Over the last 40 years, electrically conductive polymers have become well established as important electrode materials. Polyanilines, polythiophenes and polypyrroles have received particular attention due to their ease of synthesis, chemical stability, mechanical robustness and the ability to tailor their properties. Electrochemical synthesis of these materials as films have proved to be a robust and simple way to realise surface layers with controlled thickness, electrical conductivity and ion transport. In the last decade, the biomedical compatibility of electrodeposited polymers has become recognised; in particular, polypyrroles have been studied extensively and can provide an effective route to pharmaceutical drug release. The factors controlling the electrodeposition of this polymer from practical electrolytes are considered in this review including electrolyte composition and operating conditions such as the temperature and electrode potential. Voltammetry and current-time behaviour are seen to be effective techniques for film characterisation during and after their formation. The degree of take-up and the rate of drug release depend greatly on the structure, composition and oxidation state of the polymer film. Specialised aspects are considered, including galvanic cells with a Mg anode, use of catalytic nanomotors or implantable biofuel cells for a self-powered drug delivery system and nanoporous surfaces and nanostructures. Following a survey of polymer and drug types, progress in this field is summarised and aspects requiring further research are highlighted.
Therapeutic drugs uploaded into conjugated conductive polymer matrices deposited on active magnesium alloys serve as controlled-dose, self-powered drug-delivery systems. Preferentially, drugs are added into polymer films in the largest amount possible, mostly to prevent long-term treatments. However, added drugs can interact with the polymer matrix affecting either the structure or the final mechanical properties of the polymer film. In this work, polypyrrole films (PPy) electrodeposited on an AZ31 Mg alloy in ibuprofen and salicylate-containing solutions are investigated in terms of their uploading capacity, surface morphology and mechanical properties. The techniques used to investigate the uploaded PPy films include cyclic voltammetry (CV), scanning electron microscopy (SEM), EDS, and depth-sensing indentation (DSI). A maximum ibuprofen concentration of 440 ± 40 μg cm −2 was obtained in PPy films in the presence of sodium salicylate. The release fraction of ibuprofen as a function of time is fitted to Avrami's equation. The hardness and reduced modulus decreased by 54 and 40 %, respectively, when the PPy films are prepared in the presence of sodium ibuprofen compared with those prepared in sodium salicylate only, indicating a more plastic film with ibuprofen.
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