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Hydrogel of a superabsorbent polymer

A hydrogel is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. A three-dimensional solid results from the hydrophilic polymer chains being held together by cross-links.[clarification needed] Because of the inherent cross-links, the structural integrity of the hydrogel network does not dissolve from the high concentration of water.[1] Hydrogels are highly absorbent (they can contain over 90% water) natural or synthetic polymeric networks.

The first appearance of the term 'hydrogel' in the literature was in 1894.[2] A hydrogel, sold under the brand Plenity, was approved to help with weight loss in 2019.[3]


An adhesive bandage with a hydrogel pad, used for blisters and burns. The central gel is clear, the adhesive waterproof plastic film is clear, the backing is white and blue.

Common uses include:


Common ingredients include polyvinyl alcohol, sodium polyacrylate, acrylate polymers and copolymers with an abundance of hydrophilic groups.

Hydrogels also possess a degree of flexibility very similar to natural tissue, due to their significant water content. As responsive "smart materials," hydrogels can encapsulate chemical systems which upon stimulation by external factors such as a change of pH may cause specific compounds such as glucose to be liberated to the environment, in most cases by a gel-sol transition to the liquid state. Chemomechanical polymers are mostly also hydrogels, which upon stimulation change their volume and can serve as actuators or sensors.


Natural hydrogel materials are being investigated for tissue engineering; these materials include agarose, methylcellulose, hyaluronan, Elastin like polypeptides and other naturally derived polymers. Hydrogels show promise for use in agriculture, as they can release agrochemicals including pesticides and phosphate fertiliser slowly, increasing efficacy and reducing runoff, and at the same time improve the water retention of drier soils such as sandy loams.[18]


  1. ^ Warren, David S.; Sutherland, Sam P. H.; Kao, Jacqueline Y.; Weal, Geoffrey R.; Mackay, Sean M. (2017-04-20). "The Preparation and Simple Analysis of a Clay Nanoparticle Composite Hydrogel". Journal of Chemical Education. 94 (11): 1772–1779. Bibcode:2017JChEd..94.1772W. doi:10.1021/acs.jchemed.6b00389. ISSN 0021-9584.
  2. ^ "Der Hydrogel und das kristallinische Hydrat des Kupferoxydes". Zeitschrift für Chemie und Industrie der Kolloide. 1 (7): 213–214. 1907. doi:10.1007/BF01830147.
  3. ^ "Ingested, transient, space occupying device for weight management and/or weight loss" (PDF). Retrieved 17 April 2019.
  4. ^ Talebian, Sepehr; Mehrali, Mehdi; Taebnia, Nayere; Pennisi, Cristian Pablo; Kadumudi, Firoz Babu; Foroughi, Javad; Hasany, Masoud; Nikkhah, Mehdi; Akbari, Mohsen; Orive, Gorka; Dolatshahi‐Pirouz, Alireza (2019). "Self-Healing Hydrogels: The Next Paradigm Shift in Tissue Engineering?". Advanced Science. 6 (16): 1801664. doi:10.1002/advs.201801664. ISSN 2198-3844. PMC 6702654. PMID 31453048.
  5. ^ Mellati, Amir; Dai, Sheng; Bi, Jingxiu; Jin, Bo; Zhang, Hu (2014). "A biodegradable thermosensitive hydrogel with tuneable properties for mimicking three-dimensional microenvironments of stem cells". RSC Adv. 4 (109): 63951–63961. doi:10.1039/C4RA12215A. ISSN 2046-2069.
  6. ^ Discher, D. E.; Janmey, P.; Wang, Y.L. (2005). "Tissue Cells Feel and Respond to the Stiffness of Their Substrate" (PDF). Science. 310 (5751): 1139–43. Bibcode:2005Sci...310.1139D. CiteSeerX doi:10.1126/science.1116995. PMID 16293750.
  7. ^ Brudno, Yevgeny (2015-12-10). "On-demand drug delivery from local depots". Journal of Controlled Release. 219: 8–17. doi:10.1016/j.jconrel.2015.09.011. PMID 26374941.
  8. ^ Lee, Jin Hyun (December 2018). "Injectable hydrogels delivering therapeutic agents for disease treatment and tissue engineering". Biomaterials Research. 22 (1): 27. doi:10.1186/s40824-018-0138-6. ISSN 2055-7124. PMC 6158836. PMID 30275970.
  9. ^ Liu, Mei; Zeng, Xin; Ma, Chao; Yi, Huan; Ali, Zeeshan; Mou, Xianbo; Li, Song; Deng, Yan; He, Nongyue (December 2017). "Injectable hydrogels for cartilage and bone tissue engineering". Bone Research. 5 (1): 17014. doi:10.1038/boneres.2017.14. ISSN 2095-6231. PMC 5448314. PMID 28584674.
  10. ^ Pupkaite, Justina; Rosenquist, Jenny; Hilborn, Jöns; Samanta, Ayan (2019-09-09). "Injectable Shape-Holding Collagen Hydrogel for Cell Encapsulation and Delivery Cross-linked Using Thiol-Michael Addition Click Reaction". Biomacromolecules. 20 (9): 3475–3484. doi:10.1021/acs.biomac.9b00769. ISSN 1525-7797.
  11. ^ Malmsten, Martin; Bysell, Helena; Hansson, Per (2010-12-01). "Biomacromolecules in microgels — Opportunities and challenges for drug delivery". Current Opinion in Colloid & Interface Science. 15 (6): 435–444. doi:10.1016/j.cocis.2010.05.016. ISSN 1359-0294.
  12. ^ Chemoresponsive Materials, Editor: Hans-Jörg Schneider, Royal Society of Chemistry, Cambridge 2015,
  13. ^ Yetisen, A. K.; Naydenova, I; Da Cruz Vasconcellos, F; Blyth, J; Lowe, C. R. (2014). "Holographic Sensors: Three-Dimensional Analyte-Sensitive Nanostructures and their Applications". Chemical Reviews. 114 (20): 10654–96. doi:10.1021/cr500116a. PMID 25211200.
  14. ^ Caló, Enrica; Khutoryanskiy, Vitaliy V. (2015). "Biomedical applications of hydrogels: A review of patents and commercial products". European Polymer Journal. 65: 252–267. doi:10.1016/j.eurpolymj.2014.11.024.
  15. ^ Cook, Michael T.; Smith, Sarah L.; Khutoryanskiy, Vitaliy V. (2015). "Novel glycopolymer hydrogels as mucosa-mimetic materials to reduce animal testing". Chem. Commun. 51 (77): 14447–14450. doi:10.1039/C5CC02428E. PMID 26221632.
  16. ^ Cook, Michael T.; Khutoryanskiy, Vitaliy V. (2015). "Mucoadhesion and mucosa-mimetic materials—A mini-review". International Journal of Pharmaceutics. 495 (2): 991–8. doi:10.1016/j.ijpharm.2015.09.064. PMID 26440734.
  17. ^ Kwon, Gu Han; Jeong, Gi Seok; Park, Joong Yull; Moon, Jin Hee; Lee, Sang-Hoon (2011). "A low-energy-consumption electroactive valveless hydrogel micropump for long-term biomedical applications". Lab on a Chip. 11 (17): 2910–5. doi:10.1039/C1LC20288J. PMID 21761057.
  18. ^ Puoci, Francesco; et al. (2008). "Polymer in Agriculture: A Review" (PDF). American Journal of Agricultural and Biological Sciences. 3 (1): 299–314. doi:10.3844/ajabssp.2008.299.314.