The Use of DEP to Shape Tissue Models

DEP can be used to gather and orient living cells into new aggregates of preselected shape. The resultant shapes can then be fixed in form by using a thermosensitive gel. 

The clumping and aggregation of cells from suspensions in culture media to form masses is well known, but the resultant aggregates except for rouleaux formation by erythrocytes, are normally rather random as to their organization. The aggregates so formed, moreover, may or may not be weakly adherent, a matter which depends strongly upon the fields. 

Since rapid collection of erstwhile single cells can be brought about by the use of dielectrophoresis, and the shape of the mass of cells so formed is controlled by the shape of the electrodes, by the frequency of the field, and by the shape of the cells, it appeared worthwhile to see if the shapes so formed could be made more permanent, so as to prepare desired structures of the cellular aggregates. To this end, the gel-forming properties of a relatively nontoxic block copolymer solution in water were used. A concentrated aqueous solution of the block copolymer of polyethylene oxide and polypropylene oxide (PEO-PPO) is quite fluid at 0°C to about 5°C, but sets reversibly to a rather stiff gel at about 30-40°C. The PEO-PPO polymer solutions are reported to be relatively nontoxic to most organisms (Pluronic resin F-127), Wyandotte Chemicals Corp.). 

The above experiments suggest that as the techniques for the use of dielectrophoresis to form tissue models improve, as better cellular organization is obtained, as improved cementing techniques are found, and as chemical or physical post-treatments for the matrices are developed, then a wide variety of interesting and perhaps functionally useful multicellular preparations can be fabricated from suitable single-celled organisms. 

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