Conductive polymer as a controlled microenvironment for the potentiometric high-throughput evaluation of ionic liquid cell toxicity

Abstract

This paper presents both biological and potentiometric evaluations of the cell toxicity of a widely used ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF(4)), to Chinese hamster lung fibroblast cells (V79 cell line). The innovative potentiometric study takes advantage of the unique properties of conductive polymer polypyrrole (PPY) for the potentiometric evaluation of cell toxicity of [bmim]BF(4) to the V79 cells in a real-time, noninvasive and high-throughput manner. The conductive polymer PPY provides a controlled microenvironment that allows the quantitative release of the anions of the ionic liquids into the cells being monitored in real time and noninvasively. Parallel biological assay results showed that V79 cells exposed to [bmim]BF(4) usually grew in clusters, and that many small vacuoles could be seen in the cytoplasm. At the 24th hour after the V79 cells had been exposed to the ionic liquid (IL), the half inhibition concentration (EC(50)) of [bmim]BF(4) was around 5 mM. From a cell cycle study performed using a FACScan flow cytometer, it was found that the V79 cells could be partially locked to the G(1) phase by [bmim]BF(4), which extended the doubling time for cell growth. Comparing with the EC(50) values of cadmium chloride and mercury chloride, [bmim]BF(4) is not very toxic, but it may have a long-term toxic effect on mammalian cells. Compared to traditional biological in vitro assays, the use of a conductive polymer substrate in combination with a potentiometric sensor array is much more sensitive, faster, and enables a simpler evaluation of chemical cell toxicity. Additionally, it simplifies the study of the reversibility of cell toxicity, i.e., cell recovery, because there is no need to refresh the culture medium since a finite amount of chemicals can be doped and released. We found that the cytotoxicity of [bmim]BF(4) at a concentration of less than 6 mM was reversible for the V79 cell line, because cell morphology and proliferation rate returned to normal after the removal of the IL from the culture medium. This finding suggests that the IL [bmim]BF(4) could be used as a tool to control mammalian cell proliferation rate.

Choice of Reference Electrode is Critical for Potentiometric Whole Cell‐based Sensor

“…Though EMF‐16 was used, only single channel port was connected for the profile, because of the presence of only one reference port. It is feasible to connect multiple reference electrodes together for multi‐channel readings 5. The meter was placed outside the incubator with only the electrode connections entering the incubator.…”

“…The cell‐based kinetics is also measured by electrical impedance sensing system (EIS), which measures the resistance produced by growing cell monolayer over the electrode 4. The potentiometric method of cytotoxicity studies gives real time data on cell survival in terms of potential 5 allowing simultaneous, continuous and comparative study of different compounds with different concentrations. This is possible by using multichannel potentiometric systems, where data can be compared with the control on the same plot on a real time basis.…”

Potentiometric biosensor for studying hydroquinone cytotoxicity in vitro

“…The setup for the potentiometric cell sensor array that allows parallel evaluation of cell toxicity was described in our early report (Qiu and Zeng 2008). Briefly, a sixteen channel potentiometric sensor array using gold indicator electrodes vs. Ag/AgCl reference electrode was immersed in the culture medium.…”

“…Thus by measuring the electrochemical potential change of the sensor relative to the culture medium with a potentiometric sensor, the cytotoxicity of a chemical compound can be evaluated to support toxicological exposure assessment of a chemical. Recently, potentiometric biosensor array based simple cytotoxicity assay was demonstrated in our laboratory (Qiu and Zeng 2008). Our results show that conductive polymers can be used as a porous ion-exchange membrane for controlled incorporation and release of ionic compounds (i.e.…”

Cytotoxicity of Plasticizers and Ionic Liquids Using Drosophila melanogaster S2 Cell Culture

“…Cytotoxicity of ILs, which is caused by their interference with normal metabolic processes to inhibit or unsettle the growth of cells [24], has been investigated in macrophages [25], the human HeLa cell line [26], leukemia cells from rats [27,28], fibroblast cells from Chinese hamster [29] and bacterial cultures [19,[30][31][32][33][34][35]. With the growing interest in using ionic liquids directly in pharmaceutical formulations, such as that described in a study on choline phosphate ILs by Weaver et al [36], EC 50 values are being determined for new ILs regularly.…”