A Highly Stable Yttrium Organic Framework as a Host for Optical Thermometry and D2 O Detection.

The yttrium organic framework (Y0.89 Tb0.10 Eu0.01 )6 (BDC)7 (OH)4 (H2 O)4 (BDC=benzene-1,4-dicarboxylate) is hydrothermally stable up to at least 513 K and thermally stable in air in excess of 673 K. The relative intensities of luminescence of Tb3+ and Eu3+ are governed by Tb3+ -to-Eu3+ phonon-assisted energy transfer and Tb3+ -to-ligand back transfer and are responsible for the differing temperature-dependent luminescence of the two ions. This provides a ratiometric luminescent thermometer in the 288-573 K temperature range, not previously seen for MOF materials, with a high sensitivity, 1.69±0.04 % K-1 at 523 K. In aqueous conditions, loosely bound H2 O can be replaced by D2 O in the same material, which modifies decay lifetimes to yield a quantitative luminescent D2 O sensor with a useful sensitivity for practical application.

Strontium Calcium Phosphate Nanotubes as Bioinspired Building Blocks for Bone Regeneration.

Calcium phosphate (CaP)-based ceramics are the most investigated materials for bone repairing and regeneration. However, the clinical performance of commercial ceramics is still far from that of the native tissue, which remains as the gold standard. Thus, reproducing the structural architecture and composition of bone matrix should trigger biomimetic response in synthetic materials. Here, we propose an innovative strategy based on the use of track-etched membranes as physical confinement to produce collagen-free strontium-substituted CaP nanotubes that tend to mimic the building block of bone, i.e., the mineralized collagen fibrils. A combination of high-resolution microscopic and spectroscopic techniques revealed the underlying mechanisms driving the nanotube formation. Under confinement, poorly crystalline apatite platelets assembled into tubes that resembled the mineralized collagen fibrils in terms of diameter and structure of bioapatite. Furthermore, the synergetic effect of Sr2+ and confinement gave rise to the stabilization of amorphous strontium CaP nanotubes. The nanotubes were tested in long-term culture of osteoblasts, supporting their maturation and mineralization without eliciting any cytotoxicity. Sr2+ released from the particles reduced the differentiation and activity of osteoclasts in a Sr2+ concentration-dependent manner. Their bioactivity was evaluated in a serum-like solution, showing that the particles spatially guided the biomimetic remineralization. Further, these effects were achieved at strikingly low concentrations of Sr2+ that is crucial to avoid side effects. Overall, these results open simple and promising pathways to develop a new generation of CaP multifunctional ceramics that are active in tissue regeneration and able to simultaneously induce biomimetic remineralization and control the imbalanced osteoclast activity responsible for bone density loss.