Nano-sized CT contrast agents

Rapid Degradation and High Renal Clearance of Cu3BiS3 Nanodots for Efficient Cancer Diagnosis and Photothermal Therapy in Vivo

A key challenge for the use of inorganic nanomedicines in clinical applications is their long-term accumulation in internal organs, which raises the common concern of the risk of adverse effects and inflammatory responses. It is thus necessary to rationally design inorganic nanomaterials with proper accumulation and clearance mechanism in vivo. Herein, we prepared ultrasmall Cu3BiS3 nanodots (NDs) as a single-phased ternary bimetal sulfide for photothermal cancer therapy guided by multispectral optoacoustic tomography (MSOT) and X-ray computed tomography (CT) due to bismuth's excellent X-ray attenuation coefficient. We then monitored and investigated their absorption, distribution, metabolism, and excretion. We also used CT imaging to demonstrate that Cu3BiS3 NDs can be quickly removed through renal clearance, which may be related to their small size, rapid chemical transformation, and degradation in an acidic lysosomal environment as characterized by synchrotron radiation-based X-ray absorption near-edge structure spectroscopy. These results reveal that Cu3BiS3 NDs act as a simple but powerful "theranostic" nanoplatform for MSOT/CT imaging-guided tumor ablation with excellent metabolism and rapid clearance that will improve safety for clinical applications in the future.

Targeted Imaging of Damaged Bone in Vivo with Gemstone Spectral Computed Tomography

Achieving high-resolution imaging of bone-cracks and even monitoring them in live organisms are of great significance for understanding their extreme biological effects but remain quite challenging, especially for adopting commercial imaging systems. Herein, we explore the use of the clinical gemstone spectral computed tomography (GSCT) technique as a powerful tool for targeted imaging of bone-cracks in rats via intramuscularly administrating crack-targeted ytterbium-based contrast agents (CAs). Material density images of GSCT reveal that bone-cracks targeted with CAs can be successfully differentiated from healthy bone based on their different X-ray attenuation characteristics, giving GSCT a distinct advantage over conventional CT. More importantly, the superior imaging capability of GSCT allows us to real-time monitor the targeting and accumulation of CAs toward bone-crack in vivo. These results highlight that clinical GSCT, combined with ytterbium-based CAs, provides a promising opportunity for understanding bone-related diseases in the future.

Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior

Fast and accurate energy calibration of photon counting spectral detectors (PCSDs) is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM) CdTe PCSD based on Medipix-2 shows some non-convergent behaviors in turning off the detector elements when a high enough threshold is applied to the comparator that produces a binary photon count pulse. More specifically, the detector elements are supposed to stop producing photon count pulses once the threshold reaches a point of the highest photon energy determined by the tube voltage. However, as the x-ray exposure time increases, the threshold giving 50% of off pixels also increases without converging to a point. We established a method to take account of the non-convergent behavior in the energy calibration. With the threshold-to-photon energy mapping function established by the proposed method, we could better identify iodine component in a phantom consisting of iodine and other components.

Comparison of small animal CT contrast agents

Non-invasive in vivo small animal computed tomography (CT) imaging provides high resolution bone scans but cannot differentiate between soft tissues. For most applications injections of contrast agents (CAs) are necessary. Aim of this study was to uncover the advantages and disadvantages of commercially available CT CAs (ExiTron nano 12 000 and 6000, eXIA 160 and 160XL, Fenestra VC and LC) regarding their pharmacokinetics, toxicological side-effects and the influence of anesthesia on the biodistribution, based on an injection volume of 100 μL/25 g body weight. The pharmacokinetics of the CAs were determined for up to five days. The CA-induced toxicological/physiological side-effects were evaluated by determining blood counts, liver enzymes, thyroxine and total protein values, pro-inflammatory mediators (messenger ribonucleic acid (mRNA)), histology and immunohistochemistry. ExiTron nano 12 000 and 6000 yielded a long-term contrast enhancement (CE) in the liver and spleen for up to five days. Some of the evaluated CAs did not show any CE at all. Anesthesia did not impair the CAs' biodistribution. The CAs differentially affected the body weight, blood counts, liver enzymes, thyroxine and total protein values. ExiTron nano 12 000 and 6000 induced histiocytes in the liver and spleen. Moreover, ExiTron nano 12 000 and eXIA 160 enhanced tumor necrosis factor (TNF) mRNA expression levels in the kidneys. Thus, we recommend ExiTron nano 12 000 and 6000 when multiple injections should be avoided. We recommend careful selection of the employed CA in order to achieve an acceptable CE in the organs of interest and to avoid influences on the animal physiology. Copyright © 2016 John Wiley & Sons, Ltd.

