The role of reactive silicates on the structure/property relationships and cell response evaluation in polyurethane nanocomposites

Highly exfoliated montmorillonite clay reinforced thermoplastic polyurethane elastomer:in situpreparation and efficient strengthening

Highly exfoliated montmorillonite (MMT) clay reinforced thermoplastic polyurethane elastomers (TPUs) were prepared by an in situ solution polymerization method. By using small amount of 4,4′-methylenediphenyl diisocyanate (MDI) modified pristine clay (MDI-MMT) as fillers, the mechanical properties of TPUs were greatly improved. For example, with the addition of only 1.0 wt% of MDI-MMT, the resultant TPU/MDI-MMT nanocomposites showed approximately 36% increase in initial Young's modulus, 70% increase in tensile strength and 46% increase in ultimate elongation at break as compared with those of neat TPU. Detailed study showed that, owing to the strong covalent bonding between the MMT sheets and TPU matrix, MMT sheets were highly exfoliated during the polymerization process, and the highly exfoliated MMT sheets gave rise to the greatly improved mechanical properties and thermomechanical properties of TPU/MDI-MMT nanocomposites. The present work demonstrates that the in situ preparation of TPU/MDI-MMT nanocomposites by using MDI-MMT as fillers is a highly efficient method for reinforcing TPU.

Highly exfoliated montmorillonite (MMT) clay reinforced thermoplastic polyurethane elastomers (TPUs) were prepared by an in situ solution polymerization method.

Self-Assembling Nanoclay Diffusion Gels for Bioactive Osteogenic Microenvironments

Laponite nanoparticles have attracted attention in the tissue engineering field for their protein interactions, gel-forming properties, and, more recently, osteogenic bioactivity. Despite growing interest in the osteogenic properties of Laponite, the application of Laponite colloidal gels to host the osteogenic differentiation of responsive stem cell populations remains unexplored. Here, the potential to harness the gel-forming properties of Laponite to generate injectable bioactive microenvironments for osteogenesis is demonstrated. A diffusion/dialysis gelation method allows the rapid formation of stable transparent gels from injectable, thixotropic Laponite suspensions in physiological fluids. Upon contact with buffered saline or blood serum, nanoporous gel networks exhibiting, respectively, fivefold and tenfold increases in gel stiffness are formed due to the reorganization of nanoparticle interactions. Laponite diffusion gels are explored as osteogenic microenvironments for skeletal stem cell containing populations. Laponite films support cell adhesion, proliferation, and differentiation of human bone marrow stromal cells in 2D. Laponite gel encapsulation significantly enhances osteogenic protein expression compared with 3D pellet culture controls. In both 2D and 3D conditions, cell associated mineralization is strongly enhanced. This study demonstrates that Laponite diffusion gels offer considerable potential as biologically active and clinically relevant bone tissue engineering scaffolds.

Clay: new opportunities for tissue regeneration and biomaterial design

Seminal recent studies that have shed new light on the remarkable properties of clay interactions suggest unexplored opportunities for biomaterial design and regenerative medicine. Here, recent conceptual and technological developments in the science of clay interactions with biomolecules, polymers, and cells are examined, focusing on the implications for tissue engineering and regenerative strategies. Pioneering studies demonstrating the utility of clay for drug-delivery and scaffold design are reviewed and areas for future research and development highlighted.