• fibronectin;
  • focal adhesion contacts and actin cytoskeleton;
  • pre-osteoblasts;
  • silicone elastomer;
  • soft tissue implants


The flexible and highly ductile silicone elastomer widely used as a soft-tissue substitute for joint reconstruction and replacement fragments prematurely because of low tensile strength and inadequate bone build-up around the implants. In this regard, an excellent vehicle to favorably modulate cellular response and retain intrinsic elastic recovery of soft tissue implants is to consider hybrid network structure elastomers with inorganic short chain cross-links. The concept involves covalently linking nanocrystalline titania with a bi-functional agent, acrylic acid, which has a carboxylic group to coordinate with titania and a vinyl group to form short chain cross-links as an integral part of the silicone network during curing at elevated pressure. This approach provides high strength-at-break and undiminished intrinsic ductility of silicone elastomer and high cytocompatibility. Interestingly, cellular response is favorably modulated, as described here. The biologic response in terms of initial cell attachment, cell viability, and proliferation was consistently greater in relation to stand alone silicone elastomer such that cell spreading, morphology, and density were distinctly different. Pre-osteoblasts grown on hybrid network structure elastomers were widely spread on the surface as a sheet after a culture time of 24 h. In contrast, these features were less pronounced on the stand alone silicone elastomer. Furthermore, immunofluorescence study illustrated distinct fibronectin expression level, stronger vinculin focal adhesion contacts associated with abundant actin stress fibers in pre-osteoblasts grown on hybrid network structure elastomer compared to stand alone silicone elastomer, implying enhanced cell–substrate interactions. This finding was consistent with the observation of total protein content and sodium dodecyl sulfate polyacrylamide gel analysis.

Based on the study described here, our hypothesis is that silicone–titania network structure elastomer with high strength–high ductility combination and favorable cellular response is a model hybrid network structure elastomer for joint reconstruction and soft tissue substitution. The integration of cellular and molecular biology with materials science and engineering aspects described here provides a new direction toward the development of new generation of hybrid network structure silicone elastomer. This subject is germane from the view point of fundamental understanding and from the view of hybrid elastomers as soft tissue reconstruction.