Size-Tuning Ionization To Optimize Gold Nanoparticles for Simultaneous Enhanced CT Imaging and Radiotherapy

Computed tomography (CT) contrast and radiosensitization usually increase with particle sizes of gold nanoparticles (AuNPs), but there is a huge challenge to improve both by adjusting sizes under the requirements of in vivo application. Here, we report that AuNPs have great size-dependent enhancements on CT imaging as well as radiotherapy (RT) in the size range of 3-50 nm. It is demonstrated that AuNPs with a size of ∼13 nm could simultaneously possess superior CT contrast ability and significant radioactive disruption. The Monte Carlo method is further used to evaluate this phenomenon and indicates that the inhomogeneity of gold atom distributions caused by sizes may influence secondary ionization in whole X-ray interactions. In vivo studies further indicate that this optimally sized AuNP improves real-time CT imaging and radiotherapeutic inhibition of tumors in living mice by effective accumulation at tumors with prolonged in vivo circulation times compared to clinically used small-molecule agents. These results suggest that ∼13 nm AuNPs may serve as multifunctional adjuvants for clinical X-ray theranostic application.

Iodinated hyaluronic acid oligomer-based nanoassemblies for tumor-targeted drug delivery and cancer imaging

Nano-sized self-assemblies based on amphiphilic iodinated hyaluronic acid (HA) were developed for use in cancer diagnosis and therapy. 2,3,5-Triiodobenzoic acid (TIBA) was conjugated to an HA oligomer as a computed tomography (CT) imaging modality and a hydrophobic residue. Nanoassembly based on HA-TIBA was fabricated for tumor-targeted delivery of doxorubicin (DOX). Cellular uptake of DOX from nanoassembly, compared to a DOX solution group, was enhanced via an HA-CD44 receptor interaction, and subsequently, the in vitro antitumor efficacy of DOX-loaded nanoassembly was improved in SCC7 (CD44 receptor positive squamous cell carcinoma) cells. Cy5.5, a near-infrared fluorescence (NIRF) dye, was attached to the HA-TIBA conjugate and the in vivo tumor targetability of HA-TIBA nanoassembly, which is based on the interaction between HA and CD44 receptor, was demonstrated in a NIRF imaging study using an SCC7 tumor-xenografted mouse model. Tumor targeting and cancer diagnosis with HA-TIBA nanoassembly were verified in a CT imaging study using the SCC7 tumor-xenografted mouse model. In addition to efficient cancer diagnosis using NIRF and CT imaging modalities, improved antitumor efficacies were shown. HA and TIBA can be used to produce HA-TIBA nanoassembly that may be a promising theranostic nanosystem for cancers that express the CD44 receptor.

High-performance dendritic contrast agents for X-ray computed tomography imaging using potent tetraiodobenzene derivatives

The use of computed tomography (CT) for vascular imaging is critical in medical emergencies requiring urgent diagnostic decisions, such as cerebral ischemia and many cardiovascular diseases. Small-molecule iodinated contrast media are often injected intravenously as radiopaque agents during CT imaging to achieve high contrast enhancement of vascular systems. The rapid excretion rate of these agents is overcome by injecting a significantly high dose of iodine, which can have serious side effects. Here we report a simple method to prepare blood-pool contrast agents for CT based on dendrimers for the first time using tetraiodobenzene derivatives as potent radiopaque moieties. Excellent in vivo safety has been demonstrated for these small (13-22nm) unimolecular water-soluble dendritic contrast agents, which exhibit high contrast enhancement in the blood-pool and effectively extend their blood half-lives. Our method is applicable to virtually any scaffold with suitable surface groups and may fulfill the current need for safer, next-generation iodinated CT contrast agents.

NaYF4:Yb/Er@PPy core-shell nanoplates: an imaging-guided multimodal platform for photothermal therapy of cancers

Imaging guided photothermal agents have attracted great attention for accurate diagnosis and treatment of tumors. Herein, multifunctional NaYF4:Yb/Er@polypyrrole (PPy) core-shell nanoplates are developed by combining a thermal decomposition reaction and a chemical oxidative polymerization reaction. Within such a composite nanomaterial, the core of the NaYF4:Yb/Er nanoplate can serve as an efficient nanoprobe for upconversion luminescence (UCL)/X-ray computed tomography (CT) dual-modal imaging, the shell of the PPy shows strong near infrared (NIR) region absorption and makes it effective in photothermal ablation of cancer cells and infrared thermal imaging in vivo. Thus, this platform can be simultaneously used for cancer diagnosis and photothermal therapy, and compensates for the deficiencies of individual imaging modalities and satisfies the higher requirements on the efficiency and accuracy for diagnosis and therapy of cancer. The results further provide some insight into the exploration of multifunctional nanocomposites in the photothermal theragnosis therapy of cancers.

