球形度,均能成功地固载β-环糊精（β-CD）基团,并且都有温度响应特性;但是,同一步法制备的微球相比,两步法制得的微球粒径明显较大,且微球固载有更多的β-CD。     

Preparation and characterization of polyseudorotaxanes based on adamantane-modified polybenzoxazines and β-cyclodextrin

β-Cyclodextrin (β-CD) forms inclusion complexes (ICs) with adamantane-modified benzoxazines (2 benzoxazine and 3 benzoxazine). These benzoxazines can readily penetrate into the CD's hydrophobic cavity, causing turbidity of their solutions, from which fine crystalline powders are obtained. We characterized these complexes by powder X-ray diffraction, ¹³C and ¹³C CP/MAS NMR spectroscopies, DSC, and TGA. The X-ray diffraction and solid-state ¹³C CP/MAS NMR spectroscopy indicate that the IC domains of the polypseudorotaxanes maintain their channel-type structures after the ring-opening curing reactions have occurred. Furthermore, DSC measurements indicate that complexing the adamantane-modified benzoxazine units with β-CDs result in stiffer main chains and, thus, higher glass transition temperature. TGA also indicates that the inclusion complexes have enhanced its thermal stability.     

Structure-retention correlation of isomeric bile acids in inclusion high-performance liquid chromatography with methyl β-cyclodextrin

The structure-retention correlation of various C₂₄ bile acid isomers was studied by the addition of methyl β-cyclodextrin (Me-β-CD) to mobile phases in reversed-phase high-performance liquid chromatography (HPLC). The compounds examined include a series of monosubstituted bile acids related to cholanoic acids differing from one another in the position and configuration of an oxygen-containing function (hydroxyl or oxo group) at the position C-3, C-6, C-7, or C-12 and the stereochemistry of the A/B-ring fusion (trans 5α-H and cis 5β-H) in the steroid nucleus. The inclusion HPLC with Me-β-CD was also applied to biologically important 4β- and 6-hydroxylated bile acids substituted by three to four hydroxyl groups in the 5β-steroid nucleus. These bile acid samples were converted into their fluorescence prelabeled 24-pyrenacyl ester derivatives and chromatographed on a Capcell Pak C₁₈ column eluted with methanol-water mixtures in the presence or absence of 5 mM Me-β-CD. The effects of Me-β-CD on the retentions of each compound were correlated quantitatively to the decreasing rate of capacity factors and the relative strength of host-guest inter-actions. On the basis of the retention data, specific and nonspecific hydrogen-bonding interactions between the bile acids and the Me-β-CD were discussed.     

Preparation and evaluation of a novel wound dressing sheet comprised of β-glucan–chitosan complex

A transparent wound dressing sheet was obtained by forming a complex between β-glucan and chitosan (CS). These materials were chosen for their biocompatible, bioabsorbable, and biodegradable properties, and they were expected to promote the therapeutic efficacy of the dressing by increasing the wound healing response. The therapeutic efficacy of the β-glucan–CS complex sheet as a wound dressing was evaluated in wounds created on the dorsal surfaces of mice. β-glucan–CS complex sheets demonstrated therapeutic efficacies comparable or superior to that of Beschitin®W, a commercial wound dressing made from CS. Additionally, the β-glucan–CS complex sheet did not dissolve during the application period, did not adhere to wounds, and was easy to remove. Cumulatively, these results indicate that β-glucan–CS complex sheets are a promising new wound dressing product.     

Crosslinking of β-cyclodextrin and combining with ammonium polyphosphate for flame-retardant polypropylene

This work presents the synthesis of crosslinked hexamethylene diisocyanate β-cyclodextrins (HDI-CDs) by reacting β-cyclodextrin (β-CD) with HDI as a crosslinking agent at different feed ratios. As a novel char-forming agent, the HDI-CDs are combined with ammonium polyphosphate (APP) and applied in polypropylene (PP) to form intumescent flame-retardant composites. The structure of HDI-CDs is characterized by Fourier transform infrared spectra (FTIR), ¹³C nuclear magnetic resonance spectroscopy, and nitrogen adsorption–desorption test. The thermogravimetric analysis (TGA) results indicate that HDI-CDs have better char-forming performance than β-CD. FTIR spectra, X-ray diffraction, and Raman spectra characterization demonstrate that the reaction between HDI-CDs and APP contributes to the formation of a more stable char layer than β-CD and APP. According to the results of TGA, scanning electron microscopy, limiting oxygen index (LOI), UL-94, and X-ray photoelectron spectroscopy test, when the crosslinking degree of HDI-CDs is high enough (not less than β-CD:HDI = 1:3.6), the PP/APP/HDI-CDs composites can form a compact and dense char layer during combustion. Among all composites, PP/APP/HDI-CD(4) shows the best flame-retardant performance, which can pass the UL 94 V-0 rating with an LOI value of 32.8% when the loading of flame retardants is 28 wt %. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48320.     

