Bio-characterisation of tosylate-doped polypyrrole films for biomedical applications

Electroactive polymers such as polypyrrole (PPy) are receiving particular interest because they can combine inherent biological properties that can specifically trigger desired cellular responses for many biological applications. The aim of the present work was to evaluate more efficient solutions, achieved by different oxidisations of tosylate-doped PPy films in different chemico-physical conditions, in view of their long-term biomedical applications. The conductivity and the release of the tosylate ion were assessed. Morpho-functional studies were also performed. A gradual increase in impedance of the oxidised tosylate-doped PPy films soaked in MEM and a reduced conductivity after over-oxidation was found. Scanning electron microscopy (SEM) analysis showed the presence of a hierarchical organisation of the PPy films and a partially different morphology between oxidised and over-oxidised films. Cell behaviour was also randomly affected in relation to the oxidative state of the studied Ppy films. On the basis of the results, growth of these tosylate-doped Ppy films directly in the sol–gel matrix or on the surface of metal alloys could be hypothesised in order to improve bioactive materials of potential use in modern regenerative medicine. However, in view of their in vivo application, over-oxidation must be considered as it may represent the degraded material that is likely to form under a biological oxidising environment.