General strategy for designing functionalized magnetic microspheres for different bioapplications.

Surface functionalization and water solubility of magnetic nanoparticles are crucial for bioapplication. Here, we describe a synthetic approach for direct preparation of a wide range of functionalized and hydrophilic magnetic polymer particles (MPPs) that is both simple and general and involves using different polymers as the source of functional groups. This simple strategy of changing the polymer used in the reaction can give rise to a wide variety of hydrophilic MPPs with a high number of functional groups. For the purpose of bioapplication, we synthesized three types of MPPs with typical functional groups, such as hydroxyl groups (-OH), amino groups (-NH2), and carboxyl groups (-COOH), and further characterized these MPPs by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The magnetic saturation of the MPPs was also studied and was adequate for most bioapplications. MPPs were shown to have good biocompatibility using cell proliferation and apoptosis assays. Two types of MPPs with different functional groups were used successfully for intracellular imaging and antibody purification. Our results demonstrate that this simple and general synthesis strategy has potential for designing hydrophilic magnetic nanoparticles with multifunctionalities that cater for a range of bioapplications.