Evaluation of Cytotoxicity of Hyaluronic Acid/Chitosan/Bacterial Cellulose-Based Membrane.

Novel wound dressing materials are required to non-cytotoxic with a viable cell ratio of above 92%. Herein, the cytotoxicity of hyaluronic acid/chitosan/bacterial cellulose-based (BC(CS/HA)) membranes are evaluated and compared to that of alginate/chitosan/bacterial cellulose-based (BC(CS/Alg)) membranes was investigated. Multilayer membranes with up to ten CS/HA or CS/Alg layers were prepared using the layer-by-layer (LBL) method. Scanning electron microscopy showed that the diameters of the fibers in the BC(CS/Alg) and BC(CS/HA) membranes were larger than those in a BC membrane. The cytotoxicity was analyzed using BALB-3T3 clone A31 cells (mouse fibroblasts, 1 × 104 cells/well). The BC(CS/HA)5 and BC(CS/HA)10 membranes exhibited high biocompatibility, with the cell viabilities of 94% and 87% at 5 d, respectively, compared to just 82% for the BC(CS/Alg)5 and BC(CS/Alg)10 membranes with same numbers of layers. These results suggested that BC(CS/HA)5 is a promising material for wound dressings.

Preparation and Characterization of Crosslinked Electrospun Gelatin Fabrics via Maillard Reactions.

In this study, nonwoven gelatin (Gel) fabrics crosslinked using N-acetyl-D-glucosamine (GlcNAc) were characterized and compared with those crosslinked using methylglyoxal (MG) and by thermal dehydration. We prepared Gel with 25% concentration along with Gel/GlcNAc and Gel/MG with a GlcNAc-to-Gel ratio of 5% and MG-to-Gel ratio of 0.6%. A high voltage of 23 kV, solution temperature of 45 °C, and distance of 10 cm between the tip and the collector were applied during electrospinning. The electrospun Gel fabrics were crosslinked by heat treatment at 140 and 150 °C for 1 d. The electrospun Gel/GlcNAc fabrics were treated at 100 and 150 °C for 2 d, while the Gel/MG fabrics were heat-treated for 1 d. The Gel/MG fabrics exhibited higher tensile strength and lower elongation than the Gel/GlcNAc fabrics. Overall, Gel/MG crosslinked at 150 °C for 1 d showed a significant enhancement in tensile strength, high hydrolytic degradation, and excellent biocompatibility, with cell viability percentages of 105 and 130% at 1 and 3 d, respectively. Therefore, MG is a promising Gel crosslinker.

Microwave-Assisted Incorporation of AgNP into Chitosan-Alginate Hydrogels for Antimicrobial Applications.

Herein, improving the antibacterial activity of a hydrogel system of sodium alginate (SA) and basic chitosan (CS) using sodium hydrogen carbonate by adding AgNPs was investigated. SA-coated AgNPs produced by ascorbic acid or microwave heating were evaluated for their antimicrobial activity. Unlike ascorbic acid, the microwave-assisted method produced uniform and stable SA-AgNPs with an optimal reaction time of 8 min. Transmission electron microscopy (TEM) confirmed the formation of SA-AgNPs with an average particle size of 9 ± 2 nm. Moreover, UV-vis spectroscopy confirmed the optimal conditions for SA-AgNP synthesis (0.5% SA, 50 mM AgNO3, and pH 9 at 80 °C). Fourier transform infrared (FTIR) spectroscopy confirmed that the -COO- group of SA electrostatically interacted with either the Ag+ or -NH3+ of CS. Adding glucono-δ-lactone (GDL) to the mixture of SA-AgNPs/CS resulted in a low pH (below the pKa of CS). An SA-AgNPs/CS gel was formed successfully and retained its shape. This hydrogel exhibited 25 ± 2 mm and 21 ± 1 mm inhibition zones against E. coli and B. subtilis and showed low cytotoxicity. Additionally, the SA-AgNP/CS gel showed higher mechanical strength than SA/CS gels, possibly due to the higher crosslink density. In this work, a novel antibacterial hydrogel system was synthesized via 8 min of microwave heating.

Erratum: Fabrication of Chitin/Poly(butylene succinate)/Chondroitin Sulfate Nanoparticles Ternary Composite Hydrogel Scaffold for Skin Tissue Engineering. Polymers, 2014, 6, 2974⁻2984.

The authors wish to make a change to the published paper [...].

Preparation of thin-film electrolyte from chitosan-containing ionic liquid for application to electric double-layer capacitors.

