Poly-(vinyl alcohol) (PVA) has been widely explored as a model material for articular cartilage (AC) in biotribological evaluations. However, PVA hydrogels prepared by freeze-thawing or cast-drying methods have limitations in precisely controlling their elasticity parameters and may require reinforcement to enhance their mechanical performance and change their transparency, required in some tribological measurement setups by using fluorescence methods. To overcome these issues, poly-(hydroxyethyl methacrylate) (pHEMA) hydrogels have been introduced as alternatives. In our study, pHEMA hydrogels synthesized using free-radical polymerization with blue light under two different atmospheres (nitrogen N2 and air) were compared with natural samples of articular bovine cartilage. The optical, mechanical, swelling, and tribological properties demonstrate the superior properties of pHEMA, which may result in the replacement of the currently used PVA-based model in future studies. Synthesis under a nitrogen atmosphere (pHEMA N 2) resulted in the formation of smooth-surfaced hydrogels, whereas synthesis under a laboratory atmosphere (pHEMA air) resulted in the formation of wrinkled-surfaced hydrogels. The swelling of both the hydrogels and AC followed first-order kinetics. Pin-on-plate biotribology measurements showed that the coefficient of friction of the wrinkled-surface hydrogels resembled that of AC. Our results showed that pHEMA-based hydrogels are suitable biotribological AC models for a better understanding of the biological functions of bovine AC. This knowledge brings new insights into cartilage complex mechanisms and might be applied in both biomedical and engineering applications.

Advanced Biomaterials Group Central European Institute of Technology Brno University of Technology 621 00 Brno Czech Republic

Biotribology Research Group Faculty of Mechanical Engineering Brno University of Technology 616 69 Brno Czech Republic

Centre of Polymer Systems University Institute Tomas Bata University in Zlin 760 01 Zlin Czech Republic

Department of Mechanical Engineering Faculty of Engineering Kyushu University 744 Motooka Nishi ku 819 0395 Fukuoka Japan

Institute of Materials Chemistry Faculty of Chemistry Brno University of Technology 612 00 Brno Czech Republic

Zobrazit více v PubMed

Uzieliene I., Bironaite D., Bagdonas E., Pachaleva J., Sobolev A., Tsai W.-B., Kvederas G., Bernotiene E.. The Effects of Mechanical Load on Chondrogenic Responses of Bone Marrow Mesenchymal Stem Cells and Chondrocytes Encapsulated in Chondroitin Sulfate-Based Hydrogel. Int. J. Mol. Sci. 2023;24(3):2915. doi: 10.3390/ijms24032915. PubMed DOI PMC

Hodgkinson T., Amado I. N., O’Brien F. J., Kennedy O. D.. The Role of Mechanobiology in Bone and Cartilage Model Systems in Characterizing Initiation and Progression of Osteoarthritis. APL Bioeng. 2022;6(1):011501. doi: 10.1063/5.0068277. PubMed DOI PMC

Carballo C. B., Nakagawa Y., Sekiya I., Rodeo S. A.. Basic Science of Articular Cartilage. Clin. Sports Med. 2017;36(3):413–425. doi: 10.1016/j.csm.2017.02.001. PubMed DOI

Gilbert S. J., Bonnet C. S., Blain E. J.. Mechanical Cues: Bidirectional Reciprocity in the Extracellular Matrix Drives Mechano-Signalling in Articular Cartilage. Int. J. Mol. Sci. 2021;22(24):13595. doi: 10.3390/ijms222413595. PubMed DOI PMC

Heinegård D.. Fell-Muir Lecture: Proteoglycans and More – from Molecules to Biology. Int. J. Exp. Pathol. 2009;90(6):575–586. doi: 10.1111/j.1365-2613.2009.00695.x. PubMed DOI PMC

Sophia Fox A. J., Bedi A., Rodeo S. A.. The Basic Science of Articular Cartilage: Structure, Composition, and Function. Sport Health. 2009;1(6):461–468. doi: 10.1177/1941738109350438. PubMed DOI PMC

Lu X. L., Mow V. C.. Biomechanics of Articular Cartilage and Determination of Material Properties. Med. Sci. Sports Exerc. 2008;40(2):193–199. doi: 10.1249/mss.0b013e31815cb1fc. PubMed DOI

Belluzzi E., Todros S., Pozzuoli A., Ruggieri P., Carniel E. L., Berardo A.. Human Cartilage Biomechanics: Experimental and Theoretical Approaches towards the Identification of Mechanical Properties in Healthy and Osteoarthritic Conditions. Processes. 2023;11(4):1014. doi: 10.3390/pr11041014. DOI

Mahmood H., Eckold D., Stead I., Shepherd D. E. T., Espino D. M., Dearn K. D.. A Method for the Assessment of the Coefficient of Friction of Articular Cartilage and a Replacement Biomaterial. J. Mech. Behav. Biomed. Mater. 2020;103:103580. doi: 10.1016/j.jmbbm.2019.103580. PubMed DOI

