A Facile Novel Method to Control Surface Topography of Conducting Polymer for Improved Coronary Stent Performance

Abstract

Endothelium lines the inner layer of all the arteries, its very important for healthy artery functions, and denudation of its layer is unavoidable during angioplasty. Thereby, drug eluting coronary stents are associated with delayed healing of the endothelial cell monolayer. Our aim was to optimise factors affecting electrochemical polymerisation and establish the influence of any achieved morphology due to optimization method in terms of re-endothelialisation of stents by assessing cell adhesion, proliferation and migration. Conducting polymer- Polypyrrole(Ppy) was used by the virtue of its application, influencing factors were identified and an optimized method was proposed for developing a consistent,reproducible method for obtaining homogeneous distinct morphologies of Ppy as stent coating. A monomer(Py) and dopant(NaSa)concentration of 0.2M and 0.1M used respectively in optimised method for 5 and 15 minutes with applied potential of 0.9V, mainly resulting in two new topographies. First named as “Coral Reef” due to its resemblance to actual coral reef,characterised by long open ended tubules(≃250µm),second topography also demonstrate distinct features in the form of‘cups and bowls’, which is never reported with the aforementioned monomer and dopant using potentiostatic method.Further, a method was successfully devised to control tubules of ‘coral reef’ topography leading to a homogeneous rough lump.SEM and AFM were used for surface charecterisation. Coated wires displaying “Noble Coral Reef” morphology were seeded with EC¯s, which exhibited variance in adherence to Ppy coatings. 4 Bare metal stents coated with/without coral reef topography were inflated exceeding their expansion limits to examine adherence of coating and for any visible fragmentation using SEM. Despite the previously reported brittle nature of Ppy, this test successfully exhibited near perfect adherence strength. These findings of increased surface area are promising for enhanced drug delivery in drug eluting stents.