Presence Of Iron Oxide Particles Research Articles

Magnetic aqueous two-phase separation in preparative applications

Magnetic aqueous two-phase separation is a new technique to speed up the separation of aqueous two-phase systems (Anal. Biochem. 1987, 167, 331–339). It is based on the addition of magnetically susceptible material (e.g. 1-μ iron oxide particles) which induces rapid phase separation when a mixed system is placed in a magnetic field. The technique has been applied to a number of two-phase systems. The time for phase separation was decreased by a factor of 5–240,000, with the largest improvement for systems containing high concentrations of protein and for systems with viscous or nearly isopycnic phases. An apparatus for preparative multistage extraction with magnetic separation was constructed and tested on glycolytic enzymes present in a yeast extract using a dextran/Cibacron blue-polyethylene glycol system. The presence of iron oxide particles did not adversely affect the extracted enzymes. An electromagnet-based apparatus for continuous phase separation on a larger scale was also designed. A phase system containing crude dextran and unpurified cell homogenate was effectively processed. The apparatus also allowed effective separation when the phase containing iron oxide particles was only a small fraction (4%) of the total phase system.

A quantitative study of relaxation rate enhancement produced by iron oxide particles in polyacrylamide gels and tissue.

The proton relaxation rate enhancements produced by two types of iron oxide particles, M4125 and AM125 (Advanced Magnetics, Cambridge, MA) designed as potential MR contrast agents, have been measured in polyacrylamide gels and in liver and spleen. The organ uptakes, time courses, and biodistributions of these materials have been measured using radiolabeling. The relaxation rate enhancements produced by these particles have been related to the concentration of iron per gram material at different magnetic field strengths. The relaxation rates increase linearly as a function of concentration at field strengths varying from 0.15 to 7 T. The relaxation effects of these particles in tissue are significantly different from the behavior in vitro. These results suggest that several different mechanisms contribute to relaxation effects in the presence of iron oxide particles and they depend strongly on the way the particles are sequestered. Diffusion effects for a specified TE may be enhanced using gradient or single-spin echoes rather than multiple echoes. AM125 is significantly more effective as a relaxation agent than paramagnetic metal ions only at relatively high fields, while M4125 is less effective per unit concentration.