Streptavidin functionalized polymer nanodots fabricated by visible light lithography

Background: Two-photon polymerization, optionally combined with stimulated emission depletion (STED) lithography, allows two and three dimensional polymer fabrication with structure sizes and resolution below the diffraction limit. Structuring of polymers with photons, whose wavelength is within the visible range of the electromagnetic spectrum, gives new opportunities to a large field of applications e.g. in the field of biotechnology and tissue engineering. In order to create new biotechnological applications, versatile methods are needed to functionalize the polymeric structures. Results: Here we report the creation of polymer-nanodots with high streptavidin (SA) affinity via two-photon polymerization (TPP). Controlling the size of the polymer dots allows for limiting the number of the SA molecules. TPP dots with a diameter of a few 100 nm show up to 100% streptavidin loading. We can show that most of the dots are loaded by one to two streptavidins on average. Attached streptavidin molecules remain functional and are capable to bind 0.7 biotin molecules on average. Conclusion: The presented functionalized nanostructures may be used as platforms for a multitude of biological experimental setups. Nanoscopic well defined structures, capable of selective binding of streptavin proteins, used as linkers for other biotinylated biomolecules, may also find application in in-vitro sensing, like for example lab on chip devices with limited surface area.