A modular strategy for fabrication of responsive nanocomposites using functionalized oligocaprolactones and hydroxyapatite nanoparticles

Abstract

With the intention of mimicking the chemical structure of native bone, many researchers have emphasized the incorporation of hydroxyapatite (HA) into conventional biopolymers to fabricate tissue engineering constructs. However, the irreversible nature of these materials resulting from the covalent attachment of the components always leads to a non-responsive structure which cannot stimulate the nature of natural tissues. Of a diverse variety of responsive materials, supramolecular polymers based on the grafting of telechelic oligomers with quadruple hydrogen bonding ureido-pyrimidinone (UPy) have been of interest in recent years, although there is no report describing how the grafting efficiency can be controlled through the reaction parameters. In the present study, a systematic method based on the Taguchi experimental design approach was first developed to increase the reaction efficiency between polycaprolactone (PCL) and UPy motifs. We also demonstrated how supramolecular polymer nanocomposites based on the highly functionalized PCL and UPy-grafted HA enable us to combine both bioactivity and an exciting self-healing ability into a single modulated construct. By functionalization of PCL with UPy moieties, the properties of PCL change from a brittle and waxy solid to a strong and elastic material, and the incorporation of UPy-grafted HA into the polymer leads to a distinct improvement in the mechanical properties when compared to the supramolecular polymer alone. Given the high strength and the self-healing ability, the new supramolecular nanocomposite is expected to provide opportunities to create strong and responsive constructs for application in bone tissue engineering.