Nano-sized CT contrast agents

Multifunctional Rbx WO3 nanorods for simultaneous combined chemo-photothermal therapy and photoacoustic/CT imaging

Light-triggered drug delivery based on near-infrared (NIR)-mediated photothermal nanocarriers has received tremendous attention for the construction of cooperative therapeutic systems in nanomedicine. Herein, a new paradigm of light-responsive drug carrier that doubles as a photothermal agent is reported based on the NIR light-absorber, Rb(x) WO3 (rubidium tungsten bronze, Rb-TB) nanorods. With doxorubicin (DOX) payload, the DOX-loaded Rb-TB composite (Rb-TB-DOX) simultaneously provides a burst-like drug release and intense heating effect upon 808-nm NIR light exposure. MTT assays show the photothermally enhanced antitumor activity of Rb-TB-DOX to the MCF-7 cancer cells. Most remarkably, Rb-TB-DOX combined with NIR irradiation also shows dramatically enhanced chemotherapeutic effect to DOX-resistant MCF-7 cells compared with free DOX, demonstrating the enhanced efficacy of combinational chemo-photothermal therapy for potentially overcoming drug resistance in cancer chemotherapy. Furthermore, in vivo study of combined chemo-photothermal therapy is also conducted and realized on pancreatic (Pance-1) tumor-bearing nude mice. Apart from its promise for cancer therapy, the as-prepared Rb-TB can also be employed as a new dual-modal contrast agent for photoacoustic tomography and (PAT) X-ray computed tomography (CT) imaging because of its high NIR optical absorption capability and strong X-ray attenuation ability, respectively. The results presented in the current study suggest promise of the multifunctional Rb(x)WO3 nanorods for applications in cancer theranostics.

Ultrasmall biomolecule-anchored hybrid GdVO4 nanophosphors as a metabolizable multimodal bioimaging contrast agent

Multimodal molecular imaging has recently attracted much attention on disease diagnostics by taking advantage of individual imaging modalities. Herein, we have demonstrated a new paradigm for multimodal bioimaging based on amino acids-anchored ultrasmall lanthanide-doped GdVO4 nanoprobes. On the merit of special metal-cation complexation and abundant functional groups, these amino acids-anchored nanoprobes showed high colloidal stability and excellent dispersibility. Additionally, due to typical paramagnetic behaviour, high X-ray mass absorption coefficient and strong fluorescence, these nanoprobes would provide a unique opportunity to develop multifunctional probes for MRI, CT and luminescence imaging. More importantly, the small size and biomolecular coatings endow the nanoprobes with effective metabolisability and high biocompatibility. With the superior stability, high biocompatibility, effective metabolisability and excellent contrast performance, amino acids-capped GdVO4:Eu(3+) nanocastings are a promising candidate as multimodal contrast agents and would bring more opportunities for biological and medical applications with further modifications.

Motion based X-ray imaging modality

A new X-ray imaging method (patent pending) was developed to visualize function-related motion information. We modify existing X-ray imaging methods to provide four images without increasing the necessary measurement time or radiation dose. The most important of these images is a new "kinetic" image that represents motions inside the object or living body. The motion-based contrast of the kinetic image can help visualize details that were not accessible before. The broad range of the movements and high sensitivity of the method are illustrated by imaging the mechanics of a working clock and the chest of a living African clawed frog (Xenopus laevis). The heart, valves, aorta, and lungs of the frog are clearly visualized in spite of the low soft tissue contrast of the animal. The new technology also reconstructs a "static" image similar to the existing conventional X-ray image. The static image shows practically the same information as the conventional image. The new technology presents two more images which show the point-wise errors of the static and kinetic images. This technique gives a better estimation of errors than present methods because it is based entirely on measured data. The new technology could be used in imaging cardiopulmonary movements, nondestructive testing, or port security screening.

