Azobenzene-grafted carboxymethyl cellulose hydrogels with photo-switchable, reduction-responsive and self-healing properties for a controlled drug release system.

In this study, multifunctional hydrogels containing host-guest complex formation between azobenzene-grafted carboxymethyl cellulose (CMC-Azo) and ß-cyclodextrin (CD) dimers connected by disulfide bonds with agarose for structural support were prepared. The obtained hydrogels exhibited self-healing properties by host-guest complexation as well as gel-sol phase transition in response to ultraviolet (UV) light and reducing agents. Photo-switchable properties of the hydrogels depend on changes in the complex formation of CD-dimers through the trans(450 nm) to cis(365 nm) photo-isomerization of azobenzene. The tensile and strain sweep tests confirmed that the hydrogel's self-healing ability was 79.44% and 81.59%, respectively. In addition, drug release from the hydrogels was controlled to accelerate to 80% in 3 h using UV light or reducing agent. Since the suggested photo-switchable, reduction-responsive, and self-healable hydrogels are non-cytotoxic, they can be potentially applied as biomedical materials in the development of hydrogel-based drug release systems.

Production of L-Theanine Using Escherichia coli Whole-Cell Overexpressing γ-Glutamylmethylamide Synthetase with Bakers Yeast.

L-Theanine, found in green tea leaves has been shown to positively affect immunity and relaxation in humans. There have been many attempts to produce L-theanine through enzymatic synthesis to overcome the limitations of traditional methods. Among the many genes coding for enzymes in the L-theanine biosynthesis, glutamylmethylamide synthetase (GMAS) exhibits the greatest possibility of producing large amounts of production. Thus, GMAS from Methylovorus mays No. 9 was overexpressed in several strains including vectors with different copy numbers. BW25113(DE3) cells containing the pET24ma::gmas was selected for strains. The optimal temperature, pH, and metal ion concentration were 50°C, 7, and 5 mM MnCl2, respectively. Additionally, ATP was found to be an important factor for producing high concentration of L-theanine so several strains were tested during the reaction for ATP regeneration. Bakers yeast was found to decrease the demand for ATP most effectively. Addition of potassium phosphate source was demonstrated by producing 4-fold higher L-theanine. To enhance the conversion yield, GMAS was additionally overexpressed in the system. A maximum of 198 mM L-theanine was produced with 16.5 mmol/l/h productivity. The whole-cell reaction involving GMAS has greatest potential for scale-up production of L-theanine.

Preparation of Succinoglycan Hydrogel Coordinated With Fe3+ Ions for Controlled Drug Delivery.

Hydrogel materials with a gel-sol conversion due to external environmental changes have potential applications in a wide range of fields, including controlled drug delivery. Succinoglycans are anionic extracellular polysaccharides produced by various bacteria, including Sinorhizobium species, which have diverse applications. In this study, the rheological analysis confirmed that succinoglycan produced by Sinorhizobium meliloti Rm 1021 binds weakly to various metal ions, including Fe2+ cations, to maintain a sol form, and binds strongly to Fe3+ cations to maintain a gel form. The Fe3+-coordinated succinoglycan (Fe3+-SG) hydrogel was analyzed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, circular dichroism (CD), and field-emission scanning electron microscopy (FE-SEM). Our results revealed that the Fe3+ cations that coordinated with succinoglycan were converted to Fe2+ by a reducing agent and visible light, promoting a gel-sol conversion. The Fe3+-SG hydrogel was then successfully used for controlled drug delivery based on gel-sol conversion in the presence of reducing agents and visible light. As succinoglycan is nontoxic, it is a potential material for controlled drug delivery.

Utilization of Water-Soluble Aminoethylamino-ß-Cyclodextrin in the Pfitzinger Reaction-Catalyzed to the Synthesis of Diversely Functionalized Quinaldine.

In this study we describe the use of an aminoethylamino-ß-cyclodextrin (AEA-ß-CD) as a supramolecular homogeneous catalyst for the synthesis of a series of diversely substituted quinaldine derivatives which are medicinally important, via Pfitzinger reaction. This supramolecular catalyst exhibited remarkable catalytic activity with high substrate scope to achieve the synthetic targets in good to excellent yield, 69-92%. The structural and morphological properties of the synthesized AEA-ß-CD were determined through MALDI-TOF mass spectrometry, NMR, FT-IR, and SEM analysis. Possible reaction mechanisms were determined through molecular host-guest complexation and proposed based on 2D NMR (ROESY) spectroscopy, FT-IR, FE-SEM, and DSC.

