Inverse inkjet printed gold micro electrodes for the structured deposition of epithelial cells and fibrin

The micro structured deposition of vital cells is an important challenge in tissue engineering, biosensor technology, and in all research dealing with cell-cell and cell-substrate contacts. Hence, an inkjet printing technology has been developed to manufacture Au-based micro electrodes by sputter coating inversely printed polyester-foils. These electrodes feature minimal structure sizes of 35 microm and consist of an anode and a cathode part. They were used with fibrinogenic epithelial cell suspensions to deposit human keratinocytes (HaCaT), mouse fibroblasts (L-929) and the protein fibrin by applying DC voltage. Subsequently cells were electrophoretically attracted to the anode, following exactly its shape, while the insoluble fibrin was simultaneously precipitated due to the electrically mediated polymerization of the soluble fibrinogen molecule. Furthermore, it was demonstrated that this technique is suitable to co-deposit both cell types in a layered fashion. The lower voltage boundary for successful deposition was set at approximately 0.8 V needed for the conversion of fibrinogen into fibrin, while the upper voltage boundary was set at approximately 1.85 V, when commencing electrolysis inhibited the deposition of vital cells. Subsequent to the anodic cell-fibrin deposition, cells were cultivated for up to 4 days and then characterized by FDA+EB staining, methyl violet staining, MNF staining and SEM. The conversion from fibrinogen into fibrin was studied using ATR/FTIR.