Relaxivity enhanced magnetic nanospheres for the early detection of cancer

Abstract

In this study, to improve the sensitivity of MR up to the level where detection of molecular markers becomes possible, Magnetite Encapsulated Polymeric Nanocomposite (MEPN) have been developed. In the first part of this work, magnetite nanocrystals were synthesized by the growth-controlled coprecipitation technique of ferric aqueous solution at the room temperature. The size of nanocrystals was controlled in the range from 6 to 12 nm when picoliter droplets were used. On the basis of growth-controlled coprecipitation mechanism, growth-dominant coprecipitation using microjet technique was developed. Prepared nanocrystal shows superior magnetic property that can be used as ultrasensitive MR contrast agent for further experiments. At the second part of this work, nanocapsules containing magnetite nanoparticles were prepared by emulsification-diffusion technique and the effects of homogenization and agitation speed on the size of the nanoparticles were observed. The factor dominating the size was the homogenization strength and optimal polymer concentration. The encapsulation efficiency was precisely controlled by the ratio between magnetite and PLGA with the support of co-solvent. The magnetic properties of MEPNs were also measured. There was no size effect of magnetite in encapsulation, because the ZFC curve shows similar behavior with same blocking temperature. And the local condensation of magnetite nanoparticles due to the hydrophobic capping ligand finally leads to the separation of small amount of highly-capsuled particles and large amount of magnetite-free particles. The magnetic relaxation was finally performed for the evaluation as MRI contrast agent. The aggregation of magnetite nanoparticles gives enhanced relaxation ability to the PLGA nanoparticles over intrinsic relaxivity. For the last part of this study, antibody-conjugated MEPNs were prepared. Herceptin was effectively conjugated with MEPNs through EDC-mediated reaction. MEPNs showed no cyto...