Publications by authors named "Sang-Hyeon Nam"

12 Publications

  • Page 1 of 1

Demineralized Dentin Matrix Particle-Based Bio-Ink for Patient-Specific Shaped 3D Dental Tissue Regeneration.

Polymers (Basel) 2021 Apr 15;13(8). Epub 2021 Apr 15.

Department of Biomedical Engineering, Ulsan National Institute of Science and Technology 50, UNIST-gil, Ulju-gun, Ulsan 44919, Korea.

Demineralized dentin matrix (DDM)-based materials have been actively developed and are well-known for their excellent performance in dental tissue regeneration. However, DDM-based bio-ink suitable for fabrication of engineered dental tissues that are patient-specific in terms of shape and size, has not yet been developed. In this study, we developed a DDM particle-based bio-ink (DDMp bio-ink) with enhanced three-dimensional (3D) printability. The bio-ink was prepared by mixing DDM particles and a fibrinogen-gelatin mixture homogeneously. The effects of DDMp concentration on the 3D printability of the bio-ink and dental cell compatibility were investigated. As the DDMp concentration increased, the viscosity and shear thinning behavior of the bio-ink improved gradually, which led to the improvement of the ink's 3D printability. The higher the DDMp content, the better were the printing resolution and stacking ability of the 3D printing. The printable minimum line width of 10% / DDMp bio-ink was approximately 252 μm, whereas the fibrinogen-gelatin mixture was approximately 363 μm. The ink's cytocompatibility test with dental pulp stem cells (DPSCs) exhibited greater than 95% cell viability. In addition, as the DDMp concentration increased, odontogenic differentiation of DPSCs was significantly enhanced. Finally, we demonstrated that cellular constructs with 3D patient-specific shapes and clinically relevant sizes could be fabricated through co-printing of polycaprolactone and DPSC-laden DDMp bio-ink.
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http://dx.doi.org/10.3390/polym13081294DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8071469PMC
April 2021

Optically Activated 3D Thin-Shell TiO for Super-Sensitive Chemoresistive Responses: Toward Visible Light Activation.

Adv Sci (Weinh) 2021 Feb 3;8(3):2001883. Epub 2020 Dec 3.

Department of Materials Science and Engineering KAIST Institute for the Nanocentury Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea.

One of the well-known strategies for achieving high-performance light-activated gas sensors is to design a nanostructure for effective surface responses with its geometric advances. However, no study has gone beyond the benefits of the large surface area and provided fundamental strategies to offer a rational structure for increasing their optical and chemical performances. Here, a new class of UV-activated sensing nanoarchitecture made of highly periodic 3D TiO, which facilitates 55 times enhanced light absorption by confining the incident light in the nanostructure, is prepared as an active gas channel. The key parameters, such as the total 3D TiO film and thin-shell thicknesses, are precisely optimized by finite element analysis. Collectively, this fundamental design leads to ultrahigh chemoresistive response to NO with a theoretical detection limit of ≈200 ppt. The demonstration of high responses with visible light illumination proposes a future perspective for light-activated gas sensors based on semiconducting oxides.
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http://dx.doi.org/10.1002/advs.202001883DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7856904PMC
February 2021

Secretoneurin, a Neuropeptide, Enhances Bone Regeneration in a Mouse Calvarial Bone Defect Model.

Tissue Eng Regen Med 2021 04 3;18(2):315-324. Epub 2020 Nov 3.

Department of Oral Pathology and Regenerative Medicine, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 41940, Republic of Korea.

Background: This study investigates the effects of a neuropeptide, secretoneurin (SN), on bone regeneration in an experimental mouse model.

Methods: The effects of SN on cell proliferation, osteoblast marker genes expression, and mineralization were evaluated using the CCK-8 assay, quantitative reverse transcriptase polymerase chain reaction (RT-PCR), and alizarin red S staining, respectively. To examine the effects of SN on bone regeneration in vivo, bone defects were created in the calvaria of ICR mice, and 0.5 or 1 µg/ml SN was applied. New bone formation was analyzed by micro-computed tomography (micro-CT) and histology. New blood vessel formation was assessed by CD34 immunohistochemistry.

