Polyéthylène glycol | EPFL Graph Search

On appelle polyéthylène glycol ou PEG des polyéthers linéaires de masse molaire inférieure à fabriqués à partir de monomères d'éthylène glycol. Leurs propriétés hydrosolubles et liposolubles en font des produits utilisés dans un grand nombre d'industries (médical, cosmétique). On les appelle également macrogol dans le domaine médical. On a l'habitude d'indiquer la masse molaire moyenne du polymère après le nom, par exemple PEG-2000 (). Lorsque leur masse molaire est supérieure à , on les appelle plus communément poly(oxyde d'éthylène) ou poly(oxyéthylène). Usage comme solvant en chimie À température ambiante, le PEG est un liquide visqueux incolore lorsqu’il a une masse moléculaire inférieure à et un solide cireux lorsque sa masse moléculaire est supérieur à . Le PEG liquide est miscible en toute proportion avec l’eau tandis que le PEG solide est hautement soluble dans l’eau. Le PEG de faible masse moléculaire peut donc être utilisé comme solvant polymère, c'est-à-dir

Understanding effect of network structure of PolyEthylene Glycol Diacrylate hydrogels on cellular activities using bovine chondrocytes as a model system

Tojo Razafiarison

In this dissertation, we investigated the effect of poly(ethylene glycol) hydrogel network structures on various cellular activities such as proliferation and matrix production using chondrocytes as a cell source. We have used various methods to alter the network structure, which involves utilizing precursors with varying molecular weight and changing the degree of polymerization. The latter was achieved by varying initiator concentrations, and duration of polymerization time. PEG hydrogels constituting PEG precursors of molecular weights 3.4kDa, 6kDa, 10kDa and 20KDa were synthesized, characterized and subsequently tested for their effects on chondrocytes biosynthetic activity. The structural parameters of the hydrogel network that varied due to our experimental differences were determined. Specifically, the hydrogel structures were characterized in terms of swelling ratio, the molecular weight between crosslinks, the mesh size, and the pore size. Swelling ratio of the hydrogels decreased while gel content increased with longer UV exposure and higher photo-initiator concentration. High compressive modulus was observed with PEG 3.4kDa whereas PEG 20kDa exhibited high ultimate stress, which was 37 times higher than the other hydrogels. Cells in hydrogels with a lower MW (PEG3.4) showed higher proliferation and more ECM synthesis in comparison with high molecular weight PEG hydrogels. This could be attributed to the bigger pore size of the high molecular weight PEG hydrogels, which could result in loss of cells. However, the amount of DNA observed after week 4 normalized to day 1 revealed that cells in hydrogels with a higher MW showed a higher proliferation and the amount of ECM synthesized per cell was larger. Histology revealed that proteoglycans were more diffused in the matrix with higher MW, indicating the presence of higher pore size. Cellular aggregation was observed after 2 weeks in all the hydrogels except for the 3.4kDa hydrogels; the aggregation of cells in 20kDa was also very minimal. A low degree of polymerization led to a high proliferation rate during the first week followed by enhanced ECM production. Conversely, a high degree of polymerization led the cells to a greater amount of protein synthesis during the first week, followed by proliferation. While the cells behaved in different ways at early time points of the culture, at the end of 4 weeks, there was no significant difference between the number of cells, nor ECM production in different hydrogels. This study clearly shows that the network structure has a temporal effect on chondrocyte functions

2009

Muscle stem cell's in vitro bipolar niche

Adrien de Tonnac

In the domain of regenerative medicine research there are many fronts aimed at increasing our understanding of induced pluripotent, embryonic and adult stem cells. Recently a new front has appeared, stem cell niches, the microenvironment that is a crucial component in the regulation of stem cells. New in vitro platforms are continually being created to answer the multitude of biological questions that surround stem cell niches. The transition from in vitro to in vivo is a heavy setback in cellular research due to a huge gap between the two conditions, which can only be reduced if the in vitro conditions better mimic those found in vivo. This project has reduced the gap and has the potential to continue minimizing the differences between the two conditions in the field of muscle stem cell research. Through a combination of the forefront techniques in biological research, we were able to create a new innovative bioengineered platform, a bipolar hydrogel microenvironment. First, we took advantage of polyethylene glycol (PEG) hydrogels, which are highly hydrophilic polymer networks that have properties that mimic physiologic tissue, including high water content and low Young's Modulus. Microfabrication techniques allowed us to topographically pattern the hydrogel at micro-dimensions resembling the native cell environment. Utilizing microfluidics and micro-printing techniques, the three-dimensional hydrogel surface was also patterned with tethered niche proteins found in the in vivo muscle stem cell niche. The swelling properties of the PEG hydrogel were considered as an advantage and controlled to form niche gaps with physical properties that were tuned to correspond to those found in vivo. This new complex and controlled surface for cells to be cultured on is a tool, which will allow biologists to probe new questions and gain insight into the regulatory networks that control cell fate