Microwave-assisted one-step rapid synthesis of near-infrared gold nanoclusters for NIRF/CT dual-modal bioimaging

Highly fluorescent lysozyme-capped gold nanoclusters have been prepared using a one-step rapid microwave-assisted approach for the application of NIRF/CT dual-modal bioimaging.

Overcoming the Achilles' heel of photodynamic therapy

This review summarizes the latest progress in deep photodynamic therapy (PDT), which overcomes the Achilles' heel of PDT.

Ultra-small and size tunable PVP-NaGdF4:Dy nanoparticles with high biocompatibility for multimodal tumor imaging

Ultra-small PVP-NaGdF₄:Dy nanoprobes were prepared and they could induce obvious signal enhancement in T₁/T₂-weighted MRI and CT imaging.

Radiopaque tantalum oxide coated persistent luminescent nanoparticles as multimodal probes for in vivo near-infrared luminescence and computed tomography bioimaging

The design and fabrication of multimodal imaging nanoparticles is of great importance in medical diagnosis. Here we report the fabrication of core-shell structured Zn2.94Ga1.96Ge2O10:Cr(3+),Pr(3+)@TaOx@SiO2 nanoparticles for persistent luminescence and X-ray computed tomography (CT) imaging. Persistent luminescent nanoparticles Zn2.94Ga1.96Ge2O10:Cr(3+),Pr(3+) were used as the core to provide near-infrared luminescence, and a TaOx layer was grown on the core to serve as the contrast agent for CT. The tenuous outermost SiO2 shell was fabricated on the TaOx layer to gain high biocompatibility and to facilitate post-modification with tumor-targeting peptides. The fabricated core-shell structured nanoparticle shows intense near-infrared luminescence and the CT contrast effect. No obvious mutual interference was found in these two modalities, which ensures that each imaging modality merits could be brought in a full play. Furthermore, covalent bonding of cyclic-Asn-Gly-Arg peptides makes the core-shell structured nanoparticles promising for in vivo targeted imaging of tumor-bearing mice.

Trifunctional Polymeric Nanocomposites Incorporated with Fe₃O₄/Iodine-Containing Rare Earth Complex for Computed X-ray Tomography, Magnetic Resonance, and Optical Imaging

In this study, a novel polymerizable CT contrast agent integrating iodine with europium(III) has been developed by a facile and universal coordination chemistry method. The Fe3O4 nanoparticles are then incorporated into this iodine-containing europium complex by seed-emulsifier-free polymerization. The nanocomposites combining the difunctional complex and superparamagnetic Fe3O4 nanoparticles, which have uniform size dispersion and high encapsulation rate, are suitable for computed X-ray tomography (CT), magnetic resonance imaging (MRI), and optical imaging. They possess good paramagnetic properties with a maximum saturation magnetization of 2.16 emu/g and a transverse relaxivity rate of 260 mM(-1) s(-1), and they exhibit obvious contrast effects with an iodine payload less than 4.8 mg I/mL. In the in vivo optical imaging assessment, vivid fluorescent dots can be observed in the liver and spleen by two-photon confocal scanning laser microscopy (CLSM). All the results showed that nanocomposites as polymeric trifunctional contrast agents have great clinical potential in CT, MR, and optical imaging.

Engineering iodine-doped carbon dots as dual-modal probes for fluorescence and X-ray CT imaging

X-ray computed tomography (CT) is the most commonly used imaging technique for noninvasive diagnosis of disease. In order to improve tissue specificity and prevent adverse effects, we report the design and synthesis of iodine-doped carbon dots (I-doped CDs) as efficient CT contrast agents and fluorescence probe by a facile bottom-up hydrothermal carbonization process. The as-prepared I-doped CDs are monodispersed spherical nanoparticles (a diameter of ~2.7 nm) with favorable dispersibility and colloidal stability in water. The aqueous solution of I-doped CDs showed wavelength-dependent excitation and stable photoluminescence similar to traditional carbon quantum dots. Importantly, I-doped CDs displayed superior X-ray attenuation properties in vitro and excellent biocompatibility. After intravenous injection, I-doped CDs were distributed throughout the body and excreted by renal clearance. These findings validated that I-doped CDs with high X-ray attenuation potency and favorable photoluminescence show great promise for biomedical research and disease diagnosis.

