A key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.

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The hydrophilicity, hydrophobicity, and sliding behavior of water droplets on nanoasperities of controlled dimensions were investigated experimentally. We show that the "hemi-wicking" theory for hydrophilic SiO(2) samples successfully predicts the experimental advancing angles and that the same patterns, after silanization, become superhydrophobic in agreement with the Cassie-Baxter and Wenzel theories. Our model topographies have the same dimensional scale of some naturally occurring structures that exhibit similar wetting properties. Our results confirm that a forest of hydrophilic/hydrophobic slender pillars is the most effective superwettable/water-repellent configuration. It is shown that the shape and curvature of the edges of the asperities play an important role in determining the advancing angles.

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