Fabrication and characterization of a new MRI contrast agent based on a magnetic dextran–spermine nanoparticle system

Abstract

This study aims to fabricate and formulate a new magnetic resonance imaging (MRI) contrast agent based on a dextran–spermine nanoparticulate system loaded with super paramagnetic iron oxide nanoparticles (SPION). SPION-loaded spermine–dextran nanoparticles were prepared according to a procedure based on the ionic gelation of dextran–spermine with sodium tripolyphosphate (TPP) anions. The effects of process parameters such as pH, concentration of spermine dextran, TPP to dextran–spermine and SPION to dextran–spermine weight ratios, and TPP addition rate were fully investigated to find the optimized formulation through the response surface methodology. At the optimum condition, 75% of the magnetic iron oxide nanoparticles added to the polymeric solution were entrapped in dextran–spermine nanoparticles. Samples were investigated by transmission electron microscopy. The mean particle size of the nanoparticles determined by particle size analyzer was found to be 65 nm at the optimum condition with zeta potential of +90 mV. The SPION-loaded dextran–spermine nanoparticle formulation has the same superparamagnetic properties as SPIONs and at same iron concentration the saturation magnetization (Ms) of the SPION-loaded dextran–spermine nanoparticles was larger than SPIONs. In vitro MRI was performed with gradient echo and spin-echo sequences at 1.5 T. By increasing of iron concentration, the T 2 relaxation times were reduced. Thus, indicating that the saturation magnetization and r 2 and $$ r_{2}^{*} $$ relaxivities were enhanced, and the contrast effects were improved in comparison to commercial SPIONs.