• Macromolecular Research
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• v.10 no.2
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• pp.85-90
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• 2002

Poly (ethylene oxide)/polylatide/poly(ethylene oxide) (PEO/PL/PEO) tri-block copolymers, which each block is connected by ester bond, were synthesized by coupling reaction of PL with PEO in the presence of pyridine. PL/PEO/PL tri-block copolymer was synthesized by ring opening polymerization of L-lactide initiated by PEO in the presence of stannous octoate. Degradation behavior of the copolymers was investigated in a pH 7.4 phosphate buffer saline (PBS) at 37$\pm$1 $^{\circ}C$. Gel permeation chromatography (GPC) and $^1$H-nuclear magnetic resonance (NMR) were used to monitor the change of mass loss, molecular weight and composition of copolymers. In hydrolytic degradation, the PEO/PL/PEO tri-block copolymer with high PEO contents affected the increase of its mass loss, and resulted in the decrease of its molecular weight as well as PEO composition. However, when PL/PEO/PL and PEO/PL/PEO tri-block copolymers had similar PEO contents, PEO/PL/PEO decreased faster in molecular weight and PEO composition than PL/PEO/PL.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.39 no.2
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• pp.43-54
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• 2013

In an attempt to regain function and aesthetics in the craniofacial region, different biomaterials, including titanium, hydroxyapatite, biodegradable polymers and composites, have been widely used as a result of the loss of craniofacial bone. Although these materials presented favorable success rates, osseointegration and antibacterial properties are often hard to achieve. Although bone-implant interactions are highly dependent on the implant's surface characteristics, infections following traumatic craniofacial injuries are common. As such, poor osseointegration and infections are two of the many causes of implant failure. Further, as increasingly complex dental repairs are attempted, the likelihood of infection in these implants has also been on the rise. For these reasons, the treatment of craniofacial bone defects and dental repairs for long-term success remains a challenge. Various approaches to reduce the rate of infection and improve osseointegration have been investigated. Furthermore, recent and planned tissue engineering developments are aimed at improving the implants' physical and biological properties by improving their surfaces in order to develop craniofacial bone substitutes that will restore, maintain and improve tissue function. In this review, the commonly used biomaterials for craniofacial bone restoration and dental repair, as well as surface modification techniques, antibacterial surfaces and coatings are discussed.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.206-215
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• 2005

Polyhydroxyalkanoates (PHAs) are homo or hetero polyesters of (R)-hydroxyalkanoates accumulated in various microorganisms under growth-limiting condition in the presence of excess carbon source. They have been suggested as biodegradable substitutes for chemically synthesized polymers. Recombinant Escherichia coli is one of the promising host strains for the economical production of PHAs, and has been extensively investigated for the process development. The heterologous PHA biosynthetic pathways have been established through the metabolic engineering and inherent metabolic pathways of E. coli have been redirected to supply PHA precursors. Fermentation strategies for cultivating these recombinant E. coli strains have also been developed for the efficient production of PHAs. Nowadays, short-chain-length (SCL) PHAs are being re-invited due to its improved mechanical properties and possible applications in the biomedical area. In this article, recent advances in the development of metabolically engineered E. coli strains for the enhanced production of SCL-PHAs are reviewed. Also, medical applications of SCL-PHAs are discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.9-16
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• 2018

Recently, the demand for eco-friendly parts has increased to reduce materials and parts that use fossil fuels. This has exacerbated the increase of energy prices and the enforcement of regulations by environmental agencies. Currently, polylactic acid (PLA) is a solution, as a common and eco-friendly material. PLA is a biodegradable material that can replace traditional petrochemical polymers. PLA has great advantages since it is resistant to cracking and shrinkage. When it is manufactured, there are few harmful byproducts. Improvement in the brittleness characteristics is another important task to be monitored throughout the production of industrial parts. Improvement in the brittleness property of products lowers the tensile strength and tensile elasticity modulus of the parts. This study focused on the mechanical properties of 3D-printed PLA parts. Tensile tests are performed while varying the infill print parameters to evaluate the applicability of PLA in several industrial areas.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.7
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• pp.1270-1280
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• 2001

In this research of biodegradable polymers, it is essential to investigate the relation between biodegradability and molecular structure such as chemical constitution, hydrophilicity, molecular weight, crystallinity, chain orientation, and so on. It is also expected that hydrophilicity of polymer can affect biodegradability because biodegradation occurs with the help of enzymes and microorganisms. This study is to investigate the effect of hydrophilicity on biodegradability of polyesters. Hydrophilicity was varied by adding 5~30 mol% of amide groups, since amide groups are hydrophilic and used for improving thermal and mechanical properties. Surface energies and nitrogen contents by ESCA were measured to determine their hydrophilicity. The biodegradation was examined in activated sludge, enzyme and natural soil by $CO_2$evolution, TOC, weight loss, and observation through microscopy. The results showed that hydrophilicity of polyesteramide films increased with the addition of amide, PBAD series of shorter methylene units showed maximum hydrophilicity at 15~20 mol% of amide contents, but PBSE exhibited maximum values at 5~15 mol% of amide contents. The biodegradability increased as the hydrophilicty on surface increased. The biodegradation rate of PBAD series was higher than that of PBSE series. Therefore, it can be concluded that the addition of appropriate contents of hydrophile enhanced the biodegradability of aliphatic polyesters as well as their physical properties. Also, the experimental results revealed the relation between hydrophilicity and biodegradability of polyesteramides.

