Magnetic polymer particles

Solid-phase separation Method of fraction separation in which the binding reagent is immobilized on an insoluble material (magnetic particles, polymers, etc.)... 

Particularly attractive for numerous bioanalytical applications are colloidal metal (e.g., gold) and semiconductor quantum dot nanoparticles. The conductivity and catalytic properties of such systems have been employed for developing electrochemical gas sensors, electrochemical sensors based on molecular- or polymer-functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme-based electrodes, immunosensors, and DNA sensors. Advances in the application of molecular and biomolecular functionalized metal, semiconductor, and magnetic particles for electroanalytical and bio-electroanalytical applications have been reviewed by Katz et al. [142]. 

Separate nanometer- to micron-sized colloidal magnetic particles, often dispersed in solutions they are usually stabilized by polyions or polymers. 

Shape effect of PFPE molecules or magnetic particles in suspension, including agglomeration phenomena at low concentration, interaction among these particles, and effects of floes can be examined via solution viscosity (r ) measurement. For a very dilute polymer solution [108], there is no interaction among polymer molecules, and the solution viscosity results from the contribution of the solvent plus the contribution of the individual polymer molecules. The intrinsic viscosity, therefore, is a measure of the hydrodynamic volume of a polymer molecule as well as the particle aspect ratio. Figure 1.24 shows the determination of the intrinsic viscosity for Zdol4000 in three different solvents. 

An alternative concept, the magnetically-assisted chemical separation, involves the coating of magnetic particles with selective metal ion extractants in an organic polymer shell. Once the metal ions are removed from the target solution, the process can be reversed by stripping them off at a judiciously selected pH. 

Inoue, H., Fukke, H., and Katsumoto, H., Effect of polymer adsorbed layer on magnetic particle dispersion, IEEE Trans. Magn., 26, 75, 1990. 

In an isolation step, where yield and concentration are more important than purity, the adsorption mechanism can be considered an on/off process, and several alternative contacting schemes can be used. Ligands have been bound to magnetized particles (137, 138) for continuous countercurrent adsorption in magnetically stabilized fluidized beds. Ligands attached to liquid perfluorocarbons (143), to dextran and related polymers (144), or incorporated into liposomes (145), or reversed micelles (146) may be used for biospecific liquid-liquid extraction or "affinity partitioning". Ligands have also been attached to surfactants and biopolymers for selective precipitation of dilute protein species (147, 148). 

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