Paper BI-TuP3
Functionalization of Cerium Oxide Nanoparticles with Biocompatible Molecules to Prevent Surface Modification by Phosphate Ions

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Cerium oxide nanoparticles (CNP’s) are a promising catalytic antioxidant in biological systems, exhibiting superoxide dismutase and catalase mimetic, and nitric oxide radical scavenging activity. Nanoceria exhibits redox activity by switching between Ce 3+ and 4+ depending on environment. CNPs have also been shown to protect cells against oxidative stress. Specific formulation of cerium oxide nanoparticle is non-toxic, non-immunogenic and well tolerated both in vitro and in vivo model, which provide the rational/platform for its biological applications. Recently CNPs have become increasingly popular in biological work, both in vivo and in vitro. We have previously shown these CNPs have some potential to treat wound care, cancer therapy, retinal protection and neurodegenerative diseases. However there are several factors to consider, one being its interaction with biological molecules in different buffers, media, and serum. The common anions are phosphate, sulfate and carbonate. In our previous work, CNPs interaction with sulfate and carbonate are proven not to alter the surface chemistry of CNPs, whereas phosphate anions do. The CNPs properties are surface dependent and phosphate anions are shown to modify the surface. Current study focuses on preventing the CNPs surface modification by phosphate buffer through functionalization. Dextran and polyethylene glycol (PEG) were used to functionalize CNPs. The functionalized CNPs were incubated with phosphate ions and changing their absorbance and emission characteristic was analyzed by Ultraviolet-visible spectroscopy (UV) and photoluminescence spectroscopy (PL). The results show that CNPs functionalized with Dextran prevented interaction with PBS (phosphate ions) and preserved the redox property of the nanoparticle. However, PEG coating fails to do so. Varying pH levels in the range of 6-8 had no significant effect on the phosphate ion interaction with CNPs surface. We further investigated the surface interaction of PEG-CNPs with phosphate, while varying the concentration (5% to 40%) and the chain length (300 molecular weight to 6000 molecular weight) of PEG. The results showed that increasing the concentration or chain length of PEG did not have any effect on phosphate and cerium surface interaction. Looking into the surface charge and morphology of PEG and Dextran will allow us to gain further insight into what is occurring on the surface of these nanoparticles with phosphate ions. This basic study will help to engineer CNPs, which will be effective in biological applications and overall to prevent modification of CNPs surface.