PEGylated NaHoF4 nanoparticles as contrast agents for both X-ray computed tomography and ultra-high field magnetic resonance imaging

It is well-known that multimodal imaging can integrate the advantages of different imaging modalities by overcoming their individual limitations. As ultra-high field magnetic resonance imaging (MRI) will be inevitably used in future MRI/X-ray computed tomography (CT) scanner, it is highly expected to develop high-performance nano-contrast agents for ultra-high field MR and CT dual-modality imaging, which has not been reported yet. Moreover, specific behavior of nano-contrast agents for ultra-high field MRI is a challenging work and still remains unknown. Herein, a novel type of NaHoF4 nanoparticles (NPs) with varied particle sizes were synthesized and explored as high-performance dual-modality contrast agents for ultra-high field MR and CT imaging. The specific X-ray absorption and MR relaxivity enhancements with varied nanoparticle diameters (3 nm, 7 nm, 13 nm and 29 nm) under different magnetic field (1.5/3.0/7.0 T) are investigated. Based on experimental results and theoretical analysis, the Curie and dipolar relaxation mechanisms of NaHoF4 NPs are firstly separated. Our results will greatly promote the future medical translational development of the NaHoF4 nano-contrast agents for ultra-high field MR/CT dual-modality imaging applications.

Fluorescence-Guided Probes of Aptamer-Targeted Gold Nanoparticles with Computed Tomography Imaging Accesses for in Vivo Tumor Resection

Recent development of molecular imaging probes for fluorescence-guided surgery has shown great progresses for determining tumor margin to execute the tissue resection. Here we synthesize the fluorescent gold nanoparticles conjugated with diatrizoic acid and nucleolin-targeted AS1411 aptamer. The nanoparticle conjugates exhibit high water-solubility, good biocompatibility, visible fluorescence and strong X-ray attenuation for computed tomography (CT) contrast enhancement. The fluorescent nanoparticle conjugates are applied as a molecular contrast agent to reveal the tumor location in CL1-5 tumor-bearing mice by CT imaging. Furthermore, the orange-red fluorescence emitting from the conjugates in the CL1-5 tumor can be easily visualized by the naked eyes. After the resection, the IVIS measurements show that the fluorescence signal of the nanoparticle conjugates in the tumor is greatly enhanced in comparison to that in the controlled experiment. Our work has shown potential application of functionalized nanoparticles as a dual-function imaging agent in clinical fluorescence-guided surgery.

Emerging therapeutic delivery capabilities and challenges utilizing enzyme/protein packaged bacterial vesicles

Nanoparticle-based therapeutics are poised to play a critical role in treating disease. These complex multifunctional drug delivery vehicles provide for the passive and active targeted delivery of numerous small molecule, peptide and protein-derived pharmaceuticals. This article will first discuss some of the current state of the art nanoparticle classes (dendrimers, lipid-based, polymeric and inorganic), highlighting benefits/drawbacks associated with their implementation. We will then discuss an emerging class of nanoparticle therapeutics, bacterial outer membrane vesicles, that can provide many of the nanoparticle benefits while simplifying assembly. Through molecular biology techniques; outer membrane vesicle hijacking potentially allows for stringent control over nanoparticle production allowing for targeted protein packaged nanoparticles to be fully synthesized by bacteria.

An ultrasmall and metabolizable PEGylated NaGdF4:Dy nanoprobe for high-performance T(1)/T(2)-weighted MR and CT multimodal imaging

Lanthanide-based multimodal probes with high sensitivity, simple synthesis strategy, and good biocompatibility promise new applications for clinical diagnosis. However, today's challenge is not only to develop high-performance multimodal probes for more accurate and reliable diagnosis, but also to understand the fate of these probes in vivo. In this context, a novel PEGylated Dy-doped NaGdF4 nanoprobe (PEG-NaGdF4:Dy) was designed and fabricated as a T1/T2-weighted MRI/CT imaging agent. This nanoprobe has a distinct longitudinal relaxivity (r1 = 5.17 mM(-1) s(-1)), relatively high transverse relaxivity (r2 = 10.64 mM(-1) s(-1)), and exhibits strong X-ray attenuation properties (44.70 HU L g(-1)) in vitro. Furthermore, T1/T2-weighted MRI/CT imaging in vivo confirmed that this PEG-NaGdF4:Dy nanoprobe could lead to a significant contrast enhancement effect on liver, spleen and kidney at 24 h post injection. The MTT assay, histological analysis, and biodistribution investigation demonstrated that this multifunctional nanoprobe possessed relatively low cytotoxicity, negligible tissue damage and could be completely excreted out of the body of mice as time prolonged. Therefore, the present PEG-NaGdF4:Dy nanoprobe has the potential for the development of multifunctional T1/T2-weighted MRI/CT imaging to provide more comprehensive and accurate diagnosis information.

