Englisch103 SeitenErschienen: 2011
"Perfused bioreactors have been developed with different designs and with various cell lines such as fibroblasts, osteoblasts and C2C12 myoblasts. All these current systems are custom made and mostly capable for only one cell type. Small seeding spaces and chambers inhibit longer cell studies and the observation of cell interaction. This study presents an advanced perfusion bioreactor which allows cell observation for longer than 5 days on an area of 2.8 cm2 with a volume of 17 ml. Initial experiments investigated homogeneity of the heat distribution, which is precisely controlled and stable over the length of the experiment. The addition of perfusion to the system results in the manual feeding process with modified F12 nutrient media being unnecessary. The perfusion and perfusion rate are user controllable up to 8 ml/h. Different inlets allow cell seeding, cell feeding and chemical stimulation. Since the metabolism by-products are diluted and removed by the flow of the perfused system, no inhibited growth occurs and the pH-value will maintain constant at 7.4 which removes the need for balancing the CO2 environment. Fully enclosed and sealed assemblies with a controlled hot plate can be used outside of the incubator and incorporated into the stage of a microscope to track and monitor cell growth. The bioreactor chamber consists of three parts of transparent annealed cast Acrylic plus sealing material. Acrylic is chosen since it is machinable by laser cutting, which is a fast and easy method of manufacture. Due to the annealing process sterilizing by ethanol is possible. Heat distribution analysis was made with an IR-camera. And the pH was tested by indicator paper. The flow rate was set at 3.3 ml/h. Computer simulations for flow and heat distribution and standard tests with cell cultures showed that a round bioreactor chamber design has advantages due to more uniform conditions. To track the cells during their distribution and over their whole life cycle, a completely transparent system is being developed. It includes an Indium Tin Oxide (ITO) coated glass plate, which can be used as a hot plate with precise controlled heating properties to heat the whole chamber."ISBN: 978-3-8428-0894-2Verlag: Diplomica Verlag GmbHTags: Tissue EngineeringBioreactor EngineeringCell culturingTendon cells44,99 € inkl. gesetzl. MwSt. / ohne DRM
"Chapter 2.2.5, Hot plates or other heat systems: The general problem with temperature in artificial microenvironments is that it has to be distributed uniformly to get as homogenous conditions as possible at every point. In the case of a mini bioincubator system, a maximum heat gradient of ±0.2°C is mentioned frequently, because in ordinary incubator in laboratory scale like the Galaxy R CO2 Incubator; a maximum heat gradient of ±0.2°C is necessary for good cell growth. In 1990, a perfusion bioreactor with a perfused peltier device preheater has been created by Delbridge et. al.. In this device, the temperature gradient is ±0.2°C by their own account, but only at a perfusion rate of 3 ml/min and a swimming culture chamber in a preheated water bath. Apart from the cleaning problem of the steel tubes and high flow velocity, the problem with preheater systems is the temperature gradient over the chamber. A good alternative is mentioned by Vulkasinovich who heats up floating gas which CO2-concentration acts as pH-Buffer through a semipermeable membrane. However, Petronis found out that in tissue engineering systems special CO2-level acts as pH buffer, therefore other chemical exchange with the air is unnecessary. A promising alternative has been discussed recently: From the discussion about sheet material with metallic coatings to get homogenous heat distributions, Focht and Lin have developed transparent hot plates for cell culture chambers with indium tin oxide (ITO) coating. According to Lin, ITO microheater chips „[…] provide advantages of optical transparency, excellent thermal uniformity, precise temperature control and portability […] [and] offer an alternative route to fabricate microheater in a simple and low cost manner.”. ITO – Technical Background: Indium-Tin-Oxide (ITO) is a semiconducting coating material which is a solid solution of indium(III) oxide (In2O3) and tin(IV) oxide (SnO2). A cross-linked indium (III) oxide crystal structure (Figure 7) is doped with tin atoms (Figure 8, Sn = tin). Since tin has one valence electron more than indium it can practically act as a free electron. In the energy-band model, this electron lies in the band gap between valence band and conduction band in a so-called donor state from where it can jump easily in the conduction band, which is a typical phenomenon for an extrinsic n-type semiconductor. To get conduction properties of > 5 mS/cm, the ratio Id:Sn is about 9:1 at a coating thickness of 400 nm. The material heats up when current flows through it, which is why it can be used as a hot plate. Applicable with different deposition techniques on transparent materials like glass, PMMA, polycarbonate etc., ITO coatings have transmission rates of 80-90 % in the visible spectrum thus, investigation with inverted microscopes through it is possible. Furthermore, ITO is practically non-transparent for infrared light. ITO-based heating plates are commercially available e.g. from Honeywell Sensing & Control (78000 series) or bioscience tools (San Diego). The coating procedure is described in literature."