Carbon nanotubes as structural nanofibers for hyaluronic acid hydrogel scaffolds

We have successfully dispersed functionalized single-walled carbon nanotubes (SWNTs) within hyaluronic acid-water solutions. Hybrid hyaluronic acid (HA) hydrogels with SWNTs were then formed by cross-linking with divinyl sulfone. We have found a considerable change in the morphology of the lyophilized hybrid hydrogels compared to HA hydrogels. The high water uptake capacity, an important property of HA hydrogels, remained almost unchanged after 2 wt % SWNT (vs HA) incorporation, despite a dramatic enhancement in the dynamic mechanical properties of the hybrid hydrogels compared to native ones. We have found a 300% enhancement in the storage modulus of hybrid hydrogel with only 2 wt % of SWNTs vs HA (0.06 wt % vs total weight including water content). This apparent contradiction can be explained by a networking effect between SWNTs, mediated by HA chains. As in biological tissue, HA plays a dual role of matrix and linker for the rigid reinforcing nanofibers.     

Biomimetic nanofibrous scaffolds: preparation and characterization of PGA/chitin blend nanofibers

Electrospinning of poly(glycolic acid) (PGA)/chitin blend solutions in 1,1,1,3,3,3-hexafluoro-2-propanol was investigated to fabricate biodegradable and biomimetic nanostructured scaffolds for tissue engineering. The morphology of the electrospun PGA/chitin blend nanofibers was investigated with a field emission scanning electron microscope. The PGA/chitin blend fibers have average diameters of around 140 nm, and their diameters have a distribution in the range 50-350 nm. The miscibility of PGA/chitin blend fibers was examined by differential scanning calorimetry. The PGA and chitin were immiscible in the as-spun nanofibrous structure. An in vitro degradation study of PGA/chitin blend nanofibers was conducted in phosphate-buffered saline, pH 7.2. It was found that the hydrolytic cleavage of PGA in the blend nanofibers was accelerated by the coexistence of hydrophilic chitin. To assay the cytocompatability and cell behavior on the PGA/chitin blend nanofibrous scaffolds, cell attachment and spreading of normal human epidermal fibroblasts seeded on the scaffolds were studied. Our results indicate that the PGA/chitin blend nanofibrous matrix, particularly the one that contained 25% PGA and 75% chitin with bovine serum albumin coating, could be a good candidate for tissue engineering scaffolds, because it has an excellent cell attachment and spreading for normal human fibroblasts.     

Biomimetic nanofibrous scaffolds: preparation and characterization of chitin/silk fibroin blend nanofibers

Electrospinning of chitin/silk fibroin (SF) blend solutions in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was investigated to fabricate a biomimetic nanostructured scaffolds for tissue engineering. The morphology of the electrospun chitin/SF blend nanofibers was investigated with a field emission scanning electron microscope (FE-SEM). The average diameters of chitin/SF blend fibers decreased from 920 to 340 nm, with the increase of chitin content in blend compositions. The miscibility of chitin/SF blend fibers was examined by solution viscosity measurement. The chitin and SF were immiscible in the as-spun nanofibrous structure. The dimensional stability of chitin/SF blend nanofibers, with or without water vapor after-treatment, was conducted by immersing in water. As-spun SF-rich blend nanofibrous matrices were lost their fibrous structure after the water immersion for 24 h, and then changed into membrane-like structure. On the contrary, nanofibrous structures of water vapor-treated SF-rich blends were almost maintained. To assay the cytocompatibility and cell behavior on the chitin/SF blend nanofibrous scaffolds, cell attachment and spreading of normal human epidermal keratinocyte and fibroblasts seeded on the scaffolds were studied. Our results indicate that chitin/SF blend nanofibrous matrix, particularly the one that contained 75% chitin and 25% SF, could be a potential candidate for tissue engineering scaffolds because it has both biomimetic three-dimensional structure and an excellent cell attachment and spreading for NHEK and NHEF.     

Physicochemical characterization of cellulose from perennial ryegrass leaves (Lolium perenne)

