A composite approach: adapting emulsion templated polymers for use in bone tissue engineering

Abstract

Event Abstract Back to Event A composite approach: adapting emulsion templated polymers for use in bone tissue engineering Aaron Z. Lee1, 2, Caitlin R. Langford1, Luis M. Rodriguez-Lorenzo3, 4, Oliver Bissinger5, Helmut Thissen2 and Neil R. Cameron1 1 Monash University, Materials Science and Engineering, Australia 2 Commonwealth Scientific and Industrial Research Organisation, Manufacturing Flagship, Australia 3 ICTP-CSIC, Polymeric Nanomaterials and Biomaterials, Spain 4 CIBER-BBN, Polymeric biomateriaasl group, Spain 5 Technical University of Munich, Oral and Maxillofacial Surgery, Germany Introduction: Synthetic scaffolds are envisioned as potential medical devices capable of aiding in the repair and regeneration of host tissues. Templating based on high internal phase emulsions represents a versatile route to the creation of highly porous architectures capable of supporting cell in growth. Recent developments include the use of click chemistry and surface functionalisation to tailor the presented environment towards a given application[1]. The current work investigates the formation of a polymer composite material based on the combination of an emulsion templated polymer in conjunction with hydroxyapatite for use in bone tissue engineering. Fabricated materials were physically characterised and evaluated for biocompatibility through in vitro culture of MG63 osteosarcoma cells. Materials and Methods: A monomer mixture consisting of a trithiol [trimethylopropane tris(3-mercaptopropionate)] and a multifunctional acrylate [dipentaerythritol penta/hexa-acrylate] dissolved in 1,2-dichloroethane with Hypermer B246 as the surfactant was used to form the polymer network. Photoinitiator was added to the mixture before adding water dropwise to a total volume of 140mL. Hydroxyapatite nanoparticles were incorporated into the monomer phase and dispersed before the addition of water. Emulsions were subsequently cured by exposure to UV irradiation to form the polyHIPE. Materials were characterised by FTIR. In vitro cell culture was performed on 200μm thick sections against Alvetex® with an initial seeding density of 0.5x106 cells and cultured in DMEM + 10%FBS for up to 21 days. Samples were then fixed and stained using histological techniques. Results and Discussion: Comparison between the FTIR spectra of the polyHIPE materials allowed evaluation of the incorporation of hydroxyapatite. Notably, this is evinced through the appearance of the peaks at 568cm-1 and 1030cm-1 in the composite which correspond directly to key peaks in the spectra for hydroxyapatite. Alvetex® scaffolds, based on polystyrene, were used as control substrates to evaluate the suitability of the culture conditions. No significant adverse effects were observed on this substrate or the native polyHIPE, and both supported cell attachment and growth for the duration of the culture period. At early time points, von Kossa staining experiments showed staining of the polyHIPE + 5wt% hydroxyapatite scaffolds. Even staining was observed albeit with darker regions corresponding to particle agglomerates. After 21 days in culture, the staining pattern changed dramatically with intense clusters being observed in the space taken up by cells while the uptake of stain in the scaffold itself was diminished. Ergo, the hydroxyapatite incorporated into the polyHIPE is available for redistribution by cells, potentially accelerating mineralisation. Conclusion: By dispersing hydroxyapatite through the monomer phase, it was possible to generate composite polyHIPE materials which retained their morphology while modulating the biological response. This provides another avenue for the modular design of polyHIPEs for biomaterial applications. Monash University; CSIRO