• Biomaterials Research
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• v.22 no.4
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• pp.249-258
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• 2018

Background: Mucoadhesive polymers, which may increase the contact time between the polymer and the tissue, have been widely investigated for pharmaceutical formulations. In this study, we developed a new polysaccharide-based mucoadhesive polymer with thermogelling properties. Methods: Hexanoyl glycol chitosan (HGC), a new thermogelling polymer, was synthesized by the chemical modification of glycol chitosan using hexanoic anhydride. The HGC was further modified to include thiol groups to improve the mucoadhesive property of thermogelling HGC. The degree of thiolation of the thiolated HGCs (SH-HGCs) was controlled in the range of 5-10% by adjusting the feed molar ratio. The structure of the chemically modified polymers was characterized by $^1H$ NMR and ATR-FTIR. The sol-gel transition, mucoadhesiveness, and biocompatibility of the polymers were determined by a tube inverting method, rheological measurements, and in vitro cytotoxicity tests, respectively. Results: The aqueous solution (4 wt%) of HGC with approximately 33% substitution showed a sol-gel transition temperature of approximately $41^{\circ}C$. SH-HGCs demonstrated lower sol-gel transition temperatures ($34{\pm}1$ and $31{\pm}1^{\circ}C$) compared to that of HGC due to the introduction of thiol groups. Rheological studies of aqueous mixture solutions of SH-HGCs and mucin showed that SH-HGCs had stronger mucoadhesiveness than HGC due to the interaction between the thiol groups of SH-HGCs and mucin. Additionally, we confirmed that the thermogelling properties might improve the mucoadhesive force of polymers. Several in vitro cytotoxicity tests showed that SH-HGCs showed little toxicity at concentrations of 0.1-1.0 wt%, indicating good biocompatibility of the polymers. Conclusions: The resultant thiolated hexanoyl glycol chitosans may play a crucial role in mucoadhesive applications in biomedical areas.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2320-2327
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• 2020

The extreme hydrophobicity of expanded polytetrafluoroethylene (ePTFE) hinders bone-tissue integration, thus limiting the use of ePTFE in medical implant applications. To improve the potential of ePTFE as a biomaterial, 2-hydroxyethyl methacrylate (HEMA) was grafted onto the ePTFE surface using the gamma irradiation technique. The characteristics of the grafted ePTFE were successfully evaluated using attenuated total reflectance Fourier transform infrared (ATR-FTIR), field-emission scanning electron microscopy (FESEM)/energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). Under the tensile test, the modified ePTFE was found to be more brittle and rigid than the untreated sample. In addition, the grafted ePTFE was less hydrophobic with a higher percentage of water uptake compared to the untreated ePTFE. The protein adsorption test showed that grafted ePTFE could adsorb protein, which was denoted by the presence of N peaks in the XPS analysis. Moreover, the formation of the globular mineral on the grafted ePTFE surface was successfully visualized using the FESEM analysis, with a ratio of 1.94 for Ca:P minerals by the EDX. To summarize, the capability of the modified ePTFE to show protein adsorption and mineralization indicates the improvement of the polymer properties, and it can potentially be used as a biomaterial for implant application.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.345-351
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• 2002

The purpose of this study was to assess clinical proton MR spectroscopy (MRS) as a noninvasive method for evaluating brain tumor malignancy at 3T high field system. Using 3T MRI/MRS system, localized water-suppressed single-voxe1 technique in patients with brain tumors was employed to evaluate spectra with peaks of N-acetyl aspartate (NAA), choline-containing compounds (Cho), creatine/phosphocreatine (Cr) and lactate. On the basis of Cr, these peak areas were quantificated as a relative ratio. The variation of metabolites measurements of the designated region in 10 normal volunteers was less than 10%. Normal ranges of NAA/Cr and Cho/Cr ratios were 1.67${\pm}$018 and 1.16${\pm}$0.15, respectively. NAA/Cr ratio of all tumor tissues was significantly lower than that of the normal tissues (p=0.005), but Cho/Cr ratio of all tumor tissue was significantly higher (p=0.001). Cho/Cr ratio of high-grade gliomas was significantly higher than that of low-grade gliomas (P=0.001). Except 4 menigiomas, lactate signal was observed in all tumor cases. The present study demonstrated that the neuronal degradation or loss was observed in all tumor tissues. Higher grade of brain tumors was correlated with higher Cho/Cr ratio, indicating a significant dependence of Cho levels on malignancy of gliomas. Our results suggest that clinical proton MR spectroscopy could be useful to predict tumor malignancy.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.122.2-122.2
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• 2016

