Dual-Sizing Effects of Carbon Fiber on the Thermal, Mechanical, and Impact Properties of Carbon Fiber/ABS Composites.

Dual-sizing effects with either epoxy or polyurethane (PU) on the thermal, mechanical, and impact properties of carbon fiber/acrylonitrile-butadiene-styrene (ABS) composites produced by extrusion and injection molding processes were investigated. The heat deflection temperature, dynamic mechanical, tensile, flexural, and impact properties of the composites reinforced with either (epoxy + epoxy) or (epoxy + PU) dual-sized carbon fiber were higher than those commercially single-sized with epoxy. The result indicated that the dual-sized carbon fiber significantly contributed not only to improving the heat deflection temperature and the storage modulus, but also to improving the tensile, flexural, and impact properties of carbon fiber/ABS composites. The highest improvement of the composite properties was obtained from the composite with (epoxy + PU) dual-sized carbon fiber. The improvement of the mechanical and impact properties was explained by the enhanced interfacial bonding between carbon fiber and ABS matrix and by the length distribution analysis of carbon fibers present in the resulting composites. The fiber-matrix interfacial behavior was qualitatively well-supported in terms of fiber pull-out, fiber breaking pattern, and debonding gaps between the fiber and the matrix, as observed from the fracture surface topography. This study revealed that the properties of carbon fiber/ABS composites prepared by extrusion and injection molding processes were improved by dual-sizing carbon fiber, which was performed after a commercial epoxy sizing process, and further improved by using PU as an additional sizing material.

Effects of Waste Expanded Polypropylene as Recycled Matrix on the Flexural, Impact, and Heat Deflection Temperature Properties of Kenaf Fiber/Polypropylene Composites.

Waste Expanded polypropylene (EPP) was utilized as recycled matrix for kenaf fiber-reinforced polypropylene (PP) composites produced using chopped kenaf fibers and crushed EPP waste. The flexural properties, impact strength, and heat deflection temperature (HDT) of kenaf fiber/PP composites were highly enhanced by using waste EPP, compared to those by using virgin PP. The flexural modulus and strength of the composites with waste EPP were 98% and 55% higher than those with virgin PP at the same kenaf contents, respectively. The Izod impact strength and HDT were 31% and 12% higher with waste EPP than with virgin PP, respectively. The present study indicates that waste EPP would be feasible as recycled matrix for replacing conventional PP matrix in natural fiber composites.

Surface modification of PHBV nanofiber mats for rapid cell cultivation and harvesting.

To maintain the original function of a specific tissue for therapeutic tissue engineering, an advanced cell culture surface for repeat cell proliferation is necessary. We designed a novel cell proliferation and rapid harvesting surface by combining nonwoven nanofiber mat and a thermo-responsive polymer. Nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) mats were fabricated by the electrospinning technique. A poly(N-isopropylacrylamide) (PNIPAM) thermo-responsive layer was grafted on the PHBV nanofiber mat by electron beam irradiation. The average diameter of the PNIPAM-grafted PHBV nanofibers was determined by SEM. ATR-FTIR and ESCA were used to confirm the grafting of PNIPAM onto the PHBV nanofiber surface. Water contact angles on the mats were measured in response to temperature changes. Human adipose-derived stem cells (ADSCs) were cultured on the PNIPAM-grafted PHBV nanofiber mat to investigate cell proliferation, harvesting, and functionality during repeat subculture. Detached ADSCs from each surface by low temperature treatment and trypsin-EDTA were compared by a fluorescence-activated cell sorter (FACS) using expression of stem cell membrane-specific markers such as CD-13 PE, CD-29 PE, and CD-90 FITC. The mass cultivation and intact harvesting of stem cells by low temperature treatment using a thermo-responsive PHBV nanofiber mat is a promising technique for use in regenerative medicine and stem cell therapy.

Modification and optimization of electrospun gelatin sheets by electron beam irradiation for soft tissue engineering.

BACKGROUND: Crosslinked gelatin nanofibers are one of the widely used scaffolds for soft tissue engineering. However, modifying the biodegradation rate of chemically crosslinked gelatin is necessary to facilitate cell migration and tissue regeneration. Here, we investigated the optimal electron beam (e-beam) irradiation doses with biodegradation behavior on changes in the molecular weight, morphology, pore structure, and cell proliferation profiles of electrospun nanofibrous gelatin sheets. METHODS: The molecular weights of uncrosslinked gelatin nanofibers were measured using gel permeation chromatography. The morphology and pore structure of the gelatin scaffolds were analyzed by scanning electron microscopy and a porosimeter. Biodegradation tests were performed in phosphate-buffered saline solutions for 4 weeks. Cell proliferation and tissue regeneration profiles were examined in fibroblasts using WST-1 assays and hematoxylin and eosin staining. RESULTS: Crosslinked gelatin nanofiber sheets exposed to e-beam irradiation over 300 kGy showed approximately 50% weight loss in 2 weeks. Gelatin scaffolds exposed to e-beam irradiation at 100-200 kGy showed significantly increased cell proliferation after 7 days of incubation. CONCLUSIONS: These findings suggested that the biodegradation and cell proliferation rates of gelatin nanofiber scaffolds could be optimized by varying e-beam irradiation doses for soft tissue engineering.

