Compatibility and toxicity of polymer-coated magnetic nanoparticles on mammalian cell systems

Abstract

(cont.) produced normal growth curves in the presence of particles. However, the particles do still exhibit some toxicity towards the cells, as the maximum cell density of cells cultured with particles does not reach that of control cultures. Both particles were found to increase the oxygen transfer in an aqueous solution. A 1.5% solution of particle A enhanced the oxygen transfer 41.8% over the control, water, while 1.4% particle B enhanced 15.9% over the control. While particle A has a better effect on oxygen transfer, this particle is not suitable to be used with mammalian cell cultures as it is highly toxic.

This thesis focuses on the compatibility of polymer-coated magnetic nanoparticles with mammalian systems. The magnetic particles are designed to increase oxygen transfer in mammalian cell bioreactors. Magnetic nanoparticle A consists of a magnetite core attached to a layer of oleic acid, in which oxygen is four times as soluble as it is in water. The entire particle is coated with an attached layer of a surfactant, hitenol, to stabilize the particle against agglomeration. The entire particle has a diameter of approximately 20 nm. However, particle A was found to be extremely toxic to both [gamma]-CHO and hybridoma cells, causing complete cell death within four hours. This is most likely due to the surface surfactant, hitenol. A more biocompatible nanoparticle, particle B, was created. This particle is synthesized with a brush copolymer consisting of octadecylamine (ODA) and poly(ethylene oxide) (PEO) attached to a poly(acrylic acid) backbone. Once attached to the magnetite core, the ODA forms the inner layer that solubilizes oxygen, while PEO forms the stabilizing coating. Particle B forms nanoclusters about 100 nm in diameter. Thoroughly cleaning the nanoparticles is very important, as mammalian cells are very sensitive to foreign chemicals. Particles cleaned with dialysis did not remove all impurities, as all [gamma]-CHO cells in the presences of these particles were killed within 24 hours. High gradient magnetic separation (HGMS) was used to clean particles, and was found to be a much more effective method. However, sufficient amounts of washing fluid, about sixty column volumes, were needed to ensure proper cleaning. Once properly cleaned, the particles were found to be much less toxic towards the cells. Both [gamma]-CHO and hybridoma cells