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Kim SJ, Byun H, Lee S, Kim E, Lee GM, Huh SJ, Joo J, Shin H. Spatially arranged encapsulation of stem cell spheroids within hydrogels for the regulation of spheroid fusion and cell migration. Acta Biomater 2022; 142:60-72. [PMID: 35085797 DOI: 10.1016/j.actbio.2022.01.047] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 12/09/2021] [Accepted: 01/20/2022] [Indexed: 12/16/2022]
Abstract
Mesenchymal stem cell spheroids have been encapsulated in hydrogels for various applications because spheroids demonstrate higher cell activity than individual cells in suspension. However, there is limited information on the effect of distance between spheroids (inter-spheroid distance) on fusion or migration in a hydrogel. In this study, we developed temperature-responsive hydrogels with surface microwell patterns to culture adipose-derived stem cell (ASC) spheroids and deliver them into a Matrigel for the investigation of the effect of inter-spheroid distance on spheroid behavior. The ASC spheroids were encapsulated successfully in a Matrigel, denoted as sandwich culture, with a specific inter-spheroid distance ranging from 100 to 400 µm. Interestingly, ASCs migrated from the host spheroid and formed a bridge-like structure between spheroids, denoted as a cellular bridge, only when the inter-spheroid distance was 200 µm. Thus, we performed a sandwich culture of human umbilical vein endothelial cells (HUVECs) and ASCs in co-cultured spheroids in the Matrigel to create a homogeneous endothelial cell network in the hydrogel. The HUVECs sprouted through the ASC cellular bridge and directly interacted with the adjacent spheroid when the inter-spheroid distance was 200 µm. Similar results were obtained from an in vivo study. Thus, our study suggests the appropriate inter-spheroid distance for effective spheroid encapsulation in a hydrogel. STATEMENT OF SIGNIFICANCE: Recently, spheroid-based 3D tissue culture techniques such as spheroid encapsulation or 3D printing are being intensively investigated for various purposes. However, there is limited research regarding the effect of the inter-spheroid distance on spheroid communication. Here, we demonstrate a spatially arranged spheroid encapsulation method within a Matrigel by using a temperature-responsive hydrogel. Human adipose-derived stem cell spheroids are encapsulated with a precisely controlled inter-spheroid distance from 100 to 400 µm and show different tendencies in cell migration and spheroid fusion. Our results suggest that the inter-spheroid distance affects spheroid communication, and thus, the inter-spheroid distance needs to be considered carefully according to the purpose.
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Affiliation(s)
- Se-Jeong Kim
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; BK21 FOUR, Education and Research Group for Biopharmaceutical Innovation Leader, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Hayeon Byun
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; BK21 FOUR, Education and Research Group for Biopharmaceutical Innovation Leader, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Sangmin Lee
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; BK21 FOUR, Education and Research Group for Biopharmaceutical Innovation Leader, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Eunhyung Kim
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; BK21 FOUR, Education and Research Group for Biopharmaceutical Innovation Leader, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Gyeong Min Lee
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; BK21 FOUR, Education and Research Group for Biopharmaceutical Innovation Leader, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Seung Jae Huh
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; BK21 FOUR, Education and Research Group for Biopharmaceutical Innovation Leader, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea
| | - Jinmyoung Joo
- Department of Biomedical Engineering, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 44919, Republic of Korea.
| | - Heungsoo Shin
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; BK21 FOUR, Education and Research Group for Biopharmaceutical Innovation Leader, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea; Institute of Nano Science and Technology (INST), Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul 04763, Republic of Korea.
