Ionic liquids promote extraction of collagen from skins/leather and application of collagen-based materials

Abstract

Collagen is the key structural component of skins and leather. Currently, the commonly used methods for collagen extraction are acid treatment, alkaline treatment, or enzymatic hydrolysis. However, these approaches often compromise the native molecular structure and generate significant environmental burdens. As one of the green, and highly efficient extraction strategies, ionic liquids (ILs) technology has emerged as a promising direction. This work first outlines the advantages of the ILs extraction method over other extraction techniques. The IL extraction method can enhance collagen yield, and its extraction process is more environmentally friendly and economical. Subsequently, it reviews recent advances in collagen extraction from skins and leather using ILs, emphasizing their role in enhancing collagen yield. The work summarizes the mechanism whereby ILs disrupt hydrogen bonds and ionic bonds stabilizing collagen molecular structures, thereby forming reversible new interactions to facilitate extraction. It was found that ILs have significant advantages in the application of collagen-based materials. In addition to improving the extraction efficiency of collagen, ILs can also promote the functionalization modification of collagen. It can not only regulate the microstructure and mechanical properties of collagen, but also give collagen antibacterial, conductive and other functions. Meanwhile, due to the low volatility, low toxicity and recyclability of ILs, the cost and environmental risks are greatly reduced. Particular attention is given to practical applications in drug delivery systems, tissue engineering, flexible sensors, and leather industry, underlining the broad technological relevance of this approach. Finally, we identify current limitations and outline future research directions. By consolidating the latest findings, this review aims to accelerate broader adoption of IL technologies, fostering greener, more sustainable trajectories for collagen.

Keywords

Skins / Leather / Collagen / Ionic liquids / Extraction / Application

References

[1] Liu H, Chen X, Kang J, Shi B, Zeng Y. Modulation of hide protein resistance to enzymatic hydrolysis by calcium ions: rational design of enzyme-assisted unhairing for high-quality leather production. Collagen Leather, 2025, 7123.

[2] Tang C, Zhou K, Zhu Y, Zhang W, Xie Y, Wang Z, et al. Collagen and its derivatives: from structure and properties to their applications in food industry. Food Hydrocoll, 2022, 131: 107748.

[3] Hulgan SA, Hartgerink JD. Recent advances in collagen mimetic peptide structure and design. Biomacromol, 2022, 23414751489.

[4] Chen X, Guo Z, Zhang J, Li Y, Duan R. A new method for determining the denaturation temperature of collagen. Food Chem, 2021, 343: 128393.

[5] Fang F, Wang X, Tao Y, Su Y, Dan W, Du Z, et al. Collagen-based biomaterials in neural injury repair: current advances and future perspectives. Collagen Leather, 2025, 7127.

[6] Li R, Xu S, Guo Y, Cao C, Xu J, Hao L, et al. Application of collagen in bone regeneration. J Orthop Transl, 2025, 50: 129-143

[7] Kolliopoulos V, Harley BA. Mineralized collagen scaffolds for regenerative engineering applications. Curr Opin Biotechnol, 2024, 86: 103080.

[8] Hu C, Li K, Li L, Zhang X, Xu T, Zhang L, et al. Recombinant human collagen injection ameliorates skin photoaging via immunoregulation and collagen production. Collagen and Leather, 2025, 7122.

[9] Erkan M, Blakney K, Andrews E, Leslie R, Ozsan E, Kreplak L. Formation of linear arrays of holes in self-assembled collagen films. Fron Soft Matter, 2024, 4: 1448615.

[10] Wu Y, Deng S, Wei W, He Y, He Y, Hong G, et al. Oral collagen-based supplement as a bioactive component in functional foods. Collagen Leather, 2025, 7115.

[11] Huan H, Zhang H, Jian W, Li-Wen W, Qian L, Cheng N-W, et al. Application of recombinant collagen in biomedicine. Prog Biochem Biophys, 2025, 522395416

[12] Li X, Liao X, Jia Z, Liu S, Li P, Li L, et al. Biodegradable PLLA/PLGA microspheres/collagen composites for continuous soft tissue augmentation. Compos B, 2024, 283: 111603.

[13] Mainik P, Aponte-Santamaría C, Fladung M, Curticean RE, Wacker I, Hofhaus G, et al. Responsive 3D printed microstructures based on collagen folding and unfolding. Small, 2025, 2132408597.

