{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T15:56:24Z","timestamp":1785858984708,"version":"3.56.0"},"reference-count":48,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2024,1,19]],"date-time":"2024-01-19T00:00:00Z","timestamp":1705622400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>A tough gel composed of atelocollagen, which lacks an immunogenetic site, is a promising material for biomedical application. In this study, we created a composite hydrogel composed of atelocollagen gel cross-linked with glutaraldehyde (GA) and poly-(N,N-dimethylacrylamide) gel exhibiting biocompatibility based on the double-network (DN) gel principle. The tensile toughness of atelocollagen gel remained constant regardless of the amount of cross-linker (GA) used. In contrast, tensile tests of the DN gel indicated that mechanical properties, such as fracture stress and toughness, were significantly higher than those of the atelocollagen gel. Moreover, fibroblast cells adhered and spread on the gels, the Schiff bases of which were treated via reductive amination for detoxification from GA. These findings demonstrate the potential of the proposed gel materials as artificial alternative materials to soft tissues with sub-MPa fracture stress.<\/jats:p>","DOI":"10.3390\/polym16020283","type":"journal-article","created":{"date-parts":[[2024,1,19]],"date-time":"2024-01-19T11:04:57Z","timestamp":1705662297000},"page":"283","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["The Toughness-Enhanced Atelocollagen Double-Network Gel for Biomaterials"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0349-8129","authenticated-orcid":false,"given":"Atsushi","family":"Tsuyukubo","sequence":"first","affiliation":[{"name":"Koken Research Institute, Koken Co., Ltd., 1-18-36 Takarada, Tsuruoka 997-0011, Yamagata, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5492-4466","authenticated-orcid":false,"given":"Riku","family":"Kubota","sequence":"additional","affiliation":[{"name":"Koken Research Institute, Koken Co., Ltd., 1-18-36 Takarada, Tsuruoka 997-0011, Yamagata, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7645-8518","authenticated-orcid":false,"given":"Yuzo","family":"Sato","sequence":"additional","affiliation":[{"name":"Koken Research Institute, Koken Co., Ltd., 1-18-36 Takarada, Tsuruoka 997-0011, Yamagata, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7088-6407","authenticated-orcid":false,"given":"Ichiro","family":"Fujimoto","sequence":"additional","affiliation":[{"name":"Koken Research Institute, Koken Co., Ltd., 1-18-36 Takarada, Tsuruoka 997-0011, Yamagata, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,1,19]]},"reference":[{"key":"ref_1","first-page":"1","article-title":"Revolution in Cell Culture Technology Based on a Novel Concept for Enclosing Cells using Collagen Vitrigel Membranes","volume":"13","author":"Takezawa","year":"2021","journal-title":"Nano Biomed."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1801","DOI":"10.1007\/s10616-015-9934-1","article-title":"Development of an oxygenation culture method for activating the liver-specific functions of HepG2 cells utilizing a collagen vitrigel membrane chamber","volume":"68","author":"Takezawa","year":"2016","journal-title":"Cytotechnology"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/S0939-6411(98)00017-4","article-title":"Collagen\u2014Biomaterial for drug delivery","volume":"45","author":"Friess","year":"1998","journal-title":"Eur. J. Pharm. Biophram."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1002\/jbm.b.30096","article-title":"Antigenicity and immunogenicity of collagen","volume":"71","author":"Lynn","year":"2004","journal-title":"J. Biomed. Mater. Res. B Appl. Biomater."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1651","DOI":"10.1016\/j.addr.2003.08.005","article-title":"Atelocollagen for protein and gene delivery","volume":"55","author":"Sano","year":"2003","journal-title":"Adv. Drug Deliv. Rev."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"751","DOI":"10.2131\/jts.36.751","article-title":"Influence of systemic administration of atelocollagen on mouse livers: An ideal biomaterial for systemic drug delivery","volume":"36","author":"Ogawa","year":"2011","journal-title":"J. Toxicol. Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"369","DOI":"10.4155\/tde.14.8","article-title":"Atelocollagen-mediated SiRNA delivery: Future promise for therapeutic application","volume":"5","author":"Fujimoto","year":"2014","journal-title":"Ther. Deliv."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"E396","DOI":"10.1002\/lary.25989","article-title":"Optimal bovine collagen concentration to achieve tracheal epithelial coverage of collagen sponges","volume":"126","author":"Suzuki","year":"2016","journal-title":"Laryngoscope"},{"key":"ref_9","first-page":"960","article-title":"Micro-dimpled surface atelocollagen maintains primary human hepatocytes in culture and may promote their functionality compared with collagen coat culture","volume":"44","author":"Sato","year":"2019","journal-title":"Int. J. Mol. Med."