Alteration of 3D Matrix Stiffness Regulates Viscoelasticity of Human Mesenchymal Stem Cells

Human mesenchymal stem cells (hMSCs) possess potential of bone formation and were proposed as ideal material against osteoporosis. Although interrogation of directing effect on lineage specification by physical cues has been proposed, how mechanical stimulation impacts intracellular viscoelasticity during osteogenesis remained enigmatic. Cyto-friendly 3D matrix was prepared with polyacrylamide and conjugated fibronectin. The hMSCs were injected with fluorescent beads and chemically-induced toward osteogenesis. The mechanical properties were assessed using video particle tracking microrheology. Inverted epifluorescence microscope was exploited to capture the Brownian trajectory of hMSCs. Mean square displacement was calculated and transformed into intracellular viscoelasticity. Two different stiffness of microspheres (12 kPa, 1 kPa) were established. A total of 45 cells were assessed. hMSCs possessed equivalent mechanical traits initially in the first week, while cells cultured in rigid matrix displayed significant elevation over elastic (G′) and viscous moduli (G″) on day 7 (p < 0.01) and 14 (p < 0.01). However, after two weeks, soft niches no longer stiffened hMSCs, whereas the effect by rigid substrates was consistently during the entire differentiation course. Stiffness of matrix impacted the viscoelasticity of hMSCs. Detailed recognition of how microenvironment impacts mechanical properties and differentiation of hMSCs will facilitate the advancement of tissue engineering and regenerative medicine.

Fabrication of Soft-Oxometalates {Mo132} Clusters With Novel Azobenzene Surfactants: Size Control by Micelles and Light

Soft-oxometalates (SOMs) are colloid suspensions of superstructured assemblies of polyoxometalates (POMs) and are found to be very effective photo-catalysts in a number of chemical reactions. The stabilization of SOMs generally requires legends or stabilizers, e.g., polymers and surfactants. In this paper, a light responsive azobenzene surfactant, C10AZOC2N3, was developed and used to stable {Mo132} SOMs. Various techniques such as Dynamic light scattering, TEM, UV-Vis spectra and cyclic voltammetry were employed to characterize the experimental results. The outstanding structure-directing effect of surfactant self-assembly micelles in solution on inorganic counter-anions was demonstrated. Different amount of cyclohexane was solubilized into C10AZOC2N3 micelles to successfully control the size of {Mo132} SOMs cluster. Furthermore, the clusters exposed to UV light for a certain time can be served as a second trigger to control the size of SOMs due to the trans-cis conformation transition of surfactant molecules. The redox potentials of C10AZOC2N3-{Mo132} SOMs were investigated as the cluster size varied. Interestingly, the redox potential of {Mo132} was not affected by the cluster size, indicating that the presence of surfactant did not change the main function of {Mo132} as an electrochemical catalyst, but merely assisted in the size control of SOM aggregation.

Synthesis, crystallization and Hirshfeld surface analysis of transition metal carboxylate pentapyridines

Single X-ray diffraction studies and Hirshfeld surface analysis of three transition metal coordination complexes of Py5Me2COOH reveals the ligand's diverse coordination utility and the structure directing effect of the carboxylate moiety.

Structure-directing study of 1-methylimidazolium-based dication with tetramethylene as spacer length in the synthesis of microporous silicoaluminophosphates

In this work we study the structure-directing effect of 1-methylimidazolium-based dications with four methylene units as spacer length (4BI), as Organic Structure-Directing Agent (OSDA) in the synthesis of silicoaluminophosphate (SAPO)...

A chiral uranyl–Kemp’s tricarboxylate cubic framework: structure-directing effect of counterions with three-fold rotational symmetry

In the presence of PPh3Me+ cations, Kemp’s tricarboxylate (kta3–) complexes the uranyl cation to give [PPh3Me][UO2(kta)] (1), a triperiodic framework with cubic symmetry and srs topology. The cation is held...

Structure directing effect of aqueous alkali metal ion (Li+, Na+ and K+) clusters on polyoxoanion configuration in vanadium-molybdenum polyoxometalate solid solutions

In structural chemistry context, the dense packing and the structural directing agent (SDA) often play crucial role in the formation of desired crystal structure. Herein, we present two isomorphous decavanadate-type...

Molecular nanoparticles of cerium dioxide: structure-directing effect of halide ions

The use of halide ions in the synthesis of Ce/O clusters diverts the reaction to two halide-containing products: Cl− gives a new Ce20 nuclearity with both a high 1 : 1 Ce3+ : Ce4+ ratio and a high percentage of (100) facet coverage, whereas F− gives a known Ce6 nuclearity.