Targeted multimodal imaging modalities

Molecular imaging non-invasively visualizes and characterizes the biologic functions and mechanisms in living organisms at a molecular level. In recent years, advances in imaging instruments, imaging probes, assay methods, and quantification techniques have enabled more refined and reliable images for more accurate diagnoses. Multimodal imaging combines two or more imaging modalities into one system to produce details in clinical diagnostic imaging that are more precise than conventional imaging. Multimodal imaging offers complementary advantages: high spatial resolution, soft tissue contrast, and biological information on the molecular level with high sensitivity. However, combining all modalities into a single imaging probe involves problems yet to be solved due to the requirement of high dose contrast agents for a component of imaging modality with low sensitivity. The introduction of targeting moieties into the probes enhances the specific binding of targeted multimodal imaging modalities and selective accumulation of the imaging agents at a disease site to provide more accurate diagnoses. An extensive list of prior reports on the targeted multimodal imaging probes categorized by each modality is presented and discussed. In addition to accurate diagnosis, targeted multimodal imaging agents carrying therapeutic medications make it possible to visualize the theranostic effect and the progress of disease. This will facilitate the development of an imaging-guided therapy, which will widen the application of the targeted multimodal imaging field to experiments in vivo.

Homo- and heteroleptic bismuth(III/V) thiolates from N-heterocyclic thiones: synthesis, structure and anti-microbial activity

Homo- and heteroleptic bismuth thiolato complexes have been synthesised and characterised from biologically relevant tetrazole-, imidazole-, thiadiazole- and thiazole-based heterocyclic thiones (thiols): 1-methyl-1H-tetrazole-5-thiol (1-MMTZ(H)); 4-methyl-4H-1,2,4-triazole-3-thiol (4-MTT(H)); 1-methyl-1H-imidazole-2-thiol (2-MMI(H)); 5-methyl-1,3,4-thiadiazole-2-thiol (5-MMTD(H)); 1,3,4-thiadiazole-2-dithiol (2,5-DMTD(H)2 ); and 4-(4-bromophenyl)thiazole-2-thiol (4-BrMTD(H)). Reaction of BiPh3 with 1-MMTZ(H) produced the rare Bi(V) thiolato complex [BiPh(1-MMTZ)4 ], which undergoes reduction in DMSO to give [BiPh(1-MMTZ)2 {(1-MMTZ(H)}2 ]. Reactions with PhBiCl2 or BiPh3 generally produced monophenylbismuth thiolates, [BiPh(SR)2 ]. The crystal structures of [BiPh(1-MMTZ)2 {1-MMTZ(H)}2 ], [BiPh(5-MMTD)2 ], [BiPh{2,5-DMTD(H)}2 (Me2 CO)] and [Bi(4-BrMTD)3 ] were obtained. Evaluation of the bactericidal properties against M. smegmatis, S. aureus, MRSA, VRE, E. faecalis and E. coli showed complexes containing the anionic ligands 1- MMTZ, 4-MTT and 4-BrMTD to be most effective. The dithiolato dithione complexes [BiPh(4-MTT)2 {4-MTT(H)}2 ] and [BiPh(1-MMTZ)2 {1-MMTZ(H)}2 ] were most effective against all the bacteria: MICs 0.34 μM for [BiPh(4-MTT)2 {4-MTT(H)}2 ] against VRE, and 1.33 μM for [BiPh(1-MMTZ)2 {1-MMTZ(H)}2 ] against M. smegmatis and S. aureus. Tris-thiolato Bi(III) complexes were least effective overall. All complexes showed little or no toxicity towards mammalian COS-7 cells at 20 μg mL(-1) .

Tantalum oxide nanoparticles for the imaging of articular cartilage using X-ray computed tomography: visualization of ex vivo/in vivo murine tibia and ex vivo human index finger cartilage

The synthesis and characterization of tantalum oxide (Ta2O5) nanoparticles (NPs) as new X-ray contrast media for microcomputed tomography (μCT) imaging of articular cartilage are reported. NPs, approximately 5-10 nm in size, and possessing distinct surface charges, were synthesized using phosphonate (neutral), ammonium (cationic), and carboxylate (anionic) ligands as end functional groups. Assessment of a cartilage defect in a human cadaver distal metacarpophalangeal (MCP) joint with the ammonium nanoparticles showed good visualization of damage and preferential uptake in areas surrounding the defect. Finally, an optimized nontoxic cationic NP contrast agent was evaluated in an in vivo murine model and the cartilage was imaged. These nanoparticles represent a new type of contrast agent for imaging articular cartilage, and the results demonstrate the importance of surface charge in the design of nanoparticulate agents for targeting the surface or interior zones of articular cartilage.

