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Biomaterials. 2018 Oct;181:189-198. doi: 10.1016/j.biomaterials.2018.07.031. Epub 2018 Jul 24.

Hydrolytically-degradable click-crosslinked alginate hydrogels.

Author information

1
Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, 13353 Berlin, Germany.
2
School of Engineering and Applied Sciences - Harvard University, Cambridge, MA 02138, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA.
3
Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA.
4
Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, 13353 Berlin, Germany; Berlin-Brandenburg Center for Regenerative Therapies, Charité - Universitätsmedizin Berlin, 13353 Berlin, Germany.
5
Julius Wolff Institute & Center for Musculoskeletal Surgery, Charité - Universitätsmedizin Berlin, 13353 Berlin, Germany; Berlin-Brandenburg Center for Regenerative Therapies, Charité - Universitätsmedizin Berlin, 13353 Berlin, Germany; Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, 14476 Potsdam, Germany. Electronic address: amaia.cipitria@mpikg.mpg.de.

Abstract

Degradable biomaterials aim to recapitulate the dynamic microenvironment that cells are naturally exposed to. By oxidizing the alginate polymer backbone, thereby rendering it susceptible to hydrolysis, and crosslinking it via norbornene-tetrazine click chemistry, we can control rheological, mechanical, and degradation properties of resulting hydrogels. Chemical modifications were confirmed by nuclear magnetic resonance (NMR) and the resulting mechanical properties measured by rheology and unconfined compression testing, demonstrating that these are both a function of norbornene coupling and oxidation state. The degradation behavior was verified by tracking mechanical and swelling behavior over time, showing that degradation could be decoupled from initial mechanical properties. The cell compatibility was assessed in 2D and 3D using a mouse pre-osteoblast cell line and testing morphology, proliferation, and viability. Cells attached, spread and proliferated in 2D and retained a round morphology and stable number in 3D, while maintaining high viability in both contexts over 7 days. Finally, oxidized and unoxidized control materials were implanted subcutaneously into the backs of C57/Bl6 mice, and recovered after 8 weeks. Histological staining revealed morphological differences and fibrous tissue infiltration only in oxidized materials. These materials with tunable and decoupled mechanical and degradation behavior could be useful in many tissue engineering applications.

KEYWORDS:

Alginate; Click chemistry; Hydrogel; Hydrolytic degradation; Tissue engineering

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