Synthesis and Nuclear Magnetic Relaxation Properties of Composite Iron Oxide Nanoparticles

Abstract

Superparamagnetic iron oxide nanoparticles are suitable contrast agents for magnetic resonance imaging due to their effect on proton relaxation times, and excellent biocompatibility and biodistribution in tissue. In the present study, a ferrofluid formed by dextrancoated iron oxide nanoparticles was prepared by the coprecipitation method and with subsequent steps of crosslinking and addition of functionalizations on the nanoparticle´s surface (amino groups and a fluorophore). The effect of differences in the synthesis route (ratio of dextran to iron salts and temperature of the reaction) on the physico-chemical characteristics of the nanoparticles and their performance as contrast agents for magnetic resonance imaging was investigated. Overall, the nuclear magnetic relaxation times of water protons in aqueous suspensions of the nanoparticles did not show major differences among different batches, with no significant effect due to the addition of the fluorophore or changes in the dextran fraction of up to 50%. Larger reductions in the ratio of dextran to iron salts resulted in particles with slightly larger sizes, higher saturation magnetization and distinct nuclear magnetic relaxation times.

Intercomparison of radiosensitization induced by gold and iron oxide nanoparticles in human glioblastoma cells irradiated by 6 MV photons

“…The zeta potential ( ) of the different NPs dispersed in ultrapure water at pH = 7.4 is also given in Table 1 and are typical values usually found for such NP configurations. GNPs exhibit a negative zeta potential due the hydroxyl terminations from the reduction reaction with borohydride, while SPION-DX show a positive zeta potential, due the amino termination 29 – 31 . Thermal gravimetric analysis (TGA) was employed to access the mass fraction of the organic coating of the SPION-DX preparation (details in Oliveira et al.…”

“…Thermal gravimetric analysis (TGA) was employed to access the mass fraction of the organic coating of the SPION-DX preparation (details in Oliveira et al. 29 ). About 78% of the mass of the SPION-DX is composed by the dextran coating and 22% by the Fe O core.…”

“…Aminated dextran-coated superparamagnetic iron oxide nanoparticles (SPION-DX) were prepared from a mixture of Fe (II) and Fe (III) salts, according to Oliveira et al. 29 and following the method of coprecipitation with nucleation of nanoparticles directly in the presence of dextran 77 . An additional crosslinking step of the dextran shell was performed by adding 5 M NaOH and 14 mL of epichlorohydrin into the NPs solution, under magnetic stirring for 10 h. Finally, for amination of the coating, 60 mL of NH OH (28%) was added to the solution and maintained under magnetic stirring for 24 h. The ammonia excess was extracted by dialysis, using Spectra/Por membranes and changing the deionized water every 30 min.…”

Intercomparison of Radiosensitization Induced by Gold and Iron Oxide Nanoparticles in Human Glioblastoma Cells Irradiated by 6 MV Photons

“…The zeta potential (ζ ) of the different NPs dispersed in ultrapure water is also given in Table 1 and are typical values usually found for such NP configurations. SPION-DX showed a positive zeta potential, due the amino termination, while the GNPs exhibit a negative zeta potential due the hydroxyl terminations from the reduction reaction with borohydride [29][30][31] .…”

“…Gold nanoparticles (GNPs) were synthesized via the reduction of chlorouric acid (HAuCl 4 .3H 2 O) by sodium borohydride (NaBH 4 ), following a method adapted from Deraedt et al 68 . Aminated dextran-coated superparamagnetic iron oxide nanoparticles (SPION-DX) were prepared from a mixture of Fe (II) and Fe ((III) salts, according to Oliveira et al 29 and following the method of coprecipitation with nucleation of nanoparticles directly in the presence of dextran 69 . An additional crosslinking step of the dextran shell was performed by adding 5 M NaOH and 14 mL of epichlorohydrin into the NPs solution, under magnetic stirring for 10 h. Finally, for amination of the coating, 60 mL of NH 4 OH (28%) was added to the solution and maintained under magnetic stirring for 24 h. The ammonia excess was extracted by dialysis, using Spectra/Por® membranes and changing the deionized water every 30 minutes.…”