Patel J. M., Wise B. C., Bonnevie E. D., Mauck R. L.. A Systematic Review and Guide to Mechanical Testing for Articular Cartilage Tissue Engineering. Tissue Eng., Part C. 2019;25(10):593–608. doi: 10.1089/ten.tec.2019.0116. PubMed DOI PMC

Xu W., Zhu J., Hu J., Xiao L.. Engineering the Biomechanical Microenvironment of Chondrocytes towards Articular Cartilage Tissue Engineering. Life Sci. 2022;309:121043. doi: 10.1016/j.lfs.2022.121043. PubMed DOI

Petitjean N., Canadas P., Royer P., Noël D., Le Floc’h S.. Cartilage Biomechanics: From the Basic Facts to the Challenges of Tissue Engineering. J. Biomed. Mater. Res., Part A. 2023;111(7):1067–1089. doi: 10.1002/jbm.a.37478. PubMed DOI

De Bari C., Roelofs A. J.. Stem Cell-Based Therapeutic Strategies for Cartilage Defects and Osteoarthritis. Curr. Opin. Pharmacol. 2018;40:74–80. doi: 10.1016/j.coph.2018.03.009. PubMed DOI

Zhu C., Zhang W., Shao Z., Wang Z., Chang B., Ding X., Yang Y.. Biodegradable Glass Fiber Reinforced PVA Hydrogel for Cartilage Repair: Mechanical Properties, Ions Release Behavior and Cell Recruitment. J. Mater. Res. Technol. 2023;23:154–164. doi: 10.1016/j.jmrt.2022.12.166. DOI

Sakai N., Yarimitsu S., Sawae Y., Komori M., Murakami T.. Biomimetic Artificial Cartilage: Fibre-reinforcement of PVA Hydrogel to Promote Biphasic Lubrication Mechanism. Biosurf. Biotribol. 2019;5(1):13–19. doi: 10.1049/bsbt.2018.0031. DOI

Miao T., Miller E. J., McKenzie C., Oldinski R. A.. Physically Crosslinked Polyvinyl Alcohol and Gelatin Interpenetrating Polymer Network Theta-Gels for Cartilage Regeneration. J. Mater. Chem. B. 2015;3(48):9242–9249. doi: 10.1039/C5TB00989H. PubMed DOI

Branco A. C., Oliveira A. S., Monteiro I., Nolasco P., Silva D. C., Figueiredo-Pina C. G., Colaço R., Serro A. P.. PVA-Based Hydrogels Loaded with Diclofenac for Cartilage Replacement. Gels. 2022;8(3):143. doi: 10.3390/gels8030143. PubMed DOI PMC

Oliveira A. S., Seidi O., Ribeiro N., Colaço R., Serro A. P.. Tribomechanical Comparison between PVA Hydrogels Obtained Using Different Processing Conditions and Human Cartilage. Materials. 2019;12(20):3413. doi: 10.3390/ma12203413. PubMed DOI PMC

Sasaki S., Yarimitsu S., Murakami T., Suzuki A.. Effect of Drying on the Frictional Properties of PVA Cast Gel. Kobunshi Ronbunshu. 2015;72(12):760–764. doi: 10.1295/koron.2015-0036. DOI

Ito T., Nakaoki T.. Mechanical Properties of Polyvinyl Alcohol Stretched in Water as a Plasticizer. Macromol. Symp. 2023;408(1):2200093. doi: 10.1002/masy.202200093. DOI

Kobayashi M., Hyu H. S.. Development and Evaluation of Polyvinyl Alcohol-Hydrogels as an Artificial Atrticular Cartilage for Orthopedic Implants. Materials. 2010;3(4):2753–2771. doi: 10.3390/ma3042753. DOI

Pires T., Oliveira A. S., Marques A. C., Salema-Oom M., Figueiredo-Pina C. G., Silva D., Serro A. P.. Effects of Non-Conventional Sterilisation Methods on PBO-Reinforced PVA Hydrogels for Cartilage Replacement. Gels. 2022;8(10):640. doi: 10.3390/gels8100640. PubMed DOI PMC

Ye Z., Lu H., Jia E., Chen J., Fu L.. Organic Solvents Enhance Polyvinyl Alcohol/Polyethylene Glycol Self-healing Hydrogels for Artificial Cartilage. Polym. Adv. Technol. 2022;33(10):3455–3469. doi: 10.1002/pat.5799. DOI

Branco A. C., Oliveira A. S., Monteiro I., Nolasco P., Silva D. C., Figueiredo-Pina C. G., Colaço R., Serro A. P.. PVA-Based Hydrogels Loaded with Diclofenac for Cartilage Replacement. Gels. 2022;8(3):143. doi: 10.3390/gels8030143. PubMed DOI PMC

Yang M., Wang Z., Li M., Yin Z., Butt H. A.. The Synthesis, Mechanisms, and Additives for Bio-compatible Polyvinyl Alcohol Hydrogels: A Review on Current Advances, Trends, and Future Outlook. J. Vinyl Addit. Technol. 2023;29(6):939–959. doi: 10.1002/vnl.21962. DOI