Results: SN had no significant effect on proliferation and mineralization of MC3T3-E1 cells. However, SN partially induced the gene expression of osteoblast differentiation markers such as runt-related transcription factor 2, alkaline phosphatase, collagen type I alpha 1, and osteopontin. A significant increase of bone regeneration was observed in SN treated calvarial defects. The bone volume (BV), BV/tissue volume, trabecular thickness and trabecular number values were significantly increased in the collagen sponge plus 0.5 or 1 µg/ml SN group (p < 0.01) compared with the control group. Histologic analysis also revealed increased new bone formation in the SN-treated groups. Immunohistochemical staining of CD34 showed that the SN-treated groups contained more blood vessels compared with control in the calvarial defect area.

Conclusion: SN increases new bone and blood vessel formation in a calvarial defect site. This study suggests that SN may enhance new bone formation through its potent angiogenic activity.
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http://dx.doi.org/10.1007/s13770-020-00304-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8012437PMC
April 2021

Focused Electric-Field Polymer Writing: Toward Ultralarge, Multistimuli-Responsive Membranes.

ACS Nano 2020 Sep 8;14(9):12173-12183. Epub 2020 Sep 8.

Department of Materials Science and Engineering, KAIST Institute for the Nanocentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.

The cost-effective direct writing of polymer nanofibers (NFs) has garnered considerable research attention as a compelling one-pot strategy for obtaining key building blocks of electrochemical and optical devices. Among the promising applications, the changes in optical response from external stimuli such as mechanical deformation and changes in the thermal environment are of great significance for emerging applications in smart windows, privacy protection, aesthetics, artificial skin, and camouflage. Herein, we propose a rational design for the mass production of customized NFs through the development of focused electric-field polymer writing (FEPW) coupled with the roll-to-roll technique. As a proof of key applications, we demonstrate multistimuli-responsive (mechano- and thermochromism) membranes with an exceptional production scale (over 300 cm). Specifically, the membranes consist of periodically aligned ultrathin (∼60 nm) alumina nanotubes inserted in the elastomers. We performed a two-phase finite element analysis of the unit cells to verify the underlying physics of light scattering at heterogeneous interfaces of the strain-induced air gaps. By adding thermochromic dye during the FEPW, the optical modulation of transmittance change (∼83% to 37% at visible wavelength) was successfully extended to high-contrast thermal-dependent coloration.
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http://dx.doi.org/10.1021/acsnano.0c05843DOI Listing
September 2020

Bobby sox homolog regulates tooth root formation through modulation of dentin sialophosphoprotein.

J Cell Physiol 2021 Jan 14;236(1):480-488. Epub 2020 Jun 14.

Department of Oral Pathology and Regenerative Medicine, School of Dentistry, Institute for Hard Tissue and Biotooth Regeneration, Kyungpook National University, Daegu, Republic of Korea.

Tooth root development occurs through the interaction of multiple growth factors and transcription factors expressed in Hertwig's epithelial root sheath (HERS) and dental mesenchyme. Previously, we demonstrated that bobby sox homolog (Bbx) regulates odontoblast differentiation of human dental pulp stem cells. Here, we generated Bbx knockout (Bbx ) mice to address the functional role of Bbx in tooth formation. During tooth development, Bbx was expressed in both dental epithelium and mesenchyme. However, molar and incisor morphology in Bbx mice at postnatal Day 0 (P0) exhibited no prominent abnormalities compared with their wild-type (Bbx ) littermates. Until P28, the crown morphology in Bbx mice was not distinctively different from Bbx littermates. Meanwhile, the length of the mandibular base in Bbx mice was notably less at P28. Compared with Bbx mice, the mesial and distal root lengths of the first molar were reduced by 21.33% and 16.28% at P14 and 16.28% and 16.24% at P28, respectively, in Bbx mice. The second molar of Bbx mice also showed 10.16% and 6.4% reductions at P28 in the mesial and distal lengths, compared with Bbx mice, respectively. The gene expression analysis during early tooth root formation (P13) showed that the expression of dentin sialophosphoprotein (Dspp) was significantly decreased in Bbx mice. Collectively, our data suggest that Bbx participates in tooth root formation and might be associated with the regulation of Dspp expression.
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http://dx.doi.org/10.1002/jcp.29875DOI Listing
January 2021

High-Contrast Optical Modulation from Strain-Induced Nanogaps at 3D Heterogeneous Interfaces.

