The aim of this thesis is to apply interfacial electrochemiluminescence (ECL) of novel ruthenium probes to the determination of important biomolecules and the assessment of cell viability. There are six chapters in this study with Chapters 1 providing an overview of the relevant literature. Chapter 2 presents the photophysics, electrochemical and electrochemiluminescent properties of a novel 1,3,5,7-tetramethyl-8-[(2-fluorophenyl)-6-methoxy-1,5-naphthyridine-3-carboxy]-4,4'-difluoroboradiazaindacene (BODIPY-COOH) dye are reported. It was observed that the ECL turn-on potential of BODIPY-COOH could be controlled by changing the identity of the coreactant (benzoyl peroxide (BPO) or hydrogen peroxide). Also thin films of the BODIPY-COOH dye prepared on platinum electrodes exhibited strong luminescence in water, thereby making them potentially useful for ECL application in biological media. Chapter 3 reports a rapid and effective method of confining a ruthenium ECL luminophore on an electrode surface by the electrodeposition of polyaniline (PANI) film in the presence of ruthenium 2,2'-bipyridyl(2,2'-bipyridyl)-2(4-carboxyphenyl)imidazo[4,5][1,10]phenanthroline ([Ru(bpy)2PIC]2+) to form a composite Ru(bpy)2PIC]2+-PANI film that exhibited the highest ECL efficiency value (1.00%) reported for any surface confined ruthenium complex. This behaviour is attributed to the fast luminophore regeneration rate of the Ru(bpy)2PIC]2+-PANI film which improves the film’s usefulness in the development of highly sensitive ECL based sensors for biochemical species such as DNA and amino acids. In Chapter 4 the generation of a molecular light switch interface by the binding of DNA to a novel bis-(4-(4-carboxyphenyl)-2,2'-bipyridine) dipyridophenazine ruthenium (II) dichloride [Ru(dppz)(bpyArCOOH)2]2+ dye monolayer is presented. Evidence for the binding of DNA to [Ru(dppz)(bpyArCOOH)2]2+ was obtained through Raman, ECL and electrochemistry studies. The generation of ECL from living cancer cells (used as co-factor) and ruthenium 2,2'-bipyridyl-2, 2'-quarterpyridyl ([Ru(bpy)2Qbpy]2+ ) dye is explained in Chapter 5 to be due to the adenosine 5' triphosphate (ATP) released from the cancer cells, and it opens up a whole new possibility of interrogating cell health and using cell ECL as cell viability marker. Chapter 6 draws the most important insights of the thesis together and discusses useful next steps for future direction.