Structure of Atomically Dispersed Pt in a SnO2 Thin Film under Reaction Conditions: Origin of Its High Performance in Micro Electromechanical System Gas Sensor Catalysis.

A battery-driven micro electromechanical system (MEMS) gas sensor has been developed for household safety when using natural gas. The heart of the MEMS gas sensor is a 7.5 at % Pt-SnO2 thin film catalyst deposited on the SnO2 sensor layer. The catalyst enhances the sensitivity to methane, though its structure under working conditions is unclear. In this study, in situ XAFS was applied to a 7.5 at % Pt-SnO2 catalyst layer deposited on a Si substrate, and we demonstrated that atomically dispersed Pt maintains its lattice position in SnO2 with a small loss of surrounding lattice oxygen in the presence of 1% CH4 and a more reducing gas of 1% H2 at the reaction temperature (703 K), i.e., no Pt aggregation is observed. The lost oxygen is easily recovered by re-oxidation by air. This work has revealed that the atomically dispersed Pt in the SnO2 lattice is the active structure and it is stable even under reaction conditions, which guarantees a long lifetime for the gas sensor.

Interleukin-1ß-induced matrix metalloproteinase-3 via ERK1/2 pathway to promote mesenchymal stem cell migration.

Human umbilical cord Wharton's jelly derived mesenchymal stem cells (hUCMSCs), a source of cell therapy, have received a great deal of attention due to their homing or migrating ability in response to signals emanating from damaged sites. It has been found that IL-1ß possesses the ability to induce the expression of matrix metalloproteinase-3 (MMP-3) in bone marrow MSCs. MMP-3 is involved in cell migration in various types of cells, including glioblastoma, vascular smooth muscle, and adult neural progenitor cells. In this study, we proposed that IL-1ß influences hUCMSCs migration involving MMP-3. The expression level of MMP-3 in IL-1ß-induced hUCMSCs was verified using cDNA microarray analysis, quantitative real-time PCR, ELISA and Western blot. Wound-healing and trans-well assay were used to investigate the cell migration and invasion ability of IL-1ß-treated hUCMSCs. In addition, we pre-treated hUCMSCs with interleukin-1 receptor antagonist, MMP-3 inhibitors (ALX-260-165, UK 356618), or transfected with MMP-3 siRNA to confirm the role of MMP3 in IL-1ß-induced cell migration. Our results showed that IL-1ß induced MMP-3 expression is related to the migration of hUCMSCs. Moreover, extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) inhibitor U0126, p38 inhibitor SB205380, JNK inhibitor SP600125 and Akt inhibitor GSK 690693 decreased IL-1ß-induced MMP-3 mRNA and protein expression. The migration and invasion ability analyses showed that these inhibitors attenuated the IL-1ß-induced migration and invasion ability of hUCMSCs. In conclusion, we have found that IL-1ß induces the expression of MMP-3 through ERK1/2, JNK, p38 MAPK and Akt signaling pathways to enhance the migration of hUCMSCs. These results provide further understanding of the mechanisms in IL-1ß-induced hUCMSCs migration to injury sites.

Stiffness-controlled three-dimensional collagen scaffolds for differentiation of human Wharton's jelly mesenchymal stem cells into cardiac progenitor cells.

Stem cell-based regenerative therapy has emerged as a promising treatment for myocardial infarction. The aim of this study is to develop stiffness-controlled collagen scaffolds to allow proliferation and differentiation of mesenchymal stem cell (MSCs) into cardiac progenitor cells. In this study transforming growth factor ß2 (TGF-ß2), was used to induce stem cell differentiation into cardiac lineage cells. Collagen scaffolds were cross-linked with cross-linkers, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and N-Hydroxysuccinimide (NHS). The results showed that collagen scaffolds cross-linked with 25/50 and 50/50 of EDC mM/NHS mM cross-linkers exhibited little difference in shape and size, the scaffold cross-linked with 50/50 of cross-linkers demonstrated better interconnectivity and higher Young's modulus (31.8 kPa) than the other (15.4 kPa). SEM observation showed that MSCs could grow inside the scaffolds and interact with collagen scaffolds. Furthermore, greater viability and cardiac lineage differentiation were achieved in MSCs cultured on stiffer scaffolds. The results suggest that three-dimensional type I collagen scaffolds with suitable cross-linking to adjust for stiffness can affect MSC fate and direct the differentiation of MSCs into cardiac progenitor cells with/without TGF-ß2. These stiffness-controlled collagen scaffolds hold great potential as carriers for delivering MSCs differentiated cardiac progenitor cells into infracted hearts. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2234-2242, 2016.