Ultrasonic assisted preparation of lanthanide-oleate complexes for the synthesis of multifunctional monodisperse upconversion nanoparticles for multimodal imaging

The synthesis of multifunctional monodisperse upconversion nanoparticles (UCNPs) of high quality is highly desired for bioimaging. Lanthanide-oleate complexes are excellent precursors for the synthesis of high quality UCNPs with controllable size and shape. In this work, lanthanide-oleate complexes were prepared by an ultrasonic assisted procedure, and used as precursors for further synthesis of multifunctional monodisperse NaYF4:59%Yb(3+),0.5% Tm(3+)@NaYF₄:20%Gd(3+) nanoparticles without the need for further purification. Heavy doping of Yb(3+) in the core and incorporation of Gd(3+) in the shell made the UCNPs promising for upconversion luminescence (UCL), magnetic resonance (MR) and computed tomography (CT) multimodal imaging. The nanoparticles were further functionalized with bombesin peptide for in vivo UCL/MR/CT imaging of prostate tumors.

Utilization of nanoparticles as X-ray contrast agents for diagnostic imaging applications

Among all the diagnostic imaging modalities, X-ray imaging techniques are the most commonly used owing to their high resolution and low cost. The improvement of these techniques relies heavily on the development of novel X-ray contrast agents, which are molecules that enhance the visibility of internal structures within the body in X-ray imaging. To date, clinically used X-ray contrast agents consist mainly of small iodinated molecules that might cause severe adverse effects (e.g. allergies, cardiovascular diseases and nephrotoxicity) in some patients owing to the large and repeated doses that are required to achieve good contrast. For this reason, there is an increasing interest in the development of alternative X-ray contrast agents utilizing elements with high atomic numbers (e.g. gold, bismuth, ytterbium and tantalum), which are well known for exhibiting high absorption of X-rays. Nanoparticles (NPs) made from these elements have been reported to have better imaging properties, longer blood circulation times and lower toxicity than conventional iodinated X-ray contrast agents. Additionally, the combination of two or more of these elements into a single carrier allows for the development of multimodal and hybrid contrast agents. Herein, the limitations of iodinated X-ray contrast agents are discussed and the parameters that influence the efficacy of X-ray contrast agents are summarized. Several examples of the design and production of both iodinated and iodine-free NP-based X-ray contrast agents are then provided, emphasizing the studies performed to evaluate their X-ray attenuation capabilities and their toxicity in vitro and in vivo.

Solid silica nanoparticles: applications in molecular imaging

Silica and silica-based nanoparticles have been widely used for therapeutic and diagnostic applications in cancer mainly through delivery of drugs, genes and contrast agents. Development of synthesis methods has provided the possibility of fabricating silica nanoparticles with different sizes in nanometer ranges as well as silica-based multimodal nanoparticles with many innovative properties and intriguing applications in biomedicine. The surface of silica particles facilitates different methods of surface modifications and allows conjugation of various biomolecules such as proteins and nucleic acids. In this review, different methods of fabrication of silica and silica-based nanoparticles, their surface modification and the application of these nanoparticles in molecular imaging are discussed. Overall, the aim of this review is to address the development of silica and silica-based multifunctional nanoparticles that are introduced mainly for molecular imaging applications using optical, magnetic (MRI), X-ray (computed tomography) and multimodal imaging techniques.

