Photopatterning Proteins and Cells in Aqueous Environment Using TiO₂ Photocatalysis

Abstract

Organic contaminants adsorbed on the surface of titanium dioxide (TiO2) can be decomposed by photocatalysis under ultraviolet (UV) light. Here we describe a novel protocol employing the TiO2 photocatalysis to locally alter cell affinity of the substrate surface. For this experiment, a thin TiO2 film was sputter-coated on a glass coverslip, and the TiO2 surface was subsequently modified with an organosilane monolayer derived from octadecyltrichlorosilane (OTS), which inhibits cell adhesion. The sample was immersed in a cell culture medium, and focused UV light was irradiated to an octagonal region. When a neuronal cell line PC12 cells were plated on the sample, cells adhered only on the UV-irradiated area. We further show that this surface modification can also be performed in situ, i.e., even when cells are growing on the substrate. Proper modification of the surface required an extracellular matrix protein collagen to be present in the medium at the time of UV irradiation. The technique presented here can potentially be employed in patterning multiple cell types for constructing coculture systems or to arbitrarily manipulate cells under culture.

Light-Induced Cell Alignment and Harvest for Anisotropic Cell Sheet Technology

“…Though cell patterning on TiO 2 film have been reported previously, − we here described another novel method to generate micropatterned cues directly on TiO 2 surface without the cell-repellent coating. We observed the effects of UV pretreatment at aspects of wettability, protein adsorption and cell attachment to confirm the generation of micropatterned cues, as shown in Figure .…”

“…Recently, light patterning has been demonstrated as a way to fabricate the hydrophilic/hydrophobic patterns, micropatterned polymer brushes, and small-molecule organic nanowire on TiO 2 film. A novel method for fabricating cell microarrays based on photocatalysis of cell-repellent coating on TiO 2 film was also reported. − In fact, one property of TiO 2 , known as photofunctionalization, showed the great improvements in the attachment and proliferation of osteogenic cells on ultraviolet (UV) light preirradiated TiO 2 film. − Surface hydroxyl group features on TiO 2 controlled by photofunctionalization initiate a hierarchical signal processing thus guide the selective protein adsorption as well as the subsequent cell behaviors. ,, It implied the possibility of cell patterning by UV light on TiO 2 film without the cell-repellent coating and the combination with light-induced cell detachment. Meanwhile, the newly developed photopolymerizable gelatin methacrylate (GelMA), synthesized by adding methacrylate groups to amine-containing side groups of gelatin, , might be an ideal photo-cross-linkable hydrogel to integrate detachment and stack of the light-induced CS.…”

In situ modification of cell-culture scaffolds by photocatalysis of visible-light-responsive TiO2film

“…Note that the TiO 2 film sputter-deposited at room temperature without O 2 gas injection is the film we used in our previous work. [19][20][21] This indicates that the TiO 2 film exhibits photocatalytic activity upon UV exposure, although the film does not have a distinct crystal structure. If crystallinity is not always required for the photocatalytic activity of TiO 2 , the film is expected to have the VLresponsive activity since the film exhibits the absorbance in the VL region.…”

“…One promising method for the in situ cell-culture scaffold modification is TiO 2 photocatalysis, as reported previously. [19][20][21] A transparent and chemically stable TiO 2 film is compatible with conventional cell-culture experiments. Focused ultraviolet (UV) light or scanning UV laser makes it possible to decompose surface molecules in the medium in a region-selective manner.…”