Hindawi Publishing Corporation Journal of Nanomaterials Volume 2011, Article ID 910539, 13 pages doi:10.1155/2011/910539 Research Article Smart Magnetically Responsive Hydrogel Nanoparticles Prepared by a Novel Aerosol-Assisted Method for Biomedical and Drug Delivery Applications Ibrahim M. El-Sherbiny 1, 2 and Hugh D. C. Smyth 2 1 Polymer Laboratory, Chemistry Department, Faculty of Science, Mansoura University, 35516 Mansoura, Egypt 2 Division of Pharmaceutics, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA Correspondence should be addressed to Ibrahim M. El-Sherbiny, imelsherbiny@gmail.com Received 27 August 2010; Accepted 14 December 2010 Academic Editor: Xingmao Jiang Copyright © 2011 I. M. El-Sherbiny and H. D. C. Smyth. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We have developed a novel spray gelation-based method to synthesize a new series of magnetically responsive hydrogel nanoparticles for biomedical and drug delivery applications. The method is based on the production of hydrogel nanoparticles from sprayed polymeric microdroplets obtained by an air-jet nebulization process that is immediately followed by gelation in a crosslinking fluid. Oligoguluronate (G-blocks) was prepared through the partial acid hydrolysis of sodium alginate. PEG-grafted chitosan was also synthesized and characterized (FTIR, EA, and DSC). Then, magnetically responsive hydrogel nanoparticles based on alginate and alginate/G-blocks were synthesized via aerosolization followed by either ionotropic gelation or both ionotropic and polyelectrolyte complexation using CaCl 2 or PEG-g-chitosan/CaCl 2 as crosslinking agents, respectively. Particle size and dynamic swelling were determined using dynamic light scattering (DLS) and microscopy. Surface morphology of the nanoparticles was examined using SEM. The distribution of magnetic cores within the hydrogels nanoparticles was also examined using TEM. In addition, the iron and calcium contents of the particles were estimated using EDS. Spherical magnetic hydrogel nanoparticles with average particle size of 811 ± 162 to 941 ± 2 nm were obtained. This study showed that the developed method is promising for the manufacture of hydrogel nanoparticles, and it represents a relatively simple and potential low-cost system. 1. Introduction Over the last two decades, stimuli-responsive “smart” hydrogels, which can respond reversibly to external stimuli, such as pH, temperature, and electric field, have attracted a great deal of interest due to their potential applications in various fields especially in controlled drug delivery [1]. In the recent years, a significant body of research has focused on the development of biocompatible magnetically responsive nanoparticles for various drug delivery and biomedical applications such as magnetic drug targeting, enzyme immobilization, hyperthermia anticancer treatment, and the magnetic resonance imaging for clinical diagnosis [2–9]. The efficiency of magnetic nanoparticles in most of these applications depends particularly on the particle size distribution and the morphology of the polymer/magnetic nanoparticles [10, 11]. The magnetically responsive hydrogel nanoparticles with high-saturation magnetization and high susceptibility showed a good ability to trigger drug release upon applying external magnetic stimuli [12]. The major advantage of this drug delivery technology is attributed to the magnetic characteristics of the carrier system, which can be controlled remotely, and the biocompatibility of both the encapsu- lated iron oxide nanoparticles (e.g., magnetite (Fe 3 O 4 ) and maghemite (γ-Fe 2 O 3 )) and the polymeric hydrogel matri- ces. Superparamagnetic iron oxide nanoparticles (SPIONs) which can be easily magnetized and concentrated in a specific site by applying an external magnetic field and redispersed again once the magnetic field is removed have also found a recent considerable interest for drug delivery purposes [13]. The production of hydrogel nanoparticles such as acrylate-based hydrogels typically utilizes bioincompatible solvents such as dimethylformamide and acetone. Moreover,