2009

Life cycle assessment of bio-based synthetic fibers: the case of polyester substitutes

Tijana Ivanovic

Numerous studies have shown that the textile sector has a high fossil-fuel dependency, emits excessive amount of greenhouse gases and uses vast amount of water. Currently, polyester (fossil-based) makes up about a half of the industry's fiber production and the volumes are expected to increase. Polyester fiber is traditionally made out of polyethylene terephthalate (PET) polymer. In order to break from the fossil-fuel dependency, textile industry has the possibility to use alternative feedstock for the polyester by reverting to bio-sourcing – strategy where the product's carbon backbone comes partially or fully from the bio-based feedstock. The polyester fiber can be entirely substituted in its current uses by three such bio-based substitutes: bio-based PET fiber as a drop-in substitute (chemically identical to the fossil counterpart); polytrimethylene terephthalate (PTT) fiber as an intra-family substitute with properties comparable to PET fiber and nylon; and polylactic acid (PLA) fiber as a novel fiber without a fossil counterpart and with properties comparable to PET fiber. All of these fibers are produced from the homonymous polymers via melt spinning and their carbon backbone comes partially or entirely from bio-based feedstock. The environmental effects of this feedstock substitution have not been studied abundantly, in spite of the existing political will to prioritize bio-based products, e.g. as the European Green Deal does. This project therefore performs a comparative, cradle-to-gate life cycle assessment of the conventional polyester fiber and these substitutes taking into account state-of-the-art production process. In order to do so Life cycle inventories (LCI) were modelled for 6 different scenarios for bio-based PET, 2 for bio-based PTT and 1 for PLA and were based on public literature and ecoInvent data. Impact assessment was performed by applying two methods – Swiss Ecological Scarcity and European Environmental Footprint, representative of the Swiss environmental policy and of a more scientific classification of environmental and health impacts respectively. The study finds that all three bio-based fibers are produced from the first-generation feedstock (crops). Currently, only the partially bio-based PET and PTT polymers are commercialized, such that the prevailing monomer, purified terephthalic acid (PTA) remains fossil-based for both. Then, monoethylene glycol (MEG) is produced from sugarcane or corn and 1,3-propanediol (PDO) from corn respectively. PLA is a fully bio-based polymer, produced from corn. Bio-sourcing for polyester is found to offer a limited improvement in a small number of impacts (with negligible contribution to the overall score) while causing substantial additional environmental burdens elsewhere (per kg of fiber). Namely, none of the bio-based alternatives perform better than the fossil-based PET fiber on the overall score. However, the partially bio-based PTT fiber may be a viable substitute for nylon (based on lower overall score). In the absence of carbon crediting for bio-based feedstock, climate impacts are found to be worse for the alternatives than the conventional polyester. Eutrophication, acidification, water scarcity impacts and land use rise with fiber's bio-content and largely stem for the agricultural practices (up to 88%, 74%, 97% and 100% respectively). It was also seen that PTA necessitates more precise modeling to raise the certainty of conclusions for the respective fully bio-based PET and PTT scenarios. At this stage, bio-based alternatives have a worse environmental performance than fossil-based polyester. The environmental performance of the bio-based fibers may be increased with alternative feedstock options or with improved agricultural practices.

2020

Understanding effect of network structure of PolyEthylene Glycol Diacrylate hydrogels on cellular activities using bovine chondrocytes as a model system

Tojo Razafiarison

2009

Life cycle assessment of bio-based synthetic fibers: the case of polyester substitutes

Tijana Ivanovic

2020