Biyolojik Moleküllerin Tayinine Yönelik Kantilever Bazlı Biyosensör Sisteminin Geliştirilmesi

Abstract

Nowadays, demand and necessity of obtaining information is increased depending on technological developments. Early diagnosis is very important on therapeutic efficiency of diseases. So, detection of precursor molecules, which are formed during initial steps of diseases or detection of viruses in very low concentrations, is very important for patients. Governments are looking for very fast and accurate detection systems, which are able to detect any kind of organism or biomolecule that could be used as a biological war agent. Common need of drug development researches, environmental pollution controls, space, defense and medicinal researches is identifying existence of analyte molecule and detection of concentration. Current researches on biosensors are reached detection levels down to single molecule or virus detection levels, which started with studies of detection of glucose level in blood. There are many studies are going on for he development of novel sensor systems because still there is need of different type of measurement and analysis methods for different type of analytes. In this thesis, cantilever based biosensor system is prepared for detection of biological molecules in their physiological environment. Main goal was enhance the biosensor system in order to avoid the virtual mass effect arises from the nonspecific bindings on cantilever. For this purpose an atomic force microscope based system with closed liquid cell, which is able to collect data in biological mediums, is configured. Changes in mechanical properties of cantilever are measured in photo-detector, which collects laser beams reflected from cantilever surface and resonance frequency data are obtained. Relation of change in the resonance frequency of cantilever and analyte molecules deposited on surface is investigated by theoretical calculations and experimental measurements. Different geometric modifications are studied by modeling their resonance behaviors in air and liquid. Then experimental resonance frequencies are measured on cantilevers that are prepared by milling using Focused Ion Beam method. Biotin streptavidin interactions are investigated by preparation of biotin receptor layer on modified cantilever surfaces. Following, detection of Hepatitis B surface antigen by using cantilevers modified with anti-HBs surface antigen specific receptor layer. In the last section of the studies, in order to increase the response signal of analyte molecules, cantilever surfaces are modified by using biotinylated Human Serum albumin (HSA) nanoparticles and therefore cantilevers surface area and numbers of active functional groups on surface are increased. To understand effects of surface modifications, cantilever responses are investigated for biotin – streptavidin and anti-HBs – HbsAg interactions. Modification processes are characterized by using contact angle, FT-IR, XPS, SEM and AFM analyses.