Abstract：[Significance] Medical devices such as catheters, endoscopes, guidewires, artificial joints, and stents are in prolonged direct contact with human tissue. Therefore, surface treatment must be performed to enhance their lubricity and biocompatibility. Among the surface treatment techniques, lubricating coatings are widely used. The coatings reduce friction between medical devices and biological tissues, thereby minimizing tissue damage, alleviating patient discomfort due to friction, reducing the risk of rejection, infection, and inflammation, and making the treatment process smoother. With their structure similar to biological tissues and their ability to interact and retain large amounts of water, hydrogels are easily modified and less likely to cause immune rejection, making them suitable for fabricating lubricating coatings. However, the application of hydrogels as lubricating coatings faces many challenges. Initially, the physicochemical properties of hydrogels are diverse and complicated, resulting in different friction and lubrication mechanisms, and targeted modification of hydrogels for lubrication is challenging. Additionally, because of the unique formation methods and structures of hydrogels, achieving stable and strong adhesion with other substrates is difficult. Therefore, summarizing the existing research is crucial to guide further development of lubricating hydrogel coatings. [Progress] In the study of the lubrication mechanisms of hydrogels, articular cartilage was an important reference, primarily involving boundary lubrication and hydrodynamic lubrication mechanisms, relying on the synergistic interaction of various charged or polar macromolecules. The lubrication theory of synthetic hydrogels was similar to that of articular cartilage. In terms of hydrogel-solid substrate friction, the repulsion-adsorption theory explained the impact of microscopic interactions between the superficial hydrogel polymers and the solid substrate on lubrication performance. The friction between hydrogel surfaces was more complex, requiring careful consideration of the surface properties of both hydrogel counterparts. Current research on hydrogel coating modification for lubrication purposes primarily focused on three aspects: modification based on the hydrodynamic lubrication mechanism, structural modification, and intelligent response modification design. The first modification could simply and effectively improve the lubricity of the hydrogel surface. Structural modification, often bioinspired from specific biological tissue structures such as articular cartilage, aimed to balance the lubrication performance and stable mechanical properties of hydrogels. The intelligent response modification endowed the hydrogels with various responsive characteristics in lubrication performance, such as pH, light, and shear stress responses. These typical enhancements greatly improved the functionality of the hydrogel coatings from multiple perspectives. Hydrogels were primarily formed on substrates via chemical interactions such as surface bridging, surface initiation, gel coating, and biological modification. The first three methods involved the polymerization and crosslinking of hydrogels, with similar principles but different procedures, whereas biological modification directly used bacteria or other microorganisms for adhesion and gel formation. These methods were adapted to different production scenarios and were suitable for various hydrogel materials and substrates. [Conclusions and Prospects] Current lubricating hydrogel coatings excel in lubrication, reliability, stability, and ease of modification, yet they fall short of the comprehensive excellence of articular cartilage. Further research into the lubrication mechanism of hydrogels, the integration of lubrication properties, and other functional modifications with coating methods are anticipated to considerably improve the design of various hydrogel coatings with superior performance, enabling their biomedical application in various conditions.