Anti-biofouling polymer-decorated lutetium-based nanoparticulate contrast agents for in vivo high-resolution trimodal imaging

Nanomaterials have gained considerable attention and interest in the development of novel and high-resolution contrast agents for medical diagnosis and prognosis in clinic. A classical urea-based homogeneous precipitation route that combines the merits of in situ thermal decomposition and surface modification is introduced to construct polyethylene glycol molecule (PEG)-decorated hybrid lutetium oxide nanoparticles (PEG-UCNPs). By utilizing the admirable optical and magnetic properties of the yielded PEG-UCNPs, in vivo up-conversion luminescence and T1 -enhanced magnetic resonance imaging of small animals are conducted, revealing obvious signals after subcutaneous and intravenous injection, respectively. Due to the strong X-ray absorption and high atomic number of lanthanide elements, X-ray computed-tomography imaging based on PEG-UCNPs is then designed and carried out, achieving excellent imaging outcome in animal experiments. This is the first example of the usage of hybrid lutetium oxide nanoparticles as effective nanoprobes. Furthermore, biodistribution, clearance route, as well as long-term toxicity are investigated in detail after intravenous injection in a murine model, indicating the overall safety of PEG-UCNPs. Compared with previous lanthanide fluorides, our nanoprobes exhibit more advantages, such as facile construction process and nearly total excretion from the animal body within a month. Taken together, these results promise the use of PEG-UCNPs as a safe and efficient nanoparticulate contrast agent for potential application in multimodal imaging.

Magneto-plasmonic Au-Fe alloy nanoparticles designed for multimodal SERS-MRI-CT imaging

Diagnostic approaches based on multimodal imaging are needed for accurate selection of the therapeutic regimens in several diseases, although the dose of administered contrast drugs must be reduced to minimize side effects. Therefore, large efforts are deployed in the development of multimodal contrast agents (MCAs) that permit the complementary visualization of the same diseased area with different sensitivity and different spatial resolution by applying multiple diagnostic techniques. Ideally, MCAs should also allow imaging of diseased tissues with high spatial resolution during surgical interventions. Here a new system based on multifunctional Au-Fe alloy nanoparticles designed to satisfy the main requirements of an ideal MCA is reported and their biocompatibility and imaging capability are described. The MCAs show easy and versatile surface conjugation with thiolated molecules, magnetic resonance imaging (MRI) and computed X-ray tomography (CT) signals for anatomical and physiological information (i.e., diagnostic and prognostic imaging), large Raman signals amplified by surface enhanced Raman scattering (SERS) for high sensitivity and high resolution intrasurgical imaging, biocompatibility, exploitability for in vivo use and capability of selective accumulation in tumors by enhanced permeability and retention effect. Taken together, these results show that Au-Fe nanoalloys are excellent candidates as multimodal MRI-CT-SERS imaging agents.

Temporal analysis of dissolution by-products and genotoxic potential of spherical zinc-silicate bioglass: "imageable beads" for transarterial embolization

Embolization of vascular tumors is an important tool in minimally invasive surgical intervention. Radiopaque, non-degradable, and non-deformable spherical zinc-silicate glass particles were produced in a range of 45-500 μm. Three size ranges (45-150, 150-300, and 300-500 μm) were used in the current study. The glass microspheres were eluted in polar (saline solution) and non-polar (dimethyl sulfoxide) medium, and ion release profiles were recorded using inductively coupled plasma atomic emission spectroscopy. Approximately 80% of Gaussian distribution was achieved by simple sieving. The ions released from the microspheres were dependent upon surface area to volume ratio as well as the nature of elution media. Greater ions were released from smaller particles (45-150 μm) having largest surface area in polar medium. For the genotoxicity bacterial mutation Ames assay, the concentrations of all the ions were well below their therapeutic concentration reported in the literature. No mutagenic effect was observed in the bacterial mutation Ames test. Hence, it can be concluded that the glass microspheres produced herein are non-mutagenic further supporting the materials potential as a suitable embolic agent.

In vivo near-infrared photothermal therapy and computed tomography imaging of cancer cells using novel tungsten-based theranostic probe

Photothermal therapy, as a physical therapeutic technique to kill cancer, has generated a great deal of interest. Photothermal agents hence play a critical role in this modern therapy. We report the use of transition metal oxides as photothermal agents based on PEGylated WO3-x nanoparticles. The well-prepared nanoparticles presented effective results during photothermal therapy both in vitro and in vivo by using near-IR laser irradiation (980 nm, 0.5 W cm(-2)). The tumor cells were effectively damaged using low power density during a short irradiation time without destroying healthy tissues. In vitro results of photothermal therapy with PEGylated WO3-x nanoparticles proved to be effective on 4T1 murine breast cancer cells via a confocal microscopy method and MTT assay. In vivo results were further confirmed by hematoxylin and eosin (H & E) histological staining. Additionally, PEGylated WO3-x nanoparticles were shown to be effective as a CT imaging contrast agent on a tumor-bearing mouse model. Our results suggest that this generation of PEGylated WO3-x nanoparticles can potentially be used in oncological CT imaging and photothermal therapy.

