Construction And Evaluation Of Novel Magnetic Field Flow Fractionation System

Because of the outstanding magnetic responsiveness, high specific surface areaand good biocompatibility, magnetic microspheres, is widely concerned in targetedreleasing of drugs, medical imaging and cancer therapy. The preparation andcharacterization of magnetic pharmaceutical formulation is becoming an importantsubject in drugs development. The size and distribution of particle are requiredcontrolling while the magnetic susceptibility is required analyzing and determining.Developing technics to separate and analyze samples with different magneticresponsiveness based on magnetic interaction and providing reliable means forquality control of magnetic drugs, is becoming a current challenge.Existing methods aiming to magnetic properties, such as vibrating samplemagnetometer, are limited and not able to separate samples. Other methods, such asbatch magnetic separators, free-flow magnetophoresis and high gradient magneticseparator, separate magnetic microspheres only based on the different sizes anddensities of particles instead of magnetic characteristic. Majority of methods requestthe separation equipments.In order to overcome the existence question, we proposed a method of magneticfield-flow fractionation to separate materials with different magnetic susceptibilityand to measure the magnetic susceptibility distribution.Monodisperse polystyrene particles were prepared by dispersion polymerizationand seed swelling method. The polystyrene particles were indicated to have a uniformparticle size characterized by environmental scanning electron microscope (ESEM)and transmission electron microscope (TEM) analysis. Using the polystyrene particlesas the base ball, we prepared the magnetic particles by the method of layer-by-layerself-assembling. The magnetic susceptibility was characterized by vibratingsample magnetometer. The results show that microspheres with different magneticsusceptibilities or diffident sizes can be obtained by controlling the amount ofmagnetic fluid and tetraethoxysilane (TEOS).Using the spiral capillary tube as the separation channel and the static or therotary magnet as the external magnetic field, we built a magnetic fieldflow fractionation system. Particles of diffident magnetic susceptibilities (1.6and2.3emu/g) were separated using the installment of magnetic field-flow fractionation. Inthis system, the combined effect of gravitational force, magnetic force and the hydrodynamic lift force balance the particles in a particular stream layer. Being closerto the center of the capillary tube, the weakly magnetic particles have a shorterretention time, and thus can be separated with the strong magnetic particles. Theresolution effect improves a lot at high flow speed, in which the comparatively largelift force can eliminate the irreversible adsorption and aggregation. Theresolution of the method is related to parameters such as the fluid velocity, magneticdensity and the number of magnet in the static magnetic field.And in the rotarymagnetic field different susceptibility of magnetic particles could be separated bestwhen the rotating frequency was2.21Hz, the flow rate was0.16mL/min and thedistance of magnetic field was2mm. Magnetic particles of different sizes or differentmagnetic susceptibilities can be separated successfully in the static or rotary magneticfield and the rotary system has a big advantage over the static one in both theseparation efficiency and flexible operations.In this article, the methods which applied two different modes of magntic fieldflow fractionation can successfully separate different magnetic susceptibility particles.The article provide a viable mean for separating magnetic sample with differentmagnetic susceptibility and determing the distribution of magnetic susceptibility.And it also bring up a new idea for application of magntic field flow fractionation andseparation and determination of magnetic pharmaceutical formulation.