Targeted Delivery and Redox Activity of Folic Acid-Functionalized Nanoceria in Tumor Cells.

Cerium oxide nanoparticles (nanoceria) are promising catalytic nanomaterials that are widely reported to modulate intracellular reactive oxygen species (ROS). In this study, nanoceria were synthesized by flame spray pyrolysis and functionalized with a cell-targeting ligand, folic acid (FA). The surface functionalization of nanoceria was stable, and FA enhanced the uptake of nanoceria via folate receptors. Internalized nanoceria and FA-nanoceria were localized predominantly in the cytoplasm. FA-nanoceria modulated intracellular ROS to a greater extent than the nanoceria in colon carcinoma cells, but induced ROS in ovarian cancer cells, likely due to their enhanced uptake. Together these data demonstrated that the functionalization of nanoceria with FA modulated their endocytosis and redox activity, and they may find application in the delivery of anticancer drugs in the future.

Endocytosis of cerium oxide nanoparticles and modulation of reactive oxygen species in human ovarian and colon cancer cells.

Cerium oxide nanoparticles (nanoceria) are widely reported to be cytocompatible and modulate intracellular reactive oxygen species (ROS) in a range of different cell types. In this study, nanoceria (d=7 and 94nm) synthesised by flame spray pyrolysis did not affect the proliferation of SKOV3 human ovarian and WiDr human colon cancer cell lines over a 72h treatment period. The cellular accumulation of nanoceria was uniform and increased up to 24h post-treatment before decreasing. The uptake of nanoceria in both cell lines was energy-dependent and was found to occur via non-specific pathways as well as clathrin-coated vesicles and caveolae. Nanoceria were localised predominantly in the cytoplasm and, to a lesser extent, with clathrin, caveolin-1 and lysosomes. The intracellular trafficking varied with particle size, treatment time and cell type. The larger nanoceria were found to scavenge intracellular ROS to a greater extent than the smaller nanoceria, and ROS scavenging was found to increase with treatment time. Together these data demonstrated that the diameter of the nanoceria and the cell types determined their mechanisms of uptake and intracellular localisation, as well as their ROS scavenging effects. STATEMENT OF SIGNIFICANCE: Cerium oxide nanoparticles (nanoceria) are a promising biomaterial that can catalytically scavenge reactive oxygen species (ROS). Modulation of ROS may potentially minimise the inflammatory effects of cancer. However, the antioxidant properties of nanoceria are reported to be pH-dependent and, thus, dependent on their mechanisms of endocytosis. This study is the first to examine the effects of particle size on the uptake and intracellular trafficking of flame spray-synthesised nanoceria in human cancer cells. This study demonstrated that the particle diameter, treatment time and cell type determined the mechanisms of uptake and intracellular localisation of nanoceria, as well as their ROS scavenging effects. This study highlighted the importance of testing new nanoparticle systems rather than making assumptions based on previous uptake studies.

Hyaluronan coated cerium oxide nanoparticles modulate CD44 and reactive oxygen species expression in human fibroblasts.

Cerium oxide nanoparticles are being widely explored for cell therapies. In this study, nanoceria was functionalized with hyaluronan (HA) using the organosilane linker, 3-aminopropyltriethoxysilane. HA-nanoceria was found to be cytocompatible and to reduce intracellular reactive oxygen species in human fibroblasts. The HA-nanoceria was found to colocalize with CD44 on the surface of the cells and once internalized traffic to the lysosomes, be degraded and induce markers of autophagy. These particles were also effective in reducing the cell surface expression of CD44. Together these data suggest that HA-nanoceria is a promising drug delivery material to target CD44-expressing cells through a variety of mechanisms. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1736-1746, 2016.

Glycosaminoglycan functionalized nanoparticles exploit glycosaminoglycan functions.

Nanoparticles are being explored for a variety of applications including medical imaging, drug delivery, and biochemical detection. Surface functionalization of nanoparticles with glycosaminoglycans (GAGs) is an attractive strategy that is only starting to be investigated to improve their properties for biological and therapeutic applications. Herein, we describe a method to functionalize the surface of cerium oxide nanoparticles (nanoceria) with organosilane linkers, such as 3-(aminopropyl)triethoxysilane (APTES) and 3-(mercaptopropyl)trimethoxysilane (MPTMS), and GAGs, such as unfractionated and low molecular weight heparin. Examples of how the activity of these heparin functionalized nanoparticles are governed by the pendant GAGs are detailed. The activity of heparin covalently attached to the nanoceria was found to be unchanged when compared to unfractionated heparin using the activated partial clotting time (APTT) assay.

Cellular uptake and reactive oxygen species modulation of cerium oxide nanoparticles in human monocyte cell line U937.

Cerium oxide nanoparticles (nanoceria) are promising materials for intracellular oxygen free radical scavenging providing a potential therapy for reactive oxygen species (ROS)-mediated inflammatory processes. In this study rhombohedral-shaped nanoceria were synthesized by flame spray pyrolysis with tuneable particle diameters between 3 and 94 nm by changing the liquid precursor flow rate. Monocytes and macrophages are major players in inflammatory processes as their production of ROS species has important downstream effects on cell signalling. Therefore, this study examined the ability of the nanoceria to be internalised by the human monocytic cell line, U937, and scavenge intracellular ROS. U937 cells activated in the presence of phorbol 12-myristate 13-acetate (PMA) were found to be more responsive to the nanoceria than U937 cells, which may not be surprising given the role of monocyte/macrophages in phagocytosing foreign material. The smaller particles were found to contain more crystal lattice defects with which to scavenge ROS, however a greater proportion of both the U937 and activated U937 cell populations responded to the larger particles. Hence all nanoceria particle sizes examined in this study were equally effective in scavenging intracellular ROS.