Shear-thinning and self-healing hydrogels as injectable therapeutics and for 3D-printing

• Published in: Nature protocols Vol. 12; no. 8; pp. 1521 - 1541
• Main Authors: Loebel, Claudia, Rodell, Christopher B, Chen, Minna H, Burdick, Jason A
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2017; Nature Publishing Group
• Subjects: 13/100; 13/107; 14/63; 3D printing; 631/61/2296; 631/61/54/152; 631/61/54/990; 639/301/923/1027; Adamantane - metabolism; Analysis; Analytical Chemistry; Animals; beta-Cyclodextrins - metabolism; Biological Techniques; Biomolecules; Chemical compounds; Complications and side effects; Computational Biology/Bioinformatics; Covalence; Crosslinking; Cyclodextrin; Cyclodextrins; Dismantling; Dosage and administration; Drug Carriers - administration & dosage; Drug delivery systems; Drug therapy; Encapsulation; Esterification; Fluorescence; Fluorophores; Healing; Health aspects; Hyaluronic acid; Hyaluronic Acid - administration & dosage; Hydrogels; Hydrogels - administration & dosage; Hydrogels - chemistry; In vitro methods and tests; Injections; Life Sciences; Mice; Microarrays; Organic Chemistry; Polymers; Printing; Printing, Three-Dimensional; Properties (attributes); protocol; Rheological properties; Rheology; Shear; Shear forces; Shear thinning (liquids); Stoichiometry; Therapeutics; Thinning; Three dimensional printing
• ISSN: 1754-2189; 1750-2799
• DOI: 10.1038/nprot.2017.053

Hydrogels, networks of water-swollen polymers, are being exploited for the local delivery of cells and biologically relevant molecules. Loebel et al . describe the preparation of supramolecular hydrogels and their characterization. The design of injectable hydrogel systems addresses the growing demand for minimally invasive approaches for local and sustained delivery of therapeutics. We developed a class of hyaluronic acid (HA) hydrogels that form through noncovalent guest–host interactions, undergo disassembly (shear-thinning) when injected through a syringe and then reassemble within seconds (self-healing) when shear forces are removed. Its unique properties enable the use of this hydrogel system for numerous applications, such as injection in vivo (including with cells and therapeutic molecules) or as a 'bioink' in 3D-printing applications. Here, we describe the functionalization of HA either with adamantanes (guest moieties) via controlled esterification or with β-cyclodextrins (host moieties) through amidation. We also describe how to modify the HA derivatives with methacrylates for secondary covalent cross-linking and for reaction with fluorophores for in vitro and in vivo imaging. HA polymers are rationally designed from relatively low-molecular-weight starting materials, with the degree of modification controlled, and have matched guest-to-host stoichiometry, allowing the preparation of hydrogels with tailored properties. This procedure takes 3–4 weeks to complete. We detail the preparation and characterization of the guest–host hydrogels, including assessment of their rheological properties, erosion and biomolecule release in vitro . We furthermore demonstrate how to encapsulate cells in vitro and provide procedures for quantitative assessment of in vivo hydrogel degradation by imaging of fluorescently derivatized materials.