Polypyrrole-based conducting polymers and interactions with biological tissues

Journal of The Royal Society Interface, Dec 2006

Polypyrrole (PPy) is a conjugated polymer that displays particular electronic properties including conductivity. In biomedical applications, it is usually electrochemically generated with the incorporation of any anionic species including also negatively charged biological macromolecules such as proteins and polysaccharides to give composite materials. In biomedical research, it has mainly been assessed for its role as a reporting interface in biosensors. However, there is an increasing literature on the application of PPy as a potentially electrically addressable tissue/cell support substrate. Here, we review studies that have considered such PPy based conducting polymers in direct contact with biological tissues and conclude that due to its versatile functional properties, it could contribute to a new generation of biomaterials.

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Polypyrrole-based conducting polymers and interactions with biological tissues

D.D Ateh () H.A Navsaria P Vadgama 0 Centre for Cutaneous Research, Institute of Cell and Molecular Sciences, Barts and The London School of Medicine and Dentistry, Queen Mary University of London , London E1 2AT, UK 1 IRC in Biomedical Materials, Queen Mary University of London , London E14NS, UK Receive free email alerts when new articles cite this article - sign up in the box at the top right-hand corner of the article or click here - Email alerting service To subscribe to J. R. Soc. Interface go to: http://rsif.royalsocietypublishing.org/subscriptions Polypyrrole-based conducting polymers and interactions with biological tissues D. D. Ateh1,2,*, H. A. Navsaria2 and P. Vadgama1 Polypyrrole (PPy) is a conjugated polymer that displays particular electronic properties including conductivity. In biomedical applications, it is usually electrochemically generated with the incorporation of any anionic species including also negatively charged biological macromolecules such as proteins and polysaccharides to give composite materials. In biomedical research, it has mainly been assessed for its role as a reporting interface in biosensors. However, there is an increasing literature on the application of PPy as a potentially electrically addressable tissue/cell support substrate. Here, we review studies that have considered such PPy based conducting polymers in direct contact with biological tissues and conclude that due to its versatile functional properties, it could contribute to a new generation of biomaterials. 1. INTRODUCTION Through new combined knowledge of molecular biology and the biophysical correlates of material surface properties (Kasemo 1998; Castner & Ratner 2002; Tiefenauer & Ros 2002), local interactions between cells and their immediate microenvironments are increasingly better understood and recapitulated for the design of practical biomaterials (Discher et al. 2005; Liu & Chen 2005; Stevens & George 2005). Tissue engineering (Langer & Vacanti 1993) is probably one of the most likely avenues for exploitation of such new generation materials along with other niche areas such as neuroprosthetics, biosensors and drug delivery. In tissue engineering, especially with regard to bioreactors for optimal tissue growth in artificial constructs prior to implantation, the majority of cellsupporting scaffolds currently used are porous and degradable polymers (Seal et al. 2001). Such structures may be fabricated from natural materials, such as collagen or fibrin or synthetic polymers such as polyglycolide or polylactide. However, such scaffolds (or substrates) and their associated bio-functionality are now known to be important in tissue growth and guidance beyond any mesoscopic organization. For example, their topography (Curtis & Wilkinson 1997), mechanics (Wong et al. 2004) and incorporated controlled release growth factors and signal molecules (Saltzman & Olbricht 2002) can have profound effects on cell behaviour. Tailoring specific material properties, bulk as well as surface, could provide novel solutions for tissueengineered systems including controlled cell assembly (micro and nanopatterned surfaces), drug release (degradable polymers), tissue release (thermoresponsive polymers) and integrated biosensing (electroactive polymers). In addition, such materials provide a platform for the study of the fundamental underpinning science relating to tissue-material surface interactions. It is in recognition of these special requirements that researchers have engaged unique classes of materials for trial use in biological applications. Conducting polymers such as polypyrrole (PPy) offer a new class of material in this regard. This review presents research where PPy is in contact with biological tissue and outlines current achievements with an assessment of future opportunities. 2. POLYPYRROLE-BASED CONDUCTING POLYMERS 2.1. Conducting polymers Letheby in 1862 first reported the anodic oxidation of aniline in dilute sulphuric acid, yielding an insoluble blueblack shiny powdered deposit on a platinum electrode. Further experiments led Goppelsroeder in 1876 to establish that oligomers were formed by the PPy with biological tissues D. D. Ateh and others oxidation of aniline (Heinze 1989). Natta et al. (1958) synthesized polyacetylene and Dallolio et al. (1968) discovered yet another compound, PPy, at the time called pyrrole black. However, it was not until 1977 that Shirakawa and his co-workers wrote their seminal paper showing that halogen doping of polyacetylene dramatically increased its conductivity (to around 103 s mK1 in the case of I-doped trans-polyacetylene). The major breakthrough with regard to the routine synthesis of conducting polymers, however, was achieved by Diaz and co-workers (Diaz & Kanazawa 1979; Kanazawa et al. 1979; Diaz 1981) when they reported the formation of a highly conductive, stable and manageable PPy film under controlled electrochemical conditions. Since then, in the cont (...truncated)


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D.D Ateh, H.A Navsaria, P Vadgama. Polypyrrole-based conducting polymers and interactions with biological tissues, Journal of The Royal Society Interface, 2006, pp. 741-752, 3/11, DOI: 10.1098/rsif.2006.0141