| Summary: | This thesis is focused on the development of chemical sensors for the detection of molecular biomarkers and silver nanoparticles, and the application of the techniques to authentic saliva samples. As an important antioxidant in humans, the first aim of this thesis is to develop sensors for the detection of glutathione. Two different assays for glutathione detection based on electrochemical and spectrophotometric techniques are developed. The spectrophotometric assay is further applied to authentic human plasma and saliva samples, where the stability of glutathione is investigated in-vitro. The copper(II)-catalysed oxidation process which is the major cause of the loss of reduced glutathione from biological samples is next investigated and the mechanism is proposed. The spectrophotometric glutathione assay is then employed to study the potential of salivary glutathione as a biomarker for bipolar disorder. An electroanalytical assay is also developed for the detection of salivary uric acid, a potential biomarker for gout, oral cavity cancer and other several diseases. The significantly different electrochemical behaviour in authentic as compared to synthetic saliva of commonly used redox mediators such as ferrocenemethanol and ferrocyanide is further highlighted in this thesis. In addition to molecular biomarkers such as glutathione and uric acid, an electrochemical sensor is developed for the detection of ensembles and individual silver nanoparticles (AgNPs). The oxidative dissolution of AgNPs is first investigated by two electrochemical techniques: nano-impacts and anodic stripping voltammetry, where the results reveal the relative kinetics of the process. The electrochemical techniques are then directly applied to investigate the physicochemical properties of AgNPs in authentic human saliva.
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