Degradable multi(aryl azide) star copolymer as universal photo-crosslinker for elastomeric scaffolds

Abstract

Degradable elastomers with elastic properties close to those of soft tissues are necessary for tissue engineering. Most degradable elastomers developed so far are based on functional low–molecular-weight prepolymers that are combined with molecular crosslinkers to yield the elastomeric three-dimensional networks. To overcome this limitation, we present in this work the concept of star-shaped macromolecular multi(aryl azide) photo-crosslinker that has the ability to efficiently cross-link any polymer containing C-H bonds independently of its molecular weight and without the need for prefunctionalization. This concept of universal crosslinking agent is illustrated with a star-shaped block copolymer composed of an 8-arm poly(ethylene glycol) core and poly(lactide) side arms functionalized with aryl azide moieties (PEG8arm-PLA-fN3). It was selected due to its macromolecular nature that allows for an easy processing of electrospun photo-crosslinked scaffolds, while making it possible to adapt its chemical nature with one of the polymer matrices. A parameter study is first carried out on PEG8arm-PLA-fN3/PLA-Pluronic®-PLA films to evaluate the impact of the polymers' molecular weight, PEG/PLA ratios, and UV irradiation conditions on the crosslinking efficiency. This study confirms that high crosslinking efficiencies can be obtained with PEG8arm-PLA-fN3 (60%) compared with commercially available bis(aryl azide) photo-crosslinker (below 15%). Optimal conditions are then used to yield electrospun microfibers (1–2 μm) crosslinked with PEG8arm-PLA-fN3, resulting in biocompatible and highly elastomeric scaffolds (εy>100%) compared with uncrosslinked scaffolds (εy<10%). In addition, we show that the degradation rate can be controlled overtime depending on the blend content of PEG8arm-PLA-fN3. Taken together, these results demonstrate the potential of macromolecular multi(aryl azide) photo-crosslinkers to develop original degradable elastomeric scaffolds for soft tissue reconstruction.