Adv Sci (Weinh) 2020 Jun 26;7(11):1903708. Epub 2020 Apr 26.

Department of Materials Science and Engineering KAIST Institute for the NanoCentury Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea.

The realization of high-contrast modulation in optically transparent media is of great significance for emerging mechano-responsive smart windows. However, no study has provided fundamental strategies for maximizing light scattering during mechanical deformations. Here, a new type of 3D nanocomposite film consisting of an ultrathin (≈60 nm) AlO nanoshell inserted between the elastomers in a periodic 3D nanonetwork is proposed. Regardless of the stretching direction, numerous light-scattering nanogaps (corresponding to the porosity of up to ≈37.4 vol%) form at the interfaces of AlO and the elastomers under stretching. This results in the gradual modulation of transmission from ≈90% to 16% at visible wavelengths and does not degrade with repeated stretching/releasing over more than 10 000 cycles. The underlying physics is precisely predicted by finite element analysis of the unit cells. As a proof of concept, a mobile-app-enabled smart window device for Internet of Things applications is realized using the proposed 3D nanocomposite with successful expansion to the 3 × 3 in. scale.
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http://dx.doi.org/10.1002/advs.201903708DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7284194PMC
June 2020

Tussilagone Reduces Tumorigenesis by Diminishing Inflammation in Experimental Colitis-Associated Colon Cancer.

Biomedicines 2020 Apr 11;8(4). Epub 2020 Apr 11.

Department of Biomedical Science, Daegu Catholic University, Gyeongsan-Si 38430, Korea.

Background: Tussilagone, a major component of L., has anti-angiogenic and anti-inflammatory effects. However, the therapeutic and preventive activity of tussilagone in colitis-associated colon carcinogenesis is unknown.

Methods: We intended to investigate the therapeutic effects and the potential mechanism of action underlying the pharmacological activity of tussilagone on colitis-associated colon cancer induced in mice using azoxymethane (AOM)/dextran sulfate sodium (DSS). We injected BALB/c mice with AOM and administered 2% DSS in drinking water. The mice were given tussilagone (2.5 and 5 mg/kg body weight) and colon tissues was collected at 72 days. We used Western blotting, immunohistochemistry and real-time RT-PCR analyses to examine the tumorigenesis and inflammatory status of the colon.

Results: Tussilagone administration significantly reduced the formation of colonic tumors. In addition, tussilagone treatment markedly reduced the inflammatory mediators and increased heme oxygease-1 in protein and mRNA levels in colon tissues. Meanwhile, nuclear NF-κB-positive cells were elevated and nuclear Nrf2-positive cells were demised by tussilagone treatment in colon tissues. Tussilagone also reduced cell proliferation, induced apoptosis and decreased the β-catenin expression.

Conclusions: Tussilagone administration decreases the inflammation and proliferation induced by AOM/DSS and induced apoptosis in colon tissue. Overall, this study indicates the potential value of tussilagone in suppressing colon tumorigenesis.
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http://dx.doi.org/10.3390/biomedicines8040086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7235727PMC
April 2020

Stimulatory Effects of KPR-A148 on Osteoblast Differentiation and Bone Regeneration.

Tissue Eng Regen Med 2019 08 17;16(4):405-413. Epub 2019 Jul 17.

1Department of Oral Pathology and Regenerative Medicine, School of Dentistry, Institute for Hard Tissue and Bio-tooth Regeneration (IHBR), Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 41940 Republic of Korea.

