Study of magnetic particles pulse-injected into an annular SPLITT-like channel inside a quadrupole magnetic field

Advantages of the continuous magnetic flow sorting for biomedical applicati ons over current, batch-wise magnetic separations include high throughput a nd a potential for scale-up operations. A continuous magnetic sorting proce ss has been developed based on the quadrupole magnetic field centered on an annular flow channel. The performance of the sorter has been described usi ng the conceptual framework of split-flow thin (SPLITT) fractionation, a de rivative of field-flow fractionation (FFF). To eliminate the variability in herent in working with a heterogenous cell population, we developed a set o f monodisperse magnetic microspheres of a characteristic magnetization, and a magnetophoretic mobility, similar to those of the cells labeled with a m agnetic colloid. The theory of the magnetic sorting process has been tested by injecting a suspension of the magnetic beads into the carrier fluid flo wing through the sorter and by comparing the theoretical and experimental r ecovery versus total flow-rate profiles. The position of the recovery maxim a along the total flow-rate axis was a function of the average bead magneto phoretic mobility and the magnetic field intensity. The theory has correctl y predicted the position of the peak maxima on the total flow-rate axis and the dependence on the bead mobility and the field intensity, but has not c orrectly predicted the peak heights. The differences between the calculated and the measured peak heights were a function of the total flow-rate throu gh the system, indicating a fluid-mechanical origin of the deviations from the theory (such as expected of the lift force effects in the system). The well-controlled elution studies using the monodisperse magnetic beads, and the SPLITT theory, provided us with a firm basis for the future sorter eval uation using cell mixtures. (C) 2000 Elsevier Science B.V. All rights reser ved.