This paper reports a novel method of developing SMART nanocomposite membranes and coatings by in situ synthesis of iron oxide particles in a Poly(vinyl alcohol) (PVA)matrix, using co-precipitation of different amounts of Fe(II) and Fe(III) taken in an alkaline medium. Poly(vinyl alcohol) was used to encapsulate iron oxide nanoparticles, as scaffold for particle nucleation and its influence on particle size and on magnetic properties were studied. The ferrogels were prepared by a freeze/thawing process of the solutions containing magnetite nanoparticles. Magnetite particles with an average diameter of 20-40 nm were obtained homogeneously within the matrix because of the tridimensional structure and chelating capacities of PVA. Calcium-alginate PVA gel was used to encapsulate the iron oxide/PVA nanocomposite. The mechanical properties and the saturation magnetization of the system were measured. The combination of magnetic properties of iron nanoparticles with the biocompatibility of calcium-alginate suggests that these materials have great potential for use as controlled delivery systems activated externally by magnetic stimuli.