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Kim SJ, Kim EM, Yamamoto M, Park H, Shin H. Engineering Multi-Cellular Spheroids for Tissue Engineering and Regenerative Medicine. Adv Healthc Mater 2020; 9:e2000608. [PMID: 32734719 DOI: 10.1002/adhm.202000608] [Citation(s) in RCA: 94] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 07/09/2020] [Indexed: 02/06/2023]
Abstract
Multi-cellular spheroids are formed as a 3D structure with dense cell-cell/cell-extracellular matrix interactions, and thus, have been widely utilized as implantable therapeutics and various ex vivo tissue models in tissue engineering. In principle, spheroid culture methods maximize cell-cell cohesion and induce spontaneous cellular assembly while minimizing cellular interactions with substrates by using physical forces such as gravitational or centrifugal forces, protein-repellant biomaterials, and micro-structured surfaces. In addition, biofunctional materials including magnetic nanoparticles, polymer microspheres, and nanofiber particles are combined with cells to harvest composite spheroids, to accelerate spheroid formation, to increase the mechanical properties and viability of spheroids, and to direct differentiation of stem cells into desirable cell types. Biocompatible hydrogels are developed to produce microgels for the fabrication of size-controlled spheroids with high efficiency. Recently, spheroids have been further engineered to fabricate structurally and functionally reliable in vitro artificial 3D tissues of the desired shape with enhanced specific biological functions. This paper reviews the overall characteristics of spheroids and general/advanced spheroid culture techniques. Significant roles of functional biomaterials in advanced spheroid engineering with emphasis on the use of spheroids in the reconstruction of artificial 3D tissue for tissue engineering are also thoroughly discussed.
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Affiliation(s)
- Se-Jeong Kim
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul, 04763, Republic of Korea
- BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul, 04763, Republic of Korea
| | - Eun Mi Kim
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul, 04763, Republic of Korea
- BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul, 04763, Republic of Korea
| | - Masaya Yamamoto
- Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki-aza Aoba, Aoba-ku, Sendai, 980-8579, Japan
- Biomedical Engineering for Diagnosis and Treatment, Graduate School of Biomedical Engineering, Tohoku University, 6-6-02 Aramaki-aza Aoba, Aoba-ku, Sendai, 980-8579, Japan
| | - Hansoo Park
- School of Integrative Engineering, College of Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, 06974, Republic of Korea
| | - Heungsoo Shin
- Department of Bioengineering, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul, 04763, Republic of Korea
- BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul, 04763, Republic of Korea
- Institute of Nano Science & Technology (INST), Hanyang University, 222 Wangsimri-ro, Seongdong-gu, Seoul, 04763, Republic of Korea
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Multi-Spheroid-Loaded Human Acellular Dermal Matrix Carrier Preserves Its Spheroid Shape and Improves In Vivo Adipose-Derived Stem Cell Delivery and Engraftment. Tissue Eng Regen Med 2020; 17:271-283. [PMID: 32314311 DOI: 10.1007/s13770-020-00252-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 03/09/2020] [Accepted: 03/15/2020] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Current in vivo adult stem cell delivery presents limited clinical effects due to poor engraftment and survival. To overcome current challenges in cell delivery and promote surgical cell delivery for soft tissue repair, a multi-spheroid-loaded thin sectioned acellular dermal matrix (tsADM) carrier which preserves loaded spheroids' three-dimensional (3D) structure, was developed. METHODS Adipose-derived stem cells (ASCs) were used for spheroid delivery. After generating spheroids in 3D cell culture dishes, spheroid plasticity and survival in-between coverslips were evaluated. Spheroids were loaded onto tsADM, their shape changes were followed up for 14 days, and then imaged. Spheroid adhesion stability to tsADM against shear stress was also evaluated. Finally, cell delivery efficacy was compared with cell-seeded tsADM by in vivo implantation and histological evaluation. RESULTS Spheroids withstood cyclic compression stress and maintained their 3D shape without fusion after 48 h of culture in-between coverslips. Cell survival improved when spheroids were cultured on tsADM in-between the coverslips. Spheroid-loaded tsADM with coverslips maintained their spheroid outline for 14 days of culture whereas without coverslips, the group lost their outline due to spreading after 4 days in culture. Spheroids loaded onto tsADMs were more stable after six rather than 3 days in culture. Spheroid-loaded tsADMs showed about a 2.96-fold higher ASCs transplantation efficacy than cell-seeded tsADMs after 2 weeks of in vivo transplantation. CONCLUSION These results indicate that transplantation of spheroid-loaded tsADMs significantly improved cell delivery. These findings suggest that a combined approach with other cells, drugs, and nanoparticles may improve cell delivery and therapeutic efficacy.
