Hye Kyoung Shin

Preparation and characterization of keratin-based biocomposite hydrogels prepared by electron beam irradiation

The biocompatible and highly porous keratin-based hydrogels were prepared using electron beam irradiation (EBI). The conditions for keratin-based hydrogel formation were investigated depending on several conditions, including the presence of poly(vinyl alcohol) (PVA), concentration of keratin solution, EBI dose, and poly(ethylene imine) (PEI) additives. The pure keratin (human hair and wool) aqueous solution was not gelled by EBI, while the aqueous keratin solutions blended with PVA were gelled at an EBI dose of more than 90 kGy. Furthermore, in the presence of PEI, the aqueous keratin solution blended with PVA could be gelled at a considerably lower EBI dose, even at 10 kGy. This finding suggests that the PEI additives significantly influence the rate of gelation and that PEIs function as an accelerator during gelation. The resulting keratin-based hydrogels were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), gel fraction, degree of swelling, gel strength, and kinetics of swelling analyses.

Effect of discarded keratin-based biocomposite hydrogels on the wound healing process in vivo.

Biocompatible keratin-based hydrogels prepared by electron beam irradiation (EBI) were examined in wound healing. As the EBI dose increased to 60 kGy, the tensile strength of the hydrogels increased, while the percentage of elongation of the hydrogels decreased. After 7 days, the dehydrated wool-based hydrogels show the highest mechanical properties (the % elongation of 1341 and the tensile strength of 6030 g/cm(2) at an EBI dose of 30 kGy). Excision wound models were used to evaluate the effects of human hair-based hydrogels and wool-based hydrogels on various phases of healing. On post-wounding days 7 and 14, wounds treated with either human hair-based or wool-based hydrogels were greatly reduced in size compared to wounds that received other treatments, although the hydrocolloid wound dressing-treated wound also showed a pronounced reduction in size compared to an open wound as measured by a histological assay. On the 14th postoperative day, the cellular appearances were similar in the hydrocolloid wound dressing and wool-based hydrogel-treated wounds, and collagen fibers were substituted with fibroblasts and mixed with fibroblasts in the dermis. Furthermore, the wound treated with a human hair-based hydrogel showed almost complete epithelial regeneration, with the maturation of immature connective tissue and hair follicles and formation of a sebaceous gland.

The Characterization of Polyacrylonitrile Fibers Stabilized by Electron Beam Irradiation

This study investigates polyacrylonitile(PAN) fibers stabilized with various doses of electron beam irradiation (EBI) ability to produce carbon fibers. Feasibility was verified by FT-IR, the percent of gel fraction, density, DSC, XRD, and mechanical measurements. FT-IR spectra showed that the intensities of the stretching C≡N bonds decreased at 2,244 cm−1 with increasing EBI dose. This de crease was related to cyclization of nitrile groups during EBI-stabilization. The degree of cyclization was determined from the gel fraction and density tests. The gel content and density of PAN fibers stabilized by EBI increased with an increase in the EBI dose. Thermal properties were characterized by differential scanning calorimetry (DSC) and thermally activated reactions. DSC curves showed that EBI treatment influenced the quantity of released heat and the exothermic position at low temperature over a wide temperature range. The strongest diffraction peak from the PAN precursor fiber arose from the (100) plane; its stabilization index (SI) was evaluated by X-ray diffraction. The X-ray results showed that the peak intensity decreases gradually with increasing EBI dose. In addition, tensile strength decreased the EBI stabilization level.

Preparation and characterization of chlorinated cross-linked chitosan/cotton knit for biomedical applications

AbstractA new cross-linked chitosan/cotton knit was prepared by the chlorination of chitosan under acidic conditions, and its active chlorine content, mechanical and antimicrobial properties, and rechargeability were characterized. The active chlorine content of the chitosan/cotton knit increased with the concentration of chitosan or sodium hypochlorite used for the treatment and showed a slight decrease upon repeated laundering. The cross-linked chitosan/cotton knit displays lower stress and higher strain than pristine cotton knit. The chlorination of the chitosan/cotton knit resulted in powerful antimicrobial activity against both gram-negative and gram-positive bacteria. For up to 30 days of storage the knit showed excellent rechargeability, taking up chlorine to nearly initial levels. Scanning electron microscope (SEM) observations indicated that chlorination did not cause the damage to the cross-linked chitosan/cotton knit.

