The first objective of this work was to prepare biocompatible magnetic polymer microspheres with reactive functional groups that could withstand nonspecific protein adsorption from biological media.Carboxyl group-containing magnetic poly(2-hydroxyethyl methacrylate) (mgt.PHEMA) microspheres similar to 4 mu m in size were prepared by multistage swelling polymerization, precipitation of iron oxide inside their pores, and coating with an alpha-methoxy-omega-amino poly(ethylene glycol) (CH3O-PEG(750)-NH2 orCH(3)O-PEG(5,000)-NH2)/alpha-amino-omega-t-Boc-amino poly(ethylene glycol) (PhN-PEG(5,000)-NH-t-Boc) mixture.The mgt.PHEMA@PEG microspheres contained similar to 10 mu mol COOH per g. Biocompatibility of the particles was evaluated by their treatment with human embryonic kidney cells of the HEK293 line. The microspheres did not interfere with the growth of these cells, suggesting that the particles can be considered non-toxic. A second goal of this study was to address on the interaction of the developed microspheres with macrophages that commonly eliminate foreign microbodies appearing in organisms. Murine J774.2macrophages (J774.2) were cultured in the presence of the neat and PEGylated microspheres for 2h.Mgt.PHEMA@PEG(5.000) microspheres significantly adhered to the surface of J774.2 macrophages but wereminimally engulfed. Due to these properties, the mgt.PHEMA@PEG microspheres might be useful forapplication in drug delivery systems and monitoring of the efficiency of phagocytosis. (C) 2017 Elsevier B.V. All rights reserved.