Integration of biocomponents with synthetic structures: use of conducting polymer polyelectrolyte composites

New biocomposites with dynamically active properties were synthesized containing the conducting electroactive polymer, polypyrrole, dextran sulphate and a range of proteins. These composites have a hydrophilic matrix with a high water content and confer on the conducting polymer several properties useful in the design of new 'smarter' biomaterials. The composite is an excellent surface for the culture of mammalian cells. Inclusion of the polyelectrolyte also allows incorporation of protein and control of its release by reducing the polypyrrole backbone. These properties were exploited to incorporate nerve growth factor into a composite of polypyrrole and sulphated polysaccharide and after reduction to cause release of the nerve growth factor and thereby stimulate phaeochromocytoma cells to differentiate. Inclusion of polyelectrolyte also allows the incorporation of whole relatively intact cells into a polymer composite. This was demonstrated by the incorporation of human erythrocytes into the composite. The electrochemical properties of the composite were maintained raising the possibility that they could be used as the basis of an electrochemical biosensor for the detection of blood cell antigens. These new composite polymers showing protein release could be used not only as vehicles to deliver proteinaceous pharmaceuticals but also to communicate with mammalian cells during critical phases of their growth and development. The immobilization of mammalian cells in the composites could not only form the basis of biosensors but can also be used for many other applications where immobilized cells are required. Moreover the ability to control the dynamic properties of the composite and possibly the cells within it could be exploited to advantage.