Koc U., Aykut Y., Eren R.. Natural Fibers Woven Fabric Reinforced Hydrogel Composites for Enhanced Mechanical Properties. J. Ind. Textil. 2022;51(4_suppl):6315S–6332S. doi: 10.1177/1528083720944485. DOI

Koc U., Aykut Y., Eren R.. Regenerated Cellulose Woven Fabric Reinforced Hydrogel Composite. J. Text. Inst. 2022;113(5):906–914. doi: 10.1080/00405000.2021.1908007. DOI

Holloway J. L., Lowman A. M., VanLandingham M. R., Palmese G. R.. Interfacial Optimization of Fiber-Reinforced Hydrogel Composites for Soft Fibrous Tissue Applications. Acta Biomater. 2014;10(8):3581–3589. doi: 10.1016/j.actbio.2014.05.004. PubMed DOI

Holloway J. L., Lowman A. M., VanLandingham M. R., Palmese G. R.. Chemical Grafting for Improved Interfacial Shear Strength in UHMWPE/PVA-Hydrogel Fiber-Based Composites Used as Soft Fibrous Tissue Replacements. Compos. Sci. Technol. 2013;85:118–125. doi: 10.1016/j.compscitech.2013.06.007. DOI

Yin C., Huang Z., Zhang Y., Ren K., Liu S., Luo H., Zhang Q., Wan Y.. Strong, Tough, and Elastic Poly­(Vinyl Alcohol)/Polyacrylamide DN Hydrogels Based on the Hofmeister Effect for Articular Cartilage Replacement. J. Mater. Chem. B. 2024;12(12):3079–3091. doi: 10.1039/D3TB02637J. PubMed DOI

Zhang S., Li Y., Zhang H., Wang G., Wei H., Zhang X., Ma N.. Bioinspired Conductive Hydrogel with Ultrahigh Toughness and Stable Antiswelling Properties for Articular Cartilage Replacement. ACS Mater. Lett. 2021;3(6):807–814. doi: 10.1021/acsmaterialslett.1c00203. DOI

Drápalová E., Michlovská L., Poštulková H., Chamradová I., Lipový B., Holoubek J., Vacek L., Růžička F., Hanslianová M., Svobodová T., Černá E., Hrdličková B., Vojtová L.. Antimicrobial Cost-Effective Transparent Hydrogel Films from Renewable Gum Karaya/Chitosan Polysaccharides for Modern Wound Dressings. ACS Appl. Polym. Mater. 2023;5(4):2774–2786. doi: 10.1021/acsapm.3c00025. DOI

Vacek L., Polaštík Kleknerová D., Lipový B., Holoubek J., Matysková D., Černá E., Brtníková J., Jeklová E., Kobzová, Janda L., Lišková L., Diabelko D., Botka T., Pantůček R., Růžička F., Vojtová L.. Phage Therapy Combined with Gum Karaya Injectable Hydrogels for Treatment of Methicillin-Resistant Staphylococcus Aureus Deep Wound Infection in a Porcine Model. Int. J. Pharm. 2024;660:124348. doi: 10.1016/j.ijpharm.2024.124348. PubMed DOI

Ye Z., Lu H., Jia E., Chen J., Fu L.. Organic Solvents Enhance Polyvinyl Alcohol/Polyethylene Glycol Self-healing Hydrogels for Artificial Cartilage. Polym. Adv. Technol. 2022;33(10):3455–3469. doi: 10.1002/pat.5799. DOI

Ye Z., Lu H., Chai G., Wu C., Chen J., Lv L.. Glycerol-modified Poly­(Vinyl Alcohol)/Poly­(Ethylene Glycol) Self-healing Hydrogel for Artificial Cartilage. Polym. Int. 2023;72(1):27–38. doi: 10.1002/pi.6444. DOI

Chen Y., Song J., Wang S., Liu W.. PVA-Based Hydrogels: Promising Candidates for Articular Cartilage Repair. Macromol. Biosci. 2021;21(10):2100147. doi: 10.1002/mabi.202100147. PubMed DOI

Liang X., Zhong H.-J., Ding H., Yu B., Ma X., Liu X., Chong C.-M., He J.. Polyvinyl Alcohol (PVA)-Based Hydrogels: Recent Progress in Fabrication, Properties, and Multifunctional Applications. Polymers. 2024;16(19):2755. doi: 10.3390/polym16192755. PubMed DOI PMC

Wu H., Wu Y., Yan J., Wang Y., Zhang H., Liu Z., Li H., Wang J., Gao J.. Strong and Tough Hydrogels Enabled by Progressive Enhancement of Polymer Networks. Polymer. 2024;306:127223. doi: 10.1016/j.polymer.2024.127223. DOI

