Iodine in Metal-Organic Frameworks at High Pressure.

Capture of highly volatile radioactive iodine is a promising application of metal-organic frameworks (MOFs), thanks to their high porosity with flexible chemical architecture. Specifically, strong charge-transfer binding of iodine to the framework enables efficient and selective iodine uptake as well as its long-term storage. As such, precise knowledge of the electronic structure of iodine is essential for a detailed modeling of the iodine sorption process, which will allow for rational design of iodophilic MOFs in the future. Here we probe the electronic structure of iodine in MOFs at variable iodine···framework interaction by Raman and optical absorption spectroscopy at high pressure ( P). The electronic structure of iodine in the straight channels of SBMOF-1 (Ca- sdb, sdb = 4,4'-sulfonyldibenzoate) is modified irreversibly at P > 3.4 GPa by charge transfer, marking a polymerization of iodine molecules into a 1D polyiodide chain. In contrast, iodine in the sinusoidal channels of SBMOF-3 (Cd- sdb) retains its molecular (I2) character up to at least 8.4 GPa. Such divergent high-pressure behavior of iodine in the MOFs with similar port size and chemistry illustrates adaptations of the electronic structure of iodine to channel topology and strength of the iodine···framework interaction, which can be used to tailor iodine-immobilizing MOFs.

Iodine Adsorption in Metal Organic Frameworks in the Presence of Humidity.

Used nuclear fuel reprocessing represents a unique challenge when dealing with radionuclides such as isotopes of 85Kr and 129I2 due to their volatility and long half-life. Efficient capture of 129I2 ( t1/2 = 15.7 × 106 years) from the nuclear waste stream can help reduce the risk of releasing I2 radionuclide into the environment and/or potential incorporation into the human thyroid. Metal organic frameworks have the reported potential to be I2 adsorbents but the effect of water vapor, generally present in the reprocessing off-gas stream, is rarely taken into account. Moisture-stable porous metal organic frameworks that can selectively adsorb I2 in the presence of water vapor are thus of great interest. Herein, we report on the I2 adsorption capacity of two microporous metal organic frameworks at both dry and humid conditions. Single-crystal X-ray diffraction and Raman spectroscopy reveal distinct sorption sites of molecular I2 within the pores in proximity to the phenyl- and phenol-based linkers stabilized by the I···π and I···O interactions, which allow selective uptake of iodine.

Osteogenic Potential of Gingival Mesenchymal Stem Cells Over Titanium Machined Surfaces.

PURPOSE: To evaluate the biochemical composition of bone nodules deposited by gingival mesenchymal stem cells (GMSCs) over titanium machined surfaces in vitro. MATERIALS AND METHODS: GMSCs were isolated from healthy gingival tissues of patients undergoing crown-lengthening surgical procedures. GMSCs were characterized following the International Society for Cellular Therapy guidelines. After incubation of the GMSCs with titanium discs, osteogenic differentiation was induced for 28 days. Osteogenic lineage was confirmed by means of Alizarin Red S staining. Bone nodule morphology and deposition by GMSCs were characterized by scanning electron microscopy (SEM). An elemental analysis of the bone nodules was done using energy-dispersive x-ray spectroscopy (EDS). The biochemical composition of these nodules was further characterized via Raman spectroscopy, with native alveolar bone used as a control. RESULTS: GMSCs adhered and proliferated on the titanium discs and exhibited a spindle-shaped fibroblast-like morphology under standard culture conditions. Their phenotype was confirmed by the expression of CD105, CD90, CD73, and CD146, observed using flow cytometry. Deposits of calcium bone nodules were evident in the cultures after staining with Alizarin Red S, but were absent in the controls. Calcium and phosphate, the major components of hydroxyapatite, were present in the bone nodules, as shown by means of the EDS analysis. The results obtained from Raman spectra of these nodules showed the phosphate ions (ν[PO4³â»], ~960 cm¹), amide III (δ[NH], ~1,245 cm⁻¹), CH2 scissors (~1,451 cm⁻¹), amide I (ν[C = O], ~1,667 cm⁻¹), and ν(CH) (2,800-3,100 cm⁻¹) bands were similar to those observed in native bone. CONCLUSION: GMSCs can deposit a bone-like mineral highly similar to native bone (HA) over titanium surfaces. Ongoing studies are aimed at determining whether GMSCs can deposit a similar bone matrix/tissue over removed failed dental implants. If HA can be placed over removed failed dental implants, it may be possible to re-osseointegrate dental implants that are failing as a result of peri-implantitis in vivo.