Inorganic nanoparticles based contrast agents for X-ray computed tomography

Synthesis of Au-Fe3O4 heterostructured nanoparticles for in vivo computed tomography and magnetic resonance dual model imaging

Water-soluble Au-Fe3O4 heterostructured nanoparticles with high biocompatibility were synthesized and applied as a dual modality contrast agent. These nanoparticles present strong CT/MRI contrast enhancement in a rabbit model. Low concentrations of Au-Fe3O4 were found to obtain a similar effect to high concentrations of a commercial iodine agent in the CT image.

The studies on highly concentrated complex dispersions of gold nanoparticles and temperature-sensitive nanogels and their application as new blood-vessel-embolic materials with high-resolution angiography

High colloid stability of highly concentrated Au nanoparticles (GNPs) for use in blood-pool imaging was achieved, using p(N-isopropylacrylamide-co-butyl methylacrylate) nanogels.

Poly(iohexol) nanoparticles as contrast agents for in vivo X-ray computed tomography imaging

Biocompatible poly(iohexol) nanoparticles, prepared through cross-linking of iohexol and hexamethylene diisocyanate followed by coprecipitation of the resulting cross-linked polymer with mPEG-polylactide, were utilized as contrast agents for in vivo X-ray computed tomography (CT) imaging. Compared to conventional small-molecule contrast agents, poly(iohexol) nanoparticles exhibited substantially protracted retention within the tumor bed and a 36-fold increase in CT contrast 4 h post injection, which makes it possible to acquire CT images with improved diagnosis accuracy over a broad time frame without multiple administrations.

Gold nanoparticle contrast agents in advanced X-ray imaging technologies

Recently, there has been significant progress in the field of soft- and hard-X-ray imaging for a wide range of applications, both technically and scientifically, via developments in sources, optics and imaging methodologies. While one community is pursuing extensive applications of available X-ray tools, others are investigating improvements in techniques, including new optics, higher spatial resolutions and brighter compact sources. For increased image quality and more exquisite investigation on characteristic biological phenomena, contrast agents have been employed extensively in imaging technologies. Heavy metal nanoparticles are excellent absorbers of X-rays and can offer excellent improvements in medical diagnosis and X-ray imaging. In this context, the role of gold (Au) is important for advanced X-ray imaging applications. Au has a long-history in a wide range of medical applications and exhibits characteristic interactions with X-rays. Therefore, Au can offer a particular advantage as a tracer and a contrast enhancer in X-ray imaging technologies by sensing the variation in X-ray attenuation in a given sample volume. This review summarizes basic understanding on X-ray imaging from device set-up to technologies. Then this review covers recent studies in the development of X-ray imaging techniques utilizing gold nanoparticles (AuNPs) and their relevant applications, including two- and three-dimensional biological imaging, dynamical processes in a living system, single cell-based imaging and quantitative analysis of circulatory systems and so on. In addition to conventional medical applications, various novel research areas have been developed and are expected to be further developed through AuNP-based X-ray imaging technologies.

Near-infrared fluorescent silica-coated gold nanoparticle clusters for x-ray computed tomography/optical dual modal imaging of the lymphatic system

Lymph nodes (LNs) are often removed to prevent the spread of cancer because they are frequently the first site of metastases. However, the enucleation of LNs requires difficult operative techniques and lymphedema can result as a complication. Although lymphedema can be cured by anastomosis of a lymph vessel (LV) to a vein, the operative procedure is extremely difficult because LNs and LVs are too small and indistinct to be identified. Therefore, visualization of LNs and LVs is important. The combination of X-ray computed tomography (CT) and fluorescence imaging, CT/fluorescence dual modal imaging, enables the visualization of LNs and LVs before and during surgery. To accomplish this, near-infrared fluorescent silica-coated gold nanoparticle clusters (Au@SiO₂) with a high X-ray absorption coefficient are synthesized. Both fluorescence imaging and CT show that the Au@SiO₂ nanoparticles gradually accumulate in LNs through LVs. CT determines the location and size of the LNs and LVs without dissection, and fluorescence imaging facilitates their identification. The Au@SiO₂ nanoparticles have neither hepatotoxicity nor nephrotoxicity. The results demonstrate that CT/fluorescence dual modal imaging using Au@SiO₂ nanoparticles provides anatomical information, including the location and size of LNs and LVs for determining a surgery plan, and provides intraoperative visualization of LNs and LVs to facilitate the operation.

Multiplexed sensing and imaging with colloidal nano- and microparticles

Sensing and imaging with fluorescent, plasmonic, and magnetic colloidal nano- and microparticles have improved during the past decade. In this review, we describe the concepts and applications of how these techniques can be used in the multiplexed mode, that is, sensing of several analytes in parallel or imaging of several labels in parallel.

Iodinated α-tocopherol nano-emulsions as non-toxic contrast agents for preclinical X-ray imaging

Micro-computed tomography (micro-CT) is an emerging imaging modality, due to the low cost of the imagers as well as their efficiency in establishing high-resolution (1-100 μm) three-dimensional images of small laboratory animals and facilitating rapid, structural and functional in vivo visualization. However use of a contrast agent is absolutely necessary when imaging soft tissues. The main limitation of micro-CT is the low efficiency and toxicity of the commercially available blood pool contrast agents. This study proposes new, efficient and non-toxic contrast agents for micro-CT imaging. This formulation consists of iodinated vitamin E (α-tocopheryl 2,3,5-triiodobenzoate) as an oily phase, formulated as liquid nano-emulsion droplets (by low-energy nano-emulsification), surrounded by a hairy PEG layer to confer stealth properties. The originality and strength of these new contrast agents lie not only in their outstanding contrasting properties, biocompatibility and low toxicity, but also in the simplicity of their fabrication: one-step synthesis of highly iodinated oil (iodine constitutes 41.7% of the oil molecule weight) and its spontaneous emulsification. After i.v. administration in mice (8.5% of blood volume), the product shows stealth properties towards the immune system and thus acts as an efficient blood pool contrast agent (t(1/2) = 9.0 h), exhibiting blood clearance following mono-exponential decay. A gradual accumulation predominantly due to hepatocyte uptake is observed and measured in the liver, establishing a strong hepatic contrast, persistent for more than four months. To summarize, in the current range of available or developed contrast agents for preclinical X-ray imaging, this agent appears to be one of the most efficient.