No abstract

No abstract

No abstract

No abstract

No abstract

Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution and stabilized by polyvinyl alcohol (PVA) were synthesized. The particles were prepared by a coprecipitation technique using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Using a design of experiments (DOE) approach, the effect of different synthesis parameters (stirring rate and base molarity) on the structure, morphology, saturation magnetization, purity, size, and size distribution of the synthesized magnetite nanoparticles was studied by various analysis techniques including X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC) measurements, vibrating-sample magnetometer (VSM), transmission electron microscopy (TEM), UV-visible, and Fourier transform infrared (FT-IR) spectrometer. PVA not only stabilized the colloid but also played a role in preventing further growth of SPION followed by the formation of large agglomerates by chemisorption on the surface of particles. A rich behavior in particle size, particle formation, and super paramagnetic properties is observed as a function of molarity and stirring conditions. The particle size and the magnetic properties as well as particle shape and aggregation (individual nanoparticles, magnetic beads, and magnetite colloidal nanocrystal clusters (CNCs) are found to be influenced by changes in the stirring rate and the base molarity. The formation of magnetic beads results in a decrease in the saturation magnetization, while CNCs lead to an increase in saturation magnetization. On the basis of the DOE methodology and the resulting 3-D response surfaces for particle size and magnetic properties, it is shown that optimum regions for stirring rate and molarity can be obtained to achieve coated SPION with desirable size, purity, magnetization, and shape.

No abstract

Superparamagnetic iron oxide nanoparticles with proper surface coatings are increasingly being evaluated for clinical applications such as hyperthermia, drug delivery, magnetic resonance imaging, transfection, and cell/protein separation. To enhance the applicability of magnetic nanoparticles, two main problems must be overcome. First, as the drug coats the particle surface, a significant portion of it is quickly released upon injection (burst effect). Therefore, only small amounts of the drug reach the specific site after, for example, magnetic drug targeting. Second, once the surface-derivatized nanoparticles are inside the cells, the coating is likely digested, leaving the bare particles exposed to other cellular components and organelles, thereby potentially influencing the overall integrity of the cells. To overcome these two shortcomings, iron oxide nanoparticles with cross-linked poly (ethylene glycol)-co-fumarate (PEGF) coating were synthesized. The obtained material was highly stable and easy to handle due to the well-dispersed magnetic nanoparticles. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, even very high concentrations of the novel magnetic nanoparticles were found to be biocompatible. To investigate if the coating could reduce the burst effect, nanoparticles were prepared by incorporating the anticancer drug tamoxifen. The cross-linked PEGF coating reduced the burst effect rate by 21% in comparison with the noncross-linked tamoxifen nanoparticles. Our results suggest that nanoparticles with coatings based on crosslinked unsaturated aliphatic polyesters are potentially useful to develop novel carriers for drug and gene delivery applications.