A facile and novel modification method of β-cyclodextrin and its application in intumescent flame-retarding polypropylene with melamine phosphate and expandable graphite

In this paper, a facile and novel method was adopted in tailoring β-cyclodextrin (CD), which can drastically improve its surface hydrophobicity and decrease its water solubility. By this way, the interfacial compatibility between CD and polypropylene (PP) is distinctly strengthened after modification that is well certified by scanning electron microscope (SEM) and molecular dynamics simulation, respectively. Surprisingly, the flame retardant properties of PP compositing with modified CD (CM) are slightly higher than that of PP/CD. Moreover, the flame retardancy of PP/CM system can be maintained after water treatment. Except that, the synergistic effect of expandable graphite (EG) on the flame retardant properties of PP/melamine phosphate (MP)/CM system were systematically investigated. It can be observed that when the content of EG is 10 wt.%, the flame retardant properties of PP system achieve 31.2 % in limiting oxygen index tests and pass UL-94 V-0 rating in vertical burning tests. And a potential condensed flame retardant mechanism was proposed in detail.     

Synthesis of a gold(I) complex with a (thio)phosphine-modified β-cyclodextrin

A gold(I) complex with the bidentate ligand 6^A-S-[2-(diphenylphosphino)-ethyl]thio-β-cyclodextrin has been prepared. The complex has been studied by mass spectrometry as well as IR and NMR spectroscopy. The influence of the ligand:metal ratio on the coordination mode has also been examined.     

Formation mechanism of β-Sialon with different morphologies based on DFT calculation and its effect on the performance of refractory composites

β-Sialon with whisker-like, columnar, and plate-shaped structures was successfully synthesized with Al₂O₃–C refractory compositions. In the presence of a catalyst, the preferential growth face of columnar β-Sialon was (100), whereas plate-like β-Sialon preferred (101) and (111). DFT calculations demonstrated that the SiO adsorption energy on the (100), (101), and (111) faces of β-Sialon crystal were –34.95, –52.88, and –45.08 eV, respectively. Therefore, the (101) and (111) faces were more stable in Al-rich β-Sialon. With the increase in catalyst content, the Si-rich Si–Al–O–N liquid phases, which contributed to the generation of columnar β-Sialon, were converted into the Al-rich Al–Si–O–N system that was conducive to the formation of plate-like β-Sialon. Compared to the sample without the catalyst, the CMOR and HMOR of the specimen were increased by 45.07% and 60.47%, respectively, with the addition of Fe₂O₃. This was attributed to the formation of β-Sialon with a one- or two- dimensional shape.     

Physical properties of poly(?-caprolactone) coalesced from its α-cyclodextrin inclusion compound

Poly(?-caprolactone) (PCL) is a biodegradable/bioabsorbable polyester used in such biomedical applications as drug delivery and suture manufacturing. PCL has relatively poor physical properties, however, limiting its load-bearing applications. In this work, PCL was processed with α-cyclodextrin (α-CD) to form an inclusion complex (IC). The host α-CD was then stripped away to yield bulk PCL with largely extended, un-entangled polymer chains, a process referred to as coalescence. The changes in thermal, physical, and solid-state rheological properties resulting from this coalescence process were examined. It was found that elongating and un-entangling the PCL chains in this manner resulted in substantial increases in melt-crystallization temperatures, T_cs, up to 25 °C, depending on the cooling rate from the melt. Coalescence also increased the elastic storage modulus, decreased tan δ, increased the average hardness and Young’s modulus by 33 and 53%, respectively, and produced a closer packing of chains in the non-crystalline sample regions, without affecting the overall PCL crystallinity. Interestingly, the reorganized PCL chains in the non-crystalline regions of coalesced samples did not revert to the normal randomly-coiled entangled melt even after heating well above T_m (90 °C) for a month. The addition of small amounts (a few wt%) of coalesced PCL was also found to effectively nucleate the melt-crystallization of as-received PCL. Thus, the semi-crystalline morphology of PCL may be controlled by melt-processing with coalesced PCL added as a nucleant, that is not only necessarily non-toxic and biodegradable/bioabsorbable, but is also chemically compatible.     

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.     

Compatibilizing effect of β-cyclodextrin in RDP/phosphorus-containing polyacrylate composite emulsion and its synergism on the flame retardancy of the latex film

Resorcinol bis (diphenyl phosphate)/β-cyclodextrin/phosphorus-containing polyacrylate (RDP/β-CD/P-PA) composite emulsion was prepared by using β-CD as a compatibilizer. The flame retardancy of the composite latex film was investigated by microscale combustion calorimetry (MCC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Mechanical properties of the composite latex films were also studied and a possible compatibilizing mechanism was proposed. The results showed that the mechanical properties and flame retardancy of the RDP/β-CD/P-PA composite latex film were enhanced compared to the RDP/P-PA latex film. When the β-CD content increased from 0 to 10 wt%, the pendulum hardness of the RDP/β-CD/P-PA composite latex film increased from 0.18 to 0.54, and the peak heat release rate decreased from 382.1 to 311.9 W/g. TGA and MCC results demonstrated that both the char residual and the quality of the char formation were improved by the introduction of β-CD.     