[14] Roshanbinfar K, Evans AD, Samanta S, Kolesnik-Gray M, Fiedler M, Krstic V, et al. Enhancing biofabrication: shrink-resistant collagen-hyaluronan composite hydrogel for tissue engineering and 3D bioprinting applications. Biomaterials, 2025, 318: 123174.

[15] Maistrenko L, Iungin O, Pikus P, Pokholenko I, Gorbatiuk O, Moshynets O, et al. Collagen obtained from leather production waste provides suitable gels for biomedical applications. Polymers, 2022, 14214749.

[16] Zhang Q, Song Y, Wang Y-n, Shi B. Advances and trends in leather science and technology. Collagen Leather, 2025, 7119.

[17] Zhang W, Li W, Yan M, Liang H, Fan Q, Gao J, et al. Power generation from leather scrap waste: fabrication and application of a novel self-morphologized collagen fiber-based triboelectric nanogenerator. Chem Eng J, 2025, 510: 161801.

[18] Chen H, Li Y, Dai H, Chen L, Ding X, Hu Z. Collagen hydrolyzed extract derived from leather waste as a multifunctional additive for the preparation of granular fertilizer. Sustain Chem Pharm, 2023, 36: 101327.

[19] Matinong AME, Chisti Y, Pickering KL, Haverkamp RG. Collagen extraction from animal skin. Biology, 2022, 116905.

[20] Hakim T, Pratiwi A, Fitriyanto N, Abidin M, Matulessy D, Erwanto Y. Extraction of collagen from the skin of kacang goat and production of its hydrolysate as an inhibitor of angiotensin converting enzyme. Trop J Anim Sci, 2021, 442222228.

[21] Maliha M, Rashid TU, Rahman MM. A green strategy for collagen extraction from tannery raw trimmings using papain enzyme: process optimization by MW-TOPSIS for enhanced yield. Int J Biol Macromol, 2024, 262: 130040.

[22] Zhang N, Guo S, Zheng Y, Li W. Isolation and characterisation of acid soluble collagens and pepsin soluble collagens from eel (Anguilla japonica Temminck et Schlegel) skin and bone. Foods, 2025, 143502.

[23] Tian Z, Wang Y, Wang H, Zhang K. Regeneration of native collagen from hazardous waste: chrome-tanned leather shavings by acid method. Environ Sci Pollut Res, 2020, 27253130031310.

[24] Masilamani D, Madhan B, Shanmugam G, Palanivel S, Narayan B. Extraction of collagen from raw trimming wastes of tannery: a waste to wealth approach. J Cleaner Prod, 2016, 113: 338-344.

[25] Gaikwad S, Kim MJ. Investigation of lemon and green tangerine extracts as natural alternatives for acid-based extraction of collagen hydrolysates: antioxidant and physicochemical properties. Food Hydrocolloids, 2025, 167: 111417.

[26] Li L, Zhang M. The efficient extraction method of collagen from deteriorated leather artifacts. Polymers, 2023, 15163459.

[27] Bi C, Li X, Xin Q, Han W, Shi C, Guo R, et al. Effect of extraction methods on the preparation of electrospun/electrosprayed microstructures of tilapia skin collagen. J Biosci Bioeng, 2019, 1282234240.

[28] Trithavisup T, Sanpinit P, Sakulwech S, Klamchuen A, Malila Y. In vitro protein digestion of cooked spent commercial laying hen and commercial broilers breast meat. Foods, 2022, 11131853.

[29] Matinong AME, Pickering KL, Waterland MR, Chisti Y, Haverkamp RG. Gelatin and collagen from sheepskin. Polymers, 2024, 16111563.

[30] Laasri I, Bakkali M, Mejias L, Laglaoui A. Marine collagen: unveiling the blue resource-extraction techniques and multifaceted applications. Int J Biol Macromol, 2023, 253: 127253.

[31] Tujjohra F, Rahman MM. Optimizing extraction of collagen from hazardous leather shaving dusts by crude protease enzyme: chrome recovery and reuse for leather rechroming. Bioresour Technol, 2024, 28: 101995

[32] Duan Y, Cheng H. Preparation of immobilized pepsin for extraction of collagen from bovine hide. RSC Adv, 2022, 12533454834556.

[33] He J, Shi R, Ji R. Effect of ultrasound pre-treatment on extraction and characterization of collagen from bactrian camel skin. Polymers, 2023, 1581943.

