Highly Porous Amorphous Calcium Phosphate for Drug Delivery and Bio-Medical Applications

Amorphous calcium phosphate (ACP) has shown significant effects on the biomineralization and promising applications in bio-medicine. However, the limited stability and porosity of ACP material restrict its practical applications. A storage stable highly porous ACP with Brunauer-Emmett-Teller surface area of over 400 m(2)/g was synthesized by introducing phosphoric acid to a methanol suspension containing amorphous calcium carbonate nanoparticles. Electron microscopy revealed that the porous ACP was constructed with aggregated ACP nanoparticles with dimensions of several nanometers. Large angle X-ray scattering revealed a short-range atomic order of <20 angstrom in the ACP nanoparticles. The synthesized ACP demonstrated long-term stability and did not crystallize even after storage for over 14 months in air. The stability of the ACP in water and an alpha-MEM cell culture medium were also examined. The stability of ACP could be tuned by adjusting its chemical composition. The ACP synthesized in this work was cytocompatible and acted as drug carriers for the bisphosphonate drug alendronate (AL) in vitro. AL-loaded ACP released 25% of the loaded AL in the first 22 days. These properties make ACP a promising candidate material for potential application in biomedical fields such as drug delivery and bone healing

Chiral Lanthanum Metal-Organic Framework with Gated CO2 Sorption and Concerted Framework Flexibility br

A metal-organic framework (MOF)CTH-17based on lanthanum-(III) and the conformationally chiral linker 1,2,3,4,5,6-hexakis(4-carboxyphenyl)-benzene, cpb6-: [La2(cpb)]middot1.5dmf was prepared by the solvothermal method indimethylformamide (dmf) and characterized by variable-temperature X-raypowder diffraction (VTPXRD), variable-temperature X-ray single-crystal diffrac-tion (SCXRD), and thermogravimetric analysis (TGA).CTH-17is a rod-MOFwith new topologyoch. It has high-temperature stability with Sohncke spacegroupsP6122/P6522 at 90 K andP622 at 300 and 500 K, all phases characterizedwith SCXRD and at 293 K also with three-dimensional (3D) electron diffraction. VTPXRD indicates a third phase appearing after620 K and stable up to 770 K. Gas sorption isotherms with N2indicate a modest surface area of 231 m2g-1forCTH-17, roughly inagreement with the crystal structure. Carbon dioxide sorption reveals a gate-opening effect ofCTH-17where the structure opens upwhen the loading of CO2reaches approximately similar to 0.45 mmol g-1or 1 molecule per unit cell. Based on the SCXRD data, this isinterpreted asflexibility based on the concerted movements of the propeller-like hexatopic cpb linkers, the movementintramolecularly transmitted by the pi-pi stacking of the cpb linkers and helped by thefluidity of the LaO6coordination sphere. Thiswas corroborated by density functional theory (DFT) calculations yielding the chiral phase (P622) as the energy minimum and acompletely racemic phase (P6/mmm), with symmetric cpb linkers representing a saddle point in a racemization proces