Synthesis and characterization of magnetic hydrogel nanocomposites

The intrinsic magnetic properties of magnetic nanoparticles have been exploited in many industrial and biomedical applications. The unique properties displayed by the magnetic nanoparticles have stimulated considerable interest in their design and incorporation in nanomaterials where these properties are utilized. The magnetic nanoparticles have been integrated with various other materials (e.g., polymers) to obtain hybrid nanocomposite systems where the individual properties of the magnetic nanoparticles and polymers are harnessed to provide a synergistic enhancement of their functions. This work focuses on integrating magnetic nanoparticles with various functional polymers, specifically hydrogels, to obtain magnetic hydrogel nanocomposites for diverse applications.;The biocompatibility of many hydrogels has promoted their use as biomaterials in various applications such as implants, scaffolds for tissue repair and regeneration, and in drug delivery systems. Magnetically responsive hydrogel nanocomposites based on the incorporation of magnetic nanoparticles within functional polymers like temperature sensitive hydrogels can therefore be designed to enhance their versatility in the biomedical applications outlined.;For biomedical applications, the effectiveness of the magnetic nanoparticles is enhanced through the use of suitable coatings on the surface of the particles. The coatings are typically chosen to ensure the biocompatibility and provide increased stability of the magnetic nanoparticles in vivo. The coatings can also be appropriately designed to incorporate tailored functionalities which could trigger a specific response or modulate specific cell-nanoparticle interactions. This work has used temperature sensitive polymers based on poly(n-isopropylacrylamide) and polymers with stealth properties based on poly(ethylene glycol) for the functionalization of iron oxide magnetic nanoparticles. The majority of the work described here involves the use of iron oxide nanoparticles due to their proven biocompatibility with an appropriate surface coating. It must be noted that some work with cobalt ferrite is also highlighted to demonstrate the versatility of the approaches employed.;The design of the magnetic hydrogel nanocomposites in this work falls into two major categories: (i) nanocomposite systems where magnetic nanoparticles are entrapped in a hydrogel matrix and (ii) nanocomposite systems where the surface of core magnetic nanoparticles are functionalized with a hydrogel coating. In the matrix system, iron oxide nanoparticles were incorporated at different loadings in a temperature sensitive hydrogel. It was demonstrated through swelling studies that the presence of the magnetic nanoparticles did not significantly affect the temperature sensitivity of the hydrogel. The ability to obtain different swelling responses by varying the crosslink density provides the flexibility to design the nanocomposite system with desired transport properties.;In the second approach, core iron oxide nanoparticles were functionalized with temperature sensitive poly(n-isopropylacrylamide)-based and poly(ethylene glycol)-based polymers using atom transfer radical polymerization to precisely control the polymer growth. The temperature sensitivity of the poly(n-isopropylacrylamide) functionalized iron oxide was demonstrated. The heating capabilities of the nanoparticles in an alternating magnetic field are pivotal in some of the applications of the nanocomposites. For example, remotely heating the nanoparticles in an alternating magnetic field can lead to generation of heat for thermal therapy applications. The heat generated can also be used to modulate conformational changes in the nanocomposite systems with temperature sensitive polymers to regulate drug release. Synthesis conditions to maximize heat generation of the core iron oxide nanoparticles were therefore also examined.;KEYWORDS: Magnetic, hydrogel, nanocomposites, iron oxide, surface functionalization...