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M. Lunzer, L. Shi, P. Gruber, M. Markovic, D. Ossipov, A. Ovsianikov, R. Liska:
"Promoted two-photon micropatterning of biocompatible material";
Poster: 5th European Symposium of Photopolymer Science, Mulhouse, France; 03.09.2018 - 06.09.2018; in: "5th European Symposium of Photopolymer Science", 5th European Symposium of Photopolymer Science, (2018), S. P23.

Multiphoton lithography is a powerful tool that allows patterning of polymer based materials in both positive and negative tone in the (sub)micrometre range by the use of pulsed laser light. Due to its unique features, including free-form 3D-patterning and its non-invasiveness to planes out of focus, this technique is especially predestined to be used for the treatment of biomaterials.1 As a result of the high resolution of multiphoton lithography and the respectively small feature sizes of created structures, a current key interest is to increase the achievable writing speed with the aim to push the feasible dimensions in the cubic centimetre regime. Besides engineering of advanced multi-photon printing devices, the development of highly efficient two-photon induced chemistries is a major optimization strategy for this purpose.2
In this contribution, our latest method for the advancement of two-photon degradable hydrogels is presented. Such materials usually contain photocleavable groups, for example o-nitrobenzyl ester derivatives (oNB), in the backbone or a linker. Upon irradiation with cytocompatible doses of either UV-light (one-photon) or pulsed NIR-laser light (two-photon) these linkages can be cleaved and the material is locally degraded. However, as the two-photon absorption cross-sections δa of these functionalities are usually rather low,3 relatively high laser intensities and long irradiation times are required that can harm living cells encapsulated in the material. To tackle this problem, we developed a modular system permitting the sensitization of the two-photon induced oNB photoscission. By adding a water-soluble small molecule two-photon sensitizer, we demonstrate that the efficiency of the oNB photocleavage can be effectively promoted in a concentration dependent manner and demonstrate the efficacy of this method in the presence of cells.

Multiphoton lithography, patterning of polymer based materials, 3D-patterning, treatment of biomaterials