Abstract
Visualizing polymer chain growth is always a hot topic for tailoring structure‐function properties in polymer chemistry. However, current characterization methods are limited in their ...ability to differentiate the degree of polymerization in real‐time without isolating the samples from the reaction vessel, let alone to detect insoluble polymers. Herein, a reliable relationship is established between polymer chain growth and fluorescence properties through polymerization induced emission. (TPE‐C2)
2
‐Te is used to realize in situ oxidative polymerization, leading to the aggregation of fluorophores. The relationship between polymerization degree of growing polytelluoxane (PTeO) and fluorescence intensity is constructed, enabling real‐time monitoring of the polymerization reaction. More importantly, this novel method can be further applied to the observation of the polymerization process for growing insoluble polymer via surface polymerization. Therefore, the development of visualization technology will open a new avenue for visualizing polymer chain growth in real‐time, regardless of polymer solubility.
With the rising prevalence of bone-related injuries, it is crucial to improve treatments for fractures and defects. Tissue engineering offers a promising solution in the form of injectable hydrogel ...scaffolds that can sustain the release of growth factors like bone morphogenetic protein-2 (BMP-2) for bone repair. Recently, we discovered that tetra-PEG hydrogels (Tetra gels) undergo gel-gel phase separation (GGPS) at low polymer content, resulting in hydrophobicity and tissue affinity. In this work, we examined the potential of a newer class of gel, the oligo-tetra-PEG gel (Oligo gel), as a growth factor-releasing scaffold. We investigated the extent of GGPS occurring in the two gels and assessed their ability to sustain BMP-2 release and osteogenic potential in a mouse calvarial defect model. The Oligo gel underwent a greater degree of GGPS than the Tetra gel, exhibiting higher turbidity, hydrophobicity, and pore formation. The Oligo gel demonstrated sustained protein or growth factor release over a 21-day period from protein release kinetics and osteogenic cell differentiation studies. Finally, BMP-2-loaded Oligo gels achieved complete regeneration of critical-sized calvarial defects within 28 days, significantly outperforming Tetra gels. The easy formulation, injectability, and capacity for sustained release makes the Oligo gel a promising candidate therapeutic biomaterial.
•Oligo gels undergo stronger gel-gel phase separation than conventional Tetra gels at low polymer content.•Strong gel-gel phase separation provides enhanced hydrophobicity and pore formation.•Oligo gels sustain protein or growth factor release based on release kinetics and cell differentiation assays in vitro.•Oligo gels sustain bone morphogenetic protein-2, BMP-2, release to enhance critical bone defect repair in mice in vivo.
Osteopontin (OPN), a secreted phosphoprotein, is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family of cell matrix proteins and participates in many biological ...activities. Studies have shown that OPN plays a role in bone metabolism and homeostasis. OPN not only is an important factor in neuron-mediated and endocrine-regulated bone mass, but also is involved in biological activities such as proliferation, migration, and adhesion of several bone-related cells, including bone marrow mesenchymal stem cells, hematopoietic stem cells, osteoclasts, and osteoblasts. OPN has been demonstrated to be closely related to the occurrence and development of many bone-related diseases, such as osteoporosis, rheumatoid arthritis, and osteosarcoma. As expected, the functions of OPN in the bone have become a research hotspot. In this article, we try to decipher the mechanism of OPN-regulated bone metabolism and bone diseases.
A diselenide bond, as a dynamic covalent bond, is a versatile tool to construct smart interfaces, which can respond to visible light. In this work, we used microcontact printing (μCP) to construct ...diselenide patterns on quartz substrates. Fluorescent patterns were obtained on the modified surfaces via the visible-light-induced diselenide metathesis reaction, which allowed the patterning process to be fast, dynamically erasable, and compatible with different fluorescent molecules including rhodamine B and boron-dipyrromethene (BODIPY) used in this work. A variety of analytical methods offered comprehensive evidence for the success of the printing of diselenides here. We further printed diselenide and disulfide intersecting stripes on one single quartz substrate layer by layer and introduced rhodamine B and BODIPY to obtain a multicolored pattern simultaneously. By taking advantage of their responsiveness to different wavelengths, the composite pattern of disulfides and diselenides could be erased by two stepwise stages. The fluorescent images of the modified substrate showed a good agreement with the pattern of the poly(dimethylsiloxane) (PDMS) stamp, indicating the methodology with a potential application for information storage.
Background and Purpose
Melatonin is a neurohormone involved in bone homeostasis. Melatonin directs bone remodelling and the role of bone marrow mesenchymal stem cells (BMMSCs) in the regulating ...melatonin‐mediated bone formation–resorption balance remains undefined.
Experimental Approach
Osteoporosis models were established and bone tissue and serum were collected to test the effects of melatonin on bone homeostasis. Melatonin receptors were knocked down, the NF‐κB signalling pathway and receptor activator of NF‐κB ligand (RANKL) expression were investigated. Communication between bone marrow mesenchymal stem cells and osteoclasts was detected with direct‐contact or indirect‐contact system.
Key Results
Bone loss and microstructure disorder in mice were reversed after melatonin treatment, as a result of anabolic and anti‐resorptive effects. In vitro, a physiological (low) concentration of melatonin promoted the bone marrow mesenchymal stem cells, osteogenic lineage commitment and extracellular mineralization but had no impact on extracellular matrix synthesis. After MT knockdown, especially MT2, the positive effects of melatonin on osteogenesis were attenuated. The canonical NF‐κB signalling pathway was the first discovered downstream signalling pathway after MT receptor activation and was found to be down‐regulated by melatonin during osteogenesis. Melatonin suppressed BMMSC‐mediated osteoclastogenesis by inhibiting RANKL production in BMMSCs and this effect only occurred when BMMSCs and osteoclast precursors were co‐cultured in an indirect‐contact manner.
