title: Click hydrogels, microgels and nanogels: emerging platforms for drug delivery and tissue engineering.
abstract: Hydrogels, microgels and nanogels have emerged as versatile and viable platforms for sustained protein release, targeted drug delivery, and tissue engineering due to excellent biocompatibility, a microporous structure with tunable porosity and pore size, and dimensions spanning from human organs, cells to viruses. In the past decade, remarkable advances in hydrogels, microgels and nanogels have been achieved with click chemistry. It is a most promising strategy to prepare gels with varying dimensions owing to its high reactivity, superb selectivity, and mild reaction conditions. In particular, the recent development of copper-free click chemistry such as strain-promoted azide-alkyne cycloaddition, radical mediated thiol-ene chemistry, Diels-Alder reaction, tetrazole-alkene photo-click chemistry, and oxime reaction renders it possible to form hydrogels, microgels and nanogels without the use of potentially toxic catalysts or immunogenic enzymes that are commonly required. Notably, unlike other chemical approaches, click chemistry owing to its unique bioorthogonal feature does not interfere with encapsulated bioactives such as living cells, proteins and drugs and furthermore allows versatile preparation of micropatterned biomimetic hydrogels, functional microgels and nanogels. In this review, recent exciting developments in click hydrogels, microgels and nanogels, as well as their biomedical applications such as controlled protein and drug release, tissue engineering, and regenerative medicine are presented and discussed.
authors.affiliation: Biomedical Polymers Laboratory, and Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People's Republic of China.
authors.forename: Yanjiao
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Biomedical Polymers Laboratory, and Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.affiliation: Biomedical Polymers Laboratory, and Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People's Republic of China. Electronic address: cdeng@suda.edu.cn.
authors.forename: Chao
authors.initials: C
authors.lastname: Deng
authors.affiliation: Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa K1Y 4W7, Canada.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Suuronen
authors.affiliation: Biomedical Polymers Laboratory, and Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People's Republic of China. Electronic address: zyzhong@suda.edu.cn.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Zhong
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D032701:Biomimetics / Q000379:methods; D002384:Catalysis; D057930:Click Chemistry / Q000379:methods*; D061565:Cycloaddition Reaction; D016503:Drug Delivery Systems / Q000379:methods*; D006801:Humans; D020100:Hydrogels / Q000737:chemistry*; D000080385:Nanogels; D011092:Polyethylene Glycols / Q000737:chemistry*; D011094:Polyethyleneimine / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D000080385:Nanogels; D011108:Polymers; C413692:polyethylene glycol polyethyleneimine nanogel; D011092:Polyethylene Glycols; D011094:Polyethyleneimine
keywords: Click chemistry; Drug delivery; Hydrogels; Microgels; Nanogels; Tissue engineering