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Kim EM, Lee YB, Kim SJ, Park J, Lee J, Kim SW, Park H, Shin H. Fabrication of core-shell spheroids as building blocks for engineering 3D complex vascularized tissue. Acta Biomater 2019; 100:158-172. [PMID: 31542503 DOI: 10.1016/j.actbio.2019.09.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 09/06/2019] [Accepted: 09/17/2019] [Indexed: 12/12/2022]
Abstract
Cell spheroids as building blocks for engineering micro-tissue should be able to mimic the complex structure of natural tissue. However, control of the distribution of multiple cell populations within cell spheroids is difficult to achieve with current spheroid-harvest methods such as hanging-drop and with the use of microwell plates. In this study, we report the fabrication of core-shell spheroids with the ultimate goal to form 3D complex micro-tissue. We used endothelial cells and two types of stem cells (human turbinate mesenchymal stem cells (hTMSCs)/adipose-derived stem cells (ADSCs)). The stem cells and endothelial cells formed layered micro-sized cell sheets (µCSs) on polydopamine micro-patterned temperature-responsive hydrogel surfaces by a sequential seeding method, and these layered µCSs self-assembled to form core-shell spheroids by expansion of the hydrogels. The co-cultured spheroids formed a core-shell structure irrespective of stem cell type. In addition, the size of the core-shell spheroids was controlled from 90 ± 1 to 144 ± 3 µm by changing pattern sizes (200, 300, and 400 µm). The shell thickness gradually increased from 12 ± 3 to 30 ± 6 µm by adjusting the endothelial cell seeding density. Finally, we fabricated the micro-tissue by fusion of the co-cultured spheroids, and the spheroids with the core-shell structure rapidly induced in vitro vessel-like network in 3 days. Thus, the position of endothelial cells in co-cultured spheroids may be an important factor for the modulation of the vascularization process, which can be useful for the production of 3D complex micro-tissues using spheroids as building blocks. STATEMENT OF SIGNIFICANCE: This manuscript describes our work on the fabrication of core-shell spheroids as building blocks to form 3D complex vascularized micro-tissue. Stem cells (human turbinate mesenchymal stem cells (hTMSCs) or adipose-derived stem cells (ADSCs)) and endothelial cells formed layered micro-sized cell sheets (µCSs) on micro-patterned temperature-responsive hydrogel surfaces by a sequential seeding method, and these layered µCSs self-assembled to form core-shell spheroids (core - stem cells, shell - endothelial cells), irrespective of stem cell type. In addition, the size and shell thickness of the core-shell spheroids were controlled by modifying pattern size and endothelial cell seeding density. We fabricated the vascularized micro-tissue by fusion of the spheroids and demonstrated that the spheroids with a core-shell structure rapidly induced vessel-like network.
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Affiliation(s)
- Eun Mi Kim
- Department of Bioengineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea; BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University
| | - Yu Bin Lee
- Department of Bioengineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea; BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University
| | - Se-Jeong Kim
- Department of Bioengineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea; BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University
| | - Jaesung Park
- Department of Bioengineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea; BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University
| | - Jinkyu Lee
- Department of Bioengineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea; BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University
| | - Sung Won Kim
- Department of Pathology, The Catholic University of Korea, College of Medicine, Seoul, Republic of Korea
| | - Hansoo Park
- School of Integrative Engineering, College of Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul, 06974, Republic of Korea.
| | - Heungsoo Shin
- Department of Bioengineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 04763, Republic of Korea; BK21 Plus Future Biopharmaceutical Human Resources Training and Research Team, Hanyang University.