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Kubota, R., and Fujimoto, I. (2023). Synthesis, Characterization, and Potential Application of Cyclodextrin-Based Polyrotaxanes for Reinforced Atelocollagen Threads. Polymers, 15.","DOI":"10.3390\/polym15153325"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"105462","DOI":"10.1016\/j.reactfunctpolym.2022.105462","article-title":"Synthesis of a stretchable polymer crosslinker for reinforced atelocollagen threads","volume":"182","author":"Kubota","year":"2023","journal-title":"React. Funct. Polym."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1016\/j.addr.2012.09.010","article-title":"Hydrogels for biomedical applications","volume":"64","author":"Hoffman","year":"2012","journal-title":"Adv. Drug Deliv. Rev."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1345","DOI":"10.1002\/adma.200501612","article-title":"Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology","volume":"18","author":"Peppas","year":"2006","journal-title":"Adv. Mater."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"16071","DOI":"10.1038\/natrevmats.2016.71","article-title":"Designing hydrogels for controlled drug delivery","volume":"1","author":"Li","year":"2016","journal-title":"Nat. Rev. Mater."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"eaaf3267","DOI":"10.1126\/science.aaf3627","article-title":"Advances in engineering hydrogels","volume":"356","author":"Zhang","year":"2017","journal-title":"Science"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"485","DOI":"10.1002\/1521-4095(200104)13:7<485::AID-ADMA485>3.0.CO;2-T","article-title":"The Polyrotaxane Gel: A Topological Gel by Figure-of-Eight Cross-links","volume":"13","author":"Okumura","year":"2001","journal-title":"Adv. Mater."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"40509","DOI":"10.1002\/app.40509","article-title":"From Topological Gels to Slide-Ring Materials","volume":"131","author":"Noda","year":"2014","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1078","DOI":"10.1126\/science.aaz6694","article-title":"Tough hydrogels with rapid self-reinforcement","volume":"372","author":"Liu","year":"2021","journal-title":"Science"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1120","DOI":"10.1002\/1521-4095(20020816)14:16<1120::AID-ADMA1120>3.0.CO;2-9","article-title":"Nanocomposite Hydrogels: A Unique Organic-Inorganic Network Structure with Extraordinary Mechanical, Optical, and Swelling\/De-swelling Properties","volume":"14","author":"Haraguchi","year":"2002","journal-title":"Adv. Mater."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1016\/j.cossms.2008.05.001","article-title":"Nanocomposite hydrogels","volume":"11","author":"Haraguchi","year":"2007","journal-title":"Curr. Opin. Solid State Mater. Sci."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"5379","DOI":"10.1021\/ma800476x","article-title":"Design and Fabrication of a High-Strength Hydrogel with Ideally Homogeneous Network Structure from Tetrahedron-like Macromonomers","volume":"41","author":"Sakai","year":"2008","journal-title":"Macromolecules"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1155","DOI":"10.1002\/adma.200304907","article-title":"Double-Network Hydrogels with Extremely High Mechanical Strength","volume":"15","author":"Gong","year":"2003","journal-title":"Adv. Mater."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2583","DOI":"10.1039\/b924290b","article-title":"Why Are Double Network Hydrogels so Tough?","volume":"6","author":"Gong","year":"2010","journal-title":"Soft Matter"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"4426","DOI":"10.1002\/adfm.201200809","article-title":"A Universal Molecular Stent Method to Toughen Any Hydrogels Based on Double Network Concept","volume":"22","author":"Nakajima","year":"2012","journal-title":"Adv. Funct. Mater."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"477","DOI":"10.1038\/pj.2017.12","article-title":"Generalization of the sacrificial bond principle for gel and elastomer toughening","volume":"49","author":"Nakajima","year":"2017","journal-title":"Polym. J."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.biomaterials.2017.04.005","article-title":"Anisotropic tough double network hydrogel from fish collagen and its spontaneous in vivo bonding to bone","volume":"132","author":"Mredha","year":"2017","journal-title":"Biomaterials"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1038\/nature11409","article-title":"Highly stretchable and tough hydrogels","volume":"489","author":"Sun","year":"2012","journal-title":"Nature"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"932","DOI":"10.1038\/nmat3713","article-title":"Physical hydrogels composed of polyampholytes demonstrate high toughness and viscoelasticity","volume":"12","author":"Sun","year":"2013","journal-title":"Nat. Mater."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"504","DOI":"10.1126\/science.aau9533","article-title":"Mechanoresponsive self-growing hydrogels inspired by muscle training","volume":"363","author":"Matsuda","year":"2019","journal-title":"Science"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1038\/s41427-021-00302-2","article-title":"A universal method to easily design tough and stretchable hydrogels","volume":"13","author":"Norioka","year":"2021","journal-title":"NPG Asia Mater."