Synthesis of nanoparticle CT contrast agents: in vitro and in vivo studies

Water-soluble and biocompatible D-glucuronic acid coated Na₂WO₄ and BaCO₃ nanoparticles were synthesized for the first time to be used as x-ray computed tomography (CT) contrast agents. Their average particle diameters were 3.2 ± 0.1 and 2.8 ± 0.1 nm for D-glucuronic acid coated Na₂WO₄ and BaCO₃ nanoparticles, respectively. All the nanoparticles exhibited a strong x-ray attenuation. In vivo CT images were obtained after intravenous injection of an aqueous sample suspension of D-glucuronic acid coated Na₂WO₄ nanoparticles, and positive contrast enhancements in the kidney were clearly shown. These findings indicate that the nanoparticles reported in this study may be promising CT contrast agents.

Gold nanoparticles as contrast agents in x-ray imaging and computed tomography

Computed tomography enables 3D anatomic imaging at a high spatial resolution, but requires delivery of an x-ray contrast agent to distinguish tissues with similar or low x-ray attenuation. Gold nanoparticles (AuNPs) have gained recent attention as an x-ray contrast agent due to exhibiting a high x-ray attenuation, nontoxicity and facile synthesis and surface functionalization for colloidal stability and targeted delivery. Potential diagnostic applications include blood pool imaging, passive targeting and active targeting, where actively targeted AuNPs could enable molecular imaging by computed tomography. This article summarizes the current state of knowledge for AuNP x-ray contrast agents within a paradigm of key structure-property-function relationships in order to provide guidance for the design of AuNP contrast agents to meet the necessary functional requirements in a particular application. Functional requirements include delivery to the site of interest (e.g., blood, tumors or microcalcifications), nontoxicity during delivery and clearance, targeting or localization at the site of interest and contrast enhancement for the site of interest compared with surrounding tissues. Design is achieved by strategically controlling structural characteristics (composition, mass concentration, size, shape and surface functionalization) for optimized properties and functional performance. Examples from the literature are used to highlight current design trade-offs that exist between the different functional requirements.

Preclinical imaging and translational animal models of cancer for accelerated clinical implementation of nanotechnologies and macromolecular agents

The majority of animal models of cancer have performed poorly in terms of predicting clinical performance of new therapeutics, which are most often first evaluated in patients with advanced, metastatic disease. The development and use of metastatic models of cancer may enhance clinical translatability of preclinical studies focused on the development of nanotechnology-based drug delivery systems and macromolecular therapeutics, potentially accelerating their clinical implementation. It is recognized that the development and use of such models are not without challenge. Preclinical imaging tools offer a solution by allowing temporal and spatial characterization of metastatic lesions. This paper provides a review of imaging methods applicable for evaluation of novel therapeutics in clinically relevant models of advanced cancer. An overview of currently utilized models of oncology in small animals is followed by image-based development and characterization of visceral metastatic cancer models. Examples of imaging tools employed for metastatic lesion detection, evaluation of anti-tumor and anti-metastatic potential and biodistribution of novel therapies, as well as the co-development and/or use of imageable surrogates of response, are also discussed. While the focus is on development of macromolecular and nanotechnology-based therapeutics, examples with small molecules are included in some cases to illustrate concepts and approaches that can be applied in the assessment of nanotechnologies or macromolecules.

Complementary contrast media for metal artifact reduction in dual-energy computed tomography

Metal artifacts have been a problem associated with computed tomography (CT) since its introduction. Recent techniques to mitigate this problem have included utilization of high-energy (keV) virtual monochromatic spectral (VMS) images, produced via dual-energy CT (DECT). A problem with these high-keV images is that contrast enhancement provided by all commercially available contrast media is severely reduced. Contrast agents based on higher atomic number elements can maintain contrast at the higher energy levels where artifacts are reduced. This study evaluated three such candidate elements: bismuth, tantalum, and tungsten, as well as two conventional contrast elements: iodine and barium. A water-based phantom with vials containing these five elements in solution, as well as different artifact-producing metal structures, was scanned with a DECT scanner capable of rapid operating voltage switching. In the VMS datasets, substantial reductions in the contrast were observed for iodine and barium, which suffered from contrast reductions of 97% and 91%, respectively, at 140 versus 40 keV. In comparison under the same conditions, the candidate agents demonstrated contrast enhancement reductions of only 20%, 29%, and 32% for tungsten, tantalum, and bismuth, respectively. At 140 versus 40 keV, metal artifact severity was reduced by 57% to 85% depending on the phantom configuration.

