Surface modification of cell scaffold in aqueous solution using TiO₂ photocatalysis and linker protein L2 for patterning primary neurons

Titanium dioxide (TiO₂) photocatalysis can be applied to pattern proteins and cells under aqueous solution. In this work, we extended the application of this technique to patterning primary neurons, a type of cell with relatively weak adhesibility. For this purpose, we employed ribosomal protein L2 (RPL2) that has high affinity toward silica and metal oxides, including TiO₂, to stably bind a neuronal adhesion protein laminin to the TiO₂surface. We utilized two types of molecular recognition to achieve this - binding of anti-laminin antibody to its antigen (laminin) and binding of protein A to the antibody. We show that a protein complex consisting of laminin/anti-laminin antibody/protein A-RPL2 is spontaneously formed by simply mixing the precursor proteins in solution phase. We then show that the surface coated with the protein complex supports stable growth of rat hippocampal neurons. Finally, we show that the cells can be selectively grown on the protein complex patterned with the TiO₂-assisted method. The protocol established in this work is a unique combination of a top-down micropatterning of the surface using TiO₂ photocatalysis and a bottom-up self-assembly of biomolecules, which can be further applied to pattern a wide range of proteins and cells.