Cell viability studies and operation in cellular culture medium of n-type organic field-effect transistors

The possibility of the fabrication of organic devices suitable to be applied in bio-sensing fields depends largely on the availability of organic compounds displaying robust electrical properties even in aqueous solutions and effective biocompatibility features. In this paper, we report about the good cellular biocompatibility and the electrical response stability in an ionic medium of n-type organic transistors based on the recently developed PDI-8CN₂ oligomer. The biocompatibility has been tested by analyzing the adhesion and viability of two different cell lines, human epithelial HeLa cells and murine neuronal F11 cells, on PDI-8CN₂ films grown by organic molecular beam deposition (OMBD) on SiO₂ substrates. The effect of film thickness on cell attachment was also tested. Uncoated SiO₂ substrates were used as control surfaces and sexithiophene (T6) as device testing control. Moreover, the possible toxicity of –CN groups of PDI-8CN₂ was tested on HeLa cell cultures, using PDI-8 and T6 molecules as controls. Results showed that, although at high concentration these organic compounds are toxic in solution, if they are presented in form of film, cell lines can attach and grow on them. The electrical response stability of PDI-8CN₂ transistors in a cellular culture medium characterized by high concentrations of ionic species has been also investigated. For this purpose, low-voltage operation devices with V_GS ranging from −5 V to 5 V, able to strongly reduce the influence of Faradaic currents coming from the electrical operation in an highly ionic environment, have been fabricated on 35 nm thick SiO₂ layers and electrically characterized. These results are useful to experimentally define the main critical issues to be further addressed for the fabrication of reliable bio-sensors based on organic transistors.