Ranuša M., Ondra M., Rebenda D., Vrbka M., Gallo J., Křupka I.. Effects of Viscosupplementation on Tribological Behaviour of Articular Cartilage. Lubricants. 2022;10(12):361. doi: 10.3390/lubricants10120361. DOI

de Vries S. A. H., van Doeselaar M., Kaper H. J., Sharma P. K., Ito K.. Notochordal Cell Matrix as a Bioactive Lubricant for the Osteoarthritic Joint. Sci. Rep. 2018;8(1):8875. doi: 10.1038/s41598-018-27130-9. PubMed DOI PMC

Li F., Wang A., Wang C.. Analysis of Friction between Articular Cartilage and Polyvinyl Alcohol Hydrogel Artificial Cartilage. J. Mater. Sci. Mater. Med. 2016;27(5):87. doi: 10.1007/s10856-016-5700-y. PubMed DOI

Čípek P., Vrbka M., Rebenda D., Nečas D., Křupka I.. Biotribology of Synovial Cartilage: A New Method for Visualization of Lubricating Film and Simultaneous Measurement of the Friction Coefficient. Materials. 2020;13(9):2075. doi: 10.3390/ma13092075. PubMed DOI PMC

Seror J., Zhu L., Goldberg R., Day A. J., Klein J.. Supramolecular Synergy in the Boundary Lubrication of Synovial Joints. Nat. Commun. 2015;6(1):6497. doi: 10.1038/ncomms7497. PubMed DOI PMC

Krishnan R., Kopacz M., Ateshian G. A.. Experimental Verification of the Role of Interstitial Fluid Pressurization in Cartilage Lubrication. J. Orthop. Res. 2004;22(3):565–570. doi: 10.1016/j.orthres.2003.07.002. PubMed DOI PMC

Wichterle O., Lím D.. Hydrophilic Gels for Biological Use. Nature. 1960;185:117–118. doi: 10.1038/185117a0. DOI

Zare M., Bigham A., Zare M., Luo H., Rezvani Ghomi E., Ramakrishna S.. PHEMA: An Overview for Biomedical Applications. Int. J. Mol. Sci. 2021;22(12):6376. doi: 10.3390/ijms22126376. PubMed DOI PMC

Passos M. F., Carvalho N. M. S., Rodrigues A. A., Bavaresco V. P., Jardini A. L., Maciel M. R. W., Maciel Filho R.. PHEMA Hydrogels Obtained by Infrared Radiation for Cartilage Tissue Engineering. Int. J. Chem. Eng. 2019;2019:1–9. doi: 10.1155/2019/4249581. DOI

Hua Z., Hu M., Chen Y., Huang X., Gao L.. Investigation of the Friction Properties of a New Artificial Imitation Cartilage Material: PHEMA/Glycerol Gel. Materials. 2023;16(11):4023. doi: 10.3390/ma16114023. PubMed DOI PMC

Makarova E. B., Korch M. A., Fadeyev F. A., Bliznets D. G., Bugayova A. V., Shklyar T. F., Safronov A. P., Nokhrin K. A., Blyakhman F. A.. Testing of the PHEMA Hydrogel as an Implantation Material for Replacement of Osteochondral Defects in Animals. Russian J. Transplant. Artif. Organs. 2022;24(2):71–82. doi: 10.15825/1995-1191-2022-2-71-82. DOI

Hobzova R., Hrib J., Sirc J., Karpushkin E., Michalek J., Janouskova O., Gatenholm P.. Embedding of Bacterial Cellulose Nanofibers within PHEMA Hydrogel Matrices: Tunable Stiffness Composites with Potential for Biomedical Applications. J. Nanomater. 2018;2018:1–11. doi: 10.1155/2018/5217095. DOI

Krajňák T., Černá E., Šuráňová M., Šamořil T., Zicha D., Vojtová L., Čechal J.. Replica-Mold Nanopatterned PHEMA Hydrogel Surfaces for Ophthalmic Applications. Sci. Rep. 2022;12(1):14497. doi: 10.1038/s41598-022-18564-3. PubMed DOI PMC

Nečas D., Yarimitsu S., Rebenda D., Shinmori H., Vrbka M., Sawae Y., Murakami T., Křupka I.. On the Replacement of Articular Cartilage: The Friction of PVA Hydrogel Layer in Hip Simulator Test. Tribol. Int. 2023;178:108100. doi: 10.1016/j.triboint.2022.108100. DOI

Hilšer P., Suchánková A., Mendová K., Filipič K. E., Daniel M., Vrbka M.. A New Insight into More Effective Viscosupplementation Based on the Synergy of Hyaluronic Acid and Phospholipids for Cartilage Friction Reduction. Biotribology. 2021;25:100166. doi: 10.1016/j.biotri.2021.100166. DOI

Karadag E., Saraydin D., Sahiner N., Güven O.. Radiation Induced Acrylamide/Citric Acid Hydrogels and Their Swelling Behaviors. J. Macromol. Sci., Part A: Pure Appl. Chem. 2001;38(11):1105–1121. doi: 10.1081/MA-100107132. DOI

