-
Coble Ellison posted an update 12 hours, 44 minutes ago
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.Wrinkling skin layers on pre-strained polymer sheets has drawn significant interest as a method to create reconfigurable surface patterns. Compared to widely studied metal or silica films, softer polymer skins are more tolerant to crack formation when the surface topography is tuned under applied strain. This Mini-review discusses recent progress in mechano-responsive wrinkles based on polymer skin materials. Control over the skin thickness with nanometer accuracy allows for tuning of the wrinkle wavelength and orientation over length scales from nanometer to micrometer regimes. Furthermore, soft skin layers enable texturing of two-dimensional electronic materials with programmable feature sizes and structural hierarchy because of the conformal adhesion to the substrates. Soft skin systems open prospects to tailor a range of surface properties via external stimuli important for applications such as smart windows, microfluidics, and nanoelectronics.Understanding the role of non-covalent interactions that dictate and fine-tune the direction of self-assembly of functional molecules is crucial for developing stimuli responsive materials. Herein, we systematically designed and synthesized viologen derivatives with hydrophobic dodecyl chains and alkyl carboxylic acid functionalities. The complementary electronic and electrostatic counterpart of viologens was chosen as pyranine. Viologens comprising of a hydrophobic dodecyl chain on one terminal and hydrogen bonding alkyl carboxylic acid on the other (V1 and V2) underwent aggregation to a varying extent upon interaction with pyranine. The length of the alkyl carboxylic acid had a greater impact on the nature and morphology of the aggregates. read more Control molecules (V3 and V4) in which 4,4′-bipyridine was symmetrically quaternized with alkyl carboxylic acids did not aggregate upon interaction with pyranine. The delicate balance existing between the hydrophobicity of the dodecyl chains and the intermolecular hydrogen bonding interaction between the alkyl carboxylic acid groups in V1 or V2 of the corresponding charge transfer (CT) complexes was instrumental in driving the aggregation. The CT aggregates of [V1-Pyr] and [V2-Pyr] exhibited excellent stability in water which disaggregated at physiological pH. We emphasize on the importance of synergy between hydrophobic and hydrogen bonding interactions in reinforcing each other to drive the supramolecular aggregation of the CT complexes. Such pH dependent CT aggregates are of importance as scaffolds in pH controlled drug release. In the present study, the CT aggregates were evaluated for adenosine nucleotide recognition in water; [V1-Pyr] and [V2-Pyr] exhibited selective response towards adenosine monophosphate via deprotonation induced dissolution of aggregates in water leading to emission enhancement.Homochiral metal-organic frameworks (HMOFs) have garnered considerable attention due to their extrachiral properties and broad application for chiral recognition. However, assembling a pair of high-quality chiral MOFs for sensing enantiomers precisely is a formidable challenge because of the complicated chiral environment and uncontrollable coordinated conditions. Herein, one pair of homochiral UiO-66 analogues, S-1 (l-AP@UiO-66-(COOH)2) and R-1 (d-AP@UiO-66-(COOH)2), are reported for chiral recognition. They were fabricated via a condensation reaction between the carboxyl groups of UiO-66-(COOH)2 and amino groups of l/d-amino propanol (l/d-AP). These novel fluorescent probes exhibited highly enantioselective fluorescence enhancement towards l/d-phenylalaninol (l/d-PA). For example, when S-1 and R-1 were treated with l-PA or d-PA, they displayed different fluorescence responses the enantiomeric fluorescence enhancement ratio (ef) was 2.51 and 0.41 for S-1 and R-1, respectively. Hence, a visible difference in fluorescence enhancement for l-PA and d-PA and excellent enantioselective behavior between S-1 and l-PA (or R-1 and d-PA) was displayed. Measurements of fluorescence lifetime, powder X-ray diffraction, molecular-dynamic simulations and Benesi-Hildebrand plots were employed to determine the observed high enantioselectivity for l/d-PA. In brief, we found that two post-modified HMOFs, S-1 and R-1, were outstanding enantioselective sensors for detecting l-PA and d-PA. They had a prominent difference in ef and remarkable enantioselectivity factor α and ΔΔG based on steric hindrance and stereochemical difference.Mineral transformations of the gypsum-anhydrite system under microwave heating have been studied using in situ dielectric thermal analysis (MW-DETA) and Raman spectroscopy simultaneously. The dielectric properties of samples that were measured under microwave heating provided thorough information about the dynamics of the gypsum-anhydrite system transformations and its significance from the mineralogical point of view. In particular, the MW-DETA technique revealed a new intermediate phase with a γ-anhydrite structure. This phase corresponds to the soluble stage of γ-anhydrite, and it is characterized by a high ionic charge inside the crystal channels. The complete sequence is gypsum → 0.625-subhydrate → bassanite → hydro γ-anhydrite → anhydrous γ-anhydrite → β-anhydrite. The transformations were also assessed using DSC, TG, DTA and dielectric measurements at room temperature, as well as other techniques including X-ray powder diffraction (XRPD) and high-temperature XRD (HT-XRD). Correlations between the dielectric properties with temperature and the rest of the techniques elucidated the heating mechanisms of this material under microwave energy during the different stages.