[1] ADIBNIA V, MIRBAGHERI M, FAIVRE J, et al. Bioinspired polymers for lubrication and wear resistance[J]. Progress in Polymer Science, 2020, 110:101298. [2] LIU Y Y, ZHAO W W, LIU G X, et al. Self-powered artificial joint wear debris sensor based on triboelectric nanogenerator[J]. Nano Energy, 2021, 85:105967. [3] CHENG L, LIU C, WANG J, et al. Tough hydrogel coating on silicone rubber with improved antifouling and antibacterial properties[J]. ACS Applied Polymer Materials, 2022, 4(5):3462-3472. [4] [JP+3]HAN Y, LIU S Z, SUN Y L, et al. Bioinspired surface functionalization of titanium for enhanced lubrication and sustained drug release[J]. Langmuir, 2019, 35(20):6735-6741. [5] IRWIN N J, BRYANT M G, MCCOY C P, et al. Multifunctional, low friction, antimicrobial approach for biomaterial surface enhancement[J]. ACS Applied Bio Materials, 2020, 3(3):1385-1393. [6] 申佳佳. 两性离子防污减阻水凝胶涂层的研究[D]. 杭州:浙江大学, 2019. SHEN J J. Strategv to construct polvzwitterionic coating withi non-fouling and drag-reducing performance[D]. Hangzhou:Zhejiang University, 2019. (in Chinese) [7] 张大同. 软-硬接触下润滑膜厚度的测量及成膜特性的研究[D]. 青岛:青岛理工大学, 2022. ZHANG D T. Measurement of lubricating film thickness under soft-hard contact and study on film forming properties[D]. Qingdao:Qingdao University of Technology, 2022. (in Chinese) [8] 张雅涵, 崔春燕, 谢飞, 等. 水凝胶医用防污涂层研究进展[J]. 中国科学:技术科学, 2021, 51(11):1348-1361. ZHANG Y H, CUI C Y, XIE F, et al. Recent advancement in medical antifouling hydrogel coatings[J]. Scientia Sinica (Technologica), 2021, 51(11):1348-1361. (in Chinese) [9] GOMBERT Y, SIMI AČG R, RONCORONI F, et al. Structuring hydrogel surfaces for tribology[J]. Advanced Materials Interfaces, 2019, 6(22):1901320. [10] 陈凯. 仿生关节软骨的生物力学特性及其生物摩擦学研究[D]. 徐州:中国矿业大学, 2015. CHEN K. Research on biomechanical properties and bio-tribology of bionic articular cartilage[D]. Xuzhou:China University of Mining and Technology, 2015. (in Chinese) [11] [JP+2]ZHAO X D, ZHAO W Y, ZHANG Y L, et al. Recent progress of bioinspired cartilage hydrogel lubrication materials[J]. Biosurface and Biotribology, 2022, 8(3):225-243. [12] JAHN S, SEROR J, KLEIN J. Lubrication of articular cartilage[J]. Annual Review of Biomedical Engineering, 2016, 18:235-258. [13] MORGESE G, BENETTI E M, ZENOBI-WONG M. Molecularly engineered biolubricants for articular cartilage[J]. Advanced Healthcare Materials, 2018, 7(16):1701463. [14] 易佳锋, 刘宇博, 李超, 等. 关节软骨润滑机制理论及仿生软骨材料的摩擦学应用[J]. 中国组织工程研究, 2023, 27(25):4075-4084. YI J F, LIU Y B, LI C, et al. Lubrication mechanism in articular cartilage and tribological application of biomimetic cartilage materials[J]. Chinese Journal of Tissue Engineering Research, 2023, 27(25):4075-4084. (in Chinese) [15] LIN W F, KLEIN J. Hydration lubrication in biomedical applications:From cartilage to hydrogels[J]. Accounts of Materials Research, 2022, 3(2):213-223. [16] [JP+2]KLEIN J. Hydration lubrication[J]. Friction, 2013, 1(1):1-23. [17] LI Z B, LIU Q, LI Q, et al. The role of hydrated anions in hydration lubrication[J]. Nano Research, 2023, 16(1):1096-1100. [18] LIN W F, KLEIN J. Recent progress in cartilage lubrication[J]. Advanced Materials, 2021, 33(18):2005513. [19] PORTE E, CANN P, MASEN M. A lubrication replenishment theory for hydrogels[J]. Soft Matter, 2020, 16(45):10290-10300. [20] GONG J P, OSADA Y. Gel friction:A model based on surface repulsion and adsorption[J]. The Journal of Chemical Physics, 1998, 109(18):8062-8068. [21] 张宽. 