A novel thin-film electrolyte (TFE) based on chitosan (CS) with 1­ethyl­3­methylimidazolium tetrafluoroborate (EMImBF4) was prepared by a new procedure for use as a solid electrolyte in electric double-layer capacitors (EDLCs). In this system, EMImBF4 plays important roles as both a dissolving solution and a charge carrier for EDLC application. By analyzing and characterizing the obtained products, the CS-TFEs showed a surface without CS/EMImBF4 phase separation and with high thermal stability and good tensile properties. The electrochemical properties were measured as the charge-discharge performance, the discharge capacitance, and alternating-current impedance. A test cell with CS-TFE with a calculated dry thin-film content of 80 wt% EMImBF4 showed a comparable IR drop and higher discharge capacitance than a liquid-phase EMImBF4 system and also showed low electrode/electrolyte interfacial resistance. Consequently, this novel CS-TFE is suitable for high-performance EDLCs and improves the safety of such devices.

Preparation of polyelectrolyte complex gel of sodium alginate with chitosan using basic solution of chitosan.

In general, chitosan (CS) cannot be dissolved in basic solution, however it was found that the basic CS solution could be prepared using sodium hydrogen carbonate. NMR measurements revealed that CS was transformed to carbamate ion in the basic condition (around pH 8) thus it acts as anionic nature in this medium. Based on this discovery, novel polyelectrolyte complex (PEC) gel of sodium alginate (SA) and CS was successfully prepared using a basic CS solution and d-gluconolactone (GDL). Gel formation mechanism was explained based on the 1H and 13C NMR measurement results. It was found that the elastic modulus of SA/CS PEC gel were higher than that of SA/Chitosan oligomer gel. Moreover, the SA/CS PEC gel was the homogeneous gel and become over 7000 Pa for maximum of elastic modulus. This novel PEC gel will be used in several applications such as tissue engineering, drug delivery system and fuel cell.

Preparation of alginate fibers coagulated by calcium chloride or sulfuric acid: Application to the adsorption of Sr2.

The adsorption behavior of Sr2+ over alginate (Alg) fibers prepared by wet spinning was investigated. Different grades of sodium alginate (Alg-Na) were chosen. The Alg fibers were obtained by coagulation of 1% H2SO4 (Alg-acid) or 5% CaCl2 (Alg-Ca) solutions. In addition, the Sr2+ adsorption percentages of the spherical Alg-Ca beads with a 0.672-mm-diameter was 70.64% which was significantly lower than that Alg-Ca fibers (79.49%). These results suggested that the fibrous shape is more suitable than the spheres as an adsorbent from sea water. For Sr2+ adsorption capacities using different Alg fibers, the Alg-acid fibers obtained from 12% IL-2 and 8% I-2 grade solutions reached adsorption equilibrium at 99.88 and 99.27%, respectively, within 3 min. However, the Alg-Ca fiber obtained from 8% I-2 grade solution reached equilibrium at 80.01% within 30 min. Moreover, the Alg-acid fiber obtained from 8% I-2 grade solution adsorbed up to 34 mg/g of Sr2+ at an initial concentration of 1700 mg/L solutions. However, when Sr2+ co-existing cations (Ca2+, Na+, and mixtures of them) the adsorption capacity of the Alg-Ca fiber obtained from 8% I-2 grade solution slightly decreased since the egg-box structure of Alg-Ca fiber favored the selective Sr2+ adsorption and subsequent ion exchange with Ca2+.

Preparation of chitosan hydrogel and its solubility in organic acids.

The increase of the stability of chitosan (CS) in the solution is extremely important for the application of CS in various fields. In this study, we describe that the hydrogelation of CS can solve this problem. CS hydrogel was readily prepared by addition of a sodium hydroxide solution to a CS acetic acid solution. The CS hydrogel was stable in the wet state and could maintain its molecular weight for a long period of time at room temperature. The obtained CS hydrogel could be readily dissolved with addition of acids, such as acetic acid and other organic acids, as determined by measuring the pH and transmittance of the solutions. Dissolution of the CS hydrogel indicated that the amount of carboxylate ion per amino group of CS was only 0.5 molar equivalents. Moreover, the binding state between the acetic acid and amino groups of CS in an aqueous solution is discussed using results from 1H NMR spectroscopy. The methyl signals attributed to free acetic acid, acetic acid in an ionic bond, and the acetamido group of the N-acetylglucosamine residue were clearly observed, and the strength of each peak changed quantitatively with the addition of acetic acid.

Adsorption and desorption behaviors of cesium on rayon fibers coated with chitosan immobilized with Prussian blue.