[34] Scheja JM, Sigurðarson JJ, Ólafsson HG, Einarsson H. Maximizing collagen yield from underutilized lumpfish (Cyclopterus lumpus) skins by optimizing pre-cleaning and extraction methods. Mar Drugs, 2024, 2212525.

[35] Abbas AA, Shakir KA, Walsh MK. Functional properties of collagen extracted from catfish (Silurus triostegus) waste. Foods, 2022, 115633.

[36] Rabideau BD, West KN, Davis JH. Making good on a promise: ionic liquids with genuinely high degrees of thermal stability. Chem Commun, 2018, 544050195031.

[37] Wu X, Zhu Q, Chen Z, Wu W, Lu Y, Qi J. Ionic liquids as a useful tool for tailoring active pharmaceutical ingredients. J Control Release, 2021, 338: 268-283.

[38] Matuszek K, Piper SL, Brzęczek‐Szafran A, Roy B, Saher S, Pringle JM, MacFarlane DR. Unexpected energy applications of ionic liquids. Adv Mater, 2024, 36232313023.

[39] Luo Q, Ding W, Pang X, Sun J. Application of ionic liquid in leather making. China Leather, 2023, 52: 40-47

[40] Zhu N, Zhang K, Wu F, Bai Y, Wu C. Ionic liquid-based electrolytes for aluminum/magnesium/sodium-ion batteries. Energy Mater Adv, 2021.

[41] Zhou T, Gui C, Sun L, Hu Y, Lyu H, Wang Z, et al. Energy applications of ionic liquids: recent developments and future prospects. Chem Rev, 2023, 123211217012253.

[42] Gao Y, Zhang W, Li L, Wang Z, Shu Y, Wang J. Ionic liquid-based gels for biomedical applications. Chem Eng J, 2023, 452: 139248.

[43] Qian W, Texter J, Yan F. Frontiers in poly (ionic liquid) s: syntheses and applications. Chem Soc Rev, 2017, 46411241159.

[44] Xiao Z, Liu M, Bi W, Chen DDY. Ionic liquid as hydrogen bond acceptor in the extraction of nutritional natural products. Food Chem, 2023, 412: 135589.

[45] Liu S, Liu W, Li G. Effect of ionic liquids pretreatment on the extrraction of collagen from calf skin. J Am Leather Chem As. 2019;114(10).

[46] Airouyuwa JO, Sivapragasam N, Redha AA, Maqsood S. Sustainable green extraction of anthocyanins and carotenoids using deep eutectic solvents (DES): a review of recent developments. Food Chem, 2024, 448: 139061.

[47] Gao Z, Liu X, Zhao H, Xia S, Liu W, Bai H, et al. Synthesis of easily-processable collagen bio-inks using ionic liquid for 3D bioprinted liver tissue models with branched vascular networks. Sci China Chem, 2023, 66514891499.

[48] Noorzai S, Verbeek CJR, Lay MC, Swan J. Collagen extraction from various waste bovine hide sources. Waste Biomass Valori, 2020, 111156875698.

[49] Zhu L, Yu Z-L, Li S, Xu C-Z, Hou Y-J, Liao L-X, et al. Recent advances on collagen biomaterial: from extraction, cross-linking to tissue regeneration. Polym Rev, 2024, 64410311059.

[50] Swatloski RP, Spear SK, Holbrey JD, Rogers RD. Dissolution of cellose with ionic liquids. J Am Chem Soc, 2002, 1241849744975.

[51] Souto-Montero P, Gallego C, Vázquez JA, Rodil E, Soto A. Tuna skin as bioresource for gelatine: extraction with ionic liquid. Sep Purif Technol, 2025, 363: 132144.

[52] Huang L, Ding S, Chen T, Wu R, Wang X, Jia S. Structural and functional properties of collagen from tilapia scales pretreated by heat‐assisted ionic liquids. J Appl Polym Sci, 2022, 1391451903.

[53] Sosnowska A, Barycki M, Zaborowska M, Rybinska A, Puzyn T. Towards designing environmentally safe ionic liquids: the influence of the cation structure. Green Chem, 2014, 161147494757.

[54] Huang L, Makhlooghiazad F, O'Dell LA, Howlett PC, Forsyth M. Investigating the role of mixed-cation ionic liquid electrolytes in sodium battery efficiency and stability. Mater Adv, 2024, 51768996909.

