Nano-sized CT contrast agents

Epitaxial growth of gold on silver nanoplates for imaging-guided photothermal therapy

Ag@Au core-shell structure nanoparticles, integrating the good stability of Au and the high surface plasmon resonance property (LSPR) of Ag have been extensively employed for photothermal therapy. Up to now, their sophisticated synthesis still remains a great challenge due to the galvanic replacement effect. Herein, through introduction of Ag, we demonstrated that the Ag@Au core-shell nanoplates were easily synthesized in a galvanic replacement-free fashion with no compromise of heating power. Specifically, through fine-tuning the structure of Ag nanoplates that later served as seeds for the overgrowth of Au, the absorption of resultant nanocrystals can be tailored in ranges from visible to near-infrared. Upon resonant laser irradiation, these Ag@Au nanoplates show the feasibility in photothermally eliminating cancer cells. Furthermore, the high atomic numbers of both Ag and Au elements made the nanoplates promising contrast agents for computed tomography that can be harnessed to guide the tumor ablation. The noticeable regression of the solid tumor, regained body weight, along with the absence of signs indicating inflammation relating the long-term toxicity, all support the promising role of Ag@Au nanoplate as a theranostic agent.

Seeing Better and Going Deeper in Cancer Nanotheranostics

Biomedical imaging modalities in clinical practice have revolutionized oncology for several decades. State-of-the-art biomedical techniques allow visualizing both normal physiological and pathological architectures of the human body. The use of nanoparticles (NP) as contrast agents enabled visualization of refined contrast images with superior resolution, which assists clinicians in more accurate diagnoses and in planning appropriate therapy. These desirable features are due to the ability of NPs to carry high payloads (contrast agents or drugs), increased in vivo half-life, and disease-specific accumulation. We review the various NP-based interventions for treatments of deep-seated tumors, involving "seeing better" to precisely visualize early diagnosis and "going deeper" to activate selective therapeutics in situ.

Targeted gold nanoparticles enable molecular CT imaging of head and neck cancer: An in vivo study

The development of various cost-effective multifunctional contrast agent for specific targeting molecular imaging of tumors presents a great challenge. We report here the in vivo targeting imaging of folic acid (FA) gold nanoparticles (AuNPs) through cysteamine (Cys) linking for targeted of human nasopharyngeal head and neck cancer by computed tomography (CT). The toxicity of nanoparticles in kidney, heart, spleen, brain and liver was evaluated by H&E (hematoxylin and eosin) assay. We showed that the formed FA-Cys-AuNPs with an Au core size of ˜13 nm are non-cytotoxic in the particle concentration of 3 × 10³ μg/ ml. The nude mice were scanned using a 64-slice CT scan with parameters (80 kVp, slice thickness: 0.625 mm, mAs: 200, pitch: 1). CT scan was performed before and after (Three and six hours) I.V (Intra Venous) injection of AuNPs and FA-Cys-AuNPs. The distribution of nanoparticles in the nude mice was evaluated by imaging and coupled plasma optical emission spectrometry (ICP-OES) analysis. The findings clearly illustrated that a small tumor, which is undetectable via computed tomography, is enhanced by X-ray attenuation and becomes visible (4.30-times) by the molecularly targeted AuNPs. It was further demonstrated that active tumor cells targeting (FA-Cys-AuNPs) is more specific and efficient (2.03-times) than passive targeting AuNPs. According to the results, FA-Cys-AuNPs can be employed as a promising contrast agent in CT scan imaging and maybe in radiotherapy that require enhanced radiation dose.

Ultralong tumor retention of theranostic nanoparticles with short peptide-enabled active tumor homing

Computer tomography (CT) and magnetic resonance imaging (MRI) are noninvasive cancer imaging methods in clinics. Hence, a material that enables MRI/CT dual-modal imaging-guided therapy is in high demand. Currently, the available materials lack active tumor targeting, deep tumor penetration, and ultralong tumor retention and may lose their imaging elements. To overcome these drawbacks, herein, nanoparticles (NPs) were deveopled by integrating an MRI contrast-enhancing chelated gadolinium (Gd) complex within a doxorubicin (DOX)-loaded protective silica shell as well as a CT imaging/photothermal biocompatible bismuth (Bi) nano-core, which surface-displayed an MCF-7 breast tumor-homing peptide (AREYGTRFSLIGGYR, termed AR); we found that the resultant NPs AR-Bi@SiO2-Gd/DOXNPs could home to and penetrate deep into the tumors with the unexpected ultralong retention of at least 14 days (as determined by CT/MRI imaging) and the tumor retention half-life of 104.5 h (as determined by ICP-MS analysis) under the guidance of the AR peptide. These NPs can be further used to image tumors with significantly increased sharp contrasts via both CT and MRI, which are much better than the commercial standard contrast agents; moreover, they significantly inhibit tumor growth via the synergistic action of both Bi-enabled photothermal therapy and DOX-induced chemotherapy. The NPs are cleared by the spleen, liver and kidney and then excreted from the body along with faeces and urine. The precise tumor targeting and ultralong tumor retention of these unique NPs would enable both precise tumor detection for early diagnosis and signal-persistent tumor tracking for monitoring the treatment with only a single injection of these NPs.

Targeted Imaging of Renal Fibrosis Using Antibody-Conjugated Gold Nanoparticles in Renal Artery Stenosis

OBJECTIVES

The ability to determine the severity of renal fibrosis, which is involved in most chronic kidney diseases, may be beneficial for monitoring disease progression and management. The aim of this study was to assess a new method involving gold nanoparticles conjugated to an anti-collagen-I antibody (Co-I-AuNPs) as a computed tomography (CT) imaging contrast for the evaluation of renal fibrosis in situ.

MATERIALS AND METHODS

Gold nanoparticles conjugated to an anti-collagen-I antibody were prepared using gold chloride reduction with sodium citrate and coated with polyethylene glycol (PEG), and their size was determined by electron microscopy and nanoparticle tracking analysis. Anti-collagen-I antibody was then conjugated to PEG-SH/COOH on the AuNP surface. The success of antibody conjugation was tested in vitro using collagen-coated plate and mouse stenotic kidney sections and in vivo using micro-CT and multidetector CT imaging.

RESULTS

Bare AuNPs were 18.7 ± 0.6 nm and PEG-coated AuNPs were 45.3 ± 0.1 nm in size. In vitro, Co-I-AuNPs specifically bound to both a collagen-coated plate and mouse fibrotic kidneys. Furthermore, the stenotic mouse kidney showed increased Co-I-AuNPs retention compared with the contralateral kidney (59.3 ± 5.1 vs 45.1 ± 1.7 HU, P = 0.05), which correlated with its collagen deposition. Micro-CT also detected gold signals in situ in the Co-I-AuNP-injected kidney, which colocalized with histological trichrome staining.

CONCLUSION

Gold nanoparticles conjugated to an anti-collagen-I antibody are able to visualize kidney fibrosis in vitro and in situ and may be useful for nondestructive quantification of tissue fibrosis.

A new approach to developing diagnostics and therapeutics: Aggregation-induced emission-based fluorescence turn-on

Fluorescence imaging is a promising visualization tool and possesses the advantages of in situ response and facile operation; thus, it is widely exploited for bioassays. However, traditional fluorophores suffer from concentration limits because they are always quenched when they aggregate, which impedes applications, especially for trace analysis and real-time monitoring. Recently, novel molecules with aggregation-induced emission (AIE) characteristics were developed to solve the problems encountered when using traditional organic dyes, because these new molecules exhibit