Immunoisolation of Mammalian Cells

A novel cell bead system, comprising a magnetic core, a spherical annulus of agarose-immobilized cells, all conformally coated within a synthetic polymer, is proposed as a means of immunoisolating mammalian cells in a system that provides a balance between low total implant volume, retrievability, and diffusion limitations. A successful immunoisolation system could be used to transplant cells without eliciting an inappropriate host response. Chinese hamster ovary (CHO) cells were immobilized at the periphery of large ( 2 mm) agarose beads containing inert magnetic cores ( 1 mm) and coated in a hydroxyethyl methacrylate–methyl methacrylate (HEMA–MMA) copolymer by interfacial precipitation. The beads were coated in liquid gradients containing polyethylene glycol 200 (PEG) or bromooctane. Although many cells were adversely affected by the coating process, the cells that did survive (30–50% of those loaded into the beads) remained viable for a period of at least 2 weeks. This viability was much higher than achieved previously because of a number of factors, such as the aqueous agarose, the hydrophobic bromooctane intermediate layer, and faster coating times that minimize the exposure of the cells to organic solvents. Also, a mathematical model was used to describe oxygen transport within the annular agarose beads. These results provide evidence that the proposed geometry and the fabrication approach may be useful for a variety of applications that involve cell encapsulation. AU1 1Division of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts. 2Department of Chemical Engineering and Applied Chemistry and Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada. 3Present address: Division of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts. 4Rimon Therapeutics, Toronto, ON, Canada. 05-0164