Manaila E., Craciun G., Ighigeanu D., Cimpeanu C., Barna C., Fugaru V.. Hydrogels Synthesized by Electron Beam Irradiation for Heavy Metal Adsorption. Materials. 2017;10(5):540. doi: 10.3390/ma10050540. PubMed DOI PMC

Rebenda D., Vrbka M., Čípek P., Toropitsyn E., Nečas D., Pravda M., Hartl M.. On the Dependence of Rheology of Hyaluronic Acid Solutions and Frictional Behavior of Articular Cartilage. Materials. 2020;13(11):2659. doi: 10.3390/ma13112659. PubMed DOI PMC

Rebenda D., Vrbka M., Nečas D., Toropitsyn E., Yarimitsu S., Čípek P., Pravda M., Hartl M.. Rheological and Frictional Analysis of Viscosupplements towards Improved Lubrication of Human Joints. Tribol. Int. 2021;160:107030. doi: 10.1016/j.triboint.2021.107030. DOI

Galandáková A., Ulrichová J., Langová K., Hanáková A., Vrbka M., Hartl M., Gallo J.. Characteristics of Synovial Fluid Required for Optimization of Lubrication Fluid for Biotribological Experiments. J. Biomed. Mater. Res., Part B. 2017;105(6):1422–1431. doi: 10.1002/jbm.b.33663. PubMed DOI

Yamaguchi T., Sato R., Sawae Y.. Propagation of Fatigue Cracks in Friction of Brittle Hydrogels. Gels. 2018;4(2):53. doi: 10.3390/gels4020053. PubMed DOI PMC

Liu Y., Wang P., Wang J., Xu B., Xu J., Yuan J., Yu Y., Wang Q.. Transparent and Tough Poly­(2-Hydroxyethyl Methacrylate) Hydrogels Prepared in Water/IL Mixtures. New J. Chem. 2020;44(10):4092–4098. doi: 10.1039/D0NJ00214C. DOI

Podestà A., Ranucci E., Macchi L., Bongiorno G., Ferruti P., Milani P.. Micro- and Nanoscale Modification of Poly­(2-Hydroxyethyl Methacrylate) Hydrogels by AFM Lithography and Nanoparticle Incorporation. J. Nanosci. Nanotechnol. 2005;5(3):425–430. doi: 10.1166/jnn.2005.061. PubMed DOI

Yun Y., Guan Y., Zhang Y.. Patterned PHEMA Films Synthesized by Redox Polymerization for Multicellular Spheroid Generation. Ind. Eng. Chem. Res. 2019;58(25):10713–10723. doi: 10.1021/acs.iecr.9b01517. DOI

Smyth P. A., Rifkin R. E., Jackson R. L., Hanson R. R.. A Surface Roughness Comparison of Cartilage in Different Types of Synovial Joints. J. Biomech. Eng. 2012;134(2):021006. doi: 10.1115/1.4005934. PubMed DOI

Ghosh S., Bowen J., Jiang K., Espino D. M., Shepherd D. E. T.. Investigation of Techniques for the Measurement of Articular Cartilage Surface Roughness. Micron. 2013;44(1):179–184. doi: 10.1016/j.micron.2012.06.007. PubMed DOI

Mabilleau G., Baslé M. F., Chappard D.. Evaluation of Surface Roughness of Hydrogels by Fractal Texture Analysis during Swelling. Langmuir. 2006;22(10):4843–4845. doi: 10.1021/la060368v. PubMed DOI

Maldonado-Codina C., Efron N.. Impact of Manufacturing Technology and Material Composition on the Surface Characteristics of Hydrogel Contact Lenses. Clin. Exp. Optom. 2005;88(6):396–404. doi: 10.1111/j.1444-0938.2005.tb05106.x. PubMed DOI

Ouyang T., Su S., Deng H., Liu Y., Cui L., Rong J., Zhao J.. Superhydrophilic Poly­(2-Hydroxyethyl Methacrylate) Hydrogel with Nanosilica Covalent Coating: A Promising Contact Lens Material for Resisting Tear Protein Deposition and Bacterial Adhesion. ACS Biomater. Sci. Eng. 2023;9(10):5653–5665. doi: 10.1021/acsbiomaterials.3c00856. PubMed DOI

Kaczmarek H., Gałka P., Kowalonek J.. Influence of a Photoinitiator on the Photochemical Stability of Poly­(Methyl Methacrylate) Studied with Fourier Transform Infrared Spectroscopy. J. Appl. Polym. Sci. 2010;115(3):1598–1607. doi: 10.1002/app.31166. DOI

Oyarce E., Pizarro G. D. C., Oyarzún D. P., Zúñiga C., Sánchez J.. Hydrogels Based On 2-Hydroxyethyl Methacrylate: Synthesis, Characterization and Hydration Capacity. J. Chil. Chem. Soc. 2020;65(1):4682–4685. doi: 10.4067/S0717-97072020000104682. DOI

