Studying the effect of particle size and coating type on the blood kinetics of superparamagnetic iron oxide nanoparticles

Abstract

Purpose: Magnetic resonance imaging (MRI), one of the most powerful imaging techniques available, usually requires the use of an on-demand designed contrast agent to fully exploit its potential. The blood kinetics of the contrast agent represent an important factor that needs to be considered depending on the objective of the medical examination. For particulate contrast agents, such as superparamagnetic iron oxide nanoparticles (SPIOs), the key parameters are particle size and characteristics of the coating material. In this study we analyzed the effect of these two properties independently and systematically on the magnetic behavior and blood half-life of SPIOs. Methods: Eleven different SPIOs were synthesized for this study. In the first set (a), seven carboxydextran (CDX)-coated SPIOs of different sizes (19-86 nm) were obtained by fractionating a broadly size-distributed CDX-SPIO. The second set (b) contained three SPIOs of identical size (50 nm) that were stabilized with different coating materials, polyacrylic acid (PAA), polyethylene glycol, and starch. Furthermore, small PAA-SPIOs (20 nm) were synthesized to gain a global insight into the effects of particle size vs coating characteristics. Saturation magnetization and proton relaxivity were determined to represent the magnetic and imaging properties. The blood half-life was analyzed in rats using MRI, time-domain nuclear magnetic resonance, and inductively coupled plasma optical emission spectrometry. Results: By changing the particle size without modifying any other parameters, the relaxivity r 2 increased with increasing mean particle diameter. However, the blood half-life was shorter for larger particles. The effect of the coating material on magnetic properties was less pronounced, but it had a strong influence on blood kinetics depending on the ionic character of the coating material. Conclusion:In this report we systematically demonstrated that both particle size and coating material influence blood kinetics and magnetic properties of SPIO independently. These data provide key information for the selection of a contrast agent for a defined application and are additionally valuable for other nano areas, such as hyperthermia, drug delivery, and nanotoxicology.

Toxicity of iron oxide nanoparticles: Size and coating effects

“…Also, such factors as biodistribution and pharmacokinetics of IONP after injection can play an important role in understanding the toxic effects of IONP in vivo. For example, decrease in hydrodynamic size of nanoparticles may significantly increase the blood half‐life time and biodistribution of IONP, thus altering their toxic effects on different organs . As previously was shown in our works, bovine serum albumin (BSA)–coated IONP can be used for glioma visualization and drug delivery of anticancer therapeutics.…”

“…For example, decrease in hydrodynamic size of nanoparticles may significantly increase the blood half-life time and biodistribution of IONP, thus altering their toxic effects on different organs. [8] As previously was shown in our works, [9] bovine serum albumin (BSA)-coated IONP can be used for glioma visualization and drug delivery of anticancer therapeutics. Also, it was shown that a decrease in the size of nanoparticles and polyethylene glycol (PEG)coating dramatically increase their ability to visualize rat glioblastoma in vivo and aggregation stability after doxorubicin sorption.…”

In vivo delivery, pharmacokinetics, biodistribution and toxicity of iron oxide nanoparticles

“…A recent study has clearly shown the decrease of the blood half-life of IONPs from 50 to 3 minutes by increasing their hydrodynamic size from 20 to 85nm. 135 As shown in Fig. 6, IONPs with d H > 100nm quickly accumulate in the liver and spleen through macrophage phagocytosis and entrapment in liver and spleen sinusoids (§2.1.2).…”

Tracking of Magnetite Labeled Nanoparticles in the Rat Brain Using MRI

“…In agreement with relaxation theory, it could be shown that R 1 linearly increases with MLNP concentration but the relaxivity is mostly determined by the size of the magnetite. A smaller size of paramagnetic particles also increases the R 1 relaxivity while R 2 * relaxivity increases with particle size [35]. Given the limited SNR and readout bandwidth provided by a clinical scanner, this was also the reason why we focused on T 1 effects rather than on T 2 * effects in the current investigations.…”