• Biomaterials and Biomechanics in Bioengineering
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• v.5 no.1
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• pp.65-86
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• 2020

As conventional drug delivery system is being improved rapidly by target-based drug delivery system, finding suitable Drug Delivery System (DDS) for new drugs remains a challenge. Although there are many drug delivery vehicles in existence, a significant improvement is required to some DDS such as for local, implant-based treatments used for musculoskeletal infections. Many polymers have been considered for providing the improvement in DDS. Synthetic polymer, for example, has gained popularity for broad-spectrum physicochemical and mechanical properties. This article reviews the biomedical applications of Poly(TriMethylene Carbonate-co-Caprolactone) (PTMCC), which has attracted attention due to its biocompatibility, biodegradability and rubber-like properties. Its synthesis, physical properties, and degradation are also discussed here. Although it is relatively new in biomedical applications, it is readily usable for the fabrication of differing format of DDS of superior mechanical strength and degradation properties. The use of PTMCC is expected to increase in coming years as more is revealed about its potentials.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.14 no.2
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• pp.81-88
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• 2008

There are increasing public concerns that the disposal of most synthetic carbon-based plastics is a great threat to the environment. These have led to intensive research and development of degradable plastics, such as biodegradable plastics, photodegradable plastics, and multi-degradable plastics. Although these degradable plastics may not completely replace common synthetic plastics, these minimize environmental impacts caused by non degradable plastics. Photodegradable plastics are synthetic polymers into which have been incorporated copolymers or light-sensitive additives to weaken the structural bonds in polymer chains when exposed to UV radiation. A better understanding of photodegradable plastics, which also play an important role in the degradation of multi-degradable plastics, will expand the usage of degradable plastics. The aim of present article is to review the formation, degradation mechanism and properties of photodegradable plastics.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.927-933
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• 2011

Conducting polyaniline-poly($\varepsilon$-caprolactone) polymer composites were synthesized via in situ deposition techniques. By dissolving different weight percentages of poly($\varepsilon$-caprolactone) (PCL) (10%, 20%, 30%, 40%, and 50%), the oxidative polymerization of aniline was achieved using ammonium persulfate as an oxidant. FTIR, UV-vis spectra, and X-ray diffraction studies support a strong interaction between polyaniline (PANI) and PCL. Structural morphology of the PANI-PCL polymer composites was studied using scanned electron microscopy (SEM) and transmittance electron microscopy (TEM), and thermal stability was analyzed by thermogravimetric analysis (TGA) technique. The temperature-dependent DC conductivity of PANI-PCL polymer composite films was studied in the range of 305-475 K, which revealed a semiconducting behavior in the transport properties of the polymer films. Conductivity increased with the increase of PCL in below critical level, however conductivity of the polymer film was decreased with increase of PCL concentration higher than the critical value.

• Journal of Periodontal and Implant Science
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• v.28 no.2
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• pp.281-291
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• 1998

Chitosan is a biodegradable and non-toxic material with a molecular weight of 800-1,500Kd which can be obtained in various forms with extraordinary chemical structures and biological characteristics of which enables it to be used in many fields as a biomaterial. Ion irradiation is a useful tool to modify chemical structures and physical properties of high molecular weight polymers. The basic hypothesis of this study is that when surface properties of chitosan in a sponge form are modified with ion beam-irradiation and cell adhesion properties of chitosan would improve and thereby increase the regenerative ability of the damaged bone. The purpose of this study was to illuminate the changes in the cytocompatibility of chitosan sponges after ion beam-irradiation as a preliminary research. Argon($Ar^+$) ions were irradiated at doses of $5{\times}10^{13}$, $5{\times}10^{15}$ at 35 keV on surfaces of each sponges. Cell adhesion and activity of alkaline phosphatases were studied using rat fetal osteoblasts. The results of this study show hat ion beam-irradiation at optimal doses($5{\times}10^^{13}\;Ar^+\;ion/cm^2$) is a useful method to improve cytocompatibility without sacrificing cell viability and any changing cell phenotypes. These results show that ion beam-irradiated chitosan sponges can be further applied as carriers in tissue engineering and as bone filling materials.

• KSBB Journal
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• v.15 no.6
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• pp.670-672
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• 2000

Azotobacter vinelandii UWD synthesizes poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), one of the biodegradable polymers, when odd and even number carbon sources are simultaneously added to a medium. In this study, we investigated the specific growth rate of Azotobacter vinelandii UWD on propionic acid and valeric acid. The specific growth rates were $0.183 hr^{-1} and 0.137 hr^{-1}$ at 1.0∼1.5 g/L of propionic acid and 1.0 g/L of valeric acid, respectively. When a mixture of 0.75 g/L of propionic acid and 0.5 g/L of valeric acid was added to the medium, the specific growth rate was 0.196 hr(sup)-1, which was equal to or higher than those of the individual organic acids. Among 10∼50 g/L of glucose cell growth was best at 20 g/L.