Synthesis and characterization of ABn-type α-cyclodextrin monomer and its hyperbranched polymer

To obtain well-defined structures of α-cyclodextrin (α-CD) based monomer and its hyperbranehed polymer (HBP), a modified α-CD molecule with one electron-rich alkene and many electron-poor acrylates was first prepared through the esterification reaction between mono-ester undecylenic acid-α-CD and acrylic acid. It was then utilized as an AB_n-type monomer for subsequent ADMET polymerization between alkene and acrylate using the second generation Hoveyda-Grubbs catalyst in homogeneous water/organic [D₂O/(CD₃)₂CO] mixtures via acyclic diene metathesis (ADMET) polymerization. A novel cyclodextrin-based HBP was obtained in prolonged reaction time. The monomer and HBP were characterized by NMR, elemental analysis, FTIR, and MALDI-TOF MS measurements. It was found that the actual molecular structures of both monomer and polymer were identical with the designed structures. The produced polymers have molecular weights within 13.2 and 56.3 kDa, and their polydispersity indices range from 2.78 to 2.63 by multiangle laser light scattering-gel permeation chromatography. The degree of branching was determined by ¹H NMR spectroscopy and the values ranges from 0.41 to 0.52.     

Study on extraction kinetics of α-cyclopentylmandelic acid enantiomers with hydroxyethyl-β-cyclodextrin as chiral selector

In this work,the kinetic study on reactive extraction ofα-cyclopentylmandelic acid(α-CPMA)enantiomers was performed in a Lewis cell using hydroxyethyl-β-cyclodextrin(HE-β-CD)as chiral selector.The enantioselective complexation equilibrium between HE-β-CD andα-CPMA enantiomers was studied by phase solubility method.The important process parameters affecting the initial extraction rate were separately studied and the reaction rate equations were deduced.The optimal conditions for kinetic study were as follows:stirring speed of 75 r·min~(-1),interfacial area of 12.56 cm~2,pH of 2.5,initial HE-β-CD concentration of 0.05 mol·L~(-1),initialα-CPMA concentration of 5 mmol·L~(-1),and temperature of 278 K.The reaction has been found to be first order inα-CPMA and second order in HE-β-CD with the forward rate constants of 2.056×10~(-3)m~6·mol~(-2)·s~(-1)and 1.459×10~(-3)m~6·mol~(-2)·s~(-1)for(S)-α-CPMA and(R)-α-CPMA,respectively.The complexation equilibrium constants were evaluated as 61 L·mol~(-1) and 117 L·mol~(-1)for(S)-α-CPMA and(R)-α-CPMA,and the intrinsic enantioselectivity is estimated as 1.92.     

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.     

Super porous α-, β-, γ-cyclodextrin cryogels with high active agent loading and controllable release profiles

Cyclodextrins (CDs) are truncated cone-like structures that are natural cyclic oligosaccharides. Here, a simple preparation method for super porous poly(α-CD), poly(β-CD), and poly(γ-CD) cryogels crosslinking with divinyl sulfone at 150%, 100% and 125% mole ratios with respect to the α-CD, β-CD, and γ-CD molecules, respectively, under cryogenic conditions, is reported. The interconnected homogeneous pore distribution of CD-based cryogels with pore sizes in the range of 5–100 μm is confirmed by SEM analysis. The CD-based cryogels weighing 10 mg are determined as hemocompatible with <1% hemolysis ratios and >79% blood clotting indexes; whereas the same materials weighing 1 mg are biocompatible with >75% cell viability on L929 fibroblasts. Additionally, active agent adsorption/delivery efficiencies of CD-based cryogels utilizing two active agents, Bisphenol A (BPA, a carcinogenic compound) and Curcumin (CUR, a polyphenolic compound), are individually evaluated. It was revealed that p(γ-CD) cryogels exhibited the highest active agent loading capacity for BPA, 87 ± 13 mg/g, whereas p(α-CD) cryogels showed the highest loading capacity for CUR, 136 ± 4 mg/g. Moreover, the active agent release from p(α-CD), p(β-CD), and p(γ-CD) cryogel networks at pH 7.4 and 37°C were determined as 40.6 ± 2, 35.3 ± 2, and 34 ± 1 mg/g for BPA, and 1.07 ± 0.2, 1.27 ± 0.1, and 1.37 ± 0.1 mg/g for CUR, respectively, within 96 h.