Development of circumference oscillation mechanism with adjustable amplitude
According to the situation of the currently developed circumference oscillation mechanism without adjustable amplitude generally. The circular oscillation mechanism with adjustable amplitude is designed. It mainly comprises an eccentric motion mechanism and adaptive dynamic balance mechanism. The dynamic simulation and analysis is carried out on eccentric motion mechanism. The experimental results show it can achieve 0-Φ50mm adjustable amplitude and 20-350RPM adjustable oscillation frequency in the meantime, and the latter can be realized by changing eccentricity adjusting pin manually. The unbalance quality of the table can be compensated by adaptive dynamic balance mechanism in order to increase the die life. Its amplitude can be changed simply, conveniently and fast, and has the characteristics of simple and compact mechanism, rigid connection, strong bearing capacity and maintenance easily. It will be widely used in the field of biological engineering.
Tissue growth in a rotating bioreactor. Part I: mechanical stability.
We develop mathematical models to provide insights into the morphology of a tissue construct formed from a single-cell suspension in culture media, within a rotating bioreactor. The bioreactor consists of a cylindrical vessel of circular cross-section rotating about its longitudinal axis with constant angular speed. Experimental studies show that at rotation rates below a critical value, the cells 'self-assemble' to form smooth 'nodules' that are approximately cylindrical with elliptical cross-section; however, at rotation rates above a critical value, an amorphous construct forms with a highly irregular boundary. The construct is denser than the surrounding culture media and histological studies indicate that the interior of the construct, which is a mix of apoptotic cells and culture media, is surrounded by an outer rim of proliferating cells and collagen. The construct is modelled as a viscous fluid drop surrounded by an extensible membrane in a (less dense) immiscible viscous fluid within a rotating bioreactor. We consider both thin-disk and slender-pipe bioreactors for which the aspect ratio, L(*)/a(*) (where L(*) and a(*) are the bioreactor length and radius, respectively), is small and large, respectively, and obtain a series of spatially 2D problems (independent of the axial coordinate). We then examine the hypothesis that the construct morphology is a result of the mechanical forces that it experiences by considering the interfacial stability of an initially circular fluid-fluid interface to small-amplitude, oscillatory perturbations. The instability is driven by the density difference between the two fluids, and we investigate the effect of the rotation rate, the (time-dependent) gravitational field, and the material and geometrical properties of the system on the stability properties.
Microcarrier culture of recombinant Chinese hamster ovary cells for production of human immune interferon and human tissue-type plasminogen activator
SummaryRecombinant Chinese hamster ovary cells were successfully cultured semi-continuously on microcarriers of gelatin or modified dextran under non-selective conditions for up to three weeks. High and constant production rates for human immune interferon and tissue-type plasminogen activator were obtained. For cells that produced interferon, the highest cell concentration and interferon production was obtained with gelatin microcarriers though the specific production when grown in the presence of 0.2% fetal calf serum was slightly higher for cells cultured on dextran microcarriers (0.12 U/cell day versus 0.11 U/cell day). For cells that produced plasminogen activator, a slightly higher cell concentration was obtained for cells grown on dextran microcarriers (9x105 cells/ml versus 7x105 cells/ml). However, the specific and total production rates were significantly higher for cells cultured on gelatin microcarriers (6.7 pg/cell day versus 2.1 pg/cell day). The maximum cell concentration and specific production rate could be increased to 2.3x106 cells/ml and 3.4 pg/cell day for dextran microcarriers by adding 6-aminohexanoic acid to the medium. For gelatin microcarriers, the addition of 6-aminohexanoic acid increased the specific production rate to 14.4 pg/cell day. Cell growth, however, was inhibited.