Stepwise formation of patterned cell co-cultures in silicone tubing

Here, we describe a method for producing patterned cell adhesion inside silicone tubing. A platinum (Pt) needle microelectrode was inserted through the wall of the tubing and an oxidizing agent electrochemically generated at the inserted electrode. This agent caused local detachment of the anti-biofouling heparin layer from the inner surface of the tubing. The cell-adhesive protein fibronectin selectively adsorbed onto the newly exposed surface, making it possible to initiate a localized cell culture. The electrode could be readily set in place without breaking the tubular structure and, importantly, almost no culture solution leaked from the electrode insertion site after the electrode was removed. Ionic adsorption of poly-L-lysine at the tubular region retaining a heparin coating was used to switch the heparin surface from cell-repellent to cell-adhesive, thereby facilitating the adhesion of a second cell type. The combination of the electrode-based technique with layer-by-layer deposition enabled the formation of patterned co-cultures within the semi-closed tubular structure. The utility of this approach was demonstrated by patterning co-cultures of hepatocytes or endothelial cells with fibroblasts. The controlled co-cultures inside the elastic tubing should be of value for cell-cell interaction studies following application of chemical or mechanical stimuli and for tissue engineering-based bioreactors.