CT Image Contrast of High-Z Elements: Phantom Imaging Studies and Clinical Implications

PURPOSE

To quantify the computed tomographic (CT) image contrast produced by potentially useful contrast material elements in clinically relevant imaging conditions.

MATERIALS AND METHODS

Equal mass concentrations (grams of active element per milliliter of solution) of seven radiodense elements, including iodine, barium, gadolinium, tantalum, ytterbium, gold, and bismuth, were formulated as compounds in aqueous solutions. The compounds were chosen such that the active element dominated the x-ray attenuation of the solution. The solutions were imaged within a modified 32-cm CT dose index phantom at 80, 100, 120, and 140 kVp at CT. To simulate larger body sizes, 0.2-, 0.5-, and 1.0-mm-thick copper filters were applied. CT image contrast was measured and corrected for measured concentrations and presence of chlorine in some compounds.

RESULTS

Each element tested provided higher image contrast than iodine at some tube potential levels. Over the range of tube potentials that are clinically practical for average-sized and larger adults-that is, 100 kVp and higher-barium, gadolinium, ytterbium, and tantalum provided consistently increased image contrast compared with iodine, respectively demonstrating 39%, 56%, 34%, and 24% increases at 100 kVp; 39%, 66%, 53%, and 46% increases at 120 kVp; and 40%, 72%, 65%, and 60% increases at 140 kVp, with no added x-ray filter.

CONCLUSION

The consistently high image contrast produced with 100-140 kVp by tantalum compared with bismuth and iodine at equal mass concentration suggests that tantalum could potentially be favorable for use as a clinical CT contrast agent.

Poly(acrylic acid) Bridged Gadolinium Metal-Organic Framework-Gold Nanoparticle Composites as Contrast Agents for Computed Tomography and Magnetic Resonance Bimodal Imaging

Imaging contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT) have received significant attention in the development of techniques for early stage cancer diagnosis. Gadolinium (Gd)(III), which has seven unpaired electrons and a large magnetic moment, can dramatically influence the water proton relaxation and hence exhibits excellent MRI contrast. On the other hand, gold (Au), which has a high atomic number and high X-ray attenuation coefficient, is an ideal contrast agent candidate for X-ray-based CT imaging. Gd metal-organic framework (MOF) nanoparticles with tunable size, high Gd(III) loading and multivalency can potentially overcome the limitations of clinically utilized Gd chelate contrast agents. In this work, we report for the first time the integration of GdMOF nanoparticles with gold nanoparticles (AuNPs) for the preparation of a MRI/CT bimodal imaging agent. Highly stable hybrid GdMOF/AuNPs composites have been prepared by using poly(acrylic acid) as a bridge between the GdMOF nanoparticles and AuNPs. The hybrid nanocomposites were then evaluated in MRI and CT imaging. The results revealed high longitudinal relaxivity in MRI and excellent CT imaging performance. Therefore, these GdMOF/AuNPs hybrid nanocomposites potentially provide a new platform for the development of multimodal imaging probes.

Facile Synthesis of Gold Nanospheres Modified by Positively Charged Mesoporous Silica, Loaded with Near-Infrared Fluorescent Dye, for in Vivo X-ray Computed Tomography and Fluorescence Dual Mode Imaging

We developed a simple and efficient method to synthesize a novel probe for both computed tomography (CT) and fluorescence imaging. Gold nanospheres were coated with positively charged mesoporous silica (Au@mSiO2-TTA) using a one-pot method to cohydrolyze quaternary ammonium silane and tetraethyl orthosilicate. Subsequently, IR-783, a negatively charged and water-soluble near-infrared fluorescent dye, was electrostatically adsorbed into the silica shell. Transmission electron microscopy imaging, X-ray powder diffraction, and energy dispersive X-ray spectroscopy indicated that Au@mSiO2-TTA had a clear core-shell structure, was monodisperse, had a large surface area (530 m2/g), and had a uniform pore size (2.2 nm). The mesoporous structure could effectively load fluorescent dye. After loading, the zeta potential of the nanoparticle dropped from 48 mV to 30 mV, and after additional modification with polyvinylpyrrolidone, it further reduced to 6 mV. Probe fluorescence was stable over time, and the probe was an effective CT contrast agent and as a near-infrared fluorescent probe. The half-life of the probe in the blood was 1.5 h, and the probe was mainly distributed in the spleen and liver 4 h after injection. Tissue sections showed that major organs were normal and without visible morphological changes, 6 days post injection, indicating the biocompatibility of the probe.

