Use of dicationic ionic liquids as a novel liquid platform for dielectrophoretic cell manipulation

Abstract

Separation, characterization and analysis of target cells demonstrate critical cues for diagnosis and monitoring of chronic diseases. Electrokinetic cell separation methods have been previously established to have greater efficiency when compared to traditional flow cytometry methods. Ionic liquids show promise in the design of conductive buffers with required electrical properties suitable for electrokinetic manipulation of cells with an enhanced signal to noise ratio (SNR). The goal of this project is to design and test tailored ionic liquid compositions with the hypothesis that dielectrophoretic forces are enhanced on cells while creating an environment for retaining cell integrity. We analysed two uniquely synthesized methylimidazolium based ionic liquids with a low toxicity as conductive suspension buffers for cell separation. These dicationic ionic liquids possess slight electrical and structural differences with high thermal stability. The two ionic liquids were tested for cytotoxicity and their ability to enhance SNR. We validated our hypothesis using osteosarcoma cells Saos-2 and MC3T3-E1 osteoblast cells. The tests were compared against commonly used dielectrophoretic sucrose-isotonic solution. The effects of electrical neutrality, charged particle effects, free charge screening due to ionic liquids from cells were studied using a single-shell model. Effects of ionic liquid and isotonic medium on electrokinetic signal from cells were studied through dielectrophoretic force profiles as a function of non-linear displacement of cells in the two ionic liquids and control media. We observed significant differences in electrokinetic responses between healthy and cancerous cells and steady increase in signal magnitude resulting in enhanced SNR using ILs when compared against sucrose buffer.