A computational tool for the study of biodegradable composites

Abstract

Event Abstract Back to Event A computational tool for the study of biodegradable composites Ismael Moreno-Gomez1, Xiang Zhang2, Serena Best1 and Ruth Cameron1 1 University of Cambridge, Department of Materials Science and Metallurgy, United Kingdom 2 Lucideon Ltd., United Kingdom Introduction: Composites made from biodegradable polyester (poly-alpha-hydroxy-acids) and calcium-based ceramics are promising material candidates for orthopaedic applications due to their biodegradability and biocompatibility[1]. However varying the chemistry of the polymer and inorganic phases results in significantly different degradation behaviour[2],[3]. The considerable number of phenomena involved in composite degradation such as polymer hydrolysis and ceramic dissolution, together with the complexity of the interactions of the different processes mean that a full understanding of these effects has not yet been achieved. In this study, a computational tool designed to study the degradation process of these composites, is presented. Predictions from the simulation are compared with data drawn from a wide range of experiments in the literature. Materials and Methods: Computational model: The computational model for composite degradation was implemented in Python (user interface) and C++ (internal solver) based on an existing model for TCP (tricalcium phosphate) composites[4]. The composite model uses three sets of equations to characterise the degradation process: a set of differential equations to model the polymer behaviour, another set for the ceramic dissolution processes and a third set to represent the interactions between the ceramic filler and the biodegradable polymer. The computational tool can model a range of biodegradable polymers (poly-lactide (PLA), poly-glycolide (PGA) and poly-lactide-co-glycolide (PLGA)) and a range of calcium-based ceramics (TCP in both its alpha and beta allotropes, hydroxyapatite (HA), calcium deficient HA, calcium carbonate (CC) and mixtures of all the above). Experimental data: The experimental data was drawn from different sources of available literature. PLA, PGA and PLGA with different ceramic filling ranging from the nanoscale to the microscale were modelled. In addition, studies of pure polymer degradation and pure ceramic dissolution were used for further adjustment of the polymer and ceramic components of the model respectively. Results and Discussion Figure 1 shows an illustrative example of a computational prediction for a PLGA/TCP composite. The addition of the ceramic filling causes a reduction in hydrolytic degradation rate and therefore a delay in reaching the critical number averaged molecular weight that causes the release of the internal degradation products. These predictions agree with experimental data published in the literature[5]. Conclusions: The use of a simple, yet complete, computational tool allows a deeper understanding of the degradation phenomena. The predictions highlight the validity of the assumptions for most of the studied data and points at new factors to be considered where the simulation deviates from experiment. Lucideon; Obra Social "La Caixa"