Silk fibroin/hydroxyapatite composite hydrogel induced by gamma-ray irradiation for bone tissue engineering.

BACKGROUND: In this study, silk fibroin (SF) composite hydrogels containing hydroxyapatite (HAP) nanoparticles (NPs) for bone tissue engineering were fabricated using gamma-ray (γ-ray) irradiation treatment. During the irradiation, the HAP dispersed SF solution was changed to the chemically crosslinked SF hydrogel. METHODS: Distribution of HAP NPs in the SF hydrogel was examined by SEM imagery and energy dispersive X-ray spectrophotometry, and the crystalline structure of SF composite hydrogels was also confirmed by X-ray diffractometry. An optimum preparation condition of the SF/HAP composite hydrogels was determined with various HAP contents. For evaluation of the osteogenic differentiation of human mesenchymal stem cells (hMSCs), alkaline phosphatase activity (ALP), HAP nucleation in SBF and in vitro calcium accumulation were measured. RESULTS: The results revealed that compared with the pure SF hydrogels, the SF/HAP composite hydrogels improved osteogenic differentiation. CONCLUSION: This paper demonstrates the great potential of the SF/HAP composite hydrogels in terms of the production of the bone tissue engineering scaffolds for which osteogenesis is required.

Preventing postoperative tissue adhesion using injectable carboxymethyl cellulose-pullulan hydrogels.

An injectable adhesive hydrogel composed of carboxymethyl cellulose (CMC) and pullulan is developed and evaluated as a postoperative anti-adhesion barrier. CMC was modified with tyramine to introduce crosslinking site via an EDC-NHS reaction. The in situ hydrogel was prepared by an enzyme-mediated reaction of tyramine-immobilized CMC with horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). Pullulan was added to the hydrogel solution to improve adhesiveness to the wound area and accelerate biodegradation. The modified CMC was confirmed by ATR-FTIR spectroscopy. The gelation time, storage modulus (G'), and weight loss of the hydrogels were measured as functions of the amounts of HRP and H2O2. The hydrogel group showed negligible cell proliferation and cytotoxicity, compared to that shown by the control group. The in vivo animal test demonstrated that significant decrease of postoperative tissue adhesion by applying the hydrogels. The CMC-pullulan hydrogel could be a useful treatment as an injectable in situ anti-adhesive agent.

Antimicrobial Silver Chloride Nanoparticles Stabilized with Chitosan Oligomer for the Healing of Burns.

Recently, numerous compounds have been studied in order to develop antibacterial agents, which can prevent colonized wounds from infection, and assist the wound healing. For this purpose, novel silver chloride nanoparticles stabilized with chitosan oligomer (CHI-AgCl NPs) were synthesized to investigate the influence of antibacterial chitosan oligomer (CHI) exerted by the silver chloride nanoparticles (AgCl NPs) on burn wound healing in a rat model. The CHI-AgCl NPs had a spherical morphology with a mean diameter of 42 ± 15 nm. The burn wound healing of CHI-AgCl NPs ointment was compared with untreated group, Vaseline ointment, and chitosan ointment group. The burn wound treated with CHI-AgCl NPs ointment was completely healed by 14 treatment days, and was similar to normal skin. Particularly, the regenerated collagen density became the highest in the CHI-AgCl NPs ointment group. The CHI-AgCl NPs ointment is considered a suitable healing agent for burn wounds, due to dual antibacterial activity of the AgCl NPs and CHI.

Growth behavior of endothelial cells according to electrospun poly(D,L-lactic-co-glycolic acid) fiber diameter as a tissue engineering scaffold.

Investigating the effect of electrospun fiber diameter on endothelial cell proliferation provides an important guidance for the design of a fabric scaffold. In this study, we prepared biodegradable poly(D,L-lactic-co-glycolic acid) (PLGA) fibrous nonwoven mats with different fiber diameters ranged from 200 nm to 5 µm using the electrospinning technique. To control the fiber diameters of PLGA mats, 4 mixture solvents [hexafluoro-2-propanol, 2,2,2,-trifluoroethanol:dimethylformamide (9:1), 2,2,2,-trifluoroethanol:hexafluoro-2-propanol (9:1), chloroform] were used. Average diameters were 200 nm, 600 nm, 1.5 µm, and 5.0 µm, respectively. Stereoscopic structure and spatial characterization of fibrous PLGA mats were analyzed using atomic force microscopy and a porosimeter. The mechanical properties of PLGA mats were analyzed using a universal testing machine. The spreading behavior and infiltration of endothelial cells on PLGA mats were visualized by field emission scanning electron microscopy and hematoxylin and eosin staining. Cell proliferation on different PLGA fibers with different diameters was quantified using the MTT assay. Cells on 200 nm diameter PLGA mats showed rapid attachment and spreading. However, the cells did not penetrate the PLGA mat. Cells cultured on 600 nm and 1.5 µm diameter fibers could infiltrate the pores and cell proliferation was dramatically increased after 14 days. Secreted prostacyclin from endothelial cells on each mat was measured to examine the ability to inhibit platelet activation. This basic study on cell proliferation and fiber diameter with physical characterization provides a foundation for studies examining nonwoven fibrous PLGA mats as a tissue engineering scaffold.

