Magnetic Studies of Ferrofluid-Modified Microbial Cells

Microbial cells (Kluyveromyces fragilis and Chlorella vulgaris) efficiently interacted with maghemite nanoparticles stabilized as low-pH ionic magnetic fluid, leading to the formation of magnetically labeled cells. This simple procedure allows to use the prepared materials as new cheap and easy to get magnetic affinity adsorbents to the removal of water-soluble dyes from polluted water sources using magnetic separation techniques. Magnetically modified cells were investigated by means of electron spin resonance spectroscopy and conventional magnetic methods over the temperature range 4-300 K. The magnetic behavior of these materials was dominated by the superparamagnetic relaxation of isolated single domain maghemite particles although a little amount of agglomerates was also present on the cell surface. However, these agglomerates were sufficiently small to show at static conditions the superparamagnetic behavior at room temperature. Therefore, the ferrofluid-modified microbial cells represent new interesting magnetic affinity adsorbents which could be applied for large-scale magnetic separation processes.