Owing to their ability to fill ill-defined locations, injectable polymer networks attract lots of attention in the biomedical field for local drug release and/or tissue engineering. In particular, doubly crosslinked networks (DX gels) are particularly appealing as the primarily crosslinked microbeads can be injected in the presence of a reactive crosslinker to generate in situ macroscopic gels filling and fitting cavities at perfection to exert their action. Compared to other injectable hydrogels, the double hierarchisation allow for better tuning of the resulting swelling and mechanical properties. However, these DX gels are mainly obtained by radical coupling of vinyl functionalized particles, making this gelation mechanism inconvenient for in vivo applications. Quite recently, our group has published a new approach towards DX gels that exploits the potential of an ultrafast click reaction based on triazolinedione (TAD) compounds. In this context, cyclopentadienyl (Cp) functional microgels were prepared either by conventional water in oil radical suspension or microfluidic copolymerization of poly(ethylene glycol methyl ether methacrylate (Mn = 500 g/mol) with glycidyl methacrylate and ethylene glycol dimethacrylate as crosslinker. Postmodification of the microgels was subsequently achieved by reacting glycidyl functions with NaCp. The effective surface modification as well as the control of reactive Cp density were assessed by fluorescent microscopy, after clicking N(1-pyrenyl) maleimide. In a last step, the microgels are mixed with a bis-TAD functional crosslinker and self-assembled within adequate rate to form doubly crosslinked microgel networks in various medium. Beyond this efficient synthetic approach, free of any metals, the current work highlights how the resulting mechanical properties of DX gels can be tuned to be compatible with biological prerequisites.

Ultrafast gelation of injectable reactive microgels: The power of TAD click chemistry

253rd National Meeting (2017)

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