基于凝胶的载药-润滑体系及其生物摩擦性应用和静电纺PCL纳米纤维提高成骨研究[D]. 海口:海南大学, 2019. ZHANG K. Drug-lubrication system based on gels with its application in biotribology and study on improving the osteogenesis of electrospun PCL nanofibers[D]. Haikou:Hainan University, 2019. (in Chinese) [22] GONG J P, OSADA Y. Surface friction of polymer gels[J]. Progress in Polymer Science, 2002, 27(1):3-38. [23] AHMED J, YAMAMOTO T, GUO H L, et al. Friction of zwitterionic hydrogel by dynamic polymer adsorption[J]. Macromolecules, 2015, 48(15):5394-5401. [24] [JP+3]GONG J P. Friction and lubrication of hydrogels-its richness and complexity[J]. Soft Matter, 2006, 2(7):544-552. [25] BAUMBERGER T, CAROLI C, RONSIN O. Self-healing slip pulses along a gel/glass interface[J]. Physical Review Letters, 2002, 88(7):075509. [26] OOGAKI S, KAGATA G, KUROKAWA T, et al. Friction between like-charged hydrogels-combined mechanisms of boundary, hydrated and elastohydrodynamic lubrication[J]. Soft Matter, 2009, 5(9):1879-1887. [27] PITENIS A A, URUEÑA J M, SCHULZE K D, et al. Polymer fluctuation lubrication in hydrogel gemini interfaces[J]. Soft Matter, 2014, 10(44):8955-8962. [28] WANG C B, BAI X Q, GUO Z W, et al. Friction and wear behaviours of polyacrylamide hydrogel microsphere/UHMWPE composite under water lubrication[J]. Wear, 2021, 477:203841. [29] BONYADI S Z, HASAN M, KIM J, et al. Review:Friction and lubrication with high water content crosslinked hydrogels[J]. Tribology Letters, 2020, 68(4):119. [30] URUEÑA J M, PITENIS A A, NIXON R M, et al. Mesh size control of polymer fluctuation lubrication in gemini hydrogels[J]. Biotribology, 2015, 1-2:24-29. [31] AHMED J, GUO H L, YAMAMOTO T, et al. Sliding friction of zwitterionic hydrogel and its electrostatic origin[J]. Macromolecules, 2014, 47(9):3101-3107. [32] [JP+3]YASHIMA S, TAKASE N, KUROKAWA T, et al. Friction of hydrogels with controlled surface roughness on solid flat substrates[J]. Soft Matter, 2014, 10(18):3192-3199. [33] FU X K, CAO H B, AN Y L, et al. Bioinspired hydroxyapatite coating infiltrated with a graphene oxide hybrid supramolecular hydrogel orchestrates antibacterial and self-lubricating performance[J]. ACS Applied Materials & Interfaces, 2022, 14(28):31702-31714. [34] QIU F, FAN X P, CHEN W, et al. Recent progress in hydrogel-based synthetic cartilage:Focus on lubrication and load-bearing capacities[J]. Gels, 2023, 9(2):144. [35] ZHENG Y W, YANG J L, LIANG J, et al. Bioinspired hyaluronic acid/phosphorylcholine polymer with enhanced lubrication and anti-inflammation[J]. Biomacromolecules, 2019, 20(11):4135-4142. [36] WANG X W, WANG J, YU Y, et al. A polyzwitterion-based antifouling and flexible bilayer hydrogel coating[J]. Composites Part B:Engineering, 2022, 244:110164. [37] LI S Y, BAI Y P, LIU X, et al. Bio-inspired robust, superhydrophilic and superlubric artificial vascular endothelium coating for anti-thromboinflammation on blood-contacting devices[J]. Composites Part B:Engineering, 2023, 257:110670. [38] LIN W F, KLUZEK M, IUSTER N, et al. Cartilage- inspired, lipid-based boundary-lubricated hydrogels[J]. Science, 2020, 370(6514):335-338. [39] LEI Y T, WANG Y P, SHEN J L, et al. Injectable hydrogel microspheres with self-renewable hydration layers alleviate osteoarthritis[J]. Science Advances, 2022, 8(5):eabl6449. [40] XIAO F, TANG J X, HUANG X, et al. A robust, low swelling, and lipid-lubricated hydrogel for bionic articular cartilage substitute[J]. Journal of Colloid and Interface Science, 2023, 629:467-477. [41] WANG Z M, ZHANG H B, CHU A J, et al. Mechanically enhanced nested-network hydrogels as a coating material for biomedical devices[J]. Acta Biomaterialia, 2018, 70:98-109. [42] TAKAHASHI R, SHIMANO K, OKAZAKI H, et al. Tough