A biocompatible magnetic film: synthesis and characterization
© Chatterjee et al; licensee BioMed Central Ltd. 2004
Received: 21 January 2004
Accepted: 04 February 2004
Published: 04 February 2004
Biotechnology applications of magnetic gels include biosensors, targeted drug delivery, artificial muscles and magnetic buckles. These gels are produced by incorporating magnetic materials in the polymer composites.
A biocompatible magnetic gel film has been synthesized using polyvinyl alcohol. The magnetic gel was dried to generate a biocompatible magnetic film. Nanosized iron oxide particles (γ-Fe2O3, ~7 nm) have been used to produce the magnetic gel.
The surface morphology and magnetic properties of the gel films were studied. The iron oxide particles are superparamagnetic and the gel film also showed superparamagnetic behavior.
Magnetic gel made out of crosslinked magnetic nanoparticles in the polymer network was found to be stable and possess the magnetic properties of the nanoparticles.
Polyvinyl alcohol (PVA) is a unique synthetic biocompatible polymer and it has a large number of hydroxyl groups that can react with many kinds of functional groups. Apart from its different industrial uses, it is widely being used in sensors and in drug delivery system [1, 2]. Ferrogels made with PVA can mimic artificial muscle . Synthesis of PVA magnetic fiber which can be used as magnetic paper, health care cloth or electromagnetic wave absorbent has been recently reported . Here we report a synthesis of a PVA magnetic film generated from PVA magnetic gel. This film can be useful as sensors in biomedical applications. We used a two step synthesis process for generating the magnetic gel . Nanosized iron oxide particles (γ-Fe2O3, ~7 nm) have been used to make the magnetic gel. The magnetic gel was dried to generate biocompatible magnetic films of different thicknesses. The surface morphology and magnetic properties of the gel films were also studied. The iron oxide particles are superparamagnetic and the gel film also showed superparamagnetic behavior.
Polyvinyl alcohol polymers (Mw = 25,000 and 125,000) were obtained from Polysciences, Inc. Gluteraldehyde and nitric acid were obtained from Sigma Chemical Company.
A two-step process was used to form the magnetic gel film. In the first step, surface modified nanosized maghemite was synthesized. The second step was the formation of composite materials. Maghemite was formed by conventional coprecipitation process  using ferrous chloride and ferric chloride in 1:2 molar ratios. We have used ultrasonication along with coprecipitation process. Later on the surface of the maghemite was modified with a cationic surfactant, cetyldimethylethylammonium bromide .
In the second step different concentrations (2–5%) of two different polyvinyl alcohol polymers (Mw = 25,000 and 125,000) were made in water. The surface modified maghemite was then added in different weight proportions (20–50% of the weight of polymer) and sonicated at 50% amplitude for 30 s. Glutaraldehyde was used as crosslinking agent (at slightly acidic pH, about 6) using 1 M nitric acid. Formation of gel occurred almost immediately. The crosslinking density was varied by using different amounts of glutaraldehyde. The gels were formed in rectangular aluminum trays and dried. The gels were dried till they formed a film of constant weight ensuring the absence of water.
Results and Discussion
A biocompatible magnetic film has been generated from the gel. As a crosslinked gel forms a three dimensional network the film formed from is expected to have more tensile strength than the solution cast films. This gel film can be considered as a composite material with superparamagnetic property.
The work was sponsored by a grant from the Center for Materials Research and Technology (MARTECH) at Florida State University.
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