Polycaprolactone containing inorganic/organic hybrid biomaterials
File(s)
Author(s)
Sang, Tian
Type
Thesis
Abstract
Bioactive glass and its associated products are able to stimulate bone regeneration but they are brittle and unable to be applied in load bearing sites. Improvements are needed so that they can share load with bone as well as promoting new bone growth and being biodegradable. Sol-gel hybrids can achieve this by having covalently coupled inorganic and organic networks. In order to form such intimate co-network, the choice of polymer is essential. Polycaprolactone (PCL) is a biodegradable polymer that has been widely used in tissue engineering due to its slow degradation rate, however it lacks functional groups that are critical to covalently bond to the silica network. In this thesis, new PCL/silica hybrids that have covalently bonded co-network were developed to toughen the glass content for the use in bone regeneration. In the first step, novel copolymer of caprolactone (CL) and 3-glycidoxypropyl trimethoxysilane (GPTMS) were synthesised to overcome the lack of functionality in conventional PCL. Hydrolysed silane part in the new poly(CL-co-GPTMS) are able to directly bond to the silica network without further functionalization. Hybrids were made homogeneously with poly(CL-co-GPTMS). Both weight percentage and repeating units of CL and GPTMS can be used to tailor the mechanical properties so that they obtain high compressive strength (64 MPa), strain to failure (20%) and deform elastically. Pre-osteoblast cells were found to adhere on the hybrids. Calcium was then incorporated into the glass using calcium methoxyethoxide (CME) in order to make the hybrid bioactive. The hybrids promoted hydroxycarbonate apatite (HCA) formation after 3 days immersion in stimulated body fluid (SBF). CME addition has also changed the mechanical properties of the hybrids depend on how CME was added to the hybrids. Inspired by the chemistry of polyurethane and poly(urethane-co-caprolactone) copolymer, hybrids were also made with cross-linked polymer content by the addition of methylene diphenyl diisocyanate (MDI). The MDI cross-linking effect has further toughed the hybrids without reducing their biological responses. Introducing such a new hybrid platform created a new way to fabricate biomaterials for bone repair.
Version
Open Access
Date Issued
2018-10
Date Awarded
2019-02
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Jones, Julian
Publisher Department
Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)