Density Of Different Functional Groups Research Articles

Dendritic polyglycerol-conjugated gold nanostars with different densities of functional groups to regulate osteogenesis in human mesenchymal stem cells.

Nanomaterials play an important role in mimicking the biochemical and biophysical cues of the extracellular matrix in human mesenchymal stem cells (MSCs). Increasing studies have demonstrated the crucial impact of functional groups on MSCs, while limited research is available on how the functional group's density on nanoparticles regulates MSC behavior. Herein, the effects of dendritic polyglycerol (dPG)-conjugated gold nanostars (GNSs) with different densities of functional groups on the osteogenesis of MSCs are systematically investigated. dPG@GNS nanocomposites have good biocompatibility and the uptake by MSCs is in a functional group density-dependent manner. The osteogenic differentiation of MSCs is promoted by all dPG@GNS nanocomposites, in terms of alkaline phosphatase activity, calcium deposition, and expression of osteogenic protein and genes. Interestingly, the dPGOH@GNSs exhibit a slight upregulation in the expression of osteogenic markers, while the different charged densities of sulfate and amino groups show more efficacy in the promotion of osteogenesis. Meanwhile, the sulfated nanostars dPGS20@GNSs show the highest enhancement. Furthermore, various dPG@GNS nanocomposites exerted their effects by regulating the activation of Yes-associated protein (YAP) to affect osteogenic differentiation. These results indicate that dPG@GNS nanocomposites have functional group density-dependent influence on the osteogenesis of MSCs, which may provide a new insight into regulating stem cell fate.

Influence of surface etching and oxidation on the morphological growth of Al2O3 by ALD

Selective deposition using atomic layer deposition has potential as a viable method for growing patterned nanostructured materials, thus advancing the design of next-generation electronics and catalysts. This study investigated how etching HOPG produces different densities of functional groups and different morphologies that were found to influence the growth of Al2O3 structures. Hydrochloric acid produced a high density of –OH and –COOH functional sites on terrace regions on HOPG in comparison to nitric acid that produced –OH functional sites at defects. After exposure to ALD cycles of trimethylaluminum and water, different structures of Al2O3 were found to grow on the functional sites compared to defect sites. Field emission scanning electron microscopy, atomic force microscopy and Raman spectral imaging were used to characterize the changes in surface topography after etching and ALD. Vibrational spectroscopy and X-ray photoelectron spectroscopy were used to measure surface functionalization and quantify Al2O3 growth. Results suggest that the Al2O3 nucleation and growth at submonolayer coverage is affected by the surface functionalization as well as the topography and density of functional sites. This study finds that selective deposition on active areas are determined by the morphology and the functional groups that depend on the etching mechanism with the surface. These results suggest that understanding both the topography and type of functional site are necessary for designing the next-generation electronic devices and catalysts.

Structure and the dynamics of nano-confined water in the vicinity of functionalized graphene

This study investigated the structure and dynamics of water near the graphene surface with different degrees of hydrophobicity or hydrophilicity, near graphene-CH3 and graphene-OH with different densities of functional groups on surface. Our results showed that density of water molecules and hydrogen bond density increased by increasing hydrophilicity of surface and decreasing the density of functional groups on surface. These properties decreased near graphene-OH and graphene-CH3 in comparison with graphene because functional groups on surface created geometric constraint. By increasing hydrophilicity of surface, tendency of donors and acceptors in neighbor layer increased to locate in a situation where more hydrogen bond was created. Dynamics properties of water near surface decreased by increasing hydrophilicity of surface and density of functional groups on surface. Also, by increasing water molecules between graphene surface, normal density of fluid in vicinity surface decreased and hydrogen bond dynamics increased.

Disturbance‐Mediated Drift in Tree Functional Groups in Amazonian Forest Fragments

ABSTRACTThe interactive effects of forest disturbance and fragmentation on tropical tree assemblages remain poorly understood. We examined the effects of forest patch and landscape metrics, and levels of forest disturbance on the patterns of floristic composition and abundance of tree functional groups within 21 forest fragments and two continuous forest sites in southern Brazilian Amazonia. Trees were sampled within 60 (10 × 250 m) plots placed in the core areas of the fragments. Tree assemblage composition and abundance were summarized using nonmetric multidimensional scaling (NMDS). Forest patch size explained 36.2 percent and 30 percent of the variance in the proportion of small‐seeded softwood and hardwood stems in the 21 forest patches, respectively. Large fragments retained a higher abundance of hardwood tree species whereas small‐seeded softwood trees appear to proliferate rapidly in small disturbed fragments. Generalized linear mixed models showed that time since fragmentation had both positive and negative effects on the density of different functional groups of trees and on the ordination axes describing tree abundance. The composition and abundance of different tree genera were also related to time since fragmentation, distance to the nearest edge, and fire severity, despite the recent post‐isolation history of the forest patches surveyed. Both the proliferation of fast‐growing pioneer trees and the decline of hardwood trees found in our forest plots have profound consequences on the floristic composition, forest dynamics, carbon storage, and nutrient cycling in Amazonian forest fragments.