Surface topographical cues has been highlighted to control the fate of neural stem cells (NSCs). Herein we developed a hierarchically patterned substrate (HPS) platform for regulating NSC differentiation. The HPS induced cytoskeleton alignment and highly activated focal adhesion in hNSCs as indicated by enhanced expression of focal adhesion proteins such as focal adhesion kinase (FAK) and vinculin. hNSCs cultured on HPS exhibited enhanced neuronal differentiation compared to flat group. We also developed a graphene oxide (GO)-based hierarchically patterned substrates (GPS) that promote focal adhesion formation and neuronal differentiation of hNSCs. Enhanced focal adhesion and differentiation of hNSCs on the HPS was reversed by blocking the ${\beta}1$ integrin binding and mechanotransduction-associated signals including Rho-associated protein kinase (ROCK) and extracellular-regulated kinase (ERK) pathway, which may suggest a potential mechanism of beneficial effects of HPS. In addition, hNSCs on the HPS differentiated into functional neurons exhibiting sodium currents and action potentials as confirmed by whole cell patch-clamping analysis. The hierarchical topography can direct differentiation of NSCs towards functional neurons, and therefore would be an important element for the design of functional biomaterials for neural tissue regeneration applications.

• Biomaterials and Biomechanics in Bioengineering
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• v.1 no.1
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• pp.41-50
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• 2014

Gold nanorod's exceptional light to heat transduction is a robust phonomenon that has been extensively verified. The phenomenon is a trait from which many novel applications across disciplines have been proposed. In this investigation, the feasibility of utilizing heat harvested from such photothermal method to combat cancer is presented. Using non-invasive laser methods, an in vivo study is conducted on mouse ear tumors administered with gold nanorods (Au NRs). An emphasis is placed on monitoring the tumor developments after photothermal treatments, over time. The findings reveal significant tumor growth surpression at a threshold laser power of $0.6W/cm^2$ lasting 2 minutes; this energy also brought about dramatic size reduction in treated tumors. Furthermore, the apparent formation of an eschar over the laser treated region indicates extensive hemorrhagic necrosis of the tumor tissue; a phenomenon implicative to the inhibition of angiogenesis.

• Carbon letters
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• v.16 no.4
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• pp.233-240
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• 2015

Electrochemical synthesis was employed to prepare a novel hydroxyapatite/graphene (HAP/Gr) composite powder suitable for medical applications as a hard tissue implant (scaffold). The synthesis was performed in a homogeneous dispersion containing Na₂H₂EDTA·2H₂O, NaH₂PO₄ and CaCl₂ with a Ca/EDTA/PO₄³⁻ concentration ratio of 0.25/0.25/0.15M, along with 0.01 wt% added graphene nanosheets, at a current density of 137 mA cm⁻² and pH value of 9.0. The field emission scanning electron microscopy and transmission electron microscopy observations of the composite HAP/Gr powder indicated that nanosized hydroxyapatite particles were uniformly placed in the graphene overlay. Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction confirmed graphene incorporation in the HAP/Gr powder. The electrochemically prepared HAP/Gr composite powder exhibited slight antibacterial effect against the growth of the bacterial strain Staphylococcus aureus.