Conclusion and Implications
Our work suggests that melatonin plays a crucial role in bone balance, significantly accelerates the osteogenic differentiation of bone marrow mesenchymal stem cells by suppressing the MT2‐dependent NF‐κB signalling pathway, and down‐regulates osteoclastogenesis via RANKL paracrine secretion.
Significant progresses have been made in tellurium-containing polymers over the past decades. Just like other heteroatom-containing polymers, tellurium-containing polymers exhibit several unique ...properties and promising applications. However, unlike elements such as boron, silicon, sulfur and so on, tellurium in polymers remains a fresh perspective for many researchers. In this review, we shall illustrate the diversification of tellurium-containing polymers and their respective synthetic methods. Besides, the properties of tellurium-containing polymers including redox-responsiveness, coordination properties, optoelectronic properties and so on will be discussed in detail. Furthermore, the performances of tellurium-containing polymers in biomedicine, optoelectronic materials and some recent advanced fields will be demonstrated. Overall, by reviewing the recent developments and trends of tellurium-containing polymers, we wish to popularize the concepts and it is anticipated that this review could function as an easy-to-read and comprehensive handbook to provide some inspirations and possible scientific supports for researchers in the field of chemistry and materials.
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Melatonin is a neurohormone involved in bone homeostasis. Melatonin directs bone remodelling and the role of bone marrow mesenchymal stem cells (BMMSCs) in the regulating melatonin-mediated bone ...formation-resorption balance remains undefined.
Osteoporosis models were established and bone tissue and serum were collected to test the effects of melatonin on bone homeostasis. Melatonin receptors were knocked down, the NF-κB signalling pathway and receptor activator of NF-κB ligand (RANKL) expression were investigated. Communication between bone marrow mesenchymal stem cells and osteoclasts was detected with direct-contact or indirect-contact system.
Bone loss and microstructure disorder in mice were reversed after melatonin treatment, as a result of anabolic and anti-resorptive effects. In vitro, a physiological (low) concentration of melatonin promoted the bone marrow mesenchymal stem cells, osteogenic lineage commitment and extracellular mineralization but had no impact on extracellular matrix synthesis. After MT knockdown, especially MT
, the positive effects of melatonin on osteogenesis were attenuated. The canonical NF-κB signalling pathway was the first discovered downstream signalling pathway after MT receptor activation and was found to be down-regulated by melatonin during osteogenesis. Melatonin suppressed BMMSC-mediated osteoclastogenesis by inhibiting RANKL production in BMMSCs and this effect only occurred when BMMSCs and osteoclast precursors were co-cultured in an indirect-contact manner.
Our work suggests that melatonin plays a crucial role in bone balance, significantly accelerates the osteogenic differentiation of bone marrow mesenchymal stem cells by suppressing the MT
-dependent NF-κB signalling pathway, and down-regulates osteoclastogenesis via RANKL paracrine secretion.
Four-armed poly(ethylene glycol) (PEG)s are essential hydrophilic polymers extensively utilized to prepare PEG hydrogels, which are valuable tissue scaffolds. When hydrogels are used in vivo, they ...eventually dissociate due to cleavage of the backbone structure. When the cleavage occurs at the cross-linking point, the hydrogel elutes as an original polymer unit, i.e., four-armed PEG. Although four-armed PEGs have been utilized as subcutaneously implanted biomaterials, the diffusion, biodistribution, and clearance behavior of four-armed PEG from the skin are not fully understood. This paper investigates time-wise diffusion from the skin, biodistribution to distant organs, and clearance of fluorescence-labeled four-armed PEGs with molecular weight (M w) ranging from 5–40 kg/mol subcutaneously injected into the back of mice. Changes over time indicated that the fate of subcutaneously injected PEGs is M w-dependent. Four-armed PEGs with M w ≤ 10 kg/mol gradually diffused to deep adipose tissue beneath the injection site and distributed dominantly to distant organs, such as the kidney. PEGs with M w ≥ 20 kg/mol stagnated in the skin and deep adipose tissue and were mainly delivered to the heart, lung, and liver. The fundamental understanding of the M w-dependent behavior of four-armed PEGs is beneficial for preparing biomaterials using PEGs, providing a reference in the field of tissue engineering.
The flange joint is an important connection in steel tube structures. In this paper, 11 groups of flange joint tests were conducted to investigate the influences of tube diameter, flange plate ...thickness, the distance from the bolt to the tube centroid, bolt numbers and material strength on the mechanical behavior. One of two failure modes in tests is that the excessive plastic deformation on the flange plate makes the flange plate lose the bearing capacity; the other is that the steel tube yield makes the joints fail. The results show that the calculating method for flange joint in Chinese design code is so safe that amplifying the calculating results of the code by 1.2 times would be closer to the bearing capacity of specimens. For a flange joint with different tube diameters, thickening the flange plate of thinner tube or thinning the flange plate of another tube are effective to ensure the deformations on both sides of the flange plates are equivalent. The ratio of the bearing capacity of the steel tube to that of flange plate should be greater than 1.7. And the thickness of the flange plate should be thicker than 14mm to reduce the deformation caused by cutting, drilling and welding during manufacturing.
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