In this study, we investigated the physicochemical properties of the cellulosic preparations obtained from both untreated perennial ryegrass leaves and de-juiced leaves. It was found that treatment at 22 degrees C with 18% NaOH and 18% KOH for 2h, and 10% NaOH and 10% KOH for 16 h yielded 28.2%, 28.8%, 22.7%, 23.4%, respectively, of 'cellulose' residue from untreated ryegrass leaves and 35.7%, 36.8%, 32.8% and 34.6%, respectively, from the de-juiced leaves. For each cellulosic fraction, the glucose content was 71.6%, 69.6%, 67.8%, 66.7%, 69.7%, 68.6%, 63.9% and 61.7%, respectively. The structure of the cellulose samples was examined using FTIR and CP/MAS (13)C NMR spectroscopy and X-ray diffraction. The cellulosic preparations were free of bound lignin except for noticeable amounts of residual hemicelluloses (28.4-38.3%), and had intrinsic viscosities between 275.1 and 361.0 mL/g, along with molecular weights from 144,130 to 194,930 g/mol. This study found that the cellulose samples isolated from both de-juiced ryegrass leaves and the untreated leaves had a much lower percent crystallinity (33.0-38.6%) than that from wood-based fibres (60-70%) and had much shorter fibres (0.35-0.49 mm) than those of either cereal straws, bagasse or wood. In addition, a partial disruption of the hydrogen bonds and microfibrils may occur during the de-juicing process by mechanical activity, which results in a decreased cellulose crystallinity and fibre length. These findings are significant in relation to hydrolysing ryegrass cellulose for bio-ethanol production.     

Preparation and characterization of poly(acrylic acid)-hydroxyethyl cellulose graft copolymer

Poly(acrylic acid) hydroxyethyl cellulose [poly(AA)-HEC] graft copolymer was prepared by polymerizing acrylic acid (AA) with hydroxyethyl cellulose (HEC) using potassium bromate/thiourea dioxide (KBrO(3)/TUD) as redox initiation system. The polymerization reaction was carried out under a variety of conditions including concentrations of AA, KBrO(3) and TUD, material to liquor ratio and polymerization temperature. The polymerization reaction was monitored by withdrawing samples from the reaction medium and measuring the total conversion. The rheological properties of the poly(AA)-HEC graft copolymer were investigated. The total conversion and rheological properties of the graft copolymer depended on the ratio of KBrO(3) to TUD and on acrylic acid concentration as well as temperature and material to liquor ratio. Optimum conditions of the graft copolymer preparation were 30mmol KBrO(3) and 30mmol TUD/100g HEC, 100% AA (based on weight of HEC), duration 2h at temperature 50°C using a material to liquor ratio of 1:10.     

Efficient formation of cell spheroids using polymer nanofibers

Spheroid culture has been used for suspension cultures of anchorage-dependent cells. In this study, we developed a new method for the suspension cultures of anchorage-dependent animal cells using polymer nanofibers. Poly(lactic-co-glycolic acid) nanofibers (785?nm in average fiber-diameter, 88?μm in average fiber-length) fabricated by the electrospinning method were added to each suspension culture of human embryonic kidney 293 cells and human dermal fibroblasts. As compared to no addition of nanofibers to the suspension cultures, nanofibers enhanced cell spheroid formation, thereby reducing cell death resulting from a lack of cell adhesion. Efficient formation of spheroids in the presence of polymer nanofibers may be useful for the suspension cultures of anchorage-dependent cells.     

Utilization of hydroxypropyl cellulose and poly(acrylic acid)-hydroxypropyl cellulose composite as thickeners for textile printing

Trials were carried out to partially replace kerosene oil with hydroxypropyl cellulose (HPC), poly(acrylic acid)-hydroxypropyl cellulose composite (poly (AA)-HPC) and their mixture in pigment printing paste. Partial replacement was carried out under a variety of conditions. Variables studied include type and concentration of the aqueous thickening agent and type of pigment dyes. In addition to that, poly (AA)-HPC composite was tried to replace sodium alginate in reactive printing. The fastness properties, color strength and stiffness were measured for the reactive and pigment printed samples.     

Morphofunctional characterization of decellularized vena cava as tissue engineering scaffolds

Clinical experience for peripheral arterial disease treatment shows poor results when synthetic grafts are used to approach infrapopliteal arterial segments. However, tissue engineering may be an option to yield surrogate biocompatible neovessels. Thus, biological decellularized scaffolds could provide natural tissue architecture to use in tissue engineering, when the absence of ideal autologous veins reduces surgical options. The goal of this study was to evaluate different chemical induced decellularization protocols of the inferior vena cava of rabbits. They were decellularized with Triton X100 (TX100), sodium dodecyl sulfate (SDS) or sodium deoxycholate (DS). Afterwards, we assessed the remaining extracellular matrix (ECM) integrity, residual toxicity and the biomechanical resistance of the scaffolds. Our results showed that TX100 was not effective to remove the cells, while protocols using SDS 1% for 2 h and DS 2% for 1 h, efficiently removed the cells and were better characterized. These scaffolds preserved the original organization of ECM. In addition, the residual toxicity assessment did not reveal statistically significant changes while decellularized scaffolds retained the equivalent biomechanical properties when compared with the control. Our results concluded that protocols using SDS and DS were effective at obtaining decellularized scaffolds, which may be useful for blood vessel tissue engineering.     

