Dynamic in vitro hemocompatibility testing – improving the signal to noise ratio

Assigning the hemocompatibility of small vascular implants is one of the great challenges in biomedical engineering. Due to the fact, that there are no widely approved test setups1, we decided to developed a modified CHANDLER-Loop system for dynamic in vitro hemocompatibility tests. The setup allows simultaneous testing of about 30 tube rings with an inner diameter of 2,4 mm. Cardiovascular implants can be placed into these tube rings. After filling them with anticoagulated blood and closing them to loops, they were placed on a rotating disc. While the loop is rotating, the blood remains in the lower part of the loop. The relative movement between the foreign surface and the blood sample induces a blood flow without the need of mechanical pumping. A first test series with the new test setup had been conducted to achieve a highly hemocompatible tube material. The results were compared to hemocompatibility tests done by LEMM, mentioned in the ISO 10993-42,3. We could prove, that Tygon S50HL® and Polyurethane achieve similar hemocompatibility values. In addition, we did in vitro tests of bare metal stents. We recorded a difference in the index of thrombocytes of about 17 % between the loops with three stents and the control. During further experiments the difference decreases to 8 %, which might be due to adhesion processes. The ability to measure these processes demonstrates the high sensitivity and very low background activation of the test setup. This can be assured by the recorded index of hemolysis, which had been less than 0,8 % in all our experiments. By developing and improving our modified CHANDLER-Loop system, we were able to establish a dynamic in vitro test setup for the hemocompatibility testing of small vascular implants. Because of its extremely low background activation and a high variability, the system serves as a benchmark for upcoming test setups.SFB-TR37 – Q2SFB-TR37 – B

Antioxidantien als Strategie zur Optimierung der Kryokonservierung von Stammzellen für das Tissue Engineering

Kontrolliertes Einfrieren in den Temperaturbereich zwischen – 80 °C und – 196 °C erlaubt es Zellen, bei gleichzeitigem Erhalt ihrer Vitalität nach dem Auftauprozess, langfristig zu lagern. Durch die Verwendung von Antioxidantien sollte in der vorliegenden Arbeit eine Steigerung der Rekultivierbarkeit von mesenchymalen Stammzellen nach der Kryokonservierung erzielt werden. Der Zusatz von 100 μM α–Tocopherol steigerte die Rekultivierungseffzienz der Stammzellen um 117,5 % gegenüber der Kontrolle ohne Antioxidans. Darüber hinaus konnte gezeigt werden, dass eine Reduzierung der DMSO-Konzentration möglich ist, da Versuche mit 200 μM α–Tocopherol und 2,5 % bzw. 5 % DMSO vergleichbare Resultate von ca. 164 % bzw. 170 % Rekultivierbarkeit erzielten.EXC/62/

Dynamische In-Vitro-Studie zur Strömungsabhängigkeit der Degradationsrate von Magnesium

Zur Schaffung eines standardisierten Versuchsablaufs für Studien zur Magnesiumdegradation im Rahmen der Entwicklung eines biodegradablen Implantatwerkstoffs, wurde eine Steuerung für einen Prüfstand zur dynamischen in-vitro-Testung programmiert und deren Funktionsfähigkeit mit einer Testreihe bestätigt. Durch die Ergebnisse dieser Versuchsreihe konnte zudem die Strömungsabhängigkeit der Degradationsrate von Magnesium nachgewiesen werden

Entwicklung von schichtweise ausgerichteten Faserverbundstrukturen

Jedes Jahr müssen tausende defekte Herzklappen ersetzt werden. Die Verwendung von biologischen oder mechanischen Prothesen macht aufgrund der Tatsache, dass diese nicht mitwachsen, gerade bei Heranwachsenden regelmäßige Reimplantationen erforderlich. Eine mögliche Alternative sind Klappenprothesen bestehend aus einer Gerüststruktur, welche mit körpereigenen Zellen besiedelt wird. Das Gerüst wird im Laufe der Zeit vollständig durch lebendes Gewebe ersetzt. Ziel dieser Diplomarbeit ist die Herstellung von schichtweise ausgerichteten Faserverbundstrukturen, um zukünftig den aus mehreren Gewebeschichten bestehenden Aufbau der menschlichen Herzklappen nachahmen zu können und den Zellen so eine optimale Trägerstruktur bereit zu stellen

Preparation and Analysis of PCL Spun Chitosan Scaffolds as Guidance Channels for Peripheral Nerve Regeneration

