Composites of Polymeric Gels and Magnetic Nanoparticles: Preparation and Drug Release Behavior Nora J. Franc ¸ois, 1 Sabina Allo, 1 Silvia E. Jacobo, 2 Marta E. Daraio 1 1 Laboratorio de Aplicaciones de Polı ´meros Hidrofı ´licos, Departamento de Quı ´mica, Facultad de Ingenierı ´a, Universidad de Buenos Aires, Paseo Colo ´n 850, C1063ACV, Buenos Aires, Argentina 2 Laboratorio de Fisicoquı ´mica de Materiales Cera ´micos Electro ´nicos.; Departamento de Quı ´mica, Facultad de Ingenierı ´a, Universidad de Buenos Aires, Paseo Colo ´n 850, C1063ACV, Buenos Aires, Argentina Received 4 January 2007; accepted 8 February 2007 DOI 10.1002/app.26321 Published online 28 March 2007 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The article is concerned with the prepara- tion of polymer–iron oxide nanocomposites and the study as drug-delivery matrices under the influence of applied magnetic field. Biocompatible materials were prepared by incorporating an aqueous ferrofluid in poly(vinyl alcohol) and scleroglucan (SCL) hydrogels, loaded with theophyl- line as model drug for release studies. The in vitro release profile was obtained using a flat Franz cell and the kinetic parameters were derived applying a semiempirical power law. A magnetic characterization of nanoparticles con- tained in the ferrofluid was performed by obtaining the magnetization curve. For both systems, the observed drug release profiles decreased when a uniform external mag- netic field is applied suggesting they can be used as envi- ronmental responsive matrices for biomedical applications. Dynamic rheological measurements show that a higher storage modulus and a more compact structure are obtained by incorporating the ferrofluid into the hydrogels. These rheological results and environmental electron scanning microscopy micrographs point to an understand- ing of release behavior once the magnetic field is applied. Ó 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 647–655, 2007 Key words: scleroglucan; polyvinyl alcohol; composites; stimuli-sensitive polymers; drug-delivery systems INTRODUCTION In the recent years, nanotechnology has developed to such a degree that it has been possible to produce, characterize, and make use of the functional proper- ties of nanoparticles for biomedical applications. 1,2 The use of small iron oxide particles in diagnostics has been experienced for nearly 40 years. 3 Increased investigations with several types of iron oxides have been carried out in the field of nanosized magnetic particles (mostly maghemite g-Fe 2 O 3 , or magnetite, Fe 3 O 4 , single domains of about 5–20 nm in diame- ter), among which magnetite is a very promising candidate since its biocompatibility has been veri- fied. 4 They are used for in vivo treatments, such as contrast agent for magnetic resonance imaging. The coating of these particles by organic or inorganic materials provides functional groups at the surface with the possibility to be functionalized with drugs. The application of an external magnetic field allows delivering these particles (beads) to a selected region leading to drug targeting. 5 Also, magnetic poly- (ethyl-2-cyanoacrylate) nanoparticles were proposed as a highly versatile magnetic drug carrier with sus- tained release behavior. 6 However, to our knowledge, there are scarce refer- ences in the field of magnetic sensitive gels specifi- cally designed for matrix drug-delivery systems. Environmental responsive polymeric gels belong to the class of materials capable of changing its physical properties in response to external stimuli. Because of this behavior, these versatile materials are expected to have a wide application in extended fields. 7 In particular, magnetic field sensitive gels, called ferrogels, represent a new type of composites, consisting of small magnetic particles, usually in the nanometer range, dispersed in an elastic polymeric matrix. 8 In a recent work, ferrogels of micron-sized magnetite particles and polyvinylalcohol (PVA) were evaluated for artificial muscle or soft actuator appli- cations. 9 Biodegradable gels with magneto-elastic properties have been synthesized using hydroxy- propylcellulose and maghemite. 10 The incorporated colloidal particles connect the shape and physical properties of the gel to the external field, owing to interactions between solid particles and polymer chains. 11,12 Zrı ´nyi et al. reported that ferrogels can undergo controllable changes in shape by the influ- ence of an external magnetic field. 13 Recently, Liu Correspondence to: M. E. Daraio (medit@fi.uba.ar). Contract grant sponsor: University of Buenos Aires; con- tract grant numbers: UBACyT I032, UBACyT I055. Journal of Applied Polymer Science, Vol. 105, 647–655 (2007) V V C 2007 Wiley Periodicals, Inc.