Succinoglycan dialdehyde-reinforced gelatin hydrogels with toughness and thermal stability.

Pure gelatin hydrogel (PG) has limited practical applications due to their thermal instability and unfavorable mechanical properties. To overcome these limitations, dually crosslinked hydrogels were developed by imparting chemical crosslinking to existing physically crosslinked gelatin hydrogel networks using succinoglycan dialdehyde (SGDA) as a macromolecular crosslinker. SGDA-reinforced gelatin hydrogels (SGDA/Gels) displayed an 11 times higher compressive stress under identical deformation strain and a 1040% improvement in storage modulus (G') than PG. In addition, chemical crosslinking induced by SGDA increased the thermal stability of SGDA/Gels, such that they did not decompose at 60 °C, as confirmed by oscillatory temperature ramp experiments. The newly synthesized SGDA/Gels with reinforced networks and thermal stability exhibit potential for long-term use as controlled drug delivery carriers and 3D cell culture scaffolds for tissue engineering.

Mono-6-Deoxy-6-Aminopropylamino-ß-Cyclodextrin on Ag-Embedded SiO2 Nanoparticle as a Selectively Capturing Ligand to Flavonoids.

It has been increasingly important to develop a highly sensitive and selective technique that is easy to handle in detecting levels of beneficial or hazardous analytes in trace quantity. In this study, mono-6-deoxy-6-aminopropylamino-ß-cyclodextrin (pr-ß-CD)-functionalized silver-assembled silica nanoparticles (SiO2@Ag@pr-ß-CD) for flavonoid detection were successfully prepared. The presence of pr-ß-CD on the surface of SiO2@Ag enhanced the selectivity in capturing quercetin and myricetin among other similar materials (naringenin and apigenin). In addition, SiO2@Ag@pr-ß-CD was able to detect quercetin corresponding to a limit of detection (LOD) as low as 0.55 ppm. The relationship between the Raman intensity of SiO2@Ag@pr-ß-CD and the logarithm of the Que concentration obeyed linearity in the range 3.4-33.8 ppm (R2 = 0.997). The results indicate that SiO2@Ag@pr-ß-CD is a promising material for immediately analyzing samples that demand high sensitivity and selectivity of detection.

Cyclodextrin functionalized agarose gel with low gelling temperature for controlled drug delivery systems.

Conventional agaroses with high gelling temperature are limited to apply to the field of drug delivery. In this study, ß-cyclodextrin (ßCD) functionalized agarose (CFA) with low gelling temperature was successfully prepared from ethylenediamine-functionalized agarose using mono-succinyl ßCD. The gelling temperature of CFA dramatically decreased to 26.7 °C from 65 °C and the melting temperature declined from 95 °C to 66.1 °C. Upon drug loading, CFA can be used at 30 °C because of its low gelling temperature compared to agarose. CFA gel could be used both for bovine serum albumin as a full release, and for the doxorubicin (DOX) for sustained release, via inclusion complexation of ßCD. Furthermore, cytotoxicity tests revealed that CFA was noncytotoxic. DOX in the CFA gel could retain the anti-cancer activity. Newly synthesized CFA with low gelling temperature offer a new means for the development of hydrogel-based delivery systems for a variety of therapeutic drugs.

Solubility Enhancement of Atrazine by Complexation with Cyclosophoraose Isolated from Rhizobium leguminosarum biovar trifolii TA-1.

Rhizobium leguminosarum biovar trifolii TA-1, a kind of soil bacteria, produces cyclosophoraoses (Cys). Cyclosophoraoses contain various ring sizes with degrees of polymerization ranging from 17 to 23. Atrazine is a hardly-soluble herbicide that contaminates soil and drinking water, and remains in soil for a long time. To remove this insoluble contaminant from aqueous solutions, we have enhanced the solubility of atrazine by complexation with Cys. The complex formation of Cys and atrazine was confirmed using ¹H nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), field emission scanning electron microscopy (FE-SEM), rotating frame nuclear overhauser spectroscopy (ROESY), and molecular modeling studies. The aqueous solubility of atrazine was enhanced 3.69-fold according to the added concentrations (20 mM) of Cys, compared to the 1.78-fold enhancements by ß-cyclodextrin (ß-CD). Cyclosophoraoses as an excellent solubility enhancer with long glucose chains that can effectively capture insoluble materials showed a potential application of microbial polysaccharides in the removal of hazardous hardly-soluble materials from aqueous solutions in the fields of biological and environmental industry.

