Development of optical based nanosensors for the determination of adenosine

In this thesis, a novel measurement method is proposed to measure the level of adenosine nucleoside which is a significant molecule utilized as a direct or indirect indicator to detect diseases such as neurodegenerative diseases and cancer in the human body with a novel impriting technique applied onto a gold chip whose surface is activated with allyl mercaptan. The nanofilm surface modification is implemented by means of the molecular impriting technique and methacrylic acid (MAA) is utilized as the functional monomer. For the adenosine determination, a surface plasmon resonance (SPR) device is used, pH scanning is performed between 3.0 and 7.4, and the optimum pH is determined as 7.4. During the kinetic studies, on the other hand, an analysis is run with the phosphate buffer solution of pH 7.4 and of different concentrations ranging from 0.5 nM up to 400.0 nM to detect the interval of determination for a proper nanosensor operation. Guanosine and cytidine are also included in the analysis to detect the selectivity of the SPR nanosensor realized. The non-imprinted polymer (NIP) chip surface is covered with the MAA monomer, in this way, both the kinetic studies and sensitivity tests are performed with the phosphate buffer solution of pH 7.4 and different concentrations and mixtures of adenosine, guanosine and cytidine. By using the adenosine molecular imprinted polymers (MIP) nanosensor chip, adenosine detections are consecutively collected within the same day and analysis are executed within several different time intervals. Since the adenosine impriting SPR chip is intended to be used in realistic medical analysis and research, its recovery was calculated by working with artificial urine and serum samples in the range of 1.0 nM - 5.0 nM concentration in adenosine analysis. In the study, the limit of detection (LOD) value in aqueous solutions in the linear range of 0.1 nM - 100.0 nM was determined as 0.018 nM, the limit of detection value in artificial plasma was determined as 0.015 nM, and the limit of detection in artificial urine was determined as 0.013 nM. In addition, the limit of quantification (LOQ) values were calculated as 0.061 nM, 0.052 nM, and 0.046 nM in aqueous solution, artificial plasma and artificial serum, respectively. The surface of the adenosine-imprinted SPR chip was characterized by taking atomic force microscopy, ellipsometry, and contact angle measurements. Keywords: Adenosine, Molecular Imprinted Polymers, Nanofilm Surface Modification, SPR, Nanosensors