Carbon quantum dots (CQDs) were characterized and their synthesis optimized extensively over recent years. It is becoming more and more important to develop synthesis solutions for CQDs applications ...to allow simple and cheap applications with composite materials. Here, we present a one-pot CQDs reaction in an aqueous polyvinyl alcohol (PVA) solution and the synthesis of transparent UV protection films. The synthesis solution was tuned in a way that transparent UV-protection films cast from unpurified CQDs-PVA solutions could be obtained without the need of yield consuming purification steps. Measuring the impact of varying PVA, branched polyethylene imine (b-PEI), and citric acid (CA) concentrations on the solution's and film's UV/Vis transmission and absorbance allowed elucidating important factors influencing the solution to film property transition. Applying CQDs-PVA films on commercially available PET bottle films resulted in high transparency of the composite film in the visible range (>80%) and UV absorption of over 90%. Lastly, our CQDs-PVA film performed stable UV-blocking and did not show any bleaching effects over several days of UV-exposure.
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).
We present an improved synthesis route to hollow silica particles starting from tetramethyl orthosilicate (TMOS) instead of the traditionally used ethyl ester. The silica was first deposited onto ...polystyrene (PS) particles that were later removed. The here introduced, apparently minor modification in synthesis, however, allowed for a very high purity material. The improved, low density hollow silica particles were successfully implemented into polymer films and permitted maintaining optical transparency while significantly improving the heat barrier properties of the composite. Mechanistic investigations revealed the dominant role of here used methanol as a cosolvent and its role in controlling the hydrolysis rate of the silicic ester, and subsequent formation of hollow silica particles. Systematic experiments using various reaction parameters revealed a transition between regions of inhomogeneous material production at fast hydrolysis rate and reliable silica deposition on the surface of PS as a core–shell structured particle. The shell-thickness was controlled from 6.2 to 17.4 nm by increasing TMOS concentration and the diameter from 95 to 430 nm through use of the different sizes of PS particles. Hollow silica particle with the shell-thickness about 6.2 nm displayed a high light transmittance intensity up to 95% at 680 nm (length of light path ∼ 1 cm). Polyethersulfone (PES)/hollow silica composite films (35 ± 5 μm thick) exhibited a much lower thermal conductivity (0.03 ± 0.005 W m·K–1) than pure polymer films. This indicates that the prepared hollow silica is able to be used for cost and energy effective optical devices requiring thermal insulation.
In reverse genetics, a gene's function is elucidated through targeted modifications in the coding region or associated DNA cis-regulatory elements. To this purpose, recently developed customizable ...transcription activator-like effector nucleases (TALENs) have proven an invaluable tool, allowing introduction of double-strand breaks at predetermined sites in the genome. Here we describe a practical and efficient method for the targeted genome engineering in Drosophila. We demonstrate TALEN-mediated targeted gene integration and efficient identification of mutant flies using a traceable marker phenotype. Furthermore, we developed an easy TALEN assembly (easyT) method relying on simultaneous reactions of DNA Bae I digestion and ligation, enabling construction of complete TALENs from a monomer unit library in a single day. Taken together, our strategy with easyT and TALEN-plasmid microinjection simplifies mutant generation and enables isolation of desired mutant fly lines in the F1 generation.
A true biomimetic of the cartilage extracellular matrix (ECM) could greatly contribute to our ability to regenerate this tissue in a mechanically demanding, often inflamed environment. Articular ...cartilage is a composite tissue made of cells and fibrillar proteins embedded in a hydrophilic polymeric meshwork. Here, a polyanionic functionalized alginate is used to mimic the glycosaminoglycan component of the native ECM. To create the fibrillar component, cryoelectrospinning of poly(ε‐caprolactone) on a −78 °C mandrel, subsequently treated by O2 plasma, is used to create a stable, ultraporous and hydrophillic nanofiber network. In this study, cell‐laden, fiber‐reinforced composite scaffolds thicker than 1.5 mm can be created by infiltrating a chondrocyte/alginate solution into the fiber mesh, which is then physically cross‐linked. The fibrillar component significantly reinforces the chondroinductive, but mechanically weak sulfated alginate hydrogels. This allows the production of a glycosaminoglycan‐ and collagen type II‐rich matrix by the chondrocytes as well as survival of the composite in vivo. To further enhance the system, the electrospun component is loaded with dexamethasone, which protected the cells from an IL‐1β‐mediated inflammatory insult.
