Core/shell Au/MnO nanoparticles prepared through controlled oxidation of AuMn as an electrocatalyst for sensitive H2O2 detection.

Monodisperse 5 nm AuMn nanoparticles were synthesized by hydride reduction of manganese acetylacetonate in the presence of Au nanoparticles. The alloy was formed through fast Mn diffusion into the Au structure. The AuMn nanoparticles were converted to Au-MnO composite particles through air annealing at 170 °C. These Au-MnO particles, especially the core/shell Au/MnO nanoparticles, were active for the electrochemical reduction of H2 O2 , with a detection limit reaching 8 nM. This highly sensitive electrochemical sensor based on the Au/MnO nanoparticles was used to monitor H2 O2 concentrations released from living cells, from which tumorigenic cells were discovered to release higher levels of H2 O2 than the non-tumorigenic cells.

Tuning exchange bias in core/shell FeO/Fe3O4 nanoparticles.

Monodisperse 35 nm FeO nanoparticles (NPs) were synthesized and oxidized in a dry air atmosphere into core/shell FeO/Fe(3)O(4) NPs with both FeO core and Fe(3)O(4) shell dimensions controlled by reaction temperature and time. Temperature-dependent magnetic properties were studied on FeO/Fe(3)O(4) NPs obtained from the FeO NPs oxidized at 60 and 100 °C for 30 min. A large exchange bias (shift in the hysteresis loop) was observed in these core/shell NPs. The relative dimensions of the core and shell determine not only the coercivity and exchange field but also the dominant reversal mechanism of the ferrimagnetic Fe(3)O(4) component. This is the first time demonstration of tuning exchange bias and of controlling asymmetric magnetization reversal in FeO/Fe(3)O(4) NPs with antiferromagnetic core and ferrimagnetic shell.

Penetration of endothelial cell coated multicellular tumor spheroids by iron oxide nanoparticles.

Iron oxide nanoparticles are a useful diagnostic contrast agent and have great potential for therapeutic applications. Multiple emerging diagnostic and therapeutic applications and the numerous versatile parameters of the nanoparticle platform require a robust biological model for characterization and assessment. Here we investigate the use of iron oxide nanoparticles that target tumor vasculature, via the tumstatin peptide, in a novel three-dimensional tissue culture model. The developed tissue culture model more closely mimics the in vivo environment with a leaky endothelium coating around a glioma tumor mass. Tumstatin-iron oxide nanoparticles showed penetration and selective targeting to endothelial cell coating on the tumor in the three-dimensional model, and had approximately 2 times greater uptake in vitro and 2.7 times tumor neo-vascularization inhibition. Tumstatin provides targeting and therapeutic capabilities to the iron oxide nanoparticle diagnostic contrast agent platform. And the novel endothelial cell-coated tumor model provides an in vitro microtissue environment to evaluate nanoparticles without moving into costly and time-consuming animal models.

PEGylated gold nanoparticles conjugated to monoclonal F19 antibodies as targeted labeling agents for human pancreatic carcinoma tissue.

In this study, we describe optical detection of antibody-conjugated nanoparticles bound to surgically resected human pancreatic cancer tissue. Gold nanoparticles stabilized by heterobifunctional polyethylene glycol (PEG) were prepared using approximately 15 nm spherical gold cores and covalently coupled to F19 monoclonal antibodies. The heterobifunctional PEG ligands contain a dithiol group for stable anchoring onto the gold surface and a terminal carboxy group for coupling of antibodies to the outside of the PEG shell. The nanoparticle-antibody bioconjugates form highly stable dispersions and exhibit long-term resistance to agglomeration. This has been demonstrated by dynamic light scattering, size exclusion chromatography, and transmission electron microscopy. The nanoparticle bioconjugates were used to label tumor stroma in approximately 5 mum thick sections of resected human pancreatic adenocarcinoma. After rinsing away nonbound nanoparticles and fixation, the tissue samples were imaged by darkfield microscopy near the nanoparticle resonance scattering maximum (approximately 560 nm). The images display pronounced tissue features and suggest that this novel labeling method could provide for facile identification of cancer tissue. Tumor samples treated with gold nanoparticles conjugated to nonspecific control antibodies and noncancerous pancreatic tissue treated with mAb-F19-conjugated gold nanoparticles both exhibited correctly negative results and showed no tissue staining.