Vargün E., Usanmaz A.. Degradation of Poly­(2-Hydroxyethyl Methacrylate) Obtained by Radiation in Aqueous Solution. J. Macromol. Sci., Part A: Pure Appl. Chem. 2010;47(9):882–891. doi: 10.1080/10601325.2010.501304. DOI

Kim S., Shin B. H., Yang C., Jeong S., Shim J. H., Park M. H., Choy Y. B., Heo C. Y., Lee K.. Development of Poly­(HEMA-Am) Polymer Hydrogel Filler for Soft Tissue Reconstruction by Facile Polymerization. Polymers. 2018;10(7):772. doi: 10.3390/polym10070772. PubMed DOI PMC

Yang X., Cui M., Zhou J., Zhang L., Zhou H., Luo Z., Zhou L., Hu H.. Surface Fluorination Modification and Anti-Biofouling Study of a PHEMA Hydrogel. ACS Appl. Bio Mater. 2021;4(1):523–532. doi: 10.1021/acsabm.0c01071. PubMed DOI

Mucci V., Vallo C.. Efficiency of 2,2-Dimethoxy-2-Phenylacetophenone for the Photopolymerization of Methacrylate Monomers in Thick Sections. J. Appl. Polym. Sci. 2012;123(1):418–425. doi: 10.1002/app.34473. DOI

Kanagathara N., Senthilkumar K., Sabari V., Ragavendran V., Elangovan S.. Structural and Vibrational Investigation of Benzil-(1,2-Diphenylethane-1,2-Dione): Experimental and Theoretical Studies. J. Chem. 2022;2022(1):5968496. doi: 10.1155/2022/5968496. DOI

Alqahtani S. M., Al Khulaifi R. S., Alassaf M., Saeed W. S., Bedja I., Aldarwesh A., Aljubailah A., Semlali A., Aouak T.. Preparation and Characterization of Poly­(Vinyl Acetate-Co-2-Hydroxyethyl Methacrylate) and In Vitro Application as Contact Lens for Acyclovir Delivery. Int. J. Mol. Sci. 2023;24(6):5483. doi: 10.3390/ijms24065483. PubMed DOI PMC

Zhu J., Wang J., Liu Q., Liu Y., Wang L., He C., Wang H.. Anisotropic Tough Poly­(2-Hydroxyethyl Methacrylate) Hydrogels Fabricated by Directional Freezing Redox Polymerization. J. Mater. Chem. B. 2013;1(7):978–986. doi: 10.1039/C2TB00288D. PubMed DOI

Bose R. K., Lau K. K. S.. Mechanical Properties of Ultrahigh Molecular Weight PHEMA Hydrogels Synthesized Using Initiated Chemical Vapor Deposition. Biomacromolecules. 2010;11(8):2116–2122. doi: 10.1021/bm100498a. PubMed DOI

Boazak E. M., Greene V. K., Auguste D. T.. The Effect of Heterobifunctional Crosslinkers on HEMA Hydrogel Modulus and Toughness. PLoS One. 2019;14(5):e0215895. doi: 10.1371/journal.pone.0215895. PubMed DOI PMC

Moghadam M. N., Pioletti D. P.. Improving Hydrogels’ Toughness by Increasing the Dissipative Properties of Their Network. J. Mech. Behav. Biomed. Mater. 2015;41:161–167. doi: 10.1016/j.jmbbm.2014.10.010. PubMed DOI

Temple D. K., Cederlund A. A., Lawless B. M., Aspden R. M., Espino D. M.. Viscoelastic Properties of Human and Bovine Articular Cartilage: A Comparison of Frequency-Dependent Trends. BMC Muscoskelet. Disord. 2016;17(1):419. doi: 10.1186/s12891-016-1279-1. PubMed DOI PMC

Petitjean N., Canadas P., Royer P., Noël D., Le Floc’h S.. Cartilage Biomechanics: From the Basic Facts to the Challenges of Tissue Engineering. J. Biomed. Mater. Res., Part A. 2023;111(7):1067–1089. doi: 10.1002/jbm.a.37478. PubMed DOI

Akizuki S., Mow V. C., Müller F., Pita J. C., Howell D. S., Manicourt D. H.. Tensile Properties of Human Knee Joint Cartilage: I. Influence of Ionic Conditions, Weight Bearing, and Fibrillation on the Tensile Modulus. J. Orthop. Res. 1986;4(4):379–392. doi: 10.1002/jor.1100040401. PubMed DOI

Murakami T., Nakashima K., Sawae Y., Sakai N., Hosoda N.. Roles of Adsorbed Film and Gel Layer in Hydration Lubrication for Articular Cartilage. Proc. Inst. Mech. Eng., Part J. 2009;223(3):287–295. doi: 10.1243/13506501JET536. DOI

Majd S. E., Kuijer R., Köwitsch A., Groth T., Schmidt T. A., Sharma P. K.. Both Hyaluronan and Collagen Type II Keep Proteoglycan 4 (Lubricin) at the Cartilage Surface in a Condition That Provides Low Friction during Boundary Lubrication. Langmuir. 2014;30(48):14566–14572. doi: 10.1021/la504345c. PubMed DOI