Background: Xanthine derivatives have been used to treat a variety of medical conditions including respiratory disease and neural degeneration. However, few studies have reported their effects on bone regeneration. Therefore, we investigated the effects of KPR-A148, a synthetic xanthine derivative on osteoblast differentiation and bone regeneration .

Methods: The cytotoxicity of KPR-A148 was evaluated using MC3T3-E1 cells by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltertrazolium bromide assay. The effects of KPR-A148 on osteoblast differentiation were examined by alkaline phosphatase staining, Alizarin red S staining, and real-time PCR of osteoblast differentiation marker genes. To investigate the effects of KPR-A148 on bone regeneration, a KPR-A148-containing collagen sponge was implanted into a mouse calvarial defect and KPR-A148 was injected twice, weekly. Bone regeneration was evaluated quantitatively by micro-CT and qualitatively by hematoxylin and eosin, as well as Masson's Trichrome staining.

Results: KPR-A148 did not show toxicity in the MC3T3-E1 cells and promoted osteoblast differentiation in a concentration-dependent manner. 10 μM of KPR-A148 showed the most significant effect on alkaline phospatase staining and matrix mineralization. KPR-A148 increased the expression of osteoblast marker genes in both the early and late stages of differentiation. In addition, KPR-A148 significantly induced new bone formation in the calvarial defect model.

Conclusion: These results demonstrate that KPR-A148 strongly induces osteoblast differentiation and new bone formation. Therefore, it could be used as a potential therapeutic agent for regenerating bone following its destruction by disease or trauma.
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http://dx.doi.org/10.1007/s13770-019-00200-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6675851PMC
August 2019

Fermented Oyster Extract Prevents Ovariectomy-Induced Bone Loss and Suppresses Osteoclastogenesis.

Nutrients 2019 Jun 21;11(6). Epub 2019 Jun 21.

Department of Oral Pathology and Regenerative Medicine, School of Dentistry, IHBR, Kyungpook National University, Daegu 41940, Korea.

There is growing interest in bioactive substances from marine organisms for their potential use against diverse human diseases. Osteoporosis is a skeletal disorder associated with bone loss primarily occurring through enhanced osteoclast differentiation and resorption. Recently, we reported the anti-osteoclastogenic activity of fermented Pacific oyster () extract (FO) in vitro. The present study focused on investigating the anti-osteoporotic efficacy of FO in bone loss prevention in an experimental animal model of osteoporosis and elucidating the mechanism underlying its effects. Oral administration of FO significantly decreased ovariectomy-induced osteoclast formation and prevented bone loss, with reduced serum levels of bone turnover biomarkers including osteocalcin and C-terminal telopeptide fragment of type I collagen C-terminus (CTX). FO significantly suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced differentiation of bone marrow-derived macrophages (BMMs) into osteoclasts and attenuated the induction of osteoclast-specific genes required for osteoclastogenesis and bone resorption. Furthermore, FO inhibited RANKL-mediated IκBα and p65 phosphorylation in BMMs. Taken together, these results demonstrate that FO effectively suppresses osteoclastogenesis in vivo and in vitro, and that FO can be considered as a potential therapeutic option for the treatment of osteoporosis and osteoclast-mediated skeletal diseases.
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http://dx.doi.org/10.3390/nu11061392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627411PMC
June 2019

Tussilagone, a major active component in Tussilago farfara, ameliorates inflammatory responses in dextran sulphate sodium-induced murine colitis.

Chem Biol Interact 2018 Oct 22;294:74-80. Epub 2018 Aug 22.

