Dynamic culture substrate that captures a specific extracellular matrix protein in response to light

The development of methods for the off-on switching of immobilization or presentation of cell-adhesive peptides and proteins during cell culture is important because such surfaces are useful for the analysis of the dynamic processes of cell adhesion and migration. This paper describes a chemically functionalized gold substrate that captures a genetically tagged extracellular matrix protein in response to light. The substrate was composed of mixed self-assembled monolayers (SAMs) of three disulfide compounds containing (i) a photocleavable poly(ethylene glycol) (PEG), (ii) nitrilotriacetic acid (NTA) and (iii) hepta(ethylene glycol) (EG₇). Although the NTA group has an intrinsic high affinity for oligohistidine tag (His-tag) sequences in its Ni²⁺-ion complex, the interaction was suppressed by the steric hindrance of coexisting PEG on the substrate surface. Upon photoirradiation of the substrate to release the PEG chain from the surface, this interaction became possible and hence the protein was captured at the irradiated regions, while keeping the non-specific adsorption of non-His-tagged proteins blocked by the EG₇ underbrush. In this way, we selectively immobilized a His-tagged fibronectin fragment (FNIII_7-10) to the irradiated regions. In contrast, when bovine serum albumin - a major serum protein - was added as a non-His-tagged protein, the surface did not permit its capture, with or without irradiation. In agreement with these results, cells were selectively attached to the irradiated patterns only when a His-tagged FNIII_7-10 was added to the medium. These results indicate that the present method is useful for studying the cellular behavior on the specific extracellular matrix protein in cell-culturing environments.