Fabrication and characterization of thermoresponsive polystyrene nanofibrous mats for cultured cell recovery.

Rapid cell growth and rapid recovery of intact cultured cells are an invaluable technique to maintain the biological functions and viability of cells. To achieve this goal, thermoresponsive polystyrene (PS) nanofibrous mat was fabricated by electrospinning of PS solution, followed by the graft polymerization of thermoresponsive poly(N-isopropylacrylamide)(PIPAAm) on PS nanofibrous mats. Image analysis of the PS nanofiber revealed a unimodal distribution pattern with 400 nm average fiber diameter. Graft polymerization of PIPAAm on PS nanofibrous mats was confirmed by spectroscopic methods such as ATR-FTIR, ESCA, and AFM. Human fibroblasts were cultured on four different surfaces, PIPAAm-grafted and ungrafted PS dishes and PIPAAm-grafted and ungrafted PS nanofibrous mats, respectively. Cells on PIPAAm-grafted PS nanofibrous mats were well attached, spread, and proliferated significantly much more than those on other surfaces. Cultured cells were easily detached from the PIPAAm-grafted surfaces by decreasing culture temperature to 20 °C, while negligible cells were detached from ungrafted surfaces. Moreover, cells on PIPAAm-grafted PS nanofibrous mats were detached more rapidly than those on PIPAAm-grafted PS dishes. These results suggest that thermoresponsive nanofibrous mats are attractive cell culture substrates which enable rapid cell growth and recovery from the culture surface for application to tissue engineering and regenerative medicine.

The advantage of using 3-week data to predict response to aripiprazole at week 6 in first-episode psychosis.

We investigated the efficacy and safety of aripiprazole in first-episode psychosis and explored the association between early response and later response to this medication. This was a 6-week, open-label, multicenter trial. The study population consisted of 59 patients with a DSM-IV diagnosis of a schizophreniform disorder, schizoaffective disorder, schizophrenia, or psychotic disorder not otherwise specified. The primary outcome measures were the Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression-Severity scale. To assess the safety, we measured the drug-related adverse events, weight, and lipid-related variables. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the response status at weeks 2 and 3 to predict the subsequent response at week 6. Among the 59 participants, 38 were able to complete the 6-week trial. Treatment with aripiprazole resulted in significant improvement in the PANSS and Clinical Global Impression scores over time. The response rate (defined as a ≥30% decrease in the PANSS total score from baseline to the last observation) was 69.1%. The most accurate prediction of later response in terms of negative predictive value and specificity was a reduction in the PANSS total score from baseline to week 3 of at least 20%. Aripiprazole had a modest side effect burden and was characterized by a safe profile with respect to weight and metabolic side effects. These results indicate that aripiprazole is effective and safe in the treatment of first-episode psychosis. The response at week 3, rather than week 2, predicted the later response more accurately.

Effect of methylcellulose on the formation and drug release behavior of silk fibroin hydrogel.

In this study, methylcellulose (MC) was used to control the gelation time of silk fibroin (SF) aqueous solution. The gelation time was measured using a Vibro Viscometer at 50 °C. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and a texture meter were used to investigate the effect of MC on the hydrogelation of SF solution. SF/MC hydrogels could be formed by the addition of MC, although their gelation time was increased with MC content. To examine the conformational change of SF/MC hydrogels, time-resolved FT-IR spectra were obtained at constant temperature using a custom-made IR chamber. From FT-IR spectra focused on the amide I peak position, the transition of SF molecules in SF/MC solution from a random coil to a ß-sheet structure was inhibited in the presence of MC molecules. In addition, the drug release of SF/MC hydrogels loaded with 5-aminosalicylic acid was studied in 2-dimensional (2-D) and 3-dimensional (3-D) conditions in vitro. The drug release behavior of SF or SF/MC hydrogels was measured using UV-Vis spectroscopy. The release rate of 5-aminosalicylic acid in SF/MC hydrogel was lower than that of SF hydrogel, which may be closely associated with the hydrophilic interaction between MC and 5-aminosalicylic acid. This approach to controlling the sol-gel transition and the drug release of SF hydrogels by the addition of MC will be useful in the design and tailoring of novel materials for biomedical applications.

Antipsychotic effects of quetiapine in naturalistic long term follow up study.

OBJECTIVE: This study aimed to examine the effectiveness of quetiapine and the effects of dosage relates to its effectiveness on schizophrenia and schizoaffective disorder in a naturalistic setting in Korean people. METHODS: This study was a 24-week, open-label, non-comparative, naturalistic study of quetiapine in patients diagnosed with schizophrenia and schizoaffective disorder according to DSM-IV. We stratified the patients into mild [(clinical global impression severity (CGI-S) <4 at baseline)] and severe groups (CGI-S >/=4 at baseline). We investigated the response rate, defined as clinical global impression improvement (CGI-I)