Rayon fiber coated with chitosan (CTS) that contained immobilized Prussian blue (KFe) (KFe/CTS/rayon) were investigated for the removal of cesium ion (Cs+) from contaminated water. The morphology and mechanical strength of the fibers were observed using scanning electron microscopy (SEM) and a universal testing machine, respectively. The Cs+ concentration was determined by inductively coupled plasma-atomic emission spectroscopy. SEM images revealed that the surface of the KFe/CTS/rayon fiber showed the most roughness. It was found that Cs+ was absorbed from the water by the KFe on the fibers in a molar ratio of 1:1 (Cs+:KFe). After treating the KFe/CTS/rayon fiber with 1% HNO3 for 3h, 48.8% Cs+ desorption was observed. Woven fibers were interlaced with either 2 or 4 lines of the KFe/CTS/rayon fiber from 16 bobbins. The tensile strengths of those fibers were 19.06 and 14.25MPa, respectively. When silver cotton was used as the core axis of the woven fiber, the tensile strength of the fibers interlaced with 2 and 4 lines increased to 27.18 and 25.17MPa, respectively. Moreover, the results of hot tests using radioactive Cs+ showed that the woven KFe/CTS/rayon fibers could absorb up to 1000Bqg-1 from an initial concentration of 8000Bqkg-1.

Fabrication of nonwoven fabrics consisting of gelatin nanofibers cross-linked by glutaraldehyde or N-acetyl-d-glucosamine by aqueous method.

Since gelatin (Gel) undergoes a sol-gel transition, a novel dry-spinning procedure for Gel was used. Here, nonwoven fabrics of Gel were electrospun by applying the principles of dry spinning. The diameter of the fibers and the viscosity and flow rate of the solution were directly dependent on the concentration of Gel. Nonwoven fabrics spun with a 25% (w/w) Gel concentration only exhibited a nanoscale fiber diameter. In order to improve the properties of the nonwoven fabrics, they were cross-linked with glutaraldehyde (GTA) vapor after spinning or by the addition of N-acetyl-d-glucosamine (GlcNAc) to the Gel solution prior to spinning followed by heating these fibers. The developed nonwoven fibers were characterized using SEM, rheometry, FTIR, TGA, and mechanical tensile testing. The nonwoven fabrics cross-linked by the GTA vapor exhibited improved mechanical properties compared to those without cross-linking or with GlcNAc cross-linking. The swelling and water uptake ability resulted in no morphological changes in the fibers with GTA cross-linking. The TGA thermogram confirmed no phase change in the composite structure. Further, in vitro cytocompatibility studies using human mesenchymal stem cells showed the compatible nature of the developed nonwoven fibers. Our studies showed that these nonwoven fibers could be useful in medical care.

Isolation and characterization of chitin and chitosan from marine origin.

Nowadays, chitin and chitosan are produced from the shells of crabs and shrimps, and bone plate of squid in laboratory to industrial scale. Production of chitosan involved deproteinization, demineralization, and deacetylation. The characteristics of chitin and chitosan mainly depend on production processes and conditions. The characteristics of these biopolymers such as appearance of polymer, turbidity of polymer solution, degree of deacetylation, and molecular weight are of major importance on applications of these polymers. This chapter addresses the production processes and conditions to produce chitin, chitosan, and chito-oligosaccharide and methods for characterization of chitin, chitosan, and chito-oligosaccharide.

Chitin scaffolds in tissue engineering.

Tissue engineering/regeneration is based on the hypothesis that healthy stem/progenitor cells either recruited or delivered to an injured site, can eventually regenerate lost or damaged tissue. Most of the researchers working in tissue engineering and regenerative technology attempt to create tissue replacements by culturing cells onto synthetic porous three-dimensional polymeric scaffolds, which is currently regarded as an ideal approach to enhance functional tissue regeneration by creating and maintaining channels that facilitate progenitor cell migration, proliferation and differentiation. The requirements that must be satisfied by such scaffolds include providing a space with the proper size, shape and porosity for tissue development and permitting cells from the surrounding tissue to migrate into the matrix. Recently, chitin scaffolds have been widely used in tissue engineering due to their non-toxic, biodegradable and biocompatible nature. The advantage of chitin as a tissue engineering biomaterial lies in that it can be easily processed into gel and scaffold forms for a variety of biomedical applications. Moreover, chitin has been shown to enhance some biological activities such as immunological, antibacterial, drug delivery and have been shown to promote better healing at a faster rate and exhibit greater compatibility with humans. This review provides an overview of the current status of tissue engineering/regenerative medicine research using chitin scaffolds for bone, cartilage and wound healing applications. We also outline the key challenges in this field and the most likely directions for future development and we hope that this review will be helpful to the researchers working in the field of tissue engineering and regenerative medicine.

