Electrokinetic Assembly of Microsphere and Cellular Arrays
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Electrokinetic Assembly of Microsphere and Cellular Arrays Mihrimah Ozkan1, Sadik C. Esener1 and Sangeeta N. Bhatia2 1 Department of Electrical and Computer Engineering 2 Departments of Bioengineering and Medicine University of California at San Diego, La Jolla CA ABSTRACT We have developed a novel electrochemical system for field assisted, fluidic assembly of objects on a microfabricated silicon substrate by means of electrical addressing. The principle of our technique is based on the movement of charged species in solution to oppositely charged electrodes, as seen commonly in electrophoresis. Here, charged species such as beads and cells are moved electrokinetically through an aqueous solution towards a charged electrode. Micro patterning of the electrodes allows localization of charged species. We present a theoretical framework to predict the electric potential for assembly and disassembly of spherical objects. We correlate theoretical predictions with the motion of negatively charged polystyrene beads of 20 µm diameter on 100 µm feature micro patterned substrates. In addition, we extended these results to arraying of 20-30 µm diameter live mammalian cells by means of electrical addressing. This technique has applications in creation of ‘active’ cellular arrays for cell biology research, drug discovery and tissue engineering.
INTRODUCTION
The potential synergy of combining MEMS (micro-electro-mechanical systems) with biological systems has become increasingly apparent in recent years. Already, the interface between biology and micro technology has led to the development of enabling tools for biological research, clinical diagnostics, and medical devices [1,2]. At the “chip” level, this confluence of technologies has led to DNA microarrays [3], catalytic RNA arrays [4], protein arrays [5], and even live cell arrays [6,7,2]. Cell arraying technology has proven to be a useful tool for studies of cell fate, cell-cell interaction, and cell-matrix interactions. Furthermore, some investigators have proposed the use of live cells as “high content sensors” for biological event [6]. Existing cell arraying technologies primarily rely on patterned surface chemistries or localization through polymeric templates [8]; however, the process of cell arraying due to cell adhesion requires on the order of 2-12 h. Here, we propose a method to rapidly array live cells based on their negative charge rather than relying on receptor-mediated adhesion. We first develop this tool by using polystyrene beads as model “cells” and then extend this work to cell lines of human and murine origin. Here we present a new electronic micro array technology that can be used for dynamic, reversible assembly of organic objects. Photolithographically patterned conductive substrates are used to transport and array charged species (micro spheres, live cells) in solution. NN6.4.1
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Figure 1. Schematic illustration of electrochemical micro array patterning system.
Materials and Me
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