particle-based double network hydrogels for functional solid surface coatings[J]. Advanced Materials Interfaces, 2018, 5(23):1801018. [43] HASAN M, JOHNSON C L, DUNN A C. Soft contact mechanics with gradient-stiffness surfaces[J]. Langmuir, 2022, 38(31):9454-9465. [44] CHEN Q, ZHANG X Y, CHEN K, et al. Bilayer hydrogels with low friction and high load-bearing capacity by[JP+3]mimicking the oriented hierarchical structure of cartilage[J]. ACS Applied Materials & Interfaces, 2022, 14(46):52347-52358. [45] ZHANG X W, WANG J, JIN H, et al. Bioinspired supramolecular lubricating hydrogel induced by shear force[J]. Journal of the American Chemical Society, 2018, 140(9):3186-3189. [46] [JP+3]MA S H, SCARAGGI M, LIN P, et al. Nanohydrogel brushes for switchable underwater adhesion[J]. The Journal of Physical Chemistry C, 2017, 121(15):8452-8463. [47] WANG J, ZHANG X W, ZHANG S, et al. Semi-convertible hydrogel enabled photoresponsive lubrication[J]. Matter, 2021, 4(2):675-687. [48] LIU H, ZHAO X D, ZHANG Y L, et al. Cartilage mimics adaptive lubrication[J]. ACS Applied Materials & Interfaces, 2020, 12(45):51114-51121. [49] ZHAO C W, ZHOU L, CHIAO M, et al. Antibacterial hydrogel coating:Strategies in surface chemistry[J]. Advances in Colloid and Interface Science, 2020, 285:102280. [50] LIU J J, QU S X, SUO Z G, et al. Functional hydrogel coatings[J]. National Science Review, 2021, 8(2):nwaa254. [51] KUANG X, ARICAN M O, ZHOU T, et al. Functional tough hydrogels:Design, processing, and biomedical applications[J]. Accounts of Materials Research, 2023, 4(2):101-114. [52] YU Y, YUK H, PARADA G A, et al. Multifunctional "hydrogel skins" on diverse polymers with arbitrary shapes[J]. Advanced Materials, 2019, 31(7):1807101. [53] MA S H, YAN C Y, CAI M R, et al. Continuous surface polymerization via Fe(Ⅱ)-mediated redox reaction for thick hydrogel coatings on versatile substrates[J]. Advanced Materials, 2018, 30(50):1803371. [54] GAO L Y, MA S H, MA Z F, et al. In situ covalent bonding in polymerization to construct robust hydrogel lubrication coating on surface of silicone elastomer[J]. Colloids and Surfaces A:Physicochemical and Engineering Aspects, 2020, 599:124753. [55] XU R N, ZHANG Y L, MA S H, et al. A universal strategy for growing a tenacious hydrogel coating from a sticky initiation layer[J]. Advanced Materials, 2022, 34(11):2108889. [56] YAO X, LIU J J, YANG C H, et al. Hydrogel paint[J]. Advanced Materials, 2019, 31(39):1903062. [57] YAO M M, YAN Z J, SUN X, et al. Strongly adhesive zwitterionic composite hydrogel paints for surgical sutures and blood-contacting devices[J]. Acta Biomaterialia, 2023, 166:201-211. [58] YANG Z X, HE Y L, LIAO S L, et al. Renatured hydrogel painting[J]. Science Advances, 2021, 7(23):eabf9117. [59] MA H L, LIU Z Q, LOU J, et al. Bacterial cellulose/MWCNT coatings for highly sensitive and flexible paper-based humidity sensors[J]. Cellulose, 2023, 30(2):1193-1204. [60] MA L, JIANG W W, XUN X W, et al. Homogeneous silver nanoparticle loaded polydopamine/polyethyleneimine-coated bacterial cellulose nanofibers for wound dressing[J]. International Journal of Biological Macromolecules, 2023, 246:125658. [61] YANG Z F, FENG F F, JIANG W W, et al. Designment of polydopamine/bacterial cellulose incorporating copper (Ⅱ) sulfate as an antibacterial wound dressing[J]. Biomaterials Advances, 2022, 134:112591. [62] LIU X X, WANG D Y, WANG S, et al. Promoting osseointegration by in situ biosynthesis of metal ion-loaded bacterial cellulose coating on titanium surface[J]. Carbohydrate Polymers, 2022, 297:120022. [63] RVHS P A, MALOLLARI K G, BINELLI M R, et al. Conformal bacterial cellulose coatings as lubricious surfaces[J]. ACS Nano, 2020, 14(4):3885-3895.
2024, Vol. 64 
