ARTICLE IN PRESS
Sensors and Actuators B xxx (2009) xxx–xxx
Contents lists available at ScienceDirect
Sensors and Actuators B: Chemical
journal homepage: www.elsevier.com/locate/snb
Cell viability assessment by ﬂow cytometry using yeast as cell model
G. Mernier a,∗,1 , N. Piacentini a,b,1 , R. Tornay a , N. Bufﬁ a , P. Renaud a
Laboratoirede Microsystèmes LMIS4, Swiss Federal Institute of Technology, Station 17, CH-1015 Lausanne, Switzerland Dipartimento di Elettronica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
a r t i c l e
Article history: Available online xxx
i n f o
a b s t r a c t
This paper reports the new combination of cell sorting and counting capabilities on a single device. Moststate-of-the-art devices combining these technologies use optical techniques requiring complicated experimental setups and labeled samples. The use of a label-free, electrical device signiﬁcantly decreases the system complexity and makes it more appropriate for use in point-of-care diagnostics. Living and dead yeast cells are separated by dielectrophoretic forces and counted using coulter counters.The combination of these two methods allows the determination of the percentage of living and dead cells for viability studies of cell samples. The device could further be used for sorting and counting of blood cells in applications such as diagnosis of insufﬁcient cell concentrations, identiﬁcation of cell deﬁciencies or bacterial contamination. The use of dielectrophoresis (DEP) as sortingprinciple allows to separate cells based on their dielectric properties in the place of size-based separation, enabling sorting of large panels of cells and separation of infected and non-infected cells of the same type. © 2009 Elsevier B.V. All rights reserved.
Keywords: Cell sorting Cell counting Dielectrophoresis Impedance measurements Label-free Viability study
1. Introduction Recentadvances in microtechnology have enabled the fabrication of devices integrating ﬂuidic, electrical and optical components for biological applications. These lab-on-chips make use of different techniques enabling sample preparation and analysis. In sample preparation, one important technique is the sorting of cells, which can be performed optically or electrically, using among others dielectrophoresis[1,2], magnetophoresis [3,4], ﬂuorescence-activated cell sorting  or optical tweezers . On the other hand, sample analysis can be also integrated on chip, the most common example of which being cell counting. This counting can rely either on optical monitoring of a speciﬁc position on the chip [5,7], or on electrical impedance measurements inﬂuenced by the cell passage [8–11]. The lattertechnique is widely known in its coulter counter conﬁguration, ﬁrst developed by Coulter  and later miniaturised by Larsen et al. . This paper presents a lab-on-chip integrating cell sorting and counting abilities, based on dielectrophoresis and coulter counter, respectively. To the best of our knowledge, this is the ﬁrst example of a fully electric system, which has the advantages of alabel-free protocol and a relatively simple experimental setup. This device allows determining the concentration of cell subpopulations in a
sample, with applications such as viability studies and differential cell counting for point-of-care diagnosis. 2. Materials and methods 2.1. Chip design, fabrication and packaging In order to integrate cell sorting and counting, a device is developed using thedesign shown in Fig. 1, featuring microﬂuidic channels and electrodes for dielectrophoresis and impedance measurements. The fabrication of the device is described elsewhere  and brieﬂy explained here. Platinum electrodes are deposited on a titanium adhesion layer by evaporation and patterned by lift-off. Microﬂuidic channels are then deﬁned using SU8 photolithography. A silicone elastomer...