Triple-crosslinkedß-cyclodextrin oligomer self-healing hydrogel showing high mechanical strength, enhanced stability and pH responsiveness.

A novel self-healing hydrogel was prepared from a cationic ß-cyclodextrin oligomer allyl ether [C(ßCD-OM)AE] using a triple cross-linking strategy combining electrostatic interaction, host-guest complexation, and CC bonds as the macrocrosslinker. Here, the C(ßCD-OM)AE@Ad gel was successfully prepared by polymerization of synthesized C(ßCD-OM)AE, 1-adamantyl acrylate, and acrylic acid. The triple cross-linked hydrogel shows multi-functionality of high mechanical strength, enhanced stability, cytocompatibility, pH responsiveness as well as self-healing ability. Based on the cooperative and synergetic forces of non-covalent and covalent bonds, the C(ßCD-OM)AE@Ad gel shows a high tensile strain up to 1,590%, and the self-healed gel could restore up to 84% of its initial length within 24 h. Furthermore, drug release in the hydrogel was controlled by the surrounding pH and slowly released. The present work reveals the cooperativity of multiple cross-links for a 3D structured polymeric material, and the developed self-healable hydrogel can possibly be applied in various biomedical applications.

Efficient Adsorption on Benzoyl and Stearoyl Cellulose to Remove Phenanthrene and Pyrene from Aqueous Solution.

Benzoyl and stearoyl acid grafted cellulose were synthesized by a simple chemical grafting method. Using these as chemical adsorbents, polycyclic aromatic hydrocarbons (PAHs), like pyrene and phenanthrene, were effectively removed from aqueous solution. The structural and morphological properties of the synthesized adsorbents were determined through X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared (FT-IR), FE-SEM, and NMR analyses. Through this method, it was confirmed that benzoyl and stearoyl acid were successfully grafted onto the surface of cellulose. The 5 mg of stearoyl grafted cellulose (St⁻Cell) remove 96.94% pyrene and 97.61% phenanthrene as compared to unmodified cellulose, which adsorbed 1.46% pyrene and 2.99% phenanthrene from 0.08 ppm pyrene and 0.8 ppm phenanthrene aqueous solution, suggesting that those results show a very efficient adsorption performance as compared to the unmodified cellulose.

Carboxymethyl cyclosophoraoses as a flexible pH-responsive solubilizer for pindolol.

In the present study, cyclosophoraoses (CyS) (ß-1,2 linked cyclic glucans, with glucopyranose units ranging from 17 to 23) isolated from Rhizobium leguminosarum biovar viciae VF-39 were modified with carboxymethyl (CM) groups, and the pH-sensitive complexation of CM CyS with pindolol was investigated. The solubility of pindolol increased 32-fold by its complexation with 5mM CM CyS at pH 10, whereas it shows no significant change at pH 3. Pindolol, a ß-adrenergic blocking agent, has a hydrophobic nature at non-ionized state, and CM CyS could solubilize efficiently pindolol in a high alkaline solution. The carboxymethylation of flexible CyS allows them to present a more suitable cavity for the hydrophobic pindolol at pH 10, which is differentiated from CM ß-cyclodextrin (ß-CD). It can be interpreted as that the anionic repulsion effectively modulates the flexible and distorted conformation of CyS rather than rigid annular shape of ß-CD. Resultingly, the highly solubilized CM CyS/pindolol complex was characterized by UV-vis, T1 relaxation, ROESY, DOSY NMR spectroscopy, FT-IR spectroscopy, SEM, and molecular modeling studies. The antioxidant activity of pindolol was also improved 260% in the complex compared to free pindolol. The use of flexible host molecules with pH-responsive substituents would be applied in the development of smart systems for sensing or in biomedical fields.

Carbohydrate-Based Host-Guest Complexation of Hydrophobic Antibiotics for the Enhancement of Antibacterial Activity.

