Immunomagnetic sulfonated hypercrosslinked polystyrene microspheres for electrochemical detection of proteins

Poly(styrene-co-divinylbenzene) microspheres of narrow size distribution were prepared by (2-hydroxypropyl) cellulose-stabilized dispersion copolymerization of styrene and divinylbenzene in a 2-methoxyethanol/ethanol mixture under continuous addition of divinylbenzene. The copolymerization was initiated with dibenzoyl peroxide. The obtained microspheres were chloromethylated using several chloromethylation agents and then hypercrosslinked. Their porous structure was analyzed by nitrogen adsorption and mercury porosimetry. Superparamagnetic iron oxide nanoparticles were precipitated within the pores of microspheres from Fe(II) and Fe(III) chloride solution. The Fe content in the microspheres was determined by carbon analysis, atomic absorption spectroscopy and thermogravimetric analysis. Magnetic properties of the microspheres were characterized by magnetization curves and the temperature dependence of magnetic susceptibility. Finally, sulfo groups were introduced into the microspheres to prepare an immunomagnetic electrochemical biosensor for protein detection with ovalbumin as a model substance.