Predicting the optimal depth of left-sided central venous catheters in children

The aim of this study was to predict the optimal depth for insertion of a left‐sided central venous catheter in children. Using 3D chest computed tomography angiography, we measured the distance from a point where the internal jugular vein is at the superior border of the clavicle, and from a point where the subclavian vein is inferior to the anterior border of the clavicle, to the junction of the superior vena cava and the right atrium in 257 children. Linear regression analysis revealed that the distances correlated with age, weight and height. Simple formulae for the depth of a central venous catheter via the left internal jugular vein (0.07 × height (cm)) and the left subclavian vein (0.08 × height (cm)) were developed to predict placement of the central venous catheter tip at the junction of the superior vena cava with the right atrium. Using these fomulae, the proportion of catheter tips predicted to be correctly located was 98.5% (95% CI 96.8–100%) and 94.0% (95% CI 90.8–97.3%), respectively.

Novel preparation and characterization of human hair-based nanofibers using electrospinning process

Human hair-based biocomposite nanofibers (NFs) have been fabricated by an electrospinning technique. Aqueous keratin extracted from human hair was successfully blended with poly(vinyl alcohol) (PVA). The focus here is on transforming into keratin/PVA nanofibrous membranes and insoluble property of electrospun NFs. The resulting hair-based NFs were characterized using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning colorimetry (DSC), and thermogravimetric analysis (TGA). Toward the potential use of these NFs after cross-linking with various weight fractions of glyoxal, its physicochemical properties, such as morphology, mechanical strength, crystallinity, and chemical structure were investigated. Keratin/PVA ratio of 2/1 NFs with 6 wt%-glyoxal showed good uniformity in fiber morphology and suitable mechanical properties, and excellent antibacterial activity providing a potential application of hair-based NFs in biomedical field.

An overview of new oxidation methods for polyacrylonitrile-based carbon fibers

The process of oxidizing polyacrylonitrile (PAN)-based carbon fibers converts them into an infusible and non-flammable state prior to carbonization. This represents one of the most important stages in determining the mechanical properties of the final carbon fibers, but the most commonly used methods, such as thermal treatment (200°C to 300°C), tend to waste a great deal of process time, money, and energy. There is therefore a need to develop more advanced oxidation methods for PAN precursor fibers. In this review, we assess the viability of electron beam, gamma-ray, ultra-violet, and plasma treatments with a view to advancing these areas of research and their industrial application.

Facile preparation of self-assembled wool-based graphene hydrogels by electron beam irradiation

Three dimensional self-assembled graphene hydrogels were easily fabricated by electron beam irradiation (EBI) using an aqueous solution of wool/poly(vinyl alcohol) and graphene oxide (GO). After exposure to various levels of EBI radiation, the highly porous, self-assem- bled, wool-based graphene hydrogels were characterized using scanning electron micros- copy and Fourier-transform infrared spectroscopy; to determine the gel fraction, degree of swelling, gel strength, kinetics-of-swelling analyses and removal of hexavalent chromium (Cr(VI)) from the aqueous solution. X-ray diffraction results confirmed that EBI played a significantly important role in reducing GO to graphene. The adsorption equilibrium of Cr(VI) was reached within 80 min and the adsorption capacity was dramatically increased as the acidity of the initial solution was decreased from pH 5 to 2. Changes in ionic strength did not exert much effect on the adsorption behavior.

Effects of heat treatment time on aromatic yield of pyrolysis fuel oil-derived pitches

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Influence of oxidative atmosphere of the electron beam irradiation on cyclization of PAN-based fibers

In order to study the impact of atmosphere during electron beam irradiation (EBI) of polyacrylonitrile (PAN) precursor fibers, the latter were stabilized by EBI in both air and oxygen atmospheres. Gel-fraction determination indicated that EBI-stabilization under an oxygen atmosphere leads to an enhanced cyclization in the PAN fibers. In the Fourier-transform infrared spectroscopy analysis, the PAN fibers stabilized by EBI under an oxygen atmosphere exhibited a greater decrease in the peak intensity at 2244 cm-1 (C≡N vibration) and a greater increase in the peak intensity at 1628 cm-1 (C=N absorption) than the corresponding PAN fibers stabilized under an air atmosphere. From the X-ray diffraction analysis it was found that oxygen uptake in PAN fibers leads to an increase in the amorphous region, produced by cyclization.