Guiding cell adhesion and motility by modulating cross-linking and topographic properties of microgel arrays.

Biomaterial-driven modulation of cell adhesion and migration is a challenging aspect of tissue engineering. Here, we investigated the impact of surface-bound microgel arrays with variable geometry and adjustable cross-linking properties on cell adhesion and migration. We show that cell migration is inversely correlated with microgel array spacing, whereas directionality increases as array spacing increases. Focal adhesion dynamics is also modulated by microgel topography resulting in less dynamic focal adhesions on surface-bound microgels. Microgels also modulate the motility and adhesion of Sertoli cells used as a model for cell migration and adhesion. Both focal adhesion dynamics and speed are reduced on microgels. Interestingly, Gas2L1, a component of the cytoskeleton that mediates the interaction between microtubules and microfilaments, is dispensable for the regulation of cell adhesion and migration on microgels. Finally, increasing microgel cross-linking causes a clear reduction of focal adhesion turnover in Sertoli cells. These findings not only show that spacing and rigidity of surface-grafted microgels arrays can be effectively used to modulate cell adhesion and motility of diverse cellular systems, but they also form the basis for future developments in the fields of medicine and tissue engineering.

Fabrication of Microporous Coatings on Titanium Implants with Improved Mechanical, Antibacterial, and Cell-Interactive Properties.

The success of an orthopedic implant therapy depends on successful bone integration and the prevention of microbial infections. In this work, plasma electrolytic oxidation (PEO) was performed to deposit TiO2 coatings enriched with Ca, P, and Ag on titanium to improve its surface properties and antibacterial efficacy while maintaining normal biological functions and thus to enhance the performance of orthopedic implants. After PEO treatment, the surface of Ti was converted to anatase and rutile TiO2, hydroxyapatite, and calcium titanate phases. The presence of these crystalline phases was further increased with an increased Ag content in the coatings. The developed coatings also exhibited a more porous morphology with an improved surface wettability, roughness, microhardness, and frictional coefficient. In vitro antibacterial assays indicated that the Ag-doped coatings can significantly prevent the growth of both Staphylococcus aureus and Escherichia coli by releasing Ag+ ions, and the ability to prevent these bacteria was enhanced by increasing the Ag content in the coatings, resulting in a maximal 6-log reduction of E. coli and a maximal 5-log reduction of S. aureus after 24 h of incubation. Moreover, the in vitro cytocompatibility evaluation of the coatings showed that the osteoblast (MC3T3) cell integration on the PEO-based coatings was greatly improved compared to untreated Ti and no notable impact on their cytocompatibility was observed on increasing the amount of Ag in the coating. In conclusion, the coating with favorable physicochemical and mechanical properties along with controlled silver ion release can offer an excellent antibacterial performance and osteocompatibility and can thus become a prospective coating strategy to face current challenges in orthopedics.