Fluorescent Superparamagnetic Nanocrystals for Tumor Detection and Characterization

Sunday, February 14, 2016
Louis Mejia, University of California, Irvine, Irvine, CA
Due to the vast variability of surface receptors found on tumor cells, a novel molecular diagnostic method is needed for possible pharmaceutical treatment. Recent advancements in nanotechnology have led to the development of various nanoparticles for disease detection. Previous literature had devised methods for both the synthesis and coating of superparamagnetic iron oxide nanocrystals with an amphiphilic polymer layer, thereby rendering aqueous dissolution. However, current polymers are unstable in vivo and have limited magnetism due to their large size. The objective of this project is to successfully create a new magnetofluorescent nanoparticle ready for biomedical applications such as tumor detection. It uses previous methods of synthesis and coating in order to adhere polydiacetylene to the surface, which is much smaller than current polymers. If activated with ultraviolet radiation, the polymer will readily obtain a blue color and form a stable cross-linked monolayer. If further agitated via successful binding to another molecular structure, such as an antibody bound to a specific receptor, the angular strain in the cross-linkage will instead emit a red hue. This change in fluorescence coupled with magnetism allows for two powerful detection methods. Coating is achieved via dual solvent exchange, in which previously synthesized nanoparticles dissolved in hexane are placed in solvents of ever-increasing polarity. 5 mg of a polydiacetylene dissolved in chloroform is mixed with 1 mg of the iron oxide cores in toluene. With the further addition of DMSO, the polymer can successfully coat the cores, allowing water solubility. 254 nm ultraviolet light induces cross-linking and the blue color change. After concentration through several washes, the size of the particles can be determined using dynamic light scattering. Results have shown core sizes of 15 nm and a total coated particle size around 25 nm, alongside extraneous populations of micelles, liposomes, and other super-structures that unavoidably form due to polymer excess. The solution has also been shown to obtain both a blue and red color change, alongside exhibiting magnetism. Near-future experiments are aimed at separating solute populations through high-pressure liquid chromatography. Once reliable homogeneous solutions of coated magnetofluorescent nanoparticles consistently emerge, the focus can shift to modifying terminal functional groups on the polymer for eventual diagnostic applications.