[55] Batista MP, Fernández N, Gaspar FB, Bronze MdR, Duarte ARC. Extraction of biocompatible collagen from blue shark skins through the conventional extraction process intensification using natural deep eutectic solvents. Front Chem, 2022, 10: 937036.

[56] Tarannum A, Jonnalagadda RR, Nishter NF. Stability of collagen in ionic liquids: ion specific Hofmeister series effect. Spectrochim Acta A Mol Biomol Spectrosc, 2019, 212: 343-348.

[57] Tarannum A, Muvva C, Mehta A, Raghava Rao J, Fathima NN. Role of preferential ions of ammonium ionic liquid in destabilization of collagen. J Phys Chem B, 2016, 1202765156524.

[58] Tarannum A, Muvva C, Mehta A, Rao JR, Fathima NN. Phosphonium based ionic liquids-stabilizing or destabilizing agents for collagen?. RSC Adv, 2016, 6540224033.

[59] Liu S, Li Q, Li G. Investigation of the solubility and dispersion degree of calf skin collagen in ionic liquids. J Leather Sci Eng, 2020, 2119

[60] Ahmed M, Verma AK, Malik MA, Alzahrani KA, Patel R. Probing the impact of alkyl chain length of imidazolium ionic liquids on the conformational stability of collagen type-I from skin of Lutjanus erythropterus. J Mol Struct, 2023, 1290: 135855.

[61] Reslan M, Kayser V. Ionic liquids as biocompatible stabilizers of proteins. Biophys Rev, 2018, 103781793.

[62] Wysokowski M, Luu RK, Arevalo S, Khare E, Stachowiak W, Niemczak M, et al. Untapped potential of deep eutectic solvents for the synthesis of bioinspired inorganic–organic materials. Chem Mater, 2023, 351978787903.

[63] Şahin S. Tailor-designed deep eutectic liquids as a sustainable extraction media: an alternative to ionic liquids. J Pharm Biomed Anal, 2019, 174: 324-329.

[64] Hansen BB, Spittle S, Chen B, Poe D, Zhang Y, Klein JM, et al. Deep eutectic solvents: a review of fundamentals and applications. Chem Rev, 2020, 121312321285.

[65] Bisht M, Martins M, Dias AC, Ventura SP, Coutinho JA. Uncovering the potential of aqueous solutions of deep eutectic solvents on the extraction and purification of collagen type I from Atlantic codfish (Gadus morhua). Green Chem, 2021, 232289408948.

[66] Malekshah ET, Rezaei M, Naghdi S, Tahergorabi R. Eco-friendly extraction of collagen from beluga sturgeon skin using ultrasound-assisted deep eutectic solvents: efficiency and characterization. Food Chem X, 2025, 30: 102988.

[67] Xiaofeng Y, Wenxiang S, Bo X, Ying L, Ping W. Extraction of collagen from cowhide by deep eutectic solvent aqueous solutions. J Leather Sci Eng, 2024, 3462430

[68] Batista MP, Ortigueira J, Fernandez N, Gaspar FB, do Rosário Bronze M, Duarte ARC, Lopes TF. Sustainability assessment of collagen extraction from fish skins: a comparative life cycle assessment of conventional and NADES-enhanced processes. J Environ Chem Eng, 2025, 132115911.

[69] Chen Q, Liang B, Yuan X, Yu X, Li C, Wei L, et al. Sustainable extraction and characterization of type I collagen from tuna skin waste utilizing biocompatible ionic liquid-based aqueous two-phase system. Food Hydrocoll, 2025, 168: 111524.

[70] Ahangari H, King JW, Ehsani A, Yousefi M. Supercritical fluid extraction of seed oils–a short review of current trends. Trends Food Sci Technol, 2021, 111: 249-260.

[71] Sousa RO, Martins E, Carvalho DN, Alves AL, Oliveira C, Duarte ARC, et al. Collagen from Atlantic cod (Gadus morhua) skins extracted using CO₂ acidified water with potential application in healthcare. J Polym Res, 2020, 27373.

[72] Baltacioğlu C, Temizsoy B. Ultrasound extraction in food industry. In: Şaşmaz M, editor. Multidisciplinary insights: geothermal wells, preservation, engineering, and chemical processes. IKSAD Publishing House. 2023. p. 193-239.

[73] Ahmed M, Verma AK, Patel R. Collagen extraction and recent biological activities of collagen peptides derived from sea-food waste: a review. Sustain Chem Pharm, 2020, 18: 100315.

