Magnetic studies of iron(III) nanoparticles in alginate polymer for drug delivery applications

Isolated iron ions and iron oxide nanoparticles entrapped in alginate microspheres were studied by Fe-57 Mossbauer spectroscopy (MS), electron paramagnetic resonance (EPR) and magnetization measurements. Ferric alginate beads were prepared by dropping sodium alginate solution into ferric chloride solution (0.1 and 0.5 M) with stirring under Ar atmosphere. MS and EPR spectroscopy show that iron is absorbed in alginate as Fe(III). The EPR suggests that isolated Fe(III) substitutes sodium in the polymeric structure (narrow line paramagnetic species at g = 4.23). This mechanism induces the linking of the alginate units and the formation of the alginate microspheres. During this process, superparamagnetic iron hydroxide particles (broad line species at g = 2.22) are precipitated inside the polymer network. MS measurements performed in diluted and concentrated Fe(III) samples displays a paramagnetic doublet at 300 K, and two components at 4.2 K due to a paramagnetic site and blocked superparamagnetic particles. (C) 2004 Published by Elsevier B.V.