“Smart” biomaterials that exhibit dynamic changes in interfacial properties, including adherence of cells, are important in a variety of fields, ranging from fundamental cell biology to tissue engineering applications. Our group has reported electrochemical approaches to detach cells and cell sheets from a surface. In these approaches, a gold surface was first modified with a self-assembled monolayer (SAM) of alkanethiol via the gold-thiolate bond. After seeding cells onto the surface, the gold-thiolate bond is reductively cleaved by applying a negative potential, and cells are readily detached along with the desorption of the molecules. However, in this system the alkanethiol molecules may remain binding to a detached cell constructs. Considering that alkanethiol does not exist in the body, these molecules potentially could cause biocompatibility issues after transplantation. The aim of this study is to develop more reliable, biocompatible, and quick cell detachment technology. To archive this goal, we designed two zwitterionic oligopeptides which will form dense molecular layer on a gold surface because of the intermolecular electrostatic force.

　A self-assembled monolayer of the oligopeptides CGGGKEKEKEK (cell repulsive peptide) and CGGGKEKEKEGRGDSP (cell adhesive peptide) (Fig. 1) was fabricated on a gold surface via a gold-thiolate bond and the electrostatic force between the alternating charged lysine (K) and glutamic acid (E) sequence. Owing to the ionic solvation in the alternating sequence, the modified surface was resistant to the nonspecific adsorption of proteins, while cells adhered to this surface via the RGD sequence. The application of a negative potential resulted in the subsequent detachment of the attached cells along with the cleaving of the gold-thiolate bond. Quartz crystal microbalance measurement revealed that the nonspecific adsorption of proteins was significantly reduced by the modification with the cell repulsive peptide. Cells are preferably attached on the surface modified with adhesive peptide, which were then completely detached by applying a negative potential. In our previous approach, ~10% of the cells remained on the gold surface even after 5 min of potential application. In this study, probably owing to the nonfouling layer, almost all cells were completely detached within 2 min of the potential application (Fig. 2). By spatially patterning these two oligopeptides separately, cell adhesive and repulsive regions were fabricated. Fibroblasts seeded on the surface were selectively adhered onto the cell adhesive islands (Fig. 3) The proposed approach could be used to completely and rapidly detach cells from a substrate. This cell detachment approach appears to be a useful tool in building-block-based tissue engineering.

Fig. 1 Design of zwitterionic oligopeptide

Fig. 2 Electrochemical detachment of cells

Fig. 3 Micropatterning of cells on the oligopeptide modified surface