[74] Zhao Y, Zhong M, Pang S, Liu P, Sun Y, Liang Q, et al. Exploring the potential of ultrasound: novel approaches to collagen extraction, modifications, and polypeptide preparation. Ultrason Sonochem, 2025, 120: 107504.

[75] Meng Y, Yang H, Li Z, Zhang W, Guo L, Zhang Y, Jiang Y. Intelligent transformation of ultrasound-assisted novel solvent extraction plant active ingredients: tools for machine learning and deep learning. Food Chem, 2025, 486: 144649.

[76] Petcharat T, Benjakul S, Karnjanapratum S, Nalinanon S. Ultrasound‐assisted extraction of collagen from clown featherback (Chitala ornata) skin: yield and molecular characteristics. J Sci Food Agric, 2021, 1012648658.

[77] Heidari MG, Rezaei M. Extracted pepsin of trout waste and ultrasound-promoted method for green recovery of fish collagen. Sustain Chem Pharm, 2022, 30: 100854.

[78] Gaikwad S, Kim MJ. Fish by-product collagen extraction using different methods and their application. Mar Drugs, 2024, 22260.

[79] Shitov DA, Krutin DV, Tupikina EY. Mutual influence of non‐covalent interactions formed by imidazole: a systematic quantum‐chemical study. J Comput Chem, 2024, 451310461060.

[80] Liu J, Zhao S, Xu Z. Comparison of dissolution and regeneration structure of collagen with two ionic liquids:[BMIM] Cl and [BMIM] Ac. CIESC J, 2015, 66621962204

[81] Liu S, Li Q, Li G. Investigation of the solubility and dispersion degree of calf skin collagen in ionic liquids. J Leather Sci Eng, 2019, 1111.

[82] Hu Y, Liu L, Dan W, Dan N, Gu Z. Evaluation of 1‐ethyl‐3‐methylimidazolium acetate based ionic liquid systems as a suitable solvent for collagen. J Appl Polym Sci, 2013, 130422452256.

[83] Andonegi M, Correia D, Pereira N, Salado M, Costa CM, Lanceros-Mendez S, et al. Sustainable collagen blends with different ionic liquids for resistive touch sensing applications. ACS Sustai Chem Eng, 2023, 111559865998.

[84] Tarannum A, Rao JR, Fathima NN. Insights into protein-ionic liquid interaction: a comprehensive overview on theoretical and experimental approaches. Int J Biol Macromol, 2022, 209: 498-505.

[85] Meng Z, Zheng X, Tang K, Liu J, Ma Z, Zhao Q. Dissolution and regeneration of collagen fibers using ionic liquid. Int J Biol Macromol, 2012, 514440448.

[86] Tarannum A, Adams A, Blümich B, Fathima NN. Impact of ionic liquids on the structure and dynamics of collagen. J Phys Chem B, 2018, 122310601065.

[87] Bharmoria P, Tietze AA, Mondal D, Kang TS, Kumar A, Freire MG. Do ionic liquids exhibit the required characteristics to dissolve, extract, stabilize, and purify proteins? Past-present-future assessment. Chem Rev, 2024, 124630373084.

[88] Bernardi JL, Oro CED, Puton BMS, Denti AF, Ambrósio N, Junges A, et al. Exploring the extraction of chromium from wet-blue leather using ionic liquids: efficiency, kinetics, and recyclability. J Water Process Eng, 2025, 72: 107624.

[89] Luo F, Liu Z, Zhao Q, Wang S, He L, Wu Y, Chen Z. An innovative ionic liquid-aqueous biphasic system for simultaneously highly efficient dechroming and collagen recovery from chrome-tanned leather shavings at room temperature. Sep Purif Technol, 2024, 349: 127861.

[90] Zhang Y, Li K, Tang J, Bai Y, Chen YM, Lv J, Zrínyi M. Multiscale interfacial designed ionogel/leather ionic skin for multimodal sensing capability. Adv Funct Mater, 2025, 35402500640.

[91] Pei Y, Chu S, Zheng Y, Zhang J, Liu H, Zheng X, Tang K. Dissolution of collagen fibers from tannery solid wastes in 1-allyl-3-methylimidazolium chloride and modulation of regenerative morphology. ACS Sustain Chem Eng, 2018, 7225302537.

