Patent ID: 7456019

Claim:
In a method for culturing mammalian cells to produce in vitro multi-cellular, three-dimensional assemblies of predominately living mammalian cells with predominately adjacent cell membranes evidencing minimal mechanical damage, said method including the steps of: providing a bioreactor having a culture chamber rotatable about an approximately horizontal longitudinal axis, means to controllably rotate said culture chamber, means to introduce an oxygen-containing fluid throughout said culture chamber and means to remove metabolic waste products therefrom; filling said culture chamber completely with a fluid nutrient media, cell attachment substrates, and mammalian cells of a single type, to establish a culturing environment; rotating said culture chamber about its longitudinal axis while introducing an oxygen-containing fluid to said culture chamber and removing metabolic waste products therefrom to maintain said culturing environment; controlling the rotation of said culture chamber such that the fluid medium except during transient periods as the following simultaneous properties: a. localization of cells and attachment substrates with similar or differing sedimentation properties in a similar spatial region, b. freedom for three dimensional spatial orientation or assemblies formed by the culturing of the cells, c. low shear and essentially no relative motion of said culturing environment with respect to the boundaries of the chamber; and determining the trajectory of the assemblies, in response to said determining step: increasing the speed of rotation of the culture chamber if the assemblies fall excessively inward and downward on the downward side of the rotation cycle and excessively outward and insufficiently upward on the upgoing side of the rotation cycle to prevent wall impact; or decreasing the speed of rotation of the culture chamber in response to excessive accumulation of the assemblies near the outer wall of the culture vessel so as not to restrict three dimensional assembly, and as the size of the assemblies increase beyond the capability to fully satisfy the above three properties by further increase of the speed of rotation, selecting a rotational rate to visually obtain minimal collision frequency and intensity, the improvement comprising: subjecting the contents of the culture chamber to a time varying electromagnetic force driven by a pulsed square wave exerting a magnetic field of from about 0.05 to 0.5 gauss while culturing the cells in the chamber, wherein the magnetic field varies over time and can be any value within the range of from about 0.05 to 0.5 gauss.