Focusing of mammalian cells under an ultrahigh pH gradient created by unidirectional electropulsation in a confined microchamber†Electronic supplementary information (ESI) available: Figures S1-S5 and videos S1-S2. See DOI: 10.1039/c4sc00319eClick here for additional data file.Click here for additional data file.Click here for additional data file.
The transport and manipulation of cells in microfluidic structures are often critically required in cellular analysis. Cells typically make consistent movement in a dc electric field in a single direction, due to their electrophoretic mobility or electroosmotic flow or the combination of the two. Here we demonstrate that mammalian cells focus to the middle of a closed microfluidic chamber under the application of unidirectional direct current pulses. With experimental and computational data, we show that under the pulses electrochemical reactions take place in the confined microscale space and create an ultrahigh and nonlinear pH gradient (∼2 orders of magnitude higher than the ones in protein isoelectric focusing) at the middle of the chamber. The varying local pH affects the cell surface charge and the electrophoretic mobility, leading to focusing in free solution. Our approach provides a new and simple method for focusing and concentrating mammalian cells at the microscale.
Department of Chemical Engineering , Virginia Tech , Blacksburg , Virginia 24061 , USA . Email: changlu@vt.edu ; ; Tel: +1 540 231 8681.
Despina Nelie
DN
Loufakis
School of Biomedical Engineering and Sciences , Virginia Tech-Wake Forest University , Blacksburg , Virginia 24061 , USA.
Zhenning
Z
Cao
School of Biomedical Engineering and Sciences , Virginia Tech-Wake Forest University , Blacksburg , Virginia 24061 , USA.
Sai
S
Ma
Virginia Bioinformatics Institute and Department of Biological Sciences , Virginia Tech , Blacksburg , Virginia 24061 , USA.
David
D
Mittelman
Department of Chemical Engineering , Virginia Tech , Blacksburg , Virginia 24061 , USA . Email: changlu@vt.edu ; ; Tel: +1 540 231 8681 ; School of Biomedical Engineering and Sciences , Virginia Tech-Wake Forest University , Blacksburg , Virginia 24061 , USA.
Chang
C
Lu