Preparation and characterization of amphiphilic triblock terpolymer-based nanofibers as antifouling biomaterials

Antifouling surfaces are critical for the good performance of functional materials in various applications including water filtration, medical implants, and biosensors. In this study, we synthesized amphiphilic triblock terpolymers (tri-BCPs, coded as KB) and fabricated amphiphilic nanofibers by electrospinning of solutions prepared by mixing the KB with poly(lactic acid) (PLA) polymer. The resulting fibers with amphiphilic polymer groups exhibited superior antifouling performance to the fibers without such groups. The adsorption of bovine serum albumin (BSA) on the amphiphilic fibers was about 10-fold less than that on the control surfaces from PLA and PET fibers. With the increase of the KB content in the amphiphilic fibers, the resistance to adsorption of BSA was increased. BSA was released more easily from the surface of the amphiphilic fibers than from the surface of hydrophobic PLA or PET fibers. We have also investigated the structural conformation of KB in fibers before and after annealing by contact angle measurements, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and coarse-grained molecular dynamics (CGMD) simulation to probe the effect of amphiphilic chain conformation on antifouling. The results reveal that the amphiphilic KB was evenly distributed within as-spun hybrid fibers, while migrated toward the core from the fiber surface during thermal treatment, leading to the reduction in antifouling. This suggests that the antifouling effect of the amphiphilic fibers is greatly influenced by the arrangement of amphiphilic groups in the fibers.     

Design of proteins using rigid organic macrocycles as scaffolds

We have designed and synthesized new three-helix template-assembled synthetic proteins (TASPs) 1a-c. The template was the rigid cyclotribenzylene (CTB) macrocycle 2, which has C3 symmetry. Thiol moieties on the CTB template were used to link cysteine-containing peptide strands 3a-c via disulfide bonds. With designed peptide strands of 15 and 18 residues in length, the structure of TASPs 1a-c were determined to be helical in water according to circular dichroism (CD) spectroscopy. The helicities of TASPs 1a-c were unchanged over large ranges of pH (2-12) and salt concentrations (0-2 M KCl). TASPs 1a-c were also extremely resistant to chemical denaturants: it requires a guanidine hydrochloride (GnHCl) concentration of 7.4 M for TASPs 1a-c to lose 50% of their helicity. The major force for stabilization of TASPs 1a-c is the hydrophobic bundling of the helices.     

Preparation and characterization of water soluble poly(acrylic acid)–hydroxypropyl cellulose composite

Purified flax waste was obtained from flax processing wastes via subjecting the latter to alkali treatment followed by peracetic acid bleaching. The so obtained purified flax wastes were chemically modified via reacting with propylene oxide in alkaline medium. The resultant hydroxypropyl cellulose (HPC) was incorporated in a polymerization medium containing acrylic acid and potassium bromate/thiourea mixture as initiation system. The polymerization reaction was monitored by determining the total conversion percent and the rheological properties of the resultant polyacrylic acid–hydroxypropyl cellulose composite [poly(AA)–HPC]. Results obtained indicate that the optimum conditions of polymerization process were: 12 mmole KBrO₃, 4 mmole thiourea and 100 g acrylic acid/100 g HPC at 50 °C for 2 h using a material to liquor ratio of 1:5.     

Enzymatic production of ethanol from cellulose using soluble cellulose acetate as an intermediate

A two-stage process for the enzymatic conversion of cellulose to ethanol is proposed as an alternative to currently incomplete and relatively slow enzymatic conversion processes employing natural insoluble cellulose. This alternative approach is designed to promote faster and more complete conversion of cellulose to fermentable sugars through the use of a homogeneous enzymatic hydrolysis reaction. Cellulose is chemically dissolved in the first stage to form water-soluble cellulose acetate (WSCA). The WSCA is then converted to ethanol in a simultaneous saccharification-fermentation with Pestal-otiopsis westerdijkii enzymes (containing cellulolytic and acetyl esterase components) and yeast.Water-soluble cellulose acetate was successfully prepared from purified wood cellulose (Solka Floe) and chemical reagents. Enzyme pretreatment of WSCAto form metabolizable sugars was a necessary step in achieving practical conversion of WSCA to ethanol using yeast. The results showed that WSCA has a low enzyme requirement and a high convertibility to reducing sugars with enzymes from P. westerdijkii fungus. Pestalotiopsis westerdijkii enzymes were found to be superior to enzymes from Trichoderma viride in producing metabolizable glucose from WSCA. The yeast utilized 55-70% of the hydrolyzate sugars that were produced by P. westerrlijkii enzymes on WSCA and produced ethanol. The acetate that was liberated into solution by the action of acetyl esterase enzymes on WSCA was found to have a stimulatory effect on ethanol production in yeast. This is an important feature that can be used to advantage in manipulating the conversion to maximize the production of ethanol. Hence, the simultaneous saccharification-fermentation of WSCA to ethanol using P. westerdijkii enzymes and yeast has features that are highly desirable for developing an economical cellulose conversion process.     

