The Synthesis And Application Of Magnetic Composite Particles In Biological And Medical Areas

Magnetic particle is a composite particle that composed of superparamagnetic nanoparticle and macromolecules or other inorganic materials. Both nano-scale and micro-scale magnetic particles (also named magnetic microspheres or magnetic beads) have magnetically responsive property in an external magnetic field, which can separate magnetic particle from liquid phase, and when the external magnet is taken away, the magnetic particle can suspend again without magnetic memory. And this kind of magnetic property for magnetic particle is called superparamagnetic. On the other hand, the functional group on the magnetic particle could be used to immobilize biomolecules such as antibodies, antigens, nucleic acids or oligonucleotides etc. Therefore the magnetic particle has been used in immunoassay, separation and purification of nucleic acids, target drug delivery and cell sorting and so on.This thesis is focused on preparation of two kinds of magnetic particle and their application for immunoassay and purification of mRNA. The content includes two innovated ideas. First, Fe₃O₄/Au composite particle was synthesized which takes the advantages of physical-chemical properties of both magnetic particles and gold nanoparticle. Namely the Fe₃O₄/Au composite particle not only has suspension stability and superparamagnetic property but also has ability to immobilize biomolecules rapidly. Second, the isothiocyanate-functional Fe₃O₄ magnetic particle was prepared by the reaction of amino-terminal Fe₃O₄ magnetic particle and 1,4-phenylene diisothiocyanate (PDC), and this kind of functional magnetic particle could be used to couple amino-labelled oligonucleotides in one-step, comparing with the glutaraldehyde used for coupling amino-modified bio-molecules, this method is more rapid and simple.The research work in this thesis is as follows:1. The micro-scale Fe₃O₄/Au composite particle was synthesized bythiol-functionalized Fe3C>4 magnetic nanoparticle absorbing gold colloid, and the particle property was characterized. The human IgG and HBsAb were immobilized onto the FesCVAu composite particle surface, and HBsAg is detected by direct sandwich ELISA using the micro-scale FesCVAu particles as a carrier.2. The isothiocyanate-functional Fe3C>4 magnetic particle was prepared and characterized, the amino-modified oligo(dT)2o was coupled onto the particle and mRNA was purified from total RNAby using this kind of particle.