Production of colorimetric nanobiosensors

Nowadays, environmental waste accumulation increases with the rapid development of industrial and agricultural activities. The increase in the human population and the increase in the use of various chemicals and drugs cause heavy metal accumulation in the environment. Heavy metals have adverse effects on the environment and living life, and they accumulate easily in the human body through the food chain leading to toxic effects. Among the heavy metal ions that accumulate in water, air, and soil environments, mercury threatens the living system due to its high toxicity. Hg2+ ion causes water pollution due to their high solubility in water. The consumption of seafood leads to the accumulation of mercury, thus threatening human health. Due to the toxic effects of heavy metals, it is critical to determine their levels by detecting them from ecological and biological samples. The conventional methods for heavy metal detection are based on the use of instruments. These instrumental methods can analyze the desired metal sensitively and selectively, but these methods are expensive, not portable, time-consuming, and require trained personnel. For these reasons, a rapid and easy method is required for the analysis of these metals. Biosensors are systems used in various applications, facilitating analyte detection, and monitoring of disease states. Therefore, it is a popular new detection method for heavy metal detection, as in most subjects. Our aim in this thesis is to produce a nanosensor system to detect mercury ions. Silver and gold nanoparticles were investigated because of their special properties for the nanosensor system. The wide color scale of these particles allows researchers to produce colorimetric sensor systems. Silver and gold nanoparticle surfaces were modified with citrate, cystine, and cysteine surface groups, and their response to heavy metals was examined. Color changes resulting from the interaction were observed both with the naked eye and a UV-Visible Spectrophotometer. According to the calibration curve obtained from these results, a linear response of the nanoparticle was observed at the tested concentrations (y = 0.00005x + 0.01394, R² = 0.98249). LOD and LOQ values were found to be 14.4 nM and 43.2 nM, respectively. The nanosensor system was tested on real systems, and the recovery values obtained were 106% for tap water, 121.5% for lake water, 112% for industrial water, and 98% for seawater. All results showed that the synthesized CA-AgNP responds specifically to the Hg2+ ion and can detect the Hg2+ ion in real samples.