Host-guest complexation with various hydrophobic drugs has been used to enhance the solubility, permeability, and stability of guest drugs. Physical changes in hydrophobic drugs by complexation have been related to corresponding increases in the bioavailability of these drugs. Carbohydrates, including various derivatives of cyclodextrins, cyclosophoraoses, and some linear oligosaccharides, are generally used as host complexation agents in drug delivery systems. Many antibiotics with low bioavailability have some limitations to their clinical use due to their intrinsically poor aqueous solubility. Bioavailability enhancement is therefore an important step to achieve the desired concentration of antibiotics in the treatment of bacterial infections. Antibiotics encapsulated in a complexation-based drug delivery system will display improved antibacterial activity making it possible to reduce dosages and overcome the serious global problem of antibiotic resistance. Here, we review the present research trends in carbohydrate-based host-guest complexation of various hydrophobic antibiotics as an efficient delivery system to improve solubility, permeability, stability, and controlled release.

Solubility and bioavailability enhancement of ciprofloxacin by induced oval-shaped mono-6-deoxy-6-aminoethylamino-ß-cyclodextrin.

Ciprofloxacin is a broad-spectrum fluoroquinolone antibiotic used to treat bacterial infections; however, its limited aqueous solubility inhibits its broader clinical uses. This study investigated the complexation effect of mono-6-deoxy-6-aminoethylamino-ß-cyclodextrin on the aqueous solubility and bioavailability of ciprofloxacin. During complexation, the oval-shaped cavity induced by mono-aminoethylamine substitution on the primary rim of ß-cyclodextrin, was considered to be a key factor according to NMR spectroscopy and molecular modeling studies. The ciprofloxacin with mono-6-deoxy-6-aminoethylamino-ß-cyclodextrin complex was characterized using FE-SEM, DSC, FT-IR, T1 relaxation, 2D NOESY, and DOSY NMR spectroscopy and molecular modeling studies. The solubility property of ciprofloxacin complexed with mono-6-deoxy-6-aminoethylamino-ß-cyclodextrin was enhanced by seven-fold compared to that of pure ciprofloxacin. Furthermore antibacterial activity of that complex against methicillin-resistant Staphylococcus aureus was enhanced and it clearly showed the growth inhibition. The mono-6-deoxy-6-aminoethylamino-ß-cyclodextrin has the potential to be utilized for other oblong guest molecules besides ciprofloxacin based on the novel induced elliptical cavity.

SERS-Based Flavonoid Detection Using Ethylenediamine-ß-Cyclodextrin as a Capturing Ligand.

Ethylenediamine-modified ß-cyclodextrin (Et-ß-CD) was immobilized on aggregated silver nanoparticle (NP)-embedded silica NPs (SiO2@Ag@Et-ß-CD NPs) for the effective detection of flavonoids. Silica NPs were used as the template for embedding silver NPs to create hot spots and enhance surface-enhanced Raman scattering (SERS) signals. Et-ß-CD was immobilized on Ag NPs to capture flavonoids via host-guest inclusion complex formation, as indicated by enhanced ultraviolet absorption spectra. The resulting SiO2@Ag@Et-ß-CD NPs were used as the SERS substrate for detecting flavonoids, such as hesperetin, naringenin, quercetin, and luteolin. In particular, luteolin was detected more strongly in the linear range 10-7 to 10-3 M than various organic molecules, namely ethylene glycol, ß-estradiol, isopropyl alcohol, naphthalene, and toluene. In addition, the SERS signal for luteolin captured by the SiO2@Ag@Et-ß-CD NPs remained even after repeated washing. These results indicated that the SiO2@Ag@Et-ß-CD NPs can be used as a rapid, sensitive, and selective sensor for flavonoids.

Pentynyl Ether of ß-Cyclodextrin Polymer and Silica Micro-Particles: A New Hybrid Material for Adsorption of Phenanthrene from Water.

A new hybrid material for the removal of polycyclic aromatic hydrocarbons (PAH) from water was prepared by the polymerization of pentynyl beta-cyclodextrin (PyßCD) and silica micro-particles (SMP). Phenanthrene, being one of the important members of the PAH family and a potential risk for environmental pollution, was selected for this study. Results show that phenanthrene removal efficiency of the SMP was improved significantly after hybridization with PyßCD-polymer. Approximately 50% of the phenanthrene was removed in the first 60 min and more than 95% was removed in less than 7 h when 25 mL of the 2 ppm aqueous phenanthrene solution was incubated with the 100 mg of SMP-PyßCD-polymer material. Infrared spectroscopy and thermal gravimetric analysis show that the enhanced efficiency of the SMP-PyßCD-polymer compared to the unmodified SMP was due to the formation of the inclusion complexation of phenanthrene with the PyßCD. These results indicate that SMP-PyßCD polymers have a potential to be applied as molecular filters in water purification systems and also for waste water treatment.