Synthesis of PEGylated low generation dendrimer-entrapped gold nanoparticles for CT imaging applications

Dendrimer-entrapped gold nanoparticles (Au DENPs) can be formed using low-generation dendrimers pre-modified by polyethylene glycol (PEG). The formed PEGylated Au DENPs with desirable stability, cytocompatibility, and X-ray attenuation properties enable efficient computed tomography imaging of the heart and tumor model of mice.

Contrast enhancement of iohexol-cisplatin-gelatin complex under computed tomography imaging

X-ray computed tomography (CT) is one of the most powerful non-invasive diagnostic techniques nowadays. The iodinated molecules used as CT contrast agents in the clinic have short circulation times in the body, which significantly restrict its applications. Furthermore, some patients are hypersensitive to iodine. So, researchers have made tremendous efforts to improve the property of iodine. Besides, cis-diammineplatinum (II) dichloride (cisplatin), a major chemo agent for cancer treatment, possess higher X-ray attenuation coefficient being a CT contrast agent. The incorporation of cisplatin with an iodinated agent could facilitate the quality of CT images and damage cancer cells simultaneously. To reduce toxicity of a contrast agent, polymer matrix, gelatin, was incorporated for avoiding contact with nontarget cells. In this study, we combined the iodine contrast agent, 1,3-N-bis (2,3-dihydroxypropyl)-5-[N-(2,3-dihydroxypropyl)acetamido]-2,4,6-triiodobenzene-1,3-dicarboxamide (iohexol), with cisplatin, and then examined them in a micro CT with different X-ray tube voltages (50 kV, 80 kV, 100 kV) to find optimal scanning conditions for imaging. As expected, iohexol combined with cisplatin enhanced X-ray attenuation and image contrast. The optimal CT image could be acquired at iohexol and cisplatin concentrations of 50 mg/ml and 3 mg/ml, respectively, under 80 kV irradiation. Finally, the iohexol-cisplatin-gelatin solution was then fabricated into nanoparticles of sizes about 240 nm, which may suitable for in vivo delivery.

Folic acid-conjugated silica-coated gold nanorods and quantum dots for dual-modality CT and fluorescence imaging and photothermal therapy

Multifunctional nanoparticles (NPs) have great potential for multimodal cancer imaging and effective therapy. We have developed multifunctional NPs (GNR@SiO₂@QDs) by incorporating gold nanorods (GNRs) and CdSe/ZnS quantum dots (QDs) into silica. Folic acid (FA) as a targeting ligand was covalently conjugated on the surfaces of GNR@SiO₂@QDs with a silane coupling agent. Cell viability assay showed that these NPs had low cytotoxicity. And confocal fluorescence images illustrated that they could selectively target HeLa cells overexpressing folate receptors (FRs) rather than FR-deficient A549 cells. In vitro cell imaging experiments revealed that these NPs exhibited strong X-ray attenuation for X-ray computed tomography (CT) imaging and strong fluorescence for fluorescence imaging. They also showed an enhanced photothermal therapy (PTT) effect for cancer cells due to GNRs' high absorption coefficient in the near infrared (NIR) region and a better heat generation rate. All results show that they have great potential in theranostic applications such as for targeted tumor imaging and therapy.