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Park YS, Lee Y, Jin YM, Kim G, Jung SC, Park YJ, Park KD, Jo I. Sustained release of parathyroid hormone via
in situ
cross‐linking gelatin hydrogels improves the therapeutic potential of tonsil‐derived mesenchymal stem cells for hypoparathyroidism. J Tissue Eng Regen Med 2017; 12:e1747-e1756. [DOI: 10.1002/term.2430] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 01/25/2017] [Accepted: 02/23/2017] [Indexed: 12/31/2022]
Affiliation(s)
- Yoon Shin Park
- Department of Molecular Medicine, School of MedicineEwha Womans University Seoul Republic of Korea
- Ewha Tonsil‐derived Mesenchymal Stem Cells Research Center (ETSRC), School of MedicineEwha Womans University Seoul Republic of Korea
- School of Biological Sciences, College of Natural SciencesChungbuk National University Cheongju Republic of Korea
| | - Yunki Lee
- Department of Molecular Science and TechnologyAjou University Suwon Republic of Korea
| | - Yoon Mi Jin
- Department of Molecular Medicine, School of MedicineEwha Womans University Seoul Republic of Korea
- Ewha Tonsil‐derived Mesenchymal Stem Cells Research Center (ETSRC), School of MedicineEwha Womans University Seoul Republic of Korea
| | - Gyungah Kim
- Department of Molecular Medicine, School of MedicineEwha Womans University Seoul Republic of Korea
- Ewha Tonsil‐derived Mesenchymal Stem Cells Research Center (ETSRC), School of MedicineEwha Womans University Seoul Republic of Korea
| | - Sung Chul Jung
- Ewha Tonsil‐derived Mesenchymal Stem Cells Research Center (ETSRC), School of MedicineEwha Womans University Seoul Republic of Korea
- Department of Biochemistry, School of MedicineEwha Womans University Seoul Republic of Korea
| | - Yoon Jeong Park
- Department of Dental Regenerative BiotechnologyDental Research Institute, School of Dentistry, Seoul National University Seoul Republic of Korea
| | - Ki Dong Park
- Department of Molecular Science and TechnologyAjou University Suwon Republic of Korea
| | - Inho Jo
- Department of Molecular Medicine, School of MedicineEwha Womans University Seoul Republic of Korea
- Ewha Tonsil‐derived Mesenchymal Stem Cells Research Center (ETSRC), School of MedicineEwha Womans University Seoul Republic of Korea
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Park JH, Jang J, Lee JS, Cho DW. Current advances in three-dimensional tissue/organ printing. Tissue Eng Regen Med 2016; 13:612-621. [PMID: 30603443 PMCID: PMC6170865 DOI: 10.1007/s13770-016-8111-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 12/14/2015] [Accepted: 12/22/2015] [Indexed: 01/04/2023] Open
Abstract
Three-dimensional (3D) tissue/organ printing is a major aspect of recent innovation in the field of tissue engineering and regenerative medicine. 3D tissue/organ printing aims to create 3D living tissue/organ analogues, and have evolved along with advances in 3D printing techniques. A diverse range of computer-aided 3D printing techniques have been applied to dispose living cells together with biomaterials and supporting biochemical factors within pre-designed 3D tissue/organ analogues. Recent developments in printable biomaterials, such as decellularized extracellular matrix bio-inks have enabled improvements in the functionality of the resulting 3D tissue/organ analogues. Here, we provide an overview of the 3D printing techniques and biomaterials that have been used, including the development of 3D tissue/organ analogues. In addition, in vitro models are described, and future perspectives in 3D tissue/organ printing are identified.
