Houston, TX 77005
1:00 p.m. Wednesday, April 3, 2013
On Campus | Alumni
In these days, nanomaterials are applied in a variety of biomedical applications including magnetic resonance imaging (MRI), cell imaging, drug delivery, and cell separation. Most MRI contrast agents affect the longitudinal relaxation time (T1) and transverse relaxation time (T2) of water protons in the tissue and result in increased positive or negative contrast. In this work, we report the optimization of r1 or r2 relaxivity dynamics (1/T1 or 1/T2 = r1[Gd] or r2[Fe] ) with diameter controlled gadolinium oxide nanocrystals (2~22 nm) and iron based magnetic nanocrystals (4 ~33 nm). The r1 and r2 MR relaxivity values of hydrated nanocrystals were optimized and examined depending on their core diameter, surface coating, and compositions; the high r1 value of gadolinium oxide was 40-60 S-1mM-1, which is 10-15 times higher than those of Gd(III) chelates (4.3 ~4.6 S-1mM-1). Moreover, in vitro toxicological studies revealed that polymer coated nanocrystal suspensions had no significant effect on human dermal fibroblast (HDF) cells even at high concentration. Toward multimodal imaging or multifunctional ability, we prepared the iron oxide/QDs complexes, which consist of cores of iron oxide that act as nucleation sites for fluorescent QDs. The choice of variable QDs helped to visualize and remove large iron oxide materials in a magnetic separation. Additionally, diluted materials concentrated on the magnet could be fluorescently detected at very low concentration. The designed MRI or multifunctional nanocrystal agents will give great and powerful uses in biomedical applications.