Core-shell NaHoF4@TiO2 NPs: A labelling method to trace engineered nanomaterials of ubiquitous elements in the environment

Understanding the fate and behavior of nanoparticles (NPs) in the natural environment is important to assess their potential risk. Single particle inductively coupled plasma mass spectrometry (spICP-MS) allows for the detection of NPs at extremely low concentrations, but the high natural background of the constituents of many of the most widely utilized nanoscale materials makes accurate quantification of engineered particles challenging. Chemical doping, with a less naturally abundant element, is one approach to address this; however, certain materials with high natural abundance, such as TiO2 NPs, are notoriously difficult to label and differentiate from natural NPs. Using the low abundance rare earth element Ho as a marker, Ho-bearing core -TiO2 shell (NaHoF4@TiO2) NPs were designed to enable the quantification of engineered TiO2 NPs in real environmental samples. The NaHoF4@TiO2 NPs were synthesized on a large scale (gram), at relatively low temperatures, using a sacrificial Al(OH)3 template that confines the hydrolysis of TiF4 within the space surrounding the NaHoF4 NPs. The resulting NPs consist of a 60 nm NaHoF4 core and a 5 nm anatase TiO2 shell, as determined by TEM, STEM-EDX mapping, and spICPMS. The NPs exhibit excellent detectability by spICP-MS at extremely low concentrations (down to 1 × 10−3 ng/L) even in complex natural environments with high Ti background

Nanodiamond Promotes Surfactant-Mediated Triglyceride Removal from a Hydrophobic Surface at or below Room Temperature

We demonstrate that ca. 5 nm nanodiamond particles dramatically improve triglyceride lipid removal from a hydrophobic surface at room temperature using either anionic or nonionic surfactants. We prepare nanodiamond–surfactant colloids, measure their stability by dynamic light scattering and use quartz crystal microbalance–dissipation, a technique sensitive to surface mass, in order to compare their ability to remove surface–bound model triglyceride lipid with ionic and nonionic aqueous surfactants at 15–25 °C. Oxidized, reduced, ω-alkylcarboxylic acid, and ω-alkylamidoamine surface-modified adducts are prepared, and then characterized by techniques including ¹³C cross-polarization (CP) magic-angle spinning (MAS) NMR. Clear improvement in removal of triglyceride was observed in the presence of nanodiamond, even at 15 °C, both with nanodiamond–surfactant colloids, and by prior nanoparticle deposition on interfacial lipid, showing that nanodiamonds are playing a crucial role in the enhancement of the detergency process, providing unique leads in the development of new approaches to low-temperature cleaning

Bisphosphonate-Anchored PEGylation and Radiolabeling of Superparamagnetic Iron Oxide: Long-Circulating Nanoparticles for <i>in Vivo</i> Multimodal (T1 MRI-SPECT) Imaging

The efficient delivery of nanomaterials to specific targets for <i>in vivo</i> biomedical imaging is hindered by rapid sequestration by the reticuloendothelial system (RES) and consequent short circulation times. To overcome these two problems, we have prepared a new stealth PEG polymer conjugate containing a terminal 1,1-bisphosphonate (BP) group for strong and stable binding to the surface of ultrasmall-superparamagnetic oxide nanomaterials (USPIOs). This polymer, PEG(5)-BP, can be used to exchange the hydrophobic surfactants commonly used in the synthesis of USPIOs very efficiently and at room temperature using a simple method in 1 h. The resulting nanoparticles, PEG(5)-BP-USPIOs are stable in water or saline for at least 7 months and display a near-zero ζ-potential at neutral pH. The longitudinal (<i>r</i>₁) and transverse (<i>r</i>₂) relaxivities were measured at a clinically relevant magnetic field (3 T), revealing a high <i>r</i>₁ of 9.5 mM^–1 s^–1 and low <i>r</i>₂/<i>r</i>₁ ratio of 2.97, making these USPIOs attractive as T1-weighted MRI contrast agents at high magnetic fields. The strong T1-effect was demonstrated <i>in vivo</i>, revealing that PEG(5)-BP-USPIOs remain in the bloodstream and enhance its signal 6-fold, allowing the visualization of blood vessels and vascular organs with high spatial definition. Furthermore, the optimal relaxivity properties allow us to inject a dose 4 times lower than with other USPIOs. PEG(5)-BP-USPIOs can also be labeled using a radiolabeled-BP for visualization with single photon emission computed tomography (SPECT), and thus affording dual-modality contrast. The SPECT studies confirmed low RES uptake and long blood circulation times (<i>t</i>_1/2 = 2.97 h). These results demonstrate the potential of PEG(5)-BP-USPIOs for the development of targeted multimodal imaging agents for molecular imaging