Nanohydroxyapatite (HA) synthesized by biomimetic strategy is a promising nanomaterial as bone substitute due to its physicochemical features similar to those of natural nanocrystal in bone tissue. Inspired by mussel adhesive chemistry, a novel nano-HA was synthesized in our work by employing polydopamine (pDA) as template under weak alkaline condition. Subsequently, the as-prepared pDA-templated HA (tHA) was introduced into polycaprolactone (PCL) matrix via coelectrospinning, and a bioactive tHA/PCL composite nanofiber scaffold was developed targeted at bone regeneration application. Our research showed that tHA reinforced PCL composite nanofibers exhibited favorable cytocompatibility at given concentration of tHA (0-10 w.t%). Compared to pure PCL and traditional nano-HA enriched PCL (HA/PCL) composite nanofibers, enhanced cell adhesion, spreading and proliferation of human mesenchymal stem cells (hMSCs) were observed on tHA/PCL composite nanofibers on account of the contribution of pDA present in tHA. More importantly, tHA nanoparticles exposed on the surface of composite nanofibers could further promote osteogenesis of hMSCs in vitro even in the absence of osteogenesis soluble inducing factors when compared to traditional HA/PCL scaffolds, which was supported by in vivo test as well according to the histological analysis. Overall, our study demonstrated that the developed tHA/PCL composite nanofibers with enhanced cytocompatibility and osteogenic capacity hold great potential as scaffolds for bone tissue engineering.
current density of 10 mA cm −2 , which need further improvement. [13,15,16] As an important rare earth oxide, Ce oxide owns unique properties of 4f electrons, good ionic conductivity as well as high oxygen storage capacity. [17][18][19] Thus, Ce oxide has potential for synergistically improving the OER activities by modulating electron structure and enhancing charge transfer and energy conversion efficiency. [20][21][22] Recently, Jaramillo et al. [20] reported Ce-doped NiO x supported on high-conductivity Au substrate as an OER electrocatalyst, which shows improved activity with an overpotential of 271 mV at 10 mA cm −2 compared with that of NiO x . By using density functional theory (DFT) calculations, they demonstrated that Ce doping could regulate the electronic structure and optimize energetics of NiO x for OER intermediates, thus improving its intrinsic OER activity. Apart from Ce doping, embedding Ce oxide into host catalysts has been demonstrated to be an efficient strategy to improve the OER performance. For example, Gao et al. [23] prepared Ce oxide clusters embedded into NiO (Ce-NiO-E) through solgel followed by high-temperature annealing. The embedded Ce oxide could bring large specific surface area, rich surface defects, high oxygen adsorption capacity, and optimized electronic structure, contributing to superior OER performance of Ce-NiO-E. In addition, the seamless integration of active phase into the current collector with high conductivity and large electrochemical surface area was extremely desired, which can provide more accessible active sites and faster charge transfer kinetic to reduce the Schottky barriers at catalyst/electrode interfaces. [24,25] Considering that NiSe 2 owns inherently high conductivity and good chemical stability across a wide pH range, [26,27] it can act as a good support. Therefore, the simultaneous integration of Ce doping and Ce(OH) 3 embedding into Ni(OH) 2 on the NiSe 2 support is highly expected to fully exert the merits of each component and thus to systematically boost the OER performance. It is noteworthy that Ce-modified catalyst with both Ce doping and Ce(OH) 3 embedding has not been reported before. Also, no relevant studies have focused on a systematic and deep understanding of the roles of Ce doping and Ce(OH) 3 embedding in the enhanced OER activities.Based on the above considerations, a self-supported electrode of nanoflower-like Ce-modified Ni(OH) 2 grown on high-conductivity NiSe 2 octahedra nanoparticles (denoted Exploring and developing high-efficiency electrocatalysts for the oxygen evolution reaction (OER) is desirable yet challenging for cost-effective transformation of renewable electricity into fuels and chemicals. Herein, a self-supported electrode of nanoflower-like Ce-modified Ni(OH) 2 grown on high-conductivity NiSe 2 octahedra nanoparticles is designed and fabricated for the first time. By virtue of i) the high conductivity of the NiSe 2 support for favorable electron transfer; ii) the open porous structure from the nanoflower-like Ce-modifi...
The design and development of functional biomimetic systems for programmed stem cell response is a field of topical interest. To mimic bone extracellular matrix, we present an innovative strategy for constructing drug-loaded composite nanofibrous scaffolds in this study, which could integrate multiple cues from calcium phosphate mineral, bioactive molecule, and highly ordered fiber topography for the control of stem cell fate. Briefly, inspired by mussel adhesion mechanism, a polydopamine (pDA)-templated nanohydroxyapatite (tHA) was synthesized and then surface-functionalized with bone morphogenetic protein-7-derived peptides via catechol chemistry. Afterward, the resulting peptide-loaded tHA (tHA/pep) particles were blended with polycaprolactone (PCL) solution to fabricate electrospun hybrid nanofibers with random and aligned orientation. Our research demonstrated that the bioactivity of grafted peptides was retained in composite nanofibers. Compared to controls, PCL-tHA/pep composite nanofibers showed improved cytocompatibility. Moreover, the incorporated tHA/pep particles in nanofibers could further facilitate osteogenic differentiation potential of human mesenchymal stem cells (hMSCs). More importantly, the aligned PCL-tHA/pep composite nanofibers showed more osteogenic activity than did randomly oriented counterparts, even under nonosteoinductive conditions, indicating excellent performance of biomimetic design in cell fate decision. After in vivo implantation, the PCL-tHA/pep composite nanofibers with highly ordered structure could significantly promote the regeneration of lamellar-like bones in a rat calvarial critical-sized defect. Accordingly, the presented strategy in our work could be applied for a wide range of potential applications in not only bone regeneration application but also pharmaceutical science.
hNRAGE, a neurotrophin receptor p75 interacting MAGE homologue, is cloned from a human placenta cDNA library. hNRAGE can inhibit the colony formation of and arrest cell proliferation at the G1/S and G2/M stages in hNRAGE overexpressing cells. Interestingly, hNRAGE also increases the p53 protein level as well as its phosphorylation (Ser392). Further studies demonstrated that hNRAGE does not a¡ect the proliferation of mouse p533 3/3 3 embryonic ¢broblasts, suggesting that p53 function is required for hNRAGE induced cell cycle arrest. Moreover, the cell cycle inhibiting protein p21 WAF is induced by hNRAGE in a p53 dependent manner. The data provide original evidence that hNRAGE arrests cell growth through a p53 dependent pathway. ß 2004 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.
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