Department of Biomedical Science, Daegu Catholic University, Gyeongsan-Si, South Korea. Electronic address:

Inflammatory bowel disease (IBD) is a chronically relapsing inflammatory disorder of the gastrointestinal tract. Current IBD treatments are associated with poor tolerability and insufficient therapeutic efficacy, prompting the need for alternative therapeutic approaches. Recent advances suggest promising interventions based on a number of phytochemicals. Herein, we explored the beneficial effects of tussilagone, a major component of Tussilago farfara, in mice subjected to acute colitis induced by dextran sulfate sodium (DSS). Treatment with tussilagone resulted in a significant protective effect against DSS-induced acute colitis in mice via amelioration of weight loss, and attenuation of colonic inflammatory damage. Additionally, the expression of tumor necrosis factor-α and interleukin-6 and the activity of myeloperoxidase in colonic tissues were significantly reduced in tussilagone-treated mice. Furthermore, immunohistochemical analysis revealed that tussilagone treatment reduced the numbers of nuclear factor-kappa B (NF-κB) and increased the numbers of nuclear factor erythroid 2-related factor 2 (Nrf2) in nuclei of colonic tissues. Taken together, tussilagone treatment attenuated DSS-induced colitis in mice through inhibiting the activation of NF-κB and inducing Nrf2 pathways, indicating that tussilagone is a potent therapeutic candidate for treatment of intestinal inflammation.
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http://dx.doi.org/10.1016/j.cbi.2018.08.022DOI Listing
October 2018

Fluorescence Modulation of Graphene Quantum Dots Near Structured Silver Nanofilms.

ACS Appl Mater Interfaces 2018 Apr 16;10(16):14079-14086. Epub 2018 Apr 16.

Department of Materials Science and Engineering, KAIST Institute for the Nanocentury , Korea Advanced Institute of Science and Technology (KAIST) , Daejeon 34141 , South Korea.

Here, we study the plasmonic metal-enhanced fluorescence properties of blue-emitting graphene quantum dots (GQDs) and green-emitting graphene oxide quantum dots (GOQDs) using fluorescence lifetime imaging microscopy. Reactive ion sputtered silver (Ag) on zinc oxide (ZnO) thin films deposited on silicon (Si) wafers are used as the substrates. The morphology of the sputtered Ag gradually changes from nanoislands, via and elongated network and a continuous film with nanoholes, to a continuous film with increasing sputtering time. The fluorescence properties of GQD and GOQD on the Ag are modulated in terms of the intensities and lifetimes as the morphology of the Ag layers changes. Although both GQD and GOQD show similar fluorescence modulation on the Ag nanofilms, the fluorescence of GQD is enhanced, whereas that of GOQD is quenched due to the charge transfer process from GOQD to ZnO. Moreover, the GQD and GOQD exhibit different fluorescence lifetimes due to the effect of their electronic configurations. The theoretical calculation explains that the fluorescence amplification on the Ag nanofilms can largely be attributed to the enhanced absorption mechanism arising from accumulated optical fields around nanogaps and nanovoids in the Ag nanofilms.
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http://dx.doi.org/10.1021/acsami.7b19524DOI Listing
April 2018

Antiangiogenic Effects of Ziyuglycoside II, a Major Active Compound of Sanguisorba officinalis L.

Phytother Res 2017 Sep 18;31(9):1449-1456. Epub 2017 Jul 18.

Department of Biomedical Science, Catholic University of Daegu, Gyeongsan-si, 38430, Korea.

Ziyuglycoside II, a major bioactive compound of Sanguisorba officinalis L., displays anticancer potential against several human cancer cells. However, little information concerning its antiangiogenic properties and possible mechanisms is available. The aim of this study was to investigate the inhibitory effects of ziyuglycoside II on angiogenesis. Ziyuglycoside II inhibited the proliferation, migration, and tubule formation of human umbilical vein endothelial cells, as well as the number of microvessels growing from the aortic rings. The underlying antiangiogenic mechanism of ziyuglycoside II correlated with blocking vascular endothelial growth factor receptor-2 and the fibroblast growth factor receptor-1 mediated signaling pathway. Moreover, an in vivo Matrigel plug assay in mice showed a significant decrease in vascularization and hemoglobin content in the plugs from ziyuglycoside II-treated mice compared with control mice. Overall, these results suggest that ziyuglycoside II inhibits various attributes of angiogenesis, which might contribute to its reported antitumor effects. Copyright © 2017 John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/ptr.5874DOI Listing
September 2017
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