The ability of human pluripotent stem cells (hPSCs) to differentiate into different types of cells has been regarded as a significant discovery in the development of cell replacement therapy for type 1 diabetic patients. MicroRNAs can be transported to recipient cells via vesicles, so-called exosomes. Exosomal microRNA differ from those of the parent cells suggesting that cells possess an active selecting mechanism of exosomes and their contents. Therefore, microRNAs may directly or indirectly regulate the expression of pancreatic islet-specific transcription factors to control the differentiation and maturation of pancreatic islet cells. In this study, the dynamic expression of exosomal and intracellular microRNAs from human pancreatic islets were analyzed and were compared with that in stem cell-derived islet-like clusters. The study also aimed to analyze the expression levels of intracellular microRNA in human pancreatic islets and stem cell-derived islet-like clusters compared to exosomal microRNA extracted from human islet media and stem cell media, respectively. The primary method of exosome extraction was ultracentrifugation, followed by microRNA isolation using a kit. The exosomes were then characterized with NTA, and the isolated microRNAs were detected using RT-qPCR. The results showed that the expression of microRNAs was generally low in human islets compared to isolated exosomes. The microRNA expression levels in stem cell-derived islet-like clusters and their respective isolated exosomes were also analyzed and it showed that let-7a, miR-375 and miR-26a were more abundant in exosomes. The results can contribute to the generation of more functional stem cell-derived islet-like cell clusters prepared from hPSCs to some extent. However, continued research in this area is required.

Předkládaná diplomová práce se zabývá extrakcí nanočástic oxidu titaničitého z produktů osobní péče, konkrétně opalovacích krémů a následnou charakterizací těchto částic. Počet komerčně dostupných produktů s obsahem nanočástic TiO2 se neustále zvyšuje a to se sebou přináší potřebu vyhodnotit potenciální osud a nepřímou expozici TiO2 nanošástic o různých velikostí a tvarů a zkoumat jejich celý životní cyklus. Bylo zkoumáno použití ultrafiltrace a ultracentrifugace jako extrakční metody. Dvě metody pro extrakci TiO2 nanočástic byly vyvinuty a aplikovány na vzorky opalovacích krémů. Extrahované částice mohou být použity pro ekotoxikologické studie, případně experimenty v mesokosmu. Velikost částic byla stanovena pomocí metody dynamického rozptylu světla a transmisní elektronové mikroskopie.

Nanopartiklar är partiklar med storlekar i området 1 till 100 nm, och som uppvisar nanospecifika egenskaper. Egenskaperna kan variera helt mellan olika typer av nanopartiklar, även bland partiklarna och deras respektive material i bulk format på grund av deras unika storlekar, former och strukturer. I denna studie har vi analyserat storlekarna och den kolloidal stabiliteten på tre nanopartiklar, Co, Y2O3, CeO2 i färskvatten och färskvatten med naturligt organiskt material med hjälp av sonifikation, NTA, AAS och ICP analys. Nanopartiklarna lät vara utsatta i lösningarna i upp till six timmar, där analys med hand av NTA skedde efter den nollte, första och sjätte timmen. Partiklarna uppvisade olika egenskaper, och alla tre partiklar varierade i storlek under experimentet. Kobalt hade tendensen att minska i storlek i bägge lösningar, medan storlekarna på yttrium- och cerium oxid tenderade att variera. För att främja vår förståelse av nanopartiklar, behövs fler studier för att få en full förståelse för de unika egenskaperna hos dessa partiklar. / Nanoparticles are particles with sizes in the range of 1 to 100 nm, which also have nanospecific properties. Their properties vary wildly between different types of nanoparticles, even among nanoparticles and their respective particles in bulk format heeding to their highly individual shapes, sizes and structures. In this study we analyzed the sizes and colloidal stability of three different nanoparticles, Co, Y2O3 and CeO2 in freshwater and freshwater with natural organic matter solutions using sonication, NTA-, AAS-, and ICP analysis. The nanoparticles were exposed to the solutions for up to six hours, with analysis being performed at the zero, first and sixth hour. The particles indeed showed different properties, as all three particles varied in size throughout the experiment. Cobalt had the tendency to decrease in size as time progressed in both solutions, while the mean size of yttrium- and cerium oxide varied. To further our understanding of nanoparticles, more studies need to be performed to properly understand the individual properties of these nanoparticles.