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నైరూప్య

Functional Titanium Lotus-Topography Promotes the Osteoinduction of Human Adipose-Derived Stem Cells In Vitro

Andrea Deiwick, Elena Fadeeva, Lothar Koch, Reiner Gebauer, Boris Chichkov and Sabrina Schlie-Wolter

For orthopedic applications, biomaterials are required which (a) enable bone cell anchorage, (b) stimulate osteogenic differentiation, (c) reduce the risk of infections and immune rejection, and (d) have appropriate mechanical properties similar to native bone. To enhance the biological performance of titanium, surface structuring by ultrashortpulse laser ablation was tested. This nanotechnology enables high precision, reduced head-affected zones, and small amount of debris around the ablated area. Various surface features in almost all solid materials can be fabricated. In order to mimic the complex architecture of natural bone, a lotus-topography was generated. Recently, we demonstrated that lotus-features reduce immune rejection and minimize the risk of infections in vitro.

Using human adipose-derived stem cells (hASC) we show that significantly more cells were adherent on the topography due to the increased surface area for contact. The distribution of integrin subunits got organized: β1 integrins were located on the tip of the structures, α5 integrins on the bottom. Furthermore, lotus-structures enhanced cell adhesion forces, quantified by centrifugation detachment assay. We further focused on surface impacts on osteogenic differentiation. Thereby, lotus-structures presented a strong promotive effect. Predifferentiated cells did not dedifferentiate, undifferentiated cells differentiated directly. However, differences of the tested osteogenic markers were obtained: alkaline phosphatase activity was not increased by the surface features, while osteocalcin expression and calcium mineralization, the strongest bone cell marker, were significantly improved.

In a sum, lotus-structures represent a surface functionalization which advances the functionality of titanium: namely osteoinduction and bioactivity In vitro. Therefore, they hold a great promise for future orthopedic applications.