• International Journal of Oral Biology
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• v.39 no.4
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• pp.187-192
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• 2014

Nonthermal atmospheric pressure plasma has attracted great interest for biomedical applications. The plasma consists of charged particles, radicals, and a strong electric field as the fourth state of matter. This study evaluated the change in the surface roughness after tooth bleaching by plasma in combination with a low concentration (15%) of carbamide peroxide, specifically whether the application of plasma produced detriments, such as demineralization and structural change, with the goal of efficient and safe tooth bleaching. After being combined with plasma and 15% carbamide peroxide, the hydroxyapatite surface was significantly smoother with a low roughness average value. Tooth bleaching with 15% carbamide peroxide alone produced an irregular surface and increased the surface roughness with high roughness average value. Tooth bleaching with plasma resulted in no significant variations in hydroxyapatite in terms of change in surface roughness and surface topography. The application of tooth bleaching with plasma is not deleterious to dental hard tissue, implicating it as a safe tooth bleaching technique.

• Polymer(Korea)
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• v.30 no.1
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• pp.1-9
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• 2006

The development of functional polymeric materials for biomedical application has progressed on the basis of functionality, biocompatibility and biodegradability. In this paper we review the functional polymeric biomaterialsbased systems and propose a range of biomedical applications in the near future. These systems include the functional biodegradable polymers synthesized in our research laboratory, biodegradable polymeric materials, thermosensitive polymeric materials, cationic polymeric materials, non-condensing polymeric biomaterials, bio-polymeric DNA matrix for tissue engineering, and polymeric biomaterials for RNA interference (RNAi) technology.

• Archives of Plastic Surgery
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• v.33 no.1
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• pp.21-30
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• 2006

Alginate, a polymer of guluronic and mannuronic acid, is used as a scaffolding material in biomedical applications. The research was to produce highly-purified alginate from seaweeds and to evaluate the efficacy of alginate as dermal substrate. Our alginate purification method showed a production rate as high as 25%. The purified alginate contained little polyphenol contents and endotoxin, proteins. For study of wound healing, full thickness skin defects were made on the dorsal area of the animal models. And then alginate, fibroblast-growth-factor mixed alginate, alginate-collagen complex, vaseline gauze as control were applied on the wound, respectively, and were evaluated grossly and histopathologically. For biocompatibility test, alginate and alginate-collagen complex discs were implanted on the back of Sprague-Dawly rats. Four weeks after implantation, the animals were examined immunologically against alginate and collagen. Alginate and FGF-mixed alginate, alginate-collagen complex group showed statistically higher percentage of wound contraction and wound healing than control group(p<0.05). Alginate-collagen complex group and FGF-mixed alginate group showed statistically higher percentage of wound healing than alginate group. The experiment of biocompatibility and immunologic reaction against impanted alginate or collagen needs more investigation. Highly-purified alginate from seaweeds by our purification method, showed the effect of wound healing, and addition of FGF or collagen increases the alginate's wound healing effect. It shows the possibility of alginate as a dermal substrate.

• International Journal of Industrial Entomology and Biomaterials
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• v.35 no.2
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• pp.83-88
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• 2017

Silk is appealing materials for many biomedical applications involving tissue engineering and implantable devices, because of its biocompatibility, environmental stability, controlled proteolytic biodegradability and morphologic flexibility. Silk matrix is required for the treatment of a wide wound area, but the present silk matrix is made by the second processing, and thus, the labor and the cost are high. In this work, we investigated the optimal production condition of natural silk 3D matrix using the silkworms and invented Automatic Silk Matrix Making Machine (ASMMM) for natural silk 3D matrix production. As a result, we determined that optimal production condition for making A4 paper size natural silk 3D matrix was used Rough aquarelle paper on surface at $25^{\circ}C$ and 30 silkworm larvae. These results are expected to provide basic data for the efficient production of the natural silk 3D matrix, and it is suggested that the produced natural silk 3D matrix is useful as a medical biomaterials.