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Affiliation(s)
- Jeong Hun Park
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - Jinah Jang
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - Jung-Seob Lee
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - Dong-Woo Cho
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang, 37673 Korea
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Park YS, Hwang JY, Jun Y, Jin YM, Kim G, Kim HY, Kim HS, Lee SH, Jo I. Scaffold-free parathyroid tissue engineering using tonsil-derived mesenchymal stem cells. Acta Biomater 2016; 35:215-27. [PMID: 26945633 DOI: 10.1016/j.actbio.2016.03.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 02/27/2016] [Accepted: 03/01/2016] [Indexed: 01/01/2023]
Abstract
To restore damaged parathyroid function, parathyroid tissue engineering is the best option. Previously, we reported that differentiated tonsil-derived mesenchymal stem cells (dTMSC) restore in vivo parathyroid function, but only if they are embedded in a scaffold. Because of the limited biocompatibility of Matrigel, however, here we developed a more clinically applicable, scaffold-free parathyroid regeneration system. Scaffold-free dTMSC spheroids were engineered in concave microwell plates made of polydimethylsiloxane in control culture medium for the first 7days and differentiation medium (containing activin A and sonic hedgehog) for next 7days. The size of dTMSC spheroids showed a gradual and significant decrease up to day 5, whereafter it decreased much less. Cells in dTMSC spheroids were highly viable (>80%). They expressed high levels of intact parathyroid hormone (iPTH), the parathyroid secretory protein 1, and cell adhesion molecule, N-cadherin. Furthermore, dTMSC spheroids-implanted parathyroidectomized (PTX) rats revealed higher survival rates (50%) over a 3-month period with physiological levels of both serum iPTH (57.7-128.2pg/mL) and ionized calcium (0.70-1.15mmol/L), compared with PTX rats treated with either vehicle or undifferentiated TMSC spheroids. This is the first report of a scaffold-free, human stem cell-based parathyroid tissue engineering and represents a more clinically feasible strategy for hypoparathyroidism treatment than those requiring scaffolds. STATEMENT OF SIGNIFICANCE Herein, we have for the first time developed a scaffold-free parathyroid tissue spheroids using differentiated tonsil-derived mesenchymal stem cells (dTMSC) to restore in vivo parathyroid cell functions. This new strategy is effective, even for long periods (3months), and is thus likely to be more feasible in clinic for hypoparathyroidism treatment. Development of TMSC spheroids may also provide a convenient and efficient scaffold-free platform for researchers investigating conditions involving abnormal calcium homeostasis, such as osteoporosis.
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Jang JY, Park SH, Park JH, Lee BK, Yun JH, Lee B, Kim JH, Min BH, Kim MS. In Vivo Osteogenic Differentiation of Human Dental Pulp Stem Cells Embedded in an Injectable In Vivo-Forming Hydrogel. Macromol Biosci 2016; 16:1158-69. [DOI: 10.1002/mabi.201600001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 03/10/2016] [Indexed: 12/21/2022]
Affiliation(s)
- Ja Yong Jang
- Department of Molecular Science and Technology; Ajou University; Suwon 443-759 Korea
| | - Seung Hun Park
- Department of Molecular Science and Technology; Ajou University; Suwon 443-759 Korea
| | - Ji Hoon Park
- Department of Molecular Science and Technology; Ajou University; Suwon 443-759 Korea
| | - Bo Keun Lee
- Department of Molecular Science and Technology; Ajou University; Suwon 443-759 Korea
| | - Jeong-Ho Yun
- Department of Periodontology; School of Dentistry and Institute of Oral Bioscience; Chonbuk National University; Jeonju 561-712 Korea
| | - Bong Lee
- Department of Polymer Engineering; Pukyong National University; Busan 608-739 Korea
| | - Jae Ho Kim
- Department of Molecular Science and Technology; Ajou University; Suwon 443-759 Korea
| | - Byoung Hyun Min
- Department of Molecular Science and Technology; Ajou University; Suwon 443-759 Korea
| | - Moon Suk Kim
- Department of Molecular Science and Technology; Ajou University; Suwon 443-759 Korea
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