(241c) Synthesis of functional nano-composite particles for bio-separation

Magnetic Separation seems to be a promising unit operation for down stream processing of bio slurries. The technology consists of two main technology carriers: the magnetic separator and the magnetic bead. The magnetic bead is in most cases a composite material with a polymer matrix, in which magnetic particles are incorporated. The surface of the magnetic beads can be adjusted to the substance, which has to be recovered. The separation technology using magnetic beads is widely-used in the micro scale. Complicated separations of proteins or DNA-fragments are operated in biological laboratories. But the scale up of this principle to use the magnetic separation technology in production scale is limited due to the high costs of the beads. Magnetic beads have a diameter of 100 nm to about 100 µm. The separation effect derives from the sorption, complex formation or covalent bonding of the target substance to the bead surface. The higher the accessible surface is the higher is the possible load per volume unit of a magnetic bead. The common synthesis process uses emulsion or suspension polymerisation. The magnetic properties are provided by fine magnetic particles, e. g. magnetite. In presence of dispersed magnetic particles the polymerisation reaction is started. The polymer incorporates the magnetic particles into its matrix. In further process steps the functionalisation of the surface is prepared. The presence of iron of the magnetic filler negatively influences as a catalyst the functionalisation reaction. The polymerisation processes also show some weakness in the quality of dispersion of the magnetic filler. This becomes relevant, if superparamagnetic properties of the beads are requested. The recovering of the beads from a magnetic separator is less complicated, when the magnetisation curve shows no magnetic remanence. For scale up purposes the strategy of the bead production has been strongly modified. The main aim is to set up a process, which is capable to produce at least some kg per hour of magnetic beads with a basic functionalisation. The requested properties of the beads are: superparamagnetism, sufficient filler content for separation, sufficient surface volume ratio and accessible functionalised surface groups. The newly developed process starts from a magnetic fluid. Dichloromethane is used as mother liquid of the magnetic fluid. The matrix polymer is dissolved into the magnetic fluid. In an independent synthesis step polystyrene particles of 100-200 nm are produced by emulsion polymerisation. Those latex particles can be functionalised with amino or sulfone groups. The produced nano scale ion exchangers are dispersed as well into the magnetic fluid. The dispersion containing superparamagnetic magnetite particles (<15 nm), nano scale ion exchange latex particles and dissolved polymer is pumped into a spray tower. Using a two component jet the fluid is dispersed into droplets of 5-15 micron, which results in a particle size for the magnetic beads of 2-10 micron. The characterisation of the beads proves the superparamagnetic properties, the high filling degree (up to 60 %mass) and the excellent ion exchange and protein sorption properties. For characterisation TEM, XRD, SAXS, konfocal LSM, PCS have been used. With this synthesis process the application of selective sorption and magnetic separation in the field of the so called white biotechnology becomes less expensive.

Keywords: magnetic beads, magnetic fishing, HGMS, protein adsorption,