Synthesis, Characterisation and 3D printing of a Light-Curable Degradable Polymer for Craniofacial Bone Regeneration
A surgeon’s options for correcting congenital deformities, removing oral tumours and reconstructing the head and neck region are typically restricted by the equipment available to restore bone function as well as appearance for the patient. There is an increasing requirement for effective implants that cost a reasonable amount, therefore, new production techniques and implants with improved osseointegration performance are urgently needed. Non-degradable materials are used widely for bone repair; however, they will stay in the body indefinitely until removed surgically. Metals, such as titanium, can be used for three-dimensional (3D) printing of scaffolds.
3D printing has the potential to enhance the creation of anatomically fitting patient-specific devices with highly effective delivery in a cost-effective manner. However, metal implants have the disadvantage that they can release traces of material over time and induce immunological responses. Furthermore, metal implants can cause mechanical irritation from underlying fixation devices and infection. Non-degradable polymers, such as poly (methyl methacrylate), have the disadvantages that they undergo highly exothermic polymerisation, are prone to infection and lack osseointegration. Ceramics, such as calcium phosphates, have also been studied for use in craniofacial bone regeneration, however, they have poor fracture toughness, brittleness and excessive stiffness.
In view of the disadvantages associated with several of the known 3D printable materials, this thesis takes you through the development of an improved material that addresses some of the disadvantages discussed above.
In this study, the synthesis of the new material, ((((((((((((3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl)bis(oxy))bis(ethane-2,1 diyl))bis- (oxy))bis(carbonyl))bis(azanediyl))bis(methylene))bis(3,3,5-trimethylcyclohexane-5,1-diyl))bis(azanediyl))bis(carbonyl))bis- (oxy))bis(ethane-2,1-diyl)bis(2-methylacrylate),
referred to as “CSMA-2” is investigated along with its mechanical properties and the effects of the addition of different ratios of calcium phosphate (CaP) fillers to the isosorbide-based, light-curable, degradable polymer. Characterisation via Nuclear Magnetic Resonance (NMR) of the monomers confirmed the formation of the system. A comparison between two different photoinitiator systems is carried out throughout this study to ultimately find the most suited formulation for the 3D printing of the resin.
Mechanical tests showed the modulus values to be between 1.7-3 GN mm−2 in CSMA-2 and its composites dependant on the photoinitiator system used. In Vitro cell culture studies, using human bone osteosarcoma cells and human adipose-derived stem cells confirmed non-toxicity of the material. Finally, Digital Light Processing (DLP) using stereolithography (SLA) 3D printing, allowed a direct photo-polymerisation of the resin to form bone- like scaffolds ready to be implanted In Vivo.