DFT study on the feasibility of using metal doped graphene structures as biosensors for the preliminary diagnosis of lung cancer

Lung cancer is the most prevalent form of cancer globally and in Turkey, with the highest mortality rate. Due to the absence of pain perception in the lung and bronchial systems, the majority of patients are diagnosed with advanced-stage lung cancer, rendering curative treatment ineffective. Human breath analysis is a method of obtaining information about an individual's clinical status by monitoring the volatile organic compounds (VOCs) present in exhaled breath. VOCs are defined as organic compounds present in human breath that can be used as carbon-based biomarkers. The specific correlation between odour composition and disease is the fundamental principle underlying breath sensors. Biosensors are devices which employ biochemical molecules in a chemically interactive process. They are capable of encoding odours into signal patterns that are specific to each individual odour. This process is referred to as combinatorial selectivity. Breath analysis biosensors, which are also known as electronic noses, employ this strategy to perform their analyses. This thesis investigates the potential of metal-doped graphene structures as biosensors for the preliminary diagnosis of lung cancer. The adsorption and sensing properties of graphene structures doped with metal atoms (platinum, palladium, nickel, iridium and copper) against aniline, toluene, styrene and benzene gases, which are among the most important biomarkers of lung cancer, were investigated. All DFT calculations were completed using the WB97XD method. The findings revealed a notable charge transfer from the target gases to the metal-doped graphene structures. A NBO analysis was conducted on the systems, and it was determined that a charge transfer occurred from aniline, toluene, styrene, and benzene molecules to graphene and metal-doped graphene structures. The most significant interaction observed was the adsorption of the styrene molecule on the iridium-doped graphene structure, with an adsorption enthalpy value of -152.9 kJ/mol. As the Gibbs free energy was negative in all structures, the adsorption process was spontaneous in all systems. The data analyses indicated a reduction in HOMO-LUMO gap (Eg) values and alterations in work function (Φ) following the adsorption of gas molecules on copper-doped and platinum-doped graphene structures. In conclusion, it can be posited that in the pre-diagnostic stage of lung cancer, copper-doped and platinum-doped graphene structures have the potential to be used as a sensor to detect aniline, toluene, styrene and benzene gases, which are among the most important biomarkers.