Sensitizer-enhanced two-photon patterning of biomolecules in photoinstructive hydrogels

Photoresponsive hydrogels can be employed to coordinate the organization of proteins in three dimensions (3D) and thus to spatiotemporally control their physiochemical properties by light. However, reversible and user-defined tethering of proteins and protein complexes to biomaterials pose a considerable challenge as this is a cumbersome process, which, in many cases, does not support the precise localization of biomolecules in the z direction. Here, we report on the 3D patterning of proteins with polyhistidine tags based on in-situ two-photon lithography. By exploiting a two-photon activatable multivalent chelator head, we established the protein mounting of hydrogels with micrometer precision. In the presence of photosensitizers, a substantially enhanced two-photon activation of the developed tool inside hydrogels was detected, enabling the user-defined 3D protein immobilization in hydrogels with high specificity, micrometer-scale precision, and under mild light doses. Our protein-binding strategy allows the patterning of a wide variety of proteins and offers the possibility to dynamically modify the biofunctional properties of materials at defined subvolumes in 3D

Investigations on Interface Shear Fatigue of Semi-Precast Slabs with Lattice Girders

Due to their high cost efficiency and flexibility, semi-precast concrete slabs with lattice girders are widely used in constructions all over the world. Prefabricated concrete slabs, combined with in situ concrete topping, exhibit a quasi-monolithic structural behavior in which lattice girders serve as vertical shear reinforcement and ensure the transfer of longitudinal shear within the interface, acting in combination with concrete-to-concrete bonding mechanisms. To be applicable in industrial and bridge construction, semi-precast slabs need to have sufficient resistance against fatigue failure. To improve and expand the limits of application, theoretical and experimental investigations are conducted at the Institute of Structural Concrete (IMB), RWTH Aachen University. To investigate the fatigue behavior of lattice girders, small size tests with lattice girder diagonals were carried out. These test results have been used to derive an S–N curve (S: stress, N: number of load cycles) for lattice girders for a more refined fatigue design. Subsequently, the fatigue behavior of semi-precast slabs with lattice girders was investigated by fatigue tests on single-span slab segments. The fatigue design regulations of lattice girders according to technical approvals can generally be confirmed by this test program; however, they tend to be conservative. The use of the derived S–N curve leads to significantly improved agreement of fatigue behavior observed in tests and design expressions

Dritter Bericht der wissenschaftlichen Begleitung zum Modellversuch Lernbuero neue Informationstechnologien und Datenverarbeitung im Berufsfeld Wirtschaft und Verwaltung ; Verbindung von berufspraktischer und theoretischer Arbeit (Ausbildung) im Lernbuero

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