Ultrasound enhanced ferrite plating of polymer microspheres for magnetic cellular segregation

Polyacrylate microspheres of 4.5 mu m diameter were coated with a continuou s magnetite layer by ultrasound enhanced ferrite plating, at 70 degrees C f rom an aqueous solution of FeCl2, utilizing Fe2+-->Fe3+ oxidation by NaNO2. The ferrite coatings prepared in this study are similar to 100 nm in grain size, which is reduced from that (i.e, 300 similar to 400 nm) of the coati ngs prepared by ultrasound enhanced ferrite plating in our previous study. This owes to improvement in plating conditions. Turbidity analyses revealed that the present ferrite-encapsulated microspheres exhibit lower sedimenta tion rate and higher efficiency of magnetic separation than the previous on es. This will improve the performance of enzyme immunoassay which has been put to practical use utilizing the partially-ferrite-coated microspheres.