Preparation of nanostructured field effect transistors in the analysis of neurochemical processes

Author(s)

Alexandre Kisner

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2012-12-03

Examining board members

Lauro Tatsuo Kubota; Rose Mary Zumstein Georgetto Naal; Sergio Antonio Spinola Machado; Ana Flávia Nogueira; Celso Aparecido Bertran

• Advisor: Lauro Tatsuo Kubota

Abstract

Field effect transistors modified with Au nanoparticles represent an excellent tool to electrophysiology analyzes. Because the dimensions of the devices are comparable to the size of the cells, multiple measurements can be performed simultaneously. In this work, field effect transistors were fabricated with three different kinds of surface in their gates, i.e. transistor with only SiO2, SiO2 and porous anodic Al2O3, and SiO2-Al2O3 with Au nanoparticles embedded into the pores of Al2O3. The characterization of the transistors was performed by electron microscopy analysis and conventional electrical characterization. The last one showed that the anodization process and the Au nanoparticles deposition on surface of the transistors did not affect the electrical properties of the devices. The transistors presenting gates with only SiO2-Al2O3 were modified with tyrosinase and employed as biosensors to detect dopamine. The results of these analysis showed that the devices can detect dopamine in a range of concentration usually found when these molecules are released from neuronal cells. Transistors with Au nanoparticles were also applied as biosensors to detect serotonin. In doing so, the surface of the nanoparticles were modified with self-assembled monolayers that were able to interact with serotonin through electrostatic interactions. Although this approach is scarcely exploited with transistors, it showed promising results. For instance, serotonin could be detect in a linear range of concentration from 0,1 to 2 µmol L. Experiments to analyze the cell adhesion on transistors and detect the release of protons from the extruded matrix of vesicles from PC12 cells were performed and demonstrated that the interfacial processes between cells and transistors were dependent on the capacitive properties of the surface. The presence of nanoparticles can enhance the electrical sensitivity of the gates from the devices. These interfacial effects presented a relationship with the signal to noise ratio of the exocytotic signals measured for vesicles release and suggested that the employment of nanostructurated transistors are promising tools to analyze these events from PC12 cells in vitro (AU)

• FAPESP's process: 07/03604-3 - Multiple stimulation and detection of nerve cell activity employing field-effect transistors modified with Au nanoelectrodes
• Grantee: Alexandre Kisner
• Support Opportunities: Scholarships in Brazil - Doctorate