Design of iron oxide-based nanoparticles for MRI and magnetic hyperthermia

Different parameters like core size of SPION, shape, hydrodynamic diameter, size distribution, nanoparticle coating and aggregation influence the longitudinal and transverse relaxivities of iron oxide nanoparticles.

“Different parameters like core size of SPION, shape, hydrodynamic diameter, size distribution, nanoparticles coating and aggregation influence the longitudinal and transverse relaxivities of iron oxide nanoparticles.”

r2 typically shows a linear increase with increasing particle core size from 4-5 to 18 nm, while r1 remains rather invariant for particles larger than approximately 8 nm.

“While r2 typically shows a linear increase with increasing the particle core size from 4-5 to 18 nm, r1 remains rather invariant for particles larger than approximately 8 nm.”

For large clusters, if the size exceeds 90 nm, r2 decreases with increasing size due to a reduction in proton exchange rate arising from reduced surface accessibility.

“In the case of large clusters, if the size exceeds 90 nm, r2 decreases with increasing size due to a reduction in the proton exchange rate arising from the reduction in surface accessibility.”

For small clusters, r2 gradually increases with hydrodynamic diameter up until approximately 80 nm.

“Regarding the effect of hydrodynamic diameter and aggregation on relaxivities, r2 gradually increases with the hydrodynamic diameter (up until approximately 80 nm) for small clusters, because SPION are consistently dispersed in water and protons diffuse between the magnetic cores.”