Effects of chitosan-coated fibers as a scaffold for three-dimensional cultures of rabbit fibroblasts for ligament tissue engineering.

Material selection in tissue-engineering scaffolds is one of the primary factors defining cellular response and matrix formation. In this study, we fabricated chitosan-coated poly(lactic acid) (PLA) fiber scaffolds to test our hypothesis that PLA fibers coated with chitosan highly promoted cell supporting properties compared to those without chitosan. Both PLA fibers (PLA group) and chitosan-coated PLA fibers (PLA-chitosan group) were fabricated for this study. Anterior cruciate ligament (ACL) fibroblasts were isolated from Japanese white rabbits and cultured on scaffolds consisting of each type of fiber. The effects of cell adhesivity, proliferation, and synthesis of the extracellular matrix (ECM) for each fiber were analyzed by cell counting, hydroxyproline assay, scanning electron microscopy and quantitative RT-PCR. Cell adhesivity, proliferation, hydroxyproline content and the expression of type-I collagen mRNA were significantly higher in the PLA-chitosan group than in the PLA group. Scanning electron microscopic observation showed that fibroblasts proliferated with a high level of ECM synthesis around the cells. Chitosan coating improved ACL fibroblast adhesion and proliferation, and had a positive effect on matrix production. Thus, the advantages of chitosan-coated PLA fibers show them to be a suitable biomaterial for ACL tissue-engineering scaffolds.

Enantiomeric separation by MEKC using dodecyl thioglycoside surfactants: importance of an equatorially oriented hydroxy group at C-2 position in separation of dansylated amino acids.

To investigate the influence of stereogenic centers of sugar-based surfactants for enantiomeric separation, four n-dodecyl thioglycoside sulfates (CMC 1.5-3.6 mM) were chosen as micelle-forming surfactants and five dansylated hydrophobic amino acids were used as test analytes. The analytes were mutually separated by these micelles exhibiting almost similar migration times independent of the used surfactant. Baseline separations of all enantiomers were achieved using both beta-D-glucose and beta-D-galactose derivates that have an equatorially oriented hydroxy group at C-2 position. In contrast, the ability of enantioseparation was markedly decreased in the case of beta-D-mannose and 2-deoxy-beta-D-glucose derivatives. These results suggested that the structure of C-2 position of the sugar unit, namely presence of an equatorially oriented hydroxy group, is highly important for the enantiomeric separation of the chosen hydrophobic dansylated amino acids.

Novel chitosan-spotted alginate fibers from wet-spinning of alginate solutions containing emulsified chitosan-citrate complex and their characterization.

The major problem associated with the production of alginate/chitosan hybridized fibers by wet spinning is the formation of gels due to ionic interactions of the oppositely charged molecules of alginate and chitosan when these two polymers are directly mixed. Here, we proposed a novel method of using chitosan in the form of an emulsion. The emulsion was prepared by adding a primary emulsion of olive oil in a sodium dodecyl sulfate (SDS) aqueous solution into a chitosan-citrate complex. The complexation of chitosan with citric acid is the key of this method. The citrate ions neutralize the positive charges of chitosan, rendering the chitosan-citrate complex to readily penetrate into the core of the SDS/olive oil micelles. The obtained emulsified chitosan-citrate complex (hereafter, the chitosan-citrate emulsion) of varying amount was then added into an alginate aqueous solution to prepare the alginate/chitosan spinning dope suspensions. The alginate/chitosan hybridized fibers showed spotty features of the emulsified chitosan-citrate complex particles locating close to the surface and the inside of the hybridized fibers. At the lowest content of incorporated chitosan (i.e., 0.5% w/w chitosan), both the tenacity and the elongation at break of the obtained chitosan-spotted alginate fibers were the greatest. Further increase in the chitosan content resulted in a monotonous decrease in the property values. Lastly, preliminary studies demonstrated that the obtained chitosan-spotted alginate fibers showed great promises as carriers for drug delivery.

Pre-activation of fully acetylated dodecyl thioglycosides with BSP-Tf2O led to efficient glycosylation at low temperature.

Fully acetylated dodecyl thioglycosides were found to be useful as glycosyl donors by activation with 1-benzenesulfinyl piperidine (BSP) and triflic anhydride (Tf(2)O) at -78 degrees C. The glycosyl acceptor was added to the reaction mixture at the same temperature to furnish various disaccharide, including the protected Lewis a (Le(a)) trisaccharide, in good yields.

Dodecyl thioglycopyranoside sulfates: novel sugar-based surfactants for enantiomeric separations by micellar electrokinetic capillary chromatography.

