Polymer - metal organic framework (MOF) composite membranes are promising materials for gas separation and could be potentially applied within many industrial applications. However, key limitations of currently reported layered MOF-polymer composites are their lack of scalability and mechanical stability. A big challenge for synthesis of such composites is directing the growth of homogeneous, defect-free MOF crystal layers. Here, a membrane synthesis method allowing the formation of flexible, noncontinuous zeolitic imidazolate framework 8 (ZIF-8) – poly(ether sulfone) (PES) composite membranes is presented. The ZIF-8 growth is restricted to the PES pores by exploiting directed ZnO seed-nanoparticles. The seeding process is part of the membrane formation process itself and allows for specifically integrating ZnO within polymeric membranes enabling easy and scalable control of the MOF-crystal formation. During solvent casting and membrane formation, a phase separation process allows trapping ZnO seed-nanoparticles within bicontinuous PES pores. Because of ZnO serving in parallel as seed and zinc source, ZIF formation can be induced and controlled by adding only one solution containing the organic linker. This ZnO nanoparticle seeding technique enables a pore-specific in situ growth of small (<5 μm in diameter) ZIF-8 islands via solvothermal synthesis. This leads to mechanically flexible self-supporting ZIF-8 membranes exhibiting gas selectivities of 9.3 ± 3.1 (H2/CO2) and 11.5 ± 2.1 (H2/N2).
Introduction: Naturally rich in growth factors and cytokines (e.g.PDGF, VEGF), platelets play a pivotal role in wound healing.Platelet Rich Plasma (PRP) gel can be prepared from patient's own blood, has shown beneficial outcome in human and veterinary medicine (1) and can be used for cells and growth factors delivery (2-3).As biomaterial, PRP has poor mechanical properties and high degradation rate, reducing its stability and long-term effect.Here we investigate the mechanical properties and stability of PRP enriched with bioresorbable polymeric adjuvants.Methods: PRP was prepared as previously described [4].Briefly, Platelets concentrates from 3 donors (blood bank, Kantonspital Graubünden, Chur, CH) were centrifuged to obtain different concentrations of PRP: 10X, 15X and 50X higher than in the whole blood.Four polymeric adjuvants: Hyaluronic acid (HA), carboxymethyl cellulose (CMC), gelatin and polyvinyl alcohol (PVA) were added respectively to different PRP concentrations; and the jellification of PRP induced by addition of 2.5, 5 or 10U thrombin.Rheological (MCR, Anton Paar) and mechanical testing were performed, and the viscosity, elastic, viscous and Young moduli evaluated.Results: An addition of 5U thrombin independently of the PRP concentrations leads to more stable gels in the absence and the presence of adjuvants.Addition of polymeric adjuvants increases the elastic and viscous moduli of PRP 15X and 50X, although with higher increase with PVA and gelatin in comparison to HA and CMC.Conclusions: Here we show that the mechanical properties of PRP can be modulated by FDA approved polymeric adjuvants.Further experiments will assess their influence on the growth factors and cytokines release.
Resection of the thoracic wall is a common procedure in case of invasion by malignant tumors. Usually, Gore-Tex® is used to replace the defect, however, this material is inert and not degradable. Novel biodegradable materials are nowadays available that stimulate and modulate the regeneration process. Moreoever, stem cell seeding can be decisive for graft integration.
M. Zenobi-Wong and co-workers develop cell-seeded, ultraporous composite scaffolds for cartilage regeneration on page 3129. By means of cryoelectrospinning, ice crystals are co-deposited with the polymer. After sublimation, macropores are created which subsequently allow the infiltration of the electrospun membrane with a cell/hydrogel suspension. This procedure provides mechanical stability to the weak but chondrogenic alginate sulfate hydrogel.
Abstract Surgery of the chest wall is potentially required to cover large defects after removal of malignant tumours. Usually, inert and non-degradable Gore-Tex serves to replace the missing tissue. However, novel biodegradable materials combined with stem cells are available that stimulate the healing. Based on poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) and pure PLGA, a dual layer biodegradable hybrid nanocomposite was generated. Mouse adipose-derived stem cells were cultered on electrospun disks (ASCs of C57BL/6), and biomechanical tests were performed. The cell-seeded scaffolds were engrafted in C57BL/LY5.1 mice to serve as a chest wall substitute. Cell invasion into the bi-layered material, extent of CD45 + cells, inflammatory response, neo-vascularization and ECM composition were determined at 1 and 2 months post-surgery, respectively. The bi-layered hybrid nanocomposite was stable after a 2-week in vitro culture, in contrast to PLGA/aCaP without a PLGA layer. There was a complete biointegration and good vascularization in vivo . The presence of ASCs attracted more CD45 + cells (hematopoietic origin) compared to cell-free scaffolds. Inflammatory reaction was similar for both groups (±ASCs) at 8 weeks. A bi-layered hybrid nanocomposite fabricated of electrospun PLGA/aCaP and a reinforcing layer of pristine PLGA is an ideal scaffold for chest wall reconstruction. It is stable and allows a proper host tissue integration. If ASCs are seeded, they attract more CD45 + cells, supporting the regeneration process.
Epigenetic regulation underlies the robust changes in gene expression that occur during development. How precisely epigenetic enzymes contribute to development and differentiation processes is largely unclear. Here we show that one of the enzymes that removes the activating epigenetic mark of trimethylated lysine 4 on histone H3, lysine (K)-specific demethylase 5A (KDM5A), reinforces the effects of the retinoblastoma (RB) family of transcriptional repressors on differentiation. Global location analysis showed that KDM5A cooccupies a substantial portion of target genes with the E2F4 transcription factor. During ES cell differentiation, knockout of KDM5A resulted in derepression of multiple genomic loci that are targets of KDM5A, denoting a direct regulatory function. In terminally differentiated cells, common KDM5A and E2F4 gene targets were bound by the pRB-related protein p130, a DREAM complex component. KDM5A was recruited to the transcription start site regions independently of E2F4; however, it cooperated with E2F4 to promote a state of deepened repression at cell cycle genes during differentiation. These findings reveal a critical role of H3K4 demethylation by KDM5A in the transcriptional silencing of genes that are suppressed by RB family members in differentiated cells.
