| 1 | Improved Non-Covalent Biofunctionalization of Multi-Walled Carbon Nanotubes Using Carbohydrate Amphiphiles with a Butterfly-Like Polyaromatic Tail显示文摘We have developed an efficient strategy for the non-covalent functionalization of multi-walled carbon nanotubes(MWCNTs)which allows a biomimetic presentation of carbohydrates on their surface byπ-πstacking interactions.The strategy is based on the use of sugar-based amphiphiles functionalized with tetrabenzo[a,c,g,i]fluorene(Tbf),a polyaromatic compound with a topology that resembles a butterfly with open wings.The new carbohydrate-tethered Tbf amphiphiles have been synthesized in a straightforward manner using click chemistry.The reported method has been developed in order to improve the rather low ability of pyrene-based systems to exfoliate MWCNTs in water.By means of thermogravimetric analysis(TGA),ultraviolet(UV),infrared(IR),and fluorescence spectroscopies the interaction between MWCNTs and the Tbf group has been found to be stronger than those involving pyrene-based amphiphilic carbohydrates.The resulting aggregates with a multivalent sugar exposition on their surface are able to engage in specific ligand-lectin interactions similar to glycoconjugates on a cell membrane. | Mohyeddin Assali Manuel Pernía Leal Inmaculada Fernández Pablo Romero-Gomez Rachid Baati Noureddine Khiar | 2010 | Nano Research2010，3，11： | 3 |
| 4 | Effects of normobaric cyclic hypoxia exposure on mesenchymal stem-cell differentiation–pilot study on bone parameters in elderly显示文摘BACKGROUND Mesenchymal stem cells(MSC)of bone marrow are the progenitor of osteoblasts and adipocytes.MSC tend to differentiate into adipocytes,instead of osteoblasts,with aging.This favors the loss of bone mass and development of osteoporosis.Hypoxia induces hypoxia inducible factor 1αgene encoding transcription factor,which regulates the expression of genes related to energy metabolism and angiogenesis.That allows a better adaptation to low O2 conditions.Sustained hypoxia has negative effects on bone metabolism,favoring bone resorption.Yet,surprisingly,cyclic hypoxia(CH),short times of hypoxia followed by long times in normoxia,can modulate MSC differentiation and improve bone health in aging.AIM To evaluate the CH effect on MSC differentiation,and whether it improves bone mineral density in elderly.METHODS MSC cultures were induced to differentiate into osteoblasts or adipocytes,in CH(3%O2 for 1,2 or 4 h,4 d a week).Extracellular-matrix mineralization and lipid-droplet formation were studied in MSC induced to differentiate into osteoblast or adipocytes,respectively.In addition,gene expression of marker genes,for osteogenesis or adipogenesis,have been quantified by quantitative real time polymerase chain reaction.The in vivo studies with elderly(>75 years old;n=10)were carried out in a hypoxia chamber,simulating an altitude of 2500 m above sea level,or in normoxia,for 18 wk(36 CH sessions of 16 min each).Percentages of fat mass and bone mineral density from whole body,trunk and right proximal femur(femoral,femoral neck and trochanter)were assessed,using dual-energy X-ray absorptiometry.RESULTS CH(4 h of hypoxic exposure)inhibited extracellular matrix mineralization and lipid-droplet formation in MSC induced to differentiate into osteoblasts or adipocytes,respectively.However,both parameters were not significantly affected by the other shorter hypoxia times assessed.The longest periods of hypoxia downregulated the expression of genes related to extracellular matrix formation,in MSC induced to differentiate into osteoblasts.Interestingly,osteocalcin(associated to energy metabolism)was upregulated.Vascular endothelial growth factor an expression and low-density lipoprotein receptor related protein 5/6/dickkopf Wnt signaling pathway inhibitor 1(associated to Wnt/β-catenin pathway activation)increased in osteoblasts.Yet,they decreased in adipocytes after CH treatments,mainly with the longest hypoxia times.However,the same CH treatments increased the osteoprotegerin/receptor activator for nuclear factor kappa B ligand ratio in both cell types.An increase in total bone mineral density was observed in elderly people exposed to CH,but not in specific regions.The percentage of fat did not vary between groups.CONCLUSION CH may have positive effects on bone health in the elderly,due to its possible inhibitory effect on bone resorption,by increasing the osteoprotegerin/receptor activator for nuclear factor kappa B ligand ratio. | Marta Camacho-Cardenosa JoséManuel Quesada-Gómez Alba Camacho-Cardenosa Alejo Leal GabrielDorado Bárbara Torrecillas-Baena Antonio Casado-Díaz | 2020 | World Journal of Stem Cells2020，12，12： | 0 |
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