Silica-coated bismuth sulfide nanorods as multimodal contrast agents for a non-invasive visualization of the gastrointestinal tract

Non-invasive and real-time imaging of the gastrointestinal (GI) tract is particularly desirable for research and clinical studies of patients with symptoms arising from gastrointestinal diseases. Here, we designed and fabricated silica-coated bismuth sulfide nanorods (Bi2S3@SiO2 NRs) for a non-invasive spatial-temporally imaging of the GI tract. The Bi2S3 NRs were synthesized by a facile solvothermal method and then coated with a SiO2 layer to improve their biocompatibility and stability in the harsh environments of the GI tract, such as the stomach and the small intestine. Due to their strong X-ray- and near infrared-absorption abilities, we demonstrate that, following oral administration in mice, the Bi2S3@SiO2 NRs can be used as a dual-modal contrast agent for the real-time and non-invasive visualization of NRs distribution and the GI tract via both X-ray computed tomography (CT) and photoacoustic tomography (PAT) techniques. Importantly, integration of PAT with CT provides complementary information on anatomical details with high spatial resolution. In addition, we use Caenorhabditis Elegans (C. Elegans) as a simple model organism to investigate the biological response of Bi2S3@SiO2 NRs by oral administration. The results indicate that these NRs can pass through the GI tract of C. Elegans without inducing notable toxicological effects. The above results suggest that Bi2S3@SiO2 NRs pave an alternative way for the fabrication of multi-modal contrast agents which integrate CT and PAT modalities for a direct and non-invasive visualization of the GI tract with low toxicity.

Nanomedicine for the molecular diagnosis of cardiovascular pathologies

Predicting acute clinical events caused by atherosclerotic plaque rupture remains a clinical challenge. Anatomic mapping of the vascular tree provided by standard imaging technologies is not always sufficient for a robust diagnosis. Yet biological mechanisms leading to unstable plaques have been identified and corresponding biomarkers have been described. Nanosystems charged with contrast agents and targeted towards these specific biomarkers have been developed for several types of imaging modalities. The first systems that have reached the clinic are ultrasmall superparamagnetic iron oxides for Magnetic Resonance Imaging. Their potential relies on their passive accumulation by predominant physiological mechanisms in rupture-prone plaques. Active targeting strategies are under development to improve their specificity and set up other types of nanoplatforms. Preclinical results show a huge potential of nanomedicine for cardiovascular diagnosis, as long as the safety of these nanosystems in the body is studied in depth.

Nanomedicine and mammalian sperm: Lessons from the porcine model

Biomedical nanotechnology allows us to engineer versatile nanosized platforms that are comparable in size to biological molecules and intracellular organelles. These platforms can be loaded with large amounts of biological cargo, administered systemically and act at a distance, target specific cell populations, undergo intracellular internalization via endogenous uptake mechanisms, and act as contrast agents or release cargo for therapeutic purposes. Over recent years, nanomaterials have been increasingly viewed as favorable candidates for intragamete delivery. Particularly in the case of sperm, nanomaterial-based approaches have been shown to improve the efficacy of existing techniques such as sperm-mediated gene transfer, loading sperm with exogenous proteins, and tagging sperm for subsequent sex- or function-based sorting. In this short review, we provide an outline of the current state of nanotechnology for biomedical applications in reproductive biology and present highlights from a series of our studies evaluating the use of specialized silica nanoparticles in boar sperm as a potential delivery vehicle into mammalian gametes. The encouraging data obtained already from the porcine model in our laboratory have formed the basis for ethical approval of similar experiments in human sperm, thereby bringing us a step closer toward the potential use of this novel technology in the clinical environment.

Ultra High-Resolution In vivo Computed Tomography Imaging of Mouse Cerebrovasculature Using a Long Circulating Blood Pool Contrast Agent

Abnormalities in the cerebrovascular system play a central role in many neurologic diseases. The on-going expansion of rodent models of human cerebrovascular diseases and the need to use these models to understand disease progression and treatment has amplified the need for reproducible non-invasive imaging methods for high-resolution visualization of the complete cerebral vasculature. In this study, we present methods for in vivo high-resolution (19 μm isotropic) computed tomography imaging of complete mouse brain vasculature. This technique enabled 3D visualization of large cerebrovascular networks, including the Circle of Willis. Blood vessels as small as 40 μm were clearly delineated. ACTA2 mutations in humans cause cerebrovascular defects, including abnormally straightened arteries and a moyamoya-like arteriopathy characterized by bilateral narrowing of the internal carotid artery and stenosis of many large arteries. In vivo imaging studies performed in a mouse model of Acta2 mutations demonstrated the utility of this method for studying vascular morphometric changes that are practically impossible to identify using current histological methods. Specifically, the technique demonstrated changes in the width of the Circle of Willis, straightening of cerebral arteries and arterial stenoses. We believe the use of imaging methods described here will contribute substantially to the study of rodent cerebrovasculature.