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"212","DOI":"10.1126\/science.abg6320","article-title":"Fracture, fatigue, and friction of polymers in which entanglements greatly outnumber cross-links","volume":"374","author":"Kim","year":"2021","journal-title":"Science"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2206577","DOI":"10.1002\/adma.202206577","article-title":"Making Highly Elastic and Tough Hydrogels from Doughs","volume":"34","author":"Nian","year":"2022","journal-title":"Adv. Mater."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"eabk0010","DOI":"10.1126\/sciadv.abk0010","article-title":"Tri-branched gels: Rubbery materials with the lowest branching factor approach the ideal elastic limit","volume":"8","author":"Fujiyabu","year":"2022","journal-title":"Sci. Adv."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1002\/jbm.a.36222","article-title":"Fabrication of tough poly(ethylene glycol)\/collagen double network hydrogels for tissue engineering","volume":"106","author":"Chen","year":"2018","journal-title":"J. Biomed. Mater. Res. A"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Hanykov\u00e1, L., Krakovsk\u00fd, I., \u0160est\u00e1kov\u00e1, E., \u0160\u0165astn\u00e1, J., and Labuta, J. (2020). Poly(N,N\u2032-Diethylacrylamide)-Based Thermoresponsive Hydrogels with Double Network Structure. Polymers, 12.","DOI":"10.3390\/polym12112502"},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Lee, H., Hong, H.J., Ahn, S., Kim, D., Kang, S.H., Cho, K., and Koh, W.G. (2023). One-Pot Synthesis of Double-Network PEG\/Collagen Hydrogel for Enhanced Adipogenic Differentiation and Retrieval of Adipose-Derived Stem Cells. Polymers, 15.","DOI":"10.3390\/polym15071777"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Ol\u0103re\u021b, E., B\u0103l\u0103nuc\u0103, B., Ona\u0219, A.M., Ghi\u021bman, J., Iovu, H., Stancu, I.C., and Serafim, A. (2021). Double-Cross-Linked Networks Based on Methacryloyl Mucin. Polymers, 13.","DOI":"10.3390\/polym13111706"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"34942","DOI":"10.1021\/acsami.1c08421","article-title":"Polyacrylamide\/Chitosan-Based Conductive Double Network Hydrogels with Outstanding Electrical and Mechanical Performance at Low Temperatures","volume":"13","author":"Cong","year":"2021","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1002\/pol.20220510","article-title":"Recent Developments of Polysaccharide-Based Double-Network Hydrogels","volume":"61","author":"Zhang","year":"2023","journal-title":"J. Polym. Sci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"111807","DOI":"10.1016\/j.eurpolymj.2022.111807","article-title":"Double-Network Hydrogels for Biomaterials: Structure-Property Relationships and Drug Delivery","volume":"185","author":"Zhang","year":"2023","journal-title":"Eur. Polym. J."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"560","DOI":"10.1002\/(SICI)1097-4636(19981215)42:4<560::AID-JBM12>3.0.CO;2-I","article-title":"Feasibility Study of a Natural Crosslinking Reagent for Biological Tissue Fixation","volume":"42","author":"Sung","year":"1998","journal-title":"J. Biomed. Mater. Res."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"460","DOI":"10.1007\/BF00123371","article-title":"Glutaraldehyde as a crosslinking agent for collagen-based biomaterials","volume":"6","author":"Damink","year":"1995","journal-title":"J. Mater. Sci. Mater. Med."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Yonezawa, K., Kawaguchi, M., Kaneuji, A., Ichiseki, T., Iinuma, Y., Kawamura, K., Shintani, K., Oda, S., Taki, M., and Kawahara, N. (2020). Evaluation of Antibacterial and Cytotoxic Properties of a Fluorinated Diamond-like Carbon Coating for the Development of Antibacterial Medical Implants. Antibiotics, 9.","DOI":"10.3390\/antibiotics9080495"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"6040","DOI":"10.1021\/cr400341h","article-title":"Safe Clinical Use of Carbon Nanotubes as Innovative Biomaterials","volume":"114","author":"Saito","year":"2014","journal-title":"Chem. Rev."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Kavasi, R.-M., Coelho, C.C., Platania, V., Quadros, P.A., and Chatzinikolaidou, M. (2021). In Vitro Biocompatibility Assessment of Nano-hydroxyapatite. Nanomaterials, 11.","DOI":"10.3390\/nano11051152"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Nahum, A.M., and Melvin, J.W. (2002). Accidental Injury: Biomechanics and Prevention, Springer. [2nd ed.].","DOI":"10.1007\/978-0-387-21787-1"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"2943","DOI":"10.1016\/j.jbiomech.2005.10.031","article-title":"Sex-Based Differences in the Tensile Properties of the Human Anterior Cruciate Ligament","volume":"39","author":"Chandrashekar","year":"2006","journal-title":"J. Biomech."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"5917","DOI":"10.1021\/acs.nanolett.6b02828","article-title":"Microfluidics-Produced Collagen Fibers Show Extraordinary Mechanical Properties","volume":"16","author":"Haynl","year":"2016","journal-title":"Nano Lett."}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/16\/2\/283\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T13:46:11Z","timestamp":1760103971000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/16\/2\/283"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,1,19]]},"references-count":48,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2024,1]]}},"alternative-id":["polym16020283"],"URL":"https:\/\/doi.org\/10.3390\/polym16020283","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,1,19]]}}}