174 Comparison of the mechanical performance of polymeric and metallic scaffolds – testing and modelling

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Percutaneous coronary intervention is a standard procedure to resolve blockages within artery, which involves the implantation of stents to maintain vessel patency. Currently, bioresorbable scaffolds (BRSs) are in the process of replacing the metallic permanent predecessor (drug eluting stents) commonly used in stenting. BRSs are commonly made of poly (L) Lactide (PLLA), an aliphatic polyester which is biodegradable and biocompatible with a wide range of medical applications. The performance of these scaffolds is not well defined in comparison to their metallic counterparts.The aim of this project is to assess the mechanical performance of PLLA scaffolds (Figure 1), with a direct comparison to that of metallic stents. This will be achieved through mechanical testing of structural rings at different load rates and ranges. Scaffolds will also be characterised using nano/micro indentation. The results will be used to support computational work for predicting the behaviour of both stents during crimping and expansion (Figure 2).Figure 3, Nanoindentation data on BRS.Figure 4, AFM data on BRS.Preliminary work indicates that it is possible to assess the local mechanical properties of a stent by atomic force microscopy and nano-indentation through evaluation of the unloading curves (figures 3 and 4). Further work would incorporate assessing the performance of the polymer scaffolds at different degradation time points to ascertain that vessel patency is achieved before complete degradation of BRSs.Results obtained here will help gain a better understanding of local and global mechanical properties of BRSs and enable further research and development of the scaffolds.AcknowledgementThis work was supported by a grant from the British Heart Foundation (BHF).

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