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The field of bone tissue engineering combines expertise in biology, chemistry and engineering to develop new 3D scaffolds that mimic the extracellular matrix. Design criteria for such materials are (I) biocompatibility and, ideally, biodegradability, (II) adequate pore architecture, (III) mechanical strength, and (IV) adequate surface modification to interact with the biological environment. In order to address these design criteria, our group has utilized poly(lactic acid) (PLA)-based scaffolds.
A poly(lactic acid)-graft-poly(ethylene glycol) (PLA-g-PEG) copolymer was shown to have reduced non-specific protein absorption in vitro compared to unfunctionalized PLA. This is of utter importance for biomedical materials, as nonspecific interactions with the body can hamper desired interactions. In a follow-up study, signaling peptides were attached to the PEG chain termini in order to attract bone-growing cells. The fully modular synthesis of the system affords the possibility to tailor the scaffold to specific biomedical applications, also beyond bone tissue engineering. Furthermore, biodegradable peptide-polymer conjugates have scarcely been reported in the literature.
In order to address the poor mechanical properties of PLA, we rationalized that cross-linked materials should significantly increase the mechanical properties. Consequently, we designed and synthesized a block copolymer based on PLA and poly(norbornene) (PNB) (PLA-b-PNB). Crosslinkable cinnamate groups on the PNB-block imbued the material with great mechanical strength, while phase-separation of the latter and the PLA-block allowed for the formation of porous foams. Bone-growing cells can migrate into the pores and thus grow new bone material around the foam.
Current research focusses on the combination of peptide-PLA-g-PEG and PLA-b-PNB to yield a material which exhibits great mechanical strength while interacting with its environment through the signaling peptide.