The results of this work show that the process of oriented solidification and lyophilisation is able to produce porous chitosan scaffolds with appropriate porosity and pore size for nerve regeneration. Interesting in this context are the results of statistical analysis of image analysis from SEM micrographs of uncrosslinked and UV cross-linked samples. The average pore size and mean minimum pore diameter show only small differences if the cooling rate is varied from B = 1…5 K / min and the temperature gradient from G = 1, 1.5, 2.0 K / mm. The average pore size (cross sectional area) of these samples can be estimated with reasonable accuracy, with 2100 μm². The average minimum pore diameter is within the range of 36-38 μm. These values are in a favourable range for the cell growth of nerve regeneration

Optimization of a test setup for examining blood damage caused by high shear forces

If blood pumps are applied in the human body or extracorporeal, blood damage can be caused by shear forces that act on the blood during the delivery. For an accelerated development of blood pumps with help of simulations there is a need for reliable limit values for shear forces. To determine these limit values a shear force test setup was built at the Institute for Multiphase Processes. In the context of the presented master thesis the former test setup peripheral devices were evaluated, possible blood damage mechanisms were considered, blood analysis in different experiments to identify the blood damage caused by different elements were made and peripheral devices were replaced. At the same time the shear chamber was constructional reengineered in a project thesis [1]. We were able to show, that in former works the blood damage caused by test setup peripheral devices had heterodyned the results. Finally the test setup was rebuilt with the results and a test was made. Two findings of the thesis are a reduction of about 60% of the number of components in the blood-conveying tube system and an application of a new fluid seal.SFB-TR37 - Q2SFB-TR37 - B4EXC 62/

The Care of Elderly People in Vietnam

The population ageing as an unprecedented phenomenon in the history of the humanity was considered. It is slow, but persistent and, according to the opinion of the experts, it is irreversible, at least for the next hundred years. Population ageing has a profound impact on economic growth, investment and labor market, the welfare of every citizen of any country. Changes in the structure of the population in terms of aging concerns every person, society, country and the international community. The increase in the number of elderly people determines the necessity of working out new strategies for the stable development of each country in the world. Vietnam is no exception in this case. Population ageing is a contemporary challenge for the worldwide society. It requires the development of the effective strategic and tactic decisions and new systems of care for elder people, aimed at transformation of the population ageing challenges into opportunities, which provide people’s welfare. The main aim of the study is to determine the ways of perfection of the care system of the Vietnamese older people. The methods: system analysis of statistic data about the demographic structure of the Vietnamese population and the morbidity structure of the Vietnamese seniors; situation analyses. The results: specific features and conditions of the system of care of elderly people in Vietnam are studied. The analysis of the main factors that affect the system of care of the older people is conducted. The conclusions and proposals to enhance the system of care of the older people are drawn

Proof of Concept of a New Glucose Sensing Technology: Color-Changing Hydrogels Including au Nanoparticles

This Master thesis provides a proof of concept for a novel, implantable continuous glucose sensing technology. Immobilized glucose oxidase in a poly 2-hydroxyethyl methacrylate hydrogel is used to enzymatically convert an increase in glucose level to a local decrease in pH, which leads to a swelling of the hydrogel. Encapsulated gold nanoparticles in the gel allow an optical readout of the glucose concentration. Experimental methods include hydrogel synthesis, nanoparticle encapsulation and finally glucose sensing with the hydrogel by UV-vis measurements. Two possible readouts, absorbance change and frequency shift, are discussed and tested. While a frequency shift is not detected, results show that the absorbance of the gel is proportional to glucose level, making it a promising concept for continuous glucose monitoring

Encapsulating Non-Human Primate Multipotent Stromal Cells in Alginate via High Voltage for Cell-Based Therapies and Cryopreservation

Alginate cell-based therapy requires further development focused on clinical application. To assess engraftment, risk of mutations and therapeutic benefit studies should be performed in an appropriate non-human primate model, such as the common marmoset (Callithrix jacchus). In this work we encapsulated amnion derived multipotent stromal cells (MSCs) from Callithrix jacchus in defined size alginate beads using a high voltage technique. Our results indicate that i) alginate-cell mixing procedure and cell concentration do not affect the diameter of alginate beads, ii) encapsulation of high cell numbers (up to 10×106 cells/ml) can be performed in alginate beads utilizing high voltage and iii) high voltage (15–30 kV) does not alter the viability, proliferation and differentiation capacity of MSCs post-encapsulation compared with alginate encapsulated cells produced by the traditional air-flow method. The consistent results were obtained over the period of 7 days of encapsulated MSCs culture and after cryopreservation utilizing a slow cooling procedure (1 K/min). The results of this work show that high voltage encapsulation can further be maximized to develop cell-based therapies with alginate beads in a non-human primate model towards human application.DFG/EXC/62/