Four novel chiral anionic surfactants having carbohydrate hydrophilic heads, sodium n-dodecyl 1-thio-beta-D-glucopyranoside 6-hydrogen sulfate (6-betaGlcD), sodium n-dodecyl 1-thio-beta-L-glucopyranoside 6-hydrogen sulfate (6-betaGlcL), sodium n-dodecyl 1-thio-beta-L-fucopyranoside 3-hydrogen sulfate (3-betaFucL), and sodium n-dodecyl 1-thio-alpha-L-rhamnopyranoside 3-hydrogen sulfate (3-alphaRhaL), were synthesized by selective sulfation of the corresponding thioglycosides. Their CMC determined by fluorescence using pyrene as a probe in water was 1.3-2.7 mM. These surfactants found to be useful as chiral selectors for enantiomeric separation by MEKC. The enantiomeric separation was optimized with respect to pH, buffer concentration, and surfactant concentration. Under the optimized conditions (50 mM phosphate buffer at pH 6.5, 30 mM surfactant, 20 kV), the enantiomeric separations of five dansylated amino acids (Dns-AAs) were achieved within approximately 20 min with the migration order of Val

Stereoselective tris-glycosylation to introduce beta-(1-->3)-branches into gentiotetraose for the concise synthesis of phytoalexin-elicitor heptaglucoside.

Dodecyl thioglycosides (3, 4, 5) were prepared by conventional transformation of d-glucose and used as new glycosyl donors for a short-step synthesis of phytoalexin elicitor heptaglucoside. A gentio-tetraoside derivative (6) having three hydroxyl groups was synthesized by NIS-TfOH promoted glycosylate in more than 90% yield followed by selective removal of temporary protective groups. Undesired formation of alpha-glycosides at the introduction of beta-(1-->3)-branches into gentio-oligosaccharides was found to be suppressed by use of a thiophilic reagent system, BSP (1-benzenesulfinyl piperidine)-Tf2O, giving the heptaglucoside in only four glycosylation steps.

Cyclodextrin-linked alginate beads as supporting materials for Sphingomonas cloacae, a nonylphenol degrading bacteria.

Calcium alginate beads covalently linked with alpha-cyclodextrin (alpha-CD-alginate beads) were prepared and examined for their ability to serve as a supporting matrix for bacterial degradation of nonylphenol, an endocrine disruptor. Column chromatographic experiment using alpha-CD-alginate beads with diameter of 657+/-82 microm and with degree of CD substitution of 0.16 showed a strong affinity for nonylphenol adsorption. Although addition of alpha-CD (2.7-27 mM) to the culture broth of Sphingomonas cloacae retarded nonylphenol degradation, the immobilized bacteria on the CD-alginate beads were effective for the degradation. Batch degradation tests using the immobilized bacteria on alpha-CD-alginate-beads showed 46% nonylphenol recovery after 10-day incubation at 25+/-2 degrees C, and the recovery reached to about 17% when wide and shallow incubation tubes were used to facilitate uptake of the viscous liquid of nonylphenol on the surface of the medium. Scanning electron microscopic photographs revealed that multiplicated bacteria was present both on the surface and inside the beads and the matrix of CD-alginate was stable and suitable during 10-day incubation.

Rational design, synthesis, and characterization of novel inhibitors for human beta1,4-galactosyltransferase.

An affinity labeling reagent, uridine 5'-(6-amino-{2-[(7-bromomethyl-2-naphthyl)methoxycarbonylmethoxy]ethoxy}acetyl-6-deoxy-alpha-D-galactopyranosyl) diphosphate (1a), was designed on the basis of 3D docking simulation and synthesized to investigate the functional role of Trp310 residue located in the small loop near the active site of human recombinant galactosyltransferase (betaGalT-1). Mass spectrometric analysis revealed that the Trp310 residue of betaGalT1 can be selectively modified with the naphthylmethyl group of compound 1a at the C-3 position of the indole ring. This result motivated us to synthesize novel uridine-5'-diphosphogalactose (UDP-Gal) analogues as candidates for mechanism-based inhibitors for betaGalT-1. We found that uridine 5'-(6-O-[10-(2-naphthyl)-3,6,9-trioxadecanyl]-alpha-d-galactopyranosyl) diphosphate (2) is the strongest inhibitor (K(i) = 1.86 microM) against UDP-Gal (Km = 4.91 microM) among compounds reported previously. A cold spray ionization time-of-flight mass spectrometry study demonstrated that the complex of this inhibitor and betaGalT-1 cannot interact with an acceptor substrate in the presence of Mn2+.