Nanomaterials have become increasingly important in the development of new molecular probes for in vivo imaging, both experimentally and clinically. Nanoparticulate imaging probes have included semiconductor quantum dots, magnetic and magnetofluorescent nanoparticles, gold nanoparticles and nanoshells, among others. However, the use of nanomaterials for one of the most common imaging techniques, computed tomography (CT), has remained unexplored. Current CT contrast agents are based on small iodinated molecules. They are effective in absorbing X-rays, but non-specific distribution and rapid pharmacokinetics have rather limited their microvascular and targeting performance. Here we propose the use of a polymer-coated Bi(2)S(3) nanoparticle preparation as an injectable CT imaging agent. This preparation demonstrates excellent stability at high concentrations (0.25 M Bi(3+)), high X-ray absorption (fivefold better than iodine), very long circulation times (>2 h) in vivo and an efficacy/safety profile comparable to or better than iodinated imaging agents. We show the utility of these polymer-coated Bi(2)S(3) nanoparticles for enhanced in vivo imaging of the vasculature, the liver and lymph nodes in mice. These nanoparticles and their bioconjugates are expected to become an important adjunct to in vivo imaging of molecular targets and pathological conditions.
A method for the fabrication of thick films of porous anodic alumina on rigid substrates is described. The anodic alumina film was generated by the anodization of an aluminum film evaporated on the substrate. The morphology of the barrier layer between the porous film and the substrate was different from that of anodic films grown on aluminum substrates. The removal of the barrier layer and the electrochemical growth of nanowires within the ordered pores were accomplished without the need to remove the anodic film from the substrate. We fabricated porous anodic alumina samples over large areas (up to 70 cm2), and deposited in them nanowire arrays of various materials. Long nanowires were obtained with lengths of at least 9 μm and aspect ratios as high as 300. Due to their mechanical robustness and the built‐in contact between the conducting substrate and the nanowires, the structures were useful for electrical transport measurements on the arrays. The method was also demonstrated on patterned and non‐planar substrates, further expanding the range of applications of these porous alumina and nanowire assemblies.
The fabrication of surface-enhanced Raman spectroscopy (SERS) substrates that are optimized for use with specifi c laser wavelength-analyte combinations is addressed. In order to achieve large signal enhancement, temporal stability, and reproducibility over large substrate areas at low cost, only self-assembly and templating processes are employed. The resulting substrates consist of arrays of gold nanospheres with controlled diameter and spacing, properties that dictate the optical response of the structure. Tunability of the extended surface plasmon resonance is observed in the range of 520-1000 nm. It is demonstrated that the enhancement factor is maximized when the surface plasmon resonance is red-shifted with respect to the SERS instrument laser line. Despite relying on self-organization, site-to-site enhancement factor variations smaller than 10% are obtained.
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