Surface-modified complex SU-8 microstructures for indirect optical manipulation of single cells

We introduce a method that combines two-photon polymerization (TPP) and surface functionalization to enable the indirect optical manipulation of live cells. TPP-made 3D microstructures were coated specifically with a multilayer of the protein streptavidin and non-specifically with IgG antibody using polyethylene glycol diamine as a linker molecule. Protein density on their surfaces was quantified for various coating methods. The streptavidin-coated structures were shown to attach to biotinated cells reproducibly. We performed basic indirect optical micromanipulation tasks with attached structure-cell couples using complex structures and a multi-focus optical trap. The use of such extended manipulators for indirect optical trapping ensures to keep a safe distance between the trapping beams and the sensitive cell and enables their 6 degrees of freedom actuation. (C)2015 Optical Society of Americ

Aminosilane-based functionalization of two-photon polymerized 3D SU-8 microstructures.

There is an increasing interest in functionalized complex 3D microstructures with sub-micrometer features for micro- and nanotechnology applications in biology. Depending primarily on the material of the structures various methods exist to create functional layers of simple chemical groups, biological macromolecules or metal nanoparticles. Here an effective coating method is demonstrated and evaluated on SU-8 based 3D microstructures made by two-photon polymerization. Protein streptavidin and gold nanoparticles (NP) were bound to the microstructures utilizing acid treatment-mediated silane chemistry. The protein surface density, quantified with single molecule fluorescence microscopy revealed that the protein forms a third of a monolayer on the two-photon polymerized structures. The surface coverage of the gold NPs on the microstructures was simply controlled with a single parameter. The possible degrading effect of the acid treatment on the sub-micrometer features of the TPP microstructures was analyzed. Our results show that the silane chemistry-based method, used earlier for the functionalization of large-area surfaces can effectively be adapted to coat two-photon polymerized SU-8 microstructures with sub-micrometer features