MRI Contrast Agent-Based Multifunctional Materials: Diagnosis and Therapy
Figure 2
Schematic diagram of the SPIO synthesis and coating. (a) Both iron oxide cores and DSPE-PEG are dissolved in chloroform. (b) The addition of DMSO induces assembly between iron oxide cores and DSPE-PEG molecules. (c) The transition into water further strengthens the hydrophobic interaction between DSPE-PEG and oleic acid/oleylamine on the iron oxide cores. Due to its extremely low critical micelle concentration (~5 μM in water), unoccupied DSPE-PEG exists mainly in the form of empty micelles. (d) A schematic diagram of a SPIO with a 4.8-nm iron oxide core and DSPE-mPEG1000 coating. Layers 1 through 5 represent PEG, phosphate, DSPE, oleic acid/oleylamine, and the iron oxide core, respectively. The dimensions are based on transmission electron microscopy (TEM) measurements and numerical analysis (supporting information, SII and SIII). (e) Dynamic light scattering of the SPIOs coated with DSPE-mPEG1000: blue, number-weighted size distribution of 5 nm iron oxide core coated with DSPE-mPEG1000, average size 14.8 (1.2 nm; purple, 14 nm iron oxide core coated with DSPE-mPEG1000, average size) 28.6 (0.4 nm). Shown in the inset are TEM images of coated SPIOs negatively stained with phosphotungstic acid to yield a white layer surrounding the iron oxide cores that indicate the DSPE-mPEG1000 coating layer (see [16]).