[92] Luo F, Liu Z, Zhou P, Wang S, He L, Wu Y, et al. Extraction of collagen from bovine tannery solid waste preserving original conformation via radical initiation and hydrogen bond reformation. Green Chem, 2024, 261691959208.

[93] Ding S, Hülsey MJ, An H, He Q, Asakura H, Gao M, et al. Ionic liquid-stabilized single-atom Rh catalyst against leaching. CCS Chem, 2021, 31018141822.

[94] Wang Z, Liu J, Chen Q, Wu Y, Li Y, Ou M, et al. Bioactive glycyrrhizic acid ionic liquid self‐assembled nanomicelles for enhanced transdermal delivery of anti‐photoaging signal peptides. Adv Sci, 2025, 1282412581.

[95] Hashida M. Role of pharmacokinetic consideration for the development of drug delivery systems: a historical overview. Adv Drug Deliv Rev, 2020, 157: 71-82.

[96] Yue C, Ding C, Hu M, Zhang R, Cheng B. Collagen/functionalized cellulose nanofibril composite aerogels with pH-responsive characteristics for drug delivery system. Int J Biol Macromol, 2024, 261: 129650.

[97] Mendoza-Villafaña JJ, Claudio-Rizo JA, León-Campos MI, Becerra-Rodríguez JJ, Rodríguez-Fuentes N, Betancourt-Galindo R, et al. Collagen-polyurethane-maltodextrin hydrogels as bioactive scaffolds for soft and hard tissue regeneration, immunomodulation, and drug delivery. Int J Biol Macromol, 2025, 338: 149718.

[98] Du B, Feng S, Wang J, Cao K, Shi Z, Men C, et al. Collagen-based micro/nanogel delivery systems: manufacturing, release mechanisms, and biomedical applications. Chinese Med J, 2025, 1381011351152.

[99] Fan X, Liu S, Jia Z, Koh JJ, Yeo JCC, Wang C-G, et al. Ionogels: recent advances in design, material properties and emerging biomedical applications. Chem Soc Rev, 2023, 52724972527.

[100] El Mohamad M, Han Q, Dyett B, Yu H, Edgecomb S, Pride MC, et al. Cytotoxicity and cell membrane interactions of choline-based ionic liquids: comparing amino acids, acetate, and geranate anions. Chemosphere, 2024, 364: 143252.

[101] Ahmed M, Bhat AR, Verma AK, Patel R. Collagen–PVA films plasticized with choline acetate ionic liquid for sustained drug release: UV shielding, mechanical, antioxidant, and antibacterial properties. ACS Appl Bio Mater, 2023, 62663673.

[102] Lu B, Han S, Wang Z, Xie L, Zhan J, Zhang J, Zhang J. Antioxidant and anti-aging potential of collagen peptide conjugated with ionic liquid. J Mol Liq, 2024, 394: 123739.

[103] Zhang T, Zhang R, Zhang Y, Kannan PR, Li Y, Lv Y, et al. Silk-based biomaterials for tissue engineering. Adv Colloid Interface Sci, 2025, 338: 103413.

[104] Sun W, Shahrajabian MH, Ma K, Wang S. Advances in molecular function and recombinant expression of human collagen. Pharmaceuticals, 2025, 183430.

[105] Jiang Y-H, Lou Y-Y, Li T-H, Liu B-Z, Chen K, Zhang D, Li T. Cross-linking methods of type I collagen-based scaffolds for cartilage tissue engineering. Am J Transl Res, 2022, 1421146

[106] Banerjee K, Mathew C, Inbasekar C, Fathima NN. Mechanistic insights on stabilization and destabilization effect of ionic liquids on type I collagen fibrils. J Mech Behav Biomed Mater, 2024, 160: 106772.

[107] Munir M, Nosheen S, Muhammad N, Uroos M, Mustafa W, Khan R, et al. Ionic liquid treated bacterial cellulose sheets as prospective biodegradable implant materials. Cellulose, 2024, 31423272340.

[108] Iqbal B, Sarfaraz Z, Muhammad N, Ahmad P, Iqbal J, Khan ZUH, et al. Ionic liquid as a potential solvent for preparation of collagen-alginate-hydroxyapatite beads as bone filler. J Biomater Sci Polym Ed, 2018, 291011681184.

[109] Li X, Fan D. Smart collagen hydrogels based on 1-ethyl-3-methylimidazolium acetate and microbial transglutaminase for potential applications in tissue engineering and cancer therapy. ACS Biomater Sci Eng, 2019, 5735233536.