Enhancing bio-availability of ß-naphthoflavone by supramolecular complexation with 6,6'-thiobis(methylene)-ß-cyclodextrin dimer.

The aryl hydrocarbon receptor (AhR) is a ligand activated transcriptional regulator, which governs key biological processes including detoxification of carcinogens. ß-Naphthoflavone (ß-NF) is a non-toxic flavonoid, and a potent AhR agonist. Thus, ß-NF can induce the representative detoxifying enzyme cytochrome P4501A1, thereby enhancing the detoxification potential. However, its low water solubility hampers the use. We found that supramolecular complexation of ß-NF with the synthetic 6,6'-thiobis(methylene)-ß-cyclodextrin (ß-CD-S) dimer significantly enhanced ß-NF's role as an AhR agonist. The water solubility of ß-NF was increased to 469 fold by effective supramolecular complexation with the ß-CD-S dimer, and caused significant induction of cytochrome P4501A1. Stable formation of the supramolecular complex of ß-NF with ß-CD-S-dimer was verified by various analyses. In summary, supramolecular complexation of ß-NF with ß-CD-S dimer greatly enhanced bio-availability of ß-NF as an AhR agonist. Our findings provide an easy, non-destructive, and alternative approach to enhance the bio-availability of therapeutics.

Synthesis, Characterization, and Retinol Stabilization of Fatty Amide-ß-cyclodextrin Conjugates.

Amphiphilic cyclodextrin (CD) has been the object of growing scientific attention because of its two recognition sites, the cavity and the apolar heart, formed by self-assembly. In the present study, mono[6-deoxy-6-(octadecanamido)]-ß-CD and mono[6-deoxy-6-(octadecenamido)]-ß-CD were successfully synthesized by reacting mono-6-amino-6-deoxy-ß-CD with N-hydroxysuccinimide esters of corresponding fatty acids in DMF. The structures were analyzed using nuclear magnetic resonance spectroscopy and mass spectrometry. The amphiphilic ß-CDs were able to form self-assembled nano-vesicles in water, and the supramolecular architectures were characterized using fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. Using the cavity-type nano-vesicles, all-trans-retinol was efficiently encapsulated; it was then stabilized against the photo-degradation. Therefore, the present fatty amide-ß-CD conjugate will be a potential molecule for carrier systems in cosmetic and pharmaceutical applications.

ß-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons.

We designed a ß-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric ß-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of ß-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The ß-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10(-7) M to 10(-2) M with a low detection limit of 10(-8) M. Also, the ß-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the ß-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors.

Functionalized ß-cyclodextrin as supramolecular ligand and their Pd(OAc)2 complex: highly efficient and reusable catalyst for Mizoroki-Heck cross-coupling reactions in aqueous medium.

A novel class of water soluble palladium complexes with recognition abilities based on functionalized ß-cyclodextrin has been synthesized. The complex demonstrated high catalytic activity and a supramolecular platform for phosphine-free Mizoroki-Heck cross-coupling reactions in water. The efficient arylation of alkenes was carried out using different iodo- and bromo-arenes with good to excellent yields (up to 96%). The advantages, like recyclability of catalysts, operational simplicity and accessibility in aqueous medium, make this protocol eco-friendly.

Regioselective self-acylating cyclodextrins in organic solvent.

Amphiphilic cyclodextrins have been synthesized with self-acylating reaction using vinyl esters in dimethylformamide. In the present study no base, catalyst, or enzyme was used, and the structural analyses using thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry show that the cyclodextrin is substituted preferentially by one acyl moiety at the C2 position of the glucose unit, suggesting that cyclodextrin functions as a regioselective catalytic carbohydrate in organic solvent. In the self-acylation, the most acidic OH group at the 2-position and the inclusion complexing ability of cyclodextrin were considered to be significant. The substrate preference was also observed in favor of the long-chain acyl group, which could be attributed to the inclusion ability of cyclodextrin cavity. Furthermore, using the model amphiphilic building block, 2-O-mono-lauryl ß-cyclodextrin, the self-organized supramolecular architecture with nano-vesicular morphology in water was investigated by fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. The cavity-type nano-assembled vesicle and the novel synthetic methods for the preparation of mono-acylated cyclodextrin should be of great interest with regard to drug/gene delivery systems, functional surfactants, and carbohydrate derivatization methods.