A new metal-chelate adsorbent utilizing 2-methacryloylamidohistidine (MAH) was prepared as a metal-chelating ligand. MAH was synthesized using methacryloly chloride and histidine. Monosize nanospheres with an average diameter of 450 nm were produced by emulsion polymerization of 2-hydroxyetylmethacrylate (HEMA) and MAH. Then, $Fe^{3+}$ ions were chelated directly onto the monosize nanospheres. Mon-poly(HEMA-MAH) nanospheres were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and elemental analysis. $Fe^{3+}$ chelated monosize nanospheres were used in ferritin adsorption from an aqueous solution. The maximum ferritin adsorption capacity of $Fe^{3+}$-chelated mon-poly(HEMA-MAH) nanospheres was 202 mg/g at pH 4.0 in acetate buffer. The non-specific ferritin adsorption on the monpoly(HEMA-MAH) nanospheres was 20 mg/g. The adsorption behavior of ferritin could be modeled using both Langmuir and Freundlich isotherms. The adsorption capacity decreased with increasing ionic strength of the binding buffer. High desorption ratios (> 95% of the adsorbed ferritin) were achieved with 1.0 M NaCl at pH 7.0. Ferritin could be repeatedly adsorbed and desorbed with the $Fe^{3+}$-chelated mon-poly(HEMA-MAH) nanospheres without significant loss of adsorption capacity.