Semiconducting Carbon Nanotube Transistors for the Real-time Monitoring of Cellular Transport and Their Application to Drug Evaluation

Abstract

Cellular transport plays critical functions for the development and proliferation of cells. This process regulates the entry and release of biomaterials such as ions, neurotransmitters, proteins for cells. Because of its important roles, the cellular transport has been considered the key of drug development and medical therapy. In this dissertation, cellular transport such as Ca2+ influx, dopamine and cytokine release could be monitored in a real-time manner by using biosensors based on semiconducting carbon nanotube (sCNT) transistors. Furthermore, these biosensors have been utilized to quantitatively evaluate the effects of antihistamine, antipsychotic and anti-inflammatory drugs. The quantitative and real-time evaluation capability of our strategy would promise versatile applications such as drug screening and nanoscale biosensor researches. Firstly, we discussed the quantitative electrophysiological monitoring of histamine and antihistamine drug effects on live cells via reusable sensor platforms based on sCNT transistors. This method enabled us to monitor the real-time electrophysiological responses of a single HeLa cell to histamine with different concentrations. The electrophysiological responses were attributed to the activity of histamine type 1 receptors on a HeLa cell membrane by histamine. Furthermore, the effects of antihistamine drugs such as cetirizine or chlorphenamine on the electrophysiological activities of HeLa cells were also quantitatively evaluated. Significantly, we utilized only a single device to monitor the responses of multiple HeLa cells to each drug, which allowed us to quantitatively analyze the antihistamine drug effects on live cells without errors from the device-to-device variation in device characteristics. Secondly, we developed floating electrode-based carbon nanotube biosensors for the monitoring of antipsychotic drug effects on the dopamine release from PC12 cells under potassium stimulation. Here, sCNT transistors with floating electrodes were functionalized with 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•) radicals by Nafion films. This method allows us to build selective biosensors for dopamine detection with a detection limit down to 10 nM even in the presence of other neurotransmitters such as glutamate and acetylcholine, resulting from the selective interaction between ABTS• radicals and dopamine. The sensors were also utilized to monitor the real-time release of dopamine from PC12 cells upon the stimulation of high-concentrated potassium solutions. Significantly, the antipsychotic effects of pimozide on the dopamine release from potassium-stimulated PC12 cells could also be evaluated in a concentration-dependent manner by using the sensors. Lastly, we reported modified floating electrode-based sCNT sensors for the detection of tumor necrosis factor α (TNFα), a pro-inflammatory cytokine related with inflammatory bowel disease (IBD). Here, antibodies (anti-TNFα) were immobilized on the floating electrodes of sCNT sensors, enabling selective and real-time detection of TNFα among various cytokines linked to IBD. This sensor was able to detect the concentrations of TNFα with a detection limit of 1 pg/L, allowing to quantitatively monitor the anti-inflammatory effect of a drug, lupeol, on the activation of the LPS-induced nuclear factor κB signaling in mouse macrophage Raw 264.7 cells.