Regulation of postprandial blood metabolic variables by TEMPO-oxidized cellulose nanofibers

Wood cellulose was converted to individual nanofibers of approximately 4 nm width and 380-570 nm average length by TEMPO-mediated oxidation. The TEMPO-oxidized cellulose nanofibers (TOCNs) were orally administered with glucose and glyceryl trioleate to mice and postprandial responses of blood glucose, insulin, glucose-dependent insulinotropic polypeptide (GIP), and triglycerides were studied. Both blood insulin and GIP concentrations were decreased by TOCN with a carboxyl content and aspect ratio of 1.2 mmol g(-1) and 120, respectively, in dose-dependent manners (0-0.3 mg g(-1) body weight). Of the TOCNs examined, that with a carboxyl content and aspect ratio of 1.2 mmol g(-1) and 120, respectively, was the most effective in reducing postprandial blood glucose, plasma insulin, GIP, and triglyceride concentrations. Thus, TOCNs were found to exhibit characteristic biological activities when administered to mice and may have potential applications in biomedical fields for human health.     

In situ synthesis of CdS nanoparticles on bacterial cellulose nanofibers

CdS nanoparticles have been synthesized and stabilized on unique bacterial cellulose (BC) nanofibers in situ. The obtained nanocomposite material have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transformed infrared (FTIR), thermogravimetric analysis (TGA), ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy. The results indicated that CdS nanoparticles of about 30 nm diameter deposited on BC nanofibres are well-dispersed in the BC nanofibre-network and the uniform spherical CdS nanoparticles are comprised of nano-sized CdS crystal. Moreover, the crystallite sizes of CdS crystals are about 8 nm. The nanocomposites would have potential application as photocatalyst, novel luminescence and photoelectron transfer devices.     

Physicochemical characterization of Remsima?

Remsima® (infliximab) was recently approved as the world''s first biosimilar monoclonal antibody (mAb) in both the European Union and Korea. To achieve this, extensive physicochemical characterization of Remsima® in relation to Remicade® was conducted in order to demonstrate the highly similar properties between the two molecules. A multitude of state-of-the-art analyses revealed that Remsima® has identical primary as well as indistinguishable higher order structures compared with the original product. Monomer and aggregate contents of Remsima® were also found to be comparable with those of Remicade®. In terms of charge isoforms, although Remsima® was observed to contain slightly less basic variants than the original antibody, the difference was shown to be largely due to the presence of C-terminal lysine. On the other hand, this lysine was found to be rapidly clipped inside serum in vitro and in vivo, suggesting it has no effect on the biological potency or safety of the drug. Analysis of the glycan contents of the antibodies showed comparable glycan types and distributions. Recent results of clinical studies have further confirmed that the two antibody products are highly similar to each other. Based on this research as well as previous clinical and non-clinical comparability studies, Remsima® can be considered as a highly similar molecule to Remicade® in terms of physicochemical properties, efficacy, and safety for its final approval as a biosimilar product to Remicade®.     

Physicochemical characterization of konjac glucomannan

Four commercial konjac glucomannan (KGM) samples and a glucomannan derived from yeast were characterized by aqueous gel permeation chromatography coupled with multi angle laser light scattering (GPC-MALLS). Disaggregation of aqueous glucomannan solutions through controlled use of a microwave bomb facilitated reproducible molar mass distribution determination alleviating the need for derivatization of the polymer or the use of aggressive solvents. Further characterization was undertaken by use of capillary viscometry and photon correlation spectroscopy (PCS). The weight average molecular masses (M(w)) determined were in the region of 9.0 +/- 1.0 x 10(5) g mol(-1) for KGM samples and 1.3 +/- 0.4 x 10(5) g mol(-1) for the yeast glucomannan. The values determined for KGM in aqueous solution are in agreement with those reported for KGM in aqueous cadoxen. The degradation of samples observed upon autoclaving has been quantified by GPC-MALLS and intrinsic viscosity determination, allowing comparison with reported Mark-Houwink parameters. Shear flow experiments were undertaken for a range of KGM solutions of concentration 0.05 to 2.0% using a combination of controlled stress and controlled strain rheometers. The concentration dependence of the zero shear specific viscosity was determined by analysis of the data using the Ellis model. The dependence of the zero shear specific viscosity on the coil overlap parameter was defined and interpretation discussed in terms of the Martin and Tuinier equations.