Photoactive branched and linear surface architectures for functional and patterned immobilization of proteins and cells onto surfaces: a comparative study.

Molecular architecture affects the properties of surface layers. Photosensitive silanes with branched architectures allow patterning and coupling of proteins and cells on surfaces while maintaining their biofunctional state. Attachment can be directed to the activated regions of irradiated substrates with high selectivity (see image of mouse fibroblasts). Novel photosensitive silanes with a branched molecular architecture combining three end-functionalized oligoethylene glycol (OEG) and alkyl arms are presented. These molecules are synthesized and applied to the modification of silica surfaces. The resulting layers are tested in their ability for the selective, patterned and functional immobilization of proteins and cells. The results demonstrate and accurately quantify the benefits of branched OEG structures against linear analogues for preventing non-specific interactions with the biological material. Linear structures guarantee high selectivity for the attachment of proteins, however, they fail in the case of cells. Branched structures provide good antifouling properties in both cases and allow the formation of protein patterns with higher densities of the target protein, as well as cell patterns. The results demonstrate the careful balance between surface functionality, composition and architecture that is required for maximizing the performance of any surface-based assay in biology.