Oil Induced Swelling in Thermoelastic Materials

The purpose of this thesis was to find a new gasket material to be used in frequency converters manufactured by ABB. The new material has to comply to RoHS directive, because this material is going to replace the currently used material, which is not RoHS compliant. The material is going to be used in conditions, where it may be subjected to chemicals and especially oils, so it should have a good resistance to both. In addition to finding the material, this thesis considers factors affecting elastomer’s swelling in oil. Some requirements were set for the gasket material. The hardness of the material should not be over 60 Shore A and its tear strength should not be less than 23 kN/m. The material should also have a fire classification minimum of V1. The most important criterion was the oil resistance. Gasket material should not swell more than 25 percent from its initial volume when immersed in oil. The literature part of this thesis consists of introducing four material groups which have such properties which are required from the gasket material and considers those properties. These four groups are thermoplastic polyurethanes, styrene-ethylene-butylene-styrene, thermoplastic vulcanizate elastomers and co-polyester based elasto-mers. The literature part also discusses the factors which help estimate the amount of swelling based on the structure of the thermoplastic elastomer. The experiment part of this thesis introduces immersion tests which have been used to determine oil resistance of the test materials. Six materials were tested, the names of the materials are confidential, they are coded to be Materials A, B, C, D, E and F. From these results, the best suited material for the new gasket material was elected. Also from the results, it was possible to determine dependence of swelling on volume, area, vo-lume/area ratio and density of the sample. One suitable material was found in addition to a few others that require more test-ing. The only geometrical factor found to contribute materials swelling was volume/area ratio. Once the graph is made for a certain material, it helps to predict the swelling of a sample with a certain volume/area ratio made from the same material. The tests made for this thesis will continue after this thesis is completed. Some new sample geometries and new materials will be tested. /Kir1

3D-biotulostus - bioteknologian uudet tuulet lääketieteen käyttöön

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Effect of cell culture media on extracellular vesicle secretion from mesenchymal stromal cells and neurons

Publisher Copyright: © 2022Background: Extracellular vesicles (EVs) secreted by neuronal cells in vitro have promising therapeutic potential for brain diseases. Optimization of cell culture conditions and methodologies for high-yield isolation of EVs for preclinical and clinical applications, however, remains a challenge. Objective: To probe the cell culture conditions required for optimal EV secretion by human-derived neuronal cells. Methodology: First, we optimized the EV purification protocol using human mesenchymal stromal cell (MSC) cultures. Next, we compared the effects of different variables in human pluripotent stem cell (hPSC)-derived neuronal cultures on EV secretion. EVs were isolated from cell conditioned media (CCM) and control media with no cells (NCC) using ultrafiltration combined with size-exclusion chromatography (SEC). The hPSC neurons were cultured in 2 different media from which EVs were collected at 2 maturation time-points (days 46 and 60). Stimulation with 25 mM KCl was also evaluated as an activator of EV secretion by neurons. The collected SEC fractions were analyzed by nanoparticle tracking analysis (NTA), protein concentration assay, and blinded transmission electron microscopy (TEM). Results: A peak in cup-shaped particles was observed in SEC fractions 7–10 of MSC samples, but not corresponding media controls, indicating successful isolation of EVs. Culture medium had no significant effect on EV yield. The EV yield of the samples did not differ significantly according to the culture media used or the cell maturation time-points. Stimulation of neurons with KCl for 3 h reduced rather than increased the EV yield. Conclusions: We demonstrated successful EV isolation from MSC and neuronal cells using an ultrafiltration-SEC method. The EV yield from MSC and neuronal cultures exhibited a large batch effect, apparently related to the culture media used, highlighting the importance of including NCC as a negative control in all cell culture experiments.Peer reviewe

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Teema : elinsiirro

Perspectives for Clinical Translation of Adipose Stromal/Stem Cells

Adipose stromal/stem cells (ASCs) are an ideal cell type for regenerative medicine applications, as they can easily be harvested from adipose tissue in large quantities. ASCs have excellent proliferation, differentiation, and immunoregulatory capacities that have been demonstrated in numerous studies. Great interest and investment have been placed in efforts to exploit the allogeneic use and immunomodulatory and anti-inflammatory effects of ASCs. However, bridging the gap between in vitro and in vivo studies and moving into clinical practice remain a challenge. For the clinical translation of ASCs, several issues must be considered, including how to characterise such a heterogenic cell population and how to ensure their safety and efficacy. This review explores the different phases of in vitro and preclinical ASC characterisation and describes the development of appropriate potency assays. In addition, good manufacturing practice requirements are discussed, and cell-based medicinal products holding marketing authorisation in the European Union are reviewed. Moreover, the current status of clinical trials applying ASCs and the patent landscape in the field of ASC research are presented. Overall, this review highlights the applicability of ASCs for clinical cell therapies and discusses their potential.Peer reviewe

Effects of Macromolecular Crowding on Human Adipose Stem Cell Culture in Fetal Bovine Serum, Human Serum, and Defined Xeno-Free/Serum-Free Conditions

Microenvironment plays an important role for stem cell proliferation and differentiation. Macromolecular crowding (MMC) was recently shown to assist stem cells in forming their own matrix microenvironment in vitro. The ability of MMC to support adipose stem cell (ASC) proliferation, metabolism, and multilineage differentiation was studied under different conditions: fetal bovine serum- (FBS-) and human serum- (HS-) based media and xeno- and serum-free (XF/SF) media. Furthermore, the immunophenotype of ASCs under MMC was evaluated. The proliferative capacity of ASCs under MMC was attenuated in each condition. However, osteogenic differentiation was enhanced under MMC, shown by increased deposition of mineralized matrix in FBS and HS cultures. Likewise, significantly greater lipid droplet accumulation and increased collagen IV deposition indicated enhanced adipogenesis under MMC in FBS and HS cultures. In contrast, chondrogenic differentiation was attenuated in ASCs expanded under MMC. The ASC immunophenotype was maintained under MMC with significantly higher expression of CD54. However, MMC impaired metabolic activity and differentiation capacity of ASCs in XF/SF conditions. Both the supportive and inhibitory effects of MMC on ASC are culture condition dependent. In the presence of serum, MMC maintains ASC immunophenotype and enhances adipogenic and osteogenic differentiation at the cost of reduced proliferation.Peer reviewe