Abstract
Researches for cell galvanotaxis have been over one century. We can observe the movement guided by electric field no matter in vivo or in vitro. In electric fields, some cells moved toward specific direction (toward anode or cathode), while some cells moved randomly(cell did not influence by electric field).The advantages of using microfluidic devices to conduct galvanotaxis experiment are：(1)it is easy to fabricate the devices, (2)the cost for fabricating the devices is low, (3) tiny cell amount is required for the experiment, (4) it is easy to control the electric field in the device, (5) Joule heat can be removed rapidly. During the galvanotaxis experiment, we need to apply the electric field for a long time, and the electrodes may generate electrolytic products that are toxic and result in cell death. In this research, we used conductive polymer (poly diallyldimethylammonium chloride，PDADMAC) to fabricate on-chip salt bridge. This material is biocompatible and it is easy to control the shape and location of salt bridge in the microfluidic channel. For fabricating smooth and complete salt bridge, the compositions of the salt bridge we used was 96 wt% Diallyldimethylammonium chloride, 2 wt% 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and 2 wt% N,N'-methylenebisacrylamide, and the exposure time under UV light was 40s. To make sure this microfluidic device can be used for galvanotaxis experiment, we first used NIH/3T3 cell to conduct galvanotaxis experiment in direct current (DC) electric field. The experiment results are similar to those in the reference：NIH/3T3 cell moved toward cathode in DC electric field. When electric field strength increased from 292mV/cm to 3166mV/cm, the average directedness increased from 0.52 to 0.79. Most galvanotaxis experiments focused on cell’s behavior in DC electric field, and the research using AC electric field is few. Therefore, we observed the behavior of cells under AC electric field with different frequencies and strengths. The results show that：(1)in the same electric field strength, the ratio of cells moved randomly was higher in low frequency than in high frequency, (2) with the same frequency, more cells moved toward electrode when the electric field strength increased.