2010, Schmitz-Stöwe, Sabine, Becker-Willinger, Carsten, Bentz, Dirk, Abt, Britta, Veith, Michael

TiO2 nanoparticles of anatase, useful as photosensitive initiators to induce free radical polymerization in acrylic monomers have been prepared by chemical synthesis. Appropriate surface modification of TiO2 has been achieved in order to compatibilize the particles with the acrylic monomers to obtain an almost homogeneous distribution down to the primary particle size. The surface modification has been additionally fine tuned in such a way, that an efficient transfer of the electrons generated on TiO2 during UV-exposure could be achieved towards the monomer mixture in order to start the polymerization reaction. The formation of the anatase modification could be confirmed by XRD. Particle sizes were determined by UPA, which showed a distribution between 1-10 nm depending on the preparation method used. Transmission electron microscopy carried out with the UV-polymerized coating layers proved the homogeneous distribution of the anatase nanoparticles. Kinetic investigations on the photo-polymerization behavior have been accomplished by photo-DSC and Raman spectroscopy. Curing time was determined in dependence of the materials composition.

2023, Trujillo, Sara, Kasper, Jennifer, de Miguel-Jiménez, Adrián, Abt, Britta, Bauer, Alina, Mekontso, Joëlle, Pearson, Samuel, del Campo, Aránzazu

Methylsulfone derivatized poly(ethylene) glycol (PEG) macromers can be biofunctionalized with thiolated ligands and cross-linked with thiol-based cross-linkers to obtain bioactive PEG hydrogels for in situ cell encapsulation. Methylsulfonyl-thiol (MS-SH) reactions present several advantages for this purpose when compared to other thiol-based cross-linking systems. They proceed with adequate and tunable kinetics for encapsulation, they reach a high conversion degree with good selectivity, and they generate stable reaction products. Our previous work demonstrated the cytocompatibility of cross-linked PEG-MS/thiol hydrogels in contact with fibroblasts. However, the cytocompatibility of the in situ MS-SH cross-linking reaction itself, which generates methylsulfinic acid as byproduct at the cross-linked site, remains to be evaluated. These studies are necessary to evaluate the potential of these systems for in vivo applications. Here we perform an extensive cytocompatibility study of PEG hydrogels during in situ cross-linking by the methylsulfonyl-thiol reaction. We compare these results with maleimide-thiol cross-linked PEGs which are well established for cell culture and in vivo experiments and do not involve the release of a byproduct. We show that fibroblasts and endothelial cells remain viable after in situ polymerization of methylsulfonyl-thiol gels on the top of the cell layers. Cell viability seems better than after in situ cross-linking hydrogels with maleimide-thiol chemistry. The endothelial cell proinflammatory phenotype is low and similar to the one obtained by the maleimide-thiol reaction. Finally, no activation of monocytes is observed. All in all, these results demonstrate that the methylsulfonyl-thiol chemistry is cytocompatible and does not trigger high pro-inflammatory responses in endothelial cells and monocytes. These results make methylsulfonyl-thiol chemistries eligible for in vivo testing and eventually clinical application in the future.