An efficient nano-based theranostic system for multi-modal imaging-guided photothermal sterilization in gastrointestinal tract

Since understanding the healthy status of gastrointestinal tract (GI tract) is of vital importance, clinical implementation for GI tract-related disease have attracted much more attention along with the rapid development of modern medicine. Here, a multifunctional theranostic system combining X-rays/CT/photothermal/photoacoustic mapping of GI tract and imaging-guided photothermal anti-bacterial treatment is designed and constructed. PEGylated W18O49 nanosheets (PEG-W18O49) are created via a facile solvothermal method and an in situ probe-sonication approach. In terms of excellent colloidal stability, low cytotoxicity, and neglectable hemolysis of PEG-W18O49, we demonstrate the first example of high-performance four-modal imaging of GI tract by using these nanosheets as contrast agents. More importantly, due to their intrinsic absorption of NIR light, glutaraldehyde-modified PEG-W18O49 are successfully applied as fault-free targeted photothermal agents for imaging-guided killing of bacteria on a mouse infection model. Critical to pre-clinical and clinical prospects, long-term toxicity is further investigated after oral administration of these theranostic agents. These kinds of tungsten-based nanomaterials exhibit great potential as multi-modal contrast agents for directed visualization of GI tract and anti-bacterial agents for phothothermal sterilization.

Photothermal theragnosis synergistic therapy based on bimetal sulphide nanocrystals rather than nanocomposites

A new generation of photothermal theranostic agents is developed based on Cu3BiS3 nanocrystals. A computed tomography imaging response and photothermal effect, as well as near-infrared fluorescence emission, can be simultaneously achieved through Cu3BiS3 nanocrystals rather than frequently used nanocomposites. These results provide some insight into the synergistic effect from bimetal sulphide semiconductor compounds for photothermal theragnosis therapy.

Bismuth sulfide nanorods as a precision nanomedicine for in vivo multimodal imaging-guided photothermal therapy of tumor

Here, we present a precision cancer nanomedicine based on Bi(2)S(3) nanorods (NRs) designed specifically for multispectral optoacoustic tomography (MSOT)/X-ray computed tomography (CT)-guided photothermal therapy (PTT). The as-prepared Bi(2)S(3) NRs possess ideal photothermal effect and contrast enhancement in MSOT/CT bimodal imaging. These features make them simultaneously act as "satellite" and "precision targeted weapon" for the visual guide to destruction of tumors in vivo, realizing effective tumor destruction and metastasis inhibition after intravenous injection. In addition, toxicity screening confirms that Bi(2)S(3) NRs have well biocompatibility. This triple-modality-nanoparticle approach enables simultaneously precise cancer therapy and therapeutic monitoring.

Rapid, one-pot procedure to synthesise103Pd:Pd@Au nanoparticles en route for radiosensitisation and radiotherapeutic applications

Radioactive gold–palladium nanoparticles for radiotherapy.

Recent advances in gold nanoparticle-based bioengineering applications

The recently developed gold nanoparticle-based bioengineering technologies for biosensors,in vitroandin vivobioimaging, drug delivery systems for improved therapeutics and tissue engineering are discussed.

Imaging agents based on lanthanide doped nanoparticles

This review summarizes the recent progress of single and multimodal imaging agents based on lanthanide doped nanoparticles.

Silica-based nanoparticles: a versatile tool for the development of efficient imaging agents

In this review a selection of the most recent examples of imaging techniques applied to silica-based NPs for imaging is reported.

Stimuli responsive upconversion luminescence nanomaterials and films for various applications

This review highlights recent advances in upconversion luminescence materials in response to various stimuli for a broad spectrum of applications.

Identification of intracellular gold nanoparticles using surface-enhanced Raman scattering

The identification of intracellular distributions of noble metal nanoparticles is of great utility for many biomedical applications. We present an effective method to distinguish intracellular from extracellular nanoparticles by selectively quenching the SERS signals from dye molecules adsorbed onto star-shaped gold nanoparticles that have not been internalized by cells.