Chapter 1 relates the background information of the structure of antibodies, the nature of their interaction with antigen and their production as polyclonal antibodies. Examples of antibodies which have been produced against luminescent molecules are given and it is illustrated how the specific interaction of antibodies with luminescent complexes can be used to gain information on the structure, function and rotational dynamics of antibodies. The principle features of immunoassays are outlined with a focus on amperometric immunosensing including some areas of active research within amperometric immunosensing. This serves as a general introduction to Chapter 4; the development of an amperometric immunosensor based on single wall carbon nanotubes. Chapter 2 begins with a review of the fundamental chemical, photochemical and electrochemical properties of Ru(II) and Os(II) polypyridyl complexes. It is shown how their photophysical properties can be modulated by the interaction of the complexes with biomolecules such as proteins, nucleic acids and antibodies. The synthesis and characterisation of [Os(bpy)2dcbpy] and some related Os(II) and Ru(II) complexes is described. The production and characterisation of a [Os(bpy)2dcbpy]-thyroglobulin conjugate which was used as the immunogen is described, as well as the purification and characterisation of the resulting polyclonal antibody. Competition ELISA served to confirm the cross-reactivity of the antibody with the Os and Ru complexes synthesised. Chapter 3 describes the effect of antibody binding on the spectrochemical properties of the complexes. Changes in the emission spectra and lifetimes were examined. Association constants were derived from emission titrations. The extent that the antibody binding site protects the complexes from excited state deactivation via interaction with solvent was investigated. The possibility of energy transfer from [Ru(bpy)2dcbpy] to [Os(bpy)2dcbpy] when both were bound to the same antibody was investigated, as were the effects of antibody binding to a self-assembled layer of [Os(bpy)2(p2 p)2]2+. Chapter 4 begins with an introduction to the structure and properties of CNTs and outlines their application thus far in biosensing. The assembly of oxidatively shortened SWNTs onto Nafion/iron oxide coated pyrolytic graphite electrodes is described and characterised by both AFM and resonance Raman spectroscopy. The immunosensing strategy investigated involved the adsorption of anti-biotin antibody to the carbon nanotube surface. The presence of HRP-labelled biotin was determined via the reduction of hydrogen peroxide in the presence of the soluble mediator hydroquinone. A short investigation is also presented on the ability of HRP-modified SWNT forest electrodes to detect H2O2 produced by a mutant catalase negative E. coli bacteria which was co-immobilised with the HRP. Recommendations for future work arising from this thesis are given in Chapter 5.