Abstract
M.Tech. (Chemistry)
This dissertation reports on the development of an electrochemical aptasensor for hydrogen peroxide and thrombin based on a novel polyamidoamine dendrimer-streptavidin supramolecular architecture. Polyamidoamine dendrimer (PAMAM) was electrodeposited on a glassy carbon electrode using cyclic voltammetry at a potential window of -200 mV to +1100 mV at scan rate 50 mV s-1. The electrode was labelled GCE/PAMAM. A 50 μL volume of 100 μg/mL streptavidin (strept) was drop coated on the GCE/PAMAM electrode for 2 h. The electrode was labelled GCE/PAMAM/Strept and also referred to as the supramolecular platform. The platform was characterised using various techniques such as voltammetry, electrochemical impedance spectroscopy, electron microscopy etc. The supramolecular architecture (GCE, PAMAM)/ strept) was conjugated to an enzyme called horseradish peroxidase (HRP) to make the biosensor GCE/PAMAM/Strept-HRP. The biosensor i.e. GCE/PAMAM/Strept-HRP was used for the detection of hydrogen peroxide. The GCE/PAMAM/Strept-HRP biosensor was studied using electrochemical techniques (CV, SWV, EIS and chronoamperometry) and microscopic techniques (HR-SEM). The platform was conducting and electroactive exhibiting reversible electrochemistry (E°′ = 450 mV and Ipa/Ipc ≈ 1 in Fe(CN)63-/4-). The second part of the work involves the detection of thrombin using a GCE/PAMAM/Strept/TBA modified electrode. Biotinylated aptamer probe was immobilised on the platform through biotin-streptavidin interaction. The aptasensor was monitored using CV, SWV and EIS. The selectivity of the GCE/PAMAM/Strept/TBA based aptasensor was evaluated using interfering proteins of BSA, lysozyme, and haemoglobin that also co-exist with thrombin in the blood. The relative response obtained shows insignificant effect for the interfering proteins with BSA and haemoglobin having a relative response of 9.2% and 7.6% respectively. This confirms the excellent specificity of the proposed aptasensor.