CLASSIFICATION OF CELL TYPES USING MECHANICAL AND ELECTRICAL MEASUREMENT ON SINGLE CELLS J. Chen 1* , Y. Zheng 1* , Q. Tan, E. Shojaei-Baghini 1 , Y. Zhang 1 , P. Prasad 2 , X.Y. Wu 2 , and Y. Sun 1** 1 Advanced Micro and Nanosystems Lab, University of Toronto, CANADA 2 Department of Pharmaceutical Sciences, University of Toronto, CANADA ABSTRACT This paper presents a microsystem for single-cell characterization by aspirating cells continuously through a constriction channel while cell impedance profiles and images are measured to quantify transit time, the impedance amplitude ratio, and cell elongation simultaneously. The system demonstrated that osteoblasts, compared with osteocytes, have a larger cell elon- gation length, longer transit time, and a higher amplitude ratio. The system also classified EMT6 and EMT6/AR1.0 cells with success rates of 51.3% (cell elongation), 57.5% (transit time), 59.6% (amplitude ratio), and 70.2% (both) using neural net- work, further verifying the device’s capability for performing both electrical and mechanical measurements on single cells. KEYWORDS: Microfluidics, Cellular Biophysics, Single Cell Analysis, Impedance Spectroscopy, Constriction Channel, Neural Network INTRODUCTION The electrical properties of the cell membrane and cytoplasm and the mechanical properties of the cytoskeleton determine the overall biophysical properties of a cell, which have been correlated with pathophysiological states in diseases, such as cancer [1,2]. Existing microdevices for studying single-cell biophysics can only measure either electrical [3] or mechanical [4] properties of cells. The only reported microdevice performing both electrical and mechanical characterization has limited throughput, incapable of collecting statistically significant data [5]. This paper presents a microfluidic system for single-cell mechanical and electrical characterization using constriction channel and impedance spectroscopy (see Figure 1(a)). Cells are aspirated continuously through a constriction channel while cell elongations and impedance profiles are measured simultaneously. Transit time and the impedance amplitude ratio are quantified as cell’s mechanical and electrical property indicators while cell elongation length inside the channel is used as a measure of cell size. METHODS The PDMS device was replicated from a double-layer SU-8 mold and bonded to a glass slide. It was first filled with cul- ture medium, followed by a droplet of cell suspension pipetted to the entrance of the cell loading channel. A negative pressure of 10 kPa aspirated cells continuously through the constriction channel. Cell images were taken by an inverted microscope and impedance data were recorded by an impedance analyzer. Figure 1: (A) Schematic of the microfluidic system for electromechanical characterization of single cells using imped- ance spectroscopy and constriction channel. Cells are aspirated continuously through the small constriction channel with impedance data (transit time and impedance amplitude ratio), and cell elongation length measured simultane- ously.(B) Impedance measurement of single cells (amplitude vs. time). Transit time indicates cellular mechanical prop- erties and impedance amplitude ratio indicates cellular electrical properties. (C) A cell aspirated in the constriction channel. As an indicator of the cell size, the elongation length was measured from image processing approaches. A B C 978-0-9798064-4-5/μTAS 2011/$20©11CBMS-0001 795 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences October 2-6, 2011, Seattle, Washington, USA