| Popis: |
In biological research and in the biopharmaceutical industry, there is a continuing concern over the occurrence of cell damage in a variety of devices as a result of hydrodynamic forces. One of the parameters used to quantify hydrodynamic conditions is the local energy dissipation rate (EDR). The EDR is the irreversible rate of internal energy increase per unit volume, or, in other words, the irreversible conversion of mechanical energy to heat. It is a scalar value, has units of power per unit volume (i.e. W/m3), and is intrinsic to any moving fluid. It can be calculated reliably using well-established equations for simple systems and computational fluid dynamics (CFD) for more complex systems. A microfluidic device was developed to determine the sensitivity of mammalian cells to locally high levels of EDR. Using this microfluidic device, the level of cell damage was measured as a function of the EDR. Two cell types were analyzed, CHO-K1 cells transfected with bcl-2, an anti-apoptosis gene, and the wild type CHO-K1 cells. These cells were evaluated for apoptosis as well as necrosis using flow cytometry. The results were then compared to the EDR cells would encounter in many bioprocess devices, such as: tubing, pipettes, rectangular channels, Fluorescence Activated Cell Sorter (FACS) instruments, and stirred tank bioreactors. The EDR in the aforementioned device was determined using analytical and experimental techniques as well as CFD simulations. With the exception of bubble rupture in bioreactors and the FACS instrument, it was found that necrosis is unlikely in most systems. Under certain growth conditions apoptosis is possible at a lower EDR, however this lower EDR value is still at least an order of magnitude higher than what cells would typically experience in bioprocess equipment. |