Biocompatible and high-performance amino acids-capped MnWO4 nanocasting as a novel non-lanthanide contrast agent for X-ray computed tomography and T(1)-weighted magnetic resonance imaging

In the present work, a novel non-lanthanide dual-modality contrast agent, manganese tungstate (MnWO4), has been successfully constructed by a facile and versatile hydrothermal route. With the merits of a high atomic number and a well-positioned K-edge energy of tungsten, our well-prepared non-lanthanide nanoprobes provide a higher contrast efficacy than routine iodine-based agents in clinics. Additionally, the presence of Mn in these nanoparticles endow them with excellent T1-weighted MR imaging capabilities. As an alternative to T2-weighted MRI and CT dual-modality contrast agents, the nanoprobes can provide a positive contrast signal, which prevents confusion with the dark signals from hemorrhage and blood clots. To the best of our knowledge, this is the first report that a non-lanthanide imaging nanoprobe is applied for CT and T1-weighted MRI simultaneously. Moreover, comparing with gadolinium-based T1-weighted MRI and CT dual-modality contrast agents that were associated with nephrogenic systemic fibrosis (NSF), our contrast agents have superior biocompatibility, which is proved by a detailed study of the pharmacokinetics, biodistribution, and in vivo toxicology. Together with excellent dispersibility, high biocompatibility and superior contrast efficacy, these nanoprobes provide detailed and complementary information from dual-modality imaging over traditional single-mode imaging and bring more opportunities to the new generation of non-lanthanide nanoparticulate-based contrast agents.

Biomimetic RNA-silencing nanocomplexes: overcoming multidrug resistance in cancer cells

RNA interference (RNAi) is an RNA-dependent gene silencing approach controlled by an RNA-induced silencing complex (RISC). Herein, we present a synthetic RISC-mimic nanocomplex, which can actively cleave its target RNA in a sequence-specific manner. With high enzymatic stability and efficient self-delivery to target cells, the designed nanocomplex can selectively and potently induce gene silencing without cytokine activation. These nanocomplexes, which target multidrug resistance, are not only able to bypass the P-glycoprotein (Pgp) transporter, due to their nano-size effect, but also effectively suppress Pgp expression, thus resulting in successful restoration of drug sensitivity of OVCAR8/ADR cells to Pgp-transportable cytotoxic agents. This nanocomplex approach has the potential for both functional genomics and cancer therapy.

Method for obtaining silver nanoparticle concentrations within a porous medium via synchrotron X-ray computed microtomography

Attempts at understanding nanoparticle fate and transport in the subsurface environment are currently hindered by an inability to quantify nanoparticle behavior at the pore scale (within and between pores) within realistic pore networks. This paper is the first to present a method for high resolution quantification of silver nanoparticle (nAg) concentrations within porous media under controlled experimental conditions. This method makes it possible to extract silver nanoparticle concentrations within individual pores in static and quasi-dynamic (i.e., transport) systems. Quantification is achieved by employing absorption-edge synchrotron X-ray computed microtomography (SXCMT) and an extension of the Beer-Lambert law. Three-dimensional maps of X-ray mass linear attenuation are converted to SXCMT-determined nAg concentration and are found to closely match the concentrations determined by ICP analysis. In addition, factors affecting the quality of the SXCMT-determined results are investigated: 1) The acquisition of an additional above-edge data set reduced the standard deviation of SXCMT-determined concentrations; 2) X-ray refraction at the grain/water interface artificially depresses the SXCMT-determined concentrations within 18.1 μm of a grain surface; 3) By treating the approximately 20 × 10(6) voxels within each data set statistically (i.e., averaging), a high level of confidence in the SXCMT-determined mean concentrations can be obtained. This novel method provides the means to examine a wide range of properties related to nanoparticle transport in controlled laboratory porous medium experiments.

Er3+-doped YbPO4 up-conversion porous nanospheres for UCL/CT bimodal imaging in vivo and chemotherapy

PEI modified up-conversion porous nanospheres were obtained by template-free hydrothermal method, combining up-conversion luminescence/X-ray computed tomography bimodal-imaging with drug delivery.

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.

Quintuple-modality (SERS-MRI-CT-TPL-PTT) plasmonic nanoprobe for theranostics

A unique quintuple-modality theranostic nanoprobe (QMT) is developed with gold nanostars for surface-enhanced Raman scattering (SERS), magnetic resonance imaging (MRI), computed tomography (CT), two-photon luminescence (TPL) imaging and photothermal therapy (PTT). The synthesized gold nanostars were tagged with a SERS reporter and linked with an MRI contrast agent Gd(3+). In vitro experiments demonstrated the developed QMT nanoprobe to be a potential theranostic agent for future biomedical applications.