Cryoelectrospinning is used to create a stable, ultraporous nanofiber network. The electrospun scaffold can be drug‐loaded and embedded in a polyanionic alginate hydrogel. The fibrillar component significantly reinforces the chondroinductive but weak hydrogel, creating a mimic of the cartilage extracellular matrix which is stable in vivo.
A novel solvent-evaporation-based process that exploits template-particle stabilized bicontinuous emulsions for the formation of previously unreached membrane morphologies is reported in this ...article. Porous membranes have a wide range of applications spanning from water filtration, pharmaceutical purification, and battery separators to scaffolds for tissue engineering. Different situations require different membrane morphologies including various pore sizes and pore gradients. However, most of the previously reported membrane preparation procedures are restricted to specific morphologies and morphology alterations require an extensive optimization process. The tertiary system presented in this article, which consists of a poly(ether sulfone)/dimethylacetamide (PES/DMAc) solution, glycerol, and ZnO-nanoparticles, allows simple and exact tuning of pore diameters ranging from sub-20 nm, up to 100 nm. At the same time, the pore size gradient is controlled from 0 up to 840%/μm yielding extreme asymmetry. In addition to structural analysis, water flux rates of over 5600 L m–2 h–1 are measured for membranes retaining 45 nm silica beads.
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.
Malignant neoplasms infiltrating the chest wall often requires resection of the thoracic wall. To replace the defect, Gore-Tex® is usually employed as the gold standard material, however, Gore-Tex® ...is inert and not degradable. Novel materials are nowadays available which allow a full bio-integration due to their non-toxic degradability. Additionally, stem cell seeding has the capacity to reduce inflammatory response towards such grafts, thus integrating it better into the host organism.
Chemical supplementation of culture media to induce differentiation of adult stem cells seeded on a scaffold may mask other differentiation triggers such as scaffold stiffness, chemical composition ...or mechanical stimulation. However, stem cells can be differentiated towards osteoblasts without any supplementation given an appropriate osteogenic scaffold and an adequate mechanical stimulation.
Electrospun meshes of poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) in a weight ratio of 60:40 were seeded with human adipose-derived stem cells (ASCs) and cultured in DMEM. After two weeks of static cultivation, they were either further cultivated statically for another two weeks (group 1), or placed in a Bose® bioreactor with a flow rate per area of 0.16 mL cm−2 min1 (group 2). Furthermore, group 3 was also cultivated under perfusion, however, with an additional uniaxial cyclic compression. Stiffness of the scaffolds was assessed as a function of time. After a total of four weeks, minimum stem cell criteria markers as well as typical markers for osteogenesis, endothelial cell differentiation, adipogenesis and chondrogenesis were analyzed by quantitative real-time PCR, cell distribution within the scaffolds by histology and protein expression by immunohistochemistry.
Dynamic conditions (perfusion ± uniaxial cyclic compression) significantly upregulated gene and protein expression of PPAR-γ-2 compared to static cultivation, while osteogenic markers were slightly downregulated. However, the compression in the perfusion bioreactor favored osteogenesis compared to mere perfusion as indicated by upregulation of ALP, Runx2 and collagen I. This behavior was not only attributed to the compressive load, but also to the significant increase in stiffness of the scaffold. Furthermore, CD105 was significantly upregulated under compression.
Although an osteogenic electrospun composite material with an organic (PLGA) and an inorganic phase (aCaP nanoparticles) was used as scaffold, the dynamic cultivation as realized by either perfusion alone or an additional compression did not upregulate typical osteogenic genes when compared to static cultivation. In contrast, there was a significant upregulation of the adipogenic gene PPAR-γ-2. However, this anti-osteogenic starting point evoked by mere perfusion was partially reversed by an additional compression. Our findings exemplify that bone tissue engineering using adult stem cells should consider any other differentiations that may be triggered and overwhelm the desired differentiation, although experimental conditions theoretically provide cues to achieve it – like an osteogenic scaffold and mechanical stimulation.
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