[110] Ren Y, Guo J, Liu Z, Sun Z, Wu Y, Liu L, Yan F. Ionic liquid–based click-ionogels. Sci Adv, 2019, 58eaax0648.

[111] Liu Z, Wang Y, Ren Y, Jin G, Zhang C, Chen W, Yan F. Poly (ionic liquid) hydrogel-based anti-freezing ionic skin for a soft robotic gripper. Mater Horiz, 2020, 73919927.

[112] Andonegi M, Meira RM, Correia DM, Pereira N, Costa CM, Lanceros-Mendez S, et al. Biodegradable and biocompatible collagen-based hybrid materials for force sensing applications. Int J Biol Macromol, 2024, 256: 128486.

[113] Liao L, Zhang J, Ding J, Xu C, Zhu L, Hou Y, et al. Adhesive, biocompatible, antibacterial, and degradable collagen-based conductive hydrogel as strain sensor for human motion monitoring. Molecules, 2024, 29235728.

[114] Peng Z, Zheng S, Zhang X, Yang J, Wu S, Ding C, et al. Flexible wearable pressure sensor based on collagen fiber material. Micromachines, 2022, 135694.

[115] Li Q, Yi Y, Wang Y-n, Li J, Shi B. Effect of cationic monomer structure on the aggregation behavior of amphoteric acrylic polymer around isoelectric point. J Leather Sci Eng, 2022, 414.

[116] Wei C, Wang X, Sun S, Lu Q, Zou X, Xie L, et al. A “three-in-one” strategy based on an on-demand multifunctional fluorescent amphoteric polymer for ecological leather manufacturing: a disruptive wet-finishing technique. Green Chem, 2023, 251559565967.

[117] Ramalingam S, Balamurugan K, Fathima NN. Greener solvent assistant dyeing: harnessing ionic liquids for eco-friendly tone-in-tone dyeing on all leather types. ACS Sustain Chem Eng, 2024, 12271010210117.

[118] Jia L, Zeng S, Ding H, Smith AT, LaChance AM, Farooqui MM, et al. Leather‐based multi‐stimuli responsive chromisms. Adv Funct Mater, 2021, 31352104427.

[119] Sindhu A, Kumar S, Venkatesu P. Contemporary advancement of cholinium-based ionic liquids for protein stability and long-term storage: past, present, and future outlook. ACS Sustain Chem Eng, 2022, 101443234344.

[120] Gomes JM, Silva SS, Reis RL. Biocompatible ionic liquids: fundamental behaviours and applications. Chem Soc Rev, 2019, 481543174335.

[121] Andonegi M, Correia DM, Costa CM, Lanceros-Mendez S, de la Caba K, Guerrero P. Tailoring physicochemical properties of collagen-based composites with ionic liquids and wool for advanced applications. Polymer, 2022, 252: 124943.

[122] Banerjee K, Rasheeda K, Tarannum A, Fathima NN. Structural and mechanical behavior of type-I collagen fibrils in presence of induced electrostatic interactions through ionic liquids. Biophys Chem, 2024, 307: 107192.

[123] Moshikur RM, Carrier RL, Moniruzzaman M, Goto M. Recent advances in biocompatible ionic liquids in drug formulation and delivery. Pharmaceutics, 2023, 1541179.

[124] Liu T, Zhang L, Lu B, Li D, Bo Y, Wang W, et al. Noninvasive and efficient peptide delivery by a novel biocompatible ionic liquid. ACS Sustain Chem Eng, 2022, 10501661116623.

[125] Koutsoukos S, Philippi F, Malaret F, Welton T. A review on machine learning algorithms for the ionic liquid chemical space. Chem Sci, 2021, 122068206843.

[126] Duong DV, Tran H-V, Pathirannahalage SK, Brown SJ, Hassett M, Yalcin D, et al. Machine learning investigation of viscosity and ionic conductivity of protic ionic liquids in water mixtures. J Chem Phys, 2022, 156: 154503.

[127] Fan D, Xue K, Zhang R, Zhu W, Zhang H, Qi J, et al. Application of interpretable machine learning models to improve the prediction performance of ionic liquids toxicity. Sci Total Environ, 2024, 908: 168168.

Funding

Startup Foundation of Beijing Institute of Technology(3160011182007)

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