Voinier S., Moore A. C., Benson J. M., Price C., Burris D. L.. The Modes and Competing Rates of Cartilage Fluid Loss and Recovery. Acta Biomater. 2022;138:390–397. doi: 10.1016/j.actbio.2021.11.014. PubMed DOI

Baylon E. G., Levenston M. E.. Osmotic Swelling Responses Are Conserved Across Cartilaginous Tissues With Varied Sulfated-Glycosaminoglycan Contents. J. Orthop. Res. 2020;38(4):785–792. doi: 10.1002/jor.24521. PubMed DOI

Moore A. C., Burris D. L.. Tribological Rehydration of Cartilage and Its Potential Role in Preserving Joint Health. Osteoarthr. Cartil. 2017;25(1):99–107. doi: 10.1016/j.joca.2016.09.018. PubMed DOI

Ayhan H., Ayhan F.. Water Based PHEMA Hydrogels for Controlled Drug Delivery. Turk. J. Biochem. 2018;43(3):228–239. doi: 10.1515/tjb-2017-0250. DOI

Baker J. P., Blanch H. W., Prausnitz J. M.. Swelling Properties of Acrylamide-Based Ampholytic Hydrogels: Comparison of Experiment with Theory. Polymer. 1995;36(5):1061–1069. doi: 10.1016/0032-3861(95)93608-O. DOI

Pan S., Xia M., Li H., Jiang X., He P., Sun Z., Zhang Y.. Transparent, High-Strength, Stretchable, Sensitive and Anti-Freezing Poly­(Vinyl Alcohol) Ionic Hydrogel Strain Sensors for Human Motion Monitoring. J. Mater. Chem. C. 2020;8(8):2827–2837. doi: 10.1039/C9TC06338B. DOI

Refojo M. F.. Hydrophobic Interaction in Poly­(2-hydroxyethyl Methacrylate) Homogeneous Hydrogel. J. Polym. Sci., Part A-1. 1967;5(12):3103–3113. doi: 10.1002/pol.1967.150051211. PubMed DOI

Kim S. J., Shin S. R., Lee S. M., Kim I. Y., Kim S. I.. Electromechanical Properties of Hydrogels Based on Chitosan and Poly­(Hydroxyethyl Methacrylate) in NaCl Solution. Smart Mater. Struct. 2004;13(5):1036–1039. doi: 10.1088/0964-1726/13/5/008. DOI

Park S., Hung C. T., Ateshian G. A.. Mechanical Response of Bovine Articular Cartilage under Dynamic Unconfined Compression Loading at Physiological Stress Levels. Osteoarthr. Cartil. 2004;12(1):65–73. doi: 10.1016/j.joca.2003.08.005. PubMed DOI

Caligaris M., Ateshian G. A.. Effects of Sustained Interstitial Fluid Pressurization under Migrating Contact Area, and Boundary Lubrication by Synovial Fluid, on Cartilage Friction. Osteoarthr. Cartil. 2008;16(10):1220–1227. doi: 10.1016/j.joca.2008.02.020. PubMed DOI PMC

Shi Y., Xiong D., Liu Y., Wang N., Zhao X.. Swelling, Mechanical and Friction Properties of PVA/PVP Hydrogels after Swelling in Osmotic Pressure Solution. Mater. Sci. Eng., C. 2016;65:172–180. doi: 10.1016/j.msec.2016.04.042. PubMed DOI

Shi Y., Xiong D. S., Peng Y., Wang N.. Effects of Polymerization Degree on Recovery Behavior of PVA/PVP Hydrogels as Potential Articular Cartilage Prosthesis after Fatigue Test. Express Polym. Lett. 2016;10(2):125–138. doi: 10.3144/expresspolymlett.2016.13. DOI

Rudge R. E. D., Scholten E., Dijksman J. A.. Natural and Induced Surface Roughness Determine Frictional Regimes in Hydrogel Pairs. Tribol. Int. 2020;141:105903. doi: 10.1016/j.triboint.2019.105903. DOI

Simič R., Mandal J., Zhang K., Spencer N. D.. Oxygen Inhibition of Free-Radical Polymerization Is the Dominant Mechanism behind the “Mold Effect” on Hydrogels. Soft Matter. 2021;17(26):6394–6403. doi: 10.1039/D1SM00395J. PubMed DOI PMC

Simič R., Spencer N. D.. Controlling the Friction of Gels by Regulating Interfacial Oxygen During Polymerization. Tribol. Lett. 2021;69(3):86. doi: 10.1007/S11249-021-01459-1. PubMed DOI PMC

Yarimitsu S., Sasaki S., Murakami T., Suzuki A.. Evaluation of Lubrication Properties of Hydrogel Artificial Cartilage Materials for Joint Prosthesis. Biosurf. Biotribol. 2016;2(1):40–47. doi: 10.1016/j.bsbt.2016.02.005. DOI

Murakami T., Sakai N., Yarimitsu S., Nakashima K., Yamaguchi T., Sawae Y., Suzuki A.. Evaluation of Influence of Changes in Permeability with Aging on Friction and Biphasic Behaviors of Artificial Hydrogel Cartilage. Biotribology. 2021;26:100178. doi: 10.1016/j.biotri.2021.100178. DOI

Gu W. Y., Yao H., Huang C. Y., Cheung H. S.. New Insight into Deformation-Dependent Hydraulic Permeability of Gels and Cartilage, and Dynamic Behavior of Agarose Gels in Confined Compression. J. Biomech. 2003;36(4):593–598. doi: 10.1016/S0021-9290(02)00437-2. PubMed DOI

Jurvelin J. S., Buschmann M. D., Hunziker E. B.. Mechanical Anisotropy of the Human Knee Articular Cartilage in Compression. Proc. Inst. Mech. Eng., Part H. 2003;217(3):215–219. doi: 10.1243/095441103765212712. PubMed DOI

Korhonen R. K., Laasanen M. S., Töyräs J., Rieppo J., Hirvonen J., Helminen H. J., Jurvelin J. S.. Comparison of the Equilibrium Response of Articular Cartilage in Unconfined Compression, Confined Compression and Indentation. J. Biomech. 2002;35(7):903–909. doi: 10.1016/S0021-9290(02)00052-0. PubMed DOI

Mansour J., Mow V.. The Permeability of Articular Cartilage under Compressive Strain and at High Pressures. J. Bone Joint Surg. 1976;58(4):509–516. doi: 10.2106/00004623-197658040-00014. PubMed DOI

Mow V. C., Kuei S. C., Lai W. M., Armstrong C. G.. Biphasic Creep and Stress Relaxation of Articular Cartilage in Compression: Theory and Experiments. J. Biomech. Eng. 1980;102(1):73–84. doi: 10.1115/1.3138202. PubMed DOI

Reynaud B., Quinn T. M.. Anisotropic Hydraulic Permeability in Compressed Articular Cartilage. J. Biomech. 2006;39(1):131–137. doi: 10.1016/j.jbiomech.2004.10.015. PubMed DOI

Soltz M. A., Ateshian G. A.. Interstitial Fluid Pressurization During Confined Compression Cyclical Loading of Articular Cartilage. Ann. Biomed. Eng. 2000;28(2):150–159. doi: 10.1114/1.239. PubMed DOI

Wu Y., Cisewski S. E., Sachs B. L., Pellegrini Jr V. D., Kern M. J., Slate E. H., Yao H.. The Region-Dependent Biomechanical and Biochemical Properties of Bovine Cartilaginous Endplate. J. Biomech. 2015;48(12):3185–3191. doi: 10.1016/j.jbiomech.2015.07.005. PubMed DOI PMC

Yuan T.-Y., Huang C.-Y., Yong Gu W.. Novel Technique for Online Characterization of Cartilaginous Tissue Properties. J. Biomech. Eng. 2011;133(9):094504. doi: 10.1115/1.4004920. PubMed DOI PMC

Boschetti, F. ; Miotti, C. ; Massi, F. ; Colombo, M. ; Quaglini, V. ; Peretti, G. M. ; Pietrabissa, R. . An experimental study on human articular cartilage permeability. In Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society [Engineering in Medicine and Biology]; IEEE, 2002; Vol. 3, pp 2581–2582.

Ateshian G. A., Wang H., Lai W. M.. The Role of Interstitial Fluid Pressurization and Surface Porosities on the Boundary Friction of Articular Cartilage. J. Tribol. 1998;120(2):241–248. doi: 10.1115/1.2834416. DOI

Stankiewicz, A. ; Ateshian, G. A. ; Bigliani, L. U. ; Mow, V. C. . Permeability of Human Glenohumeral Joint Cartilage. In ASME 1999 International Mechanical Engineering Congress and Exposition; American Society of Mechanical Engineers, 1999; pp 231–232.

Katta J., Pawaskar S. S., Jin Z. M., Ingham E., Fisher J.. Effect of Load Variation on the Friction Properties of Articular Cartilage. Proc. Inst. Mech. Eng., Part J. 2007;221(3):175–181. doi: 10.1243/13506501JET240. DOI

Cooper B. G., Lawson T. B., Snyder B. D., Grinstaff M. W.. Reinforcement of Articular Cartilage with a Tissue-Interpenetrating Polymer Network Reduces Friction and Modulates Interstitial Fluid Load Support. Osteoarthr. Cartil. 2017;25(7):1143–1149. doi: 10.1016/j.joca.2017.03.001. PubMed DOI PMC

Li Q., Miramini S., Smith D. W., Gardiner B. S., Zhang L.. Osteochondral Junction Leakage and Cartilage Joint Lubrication. Comput. Methods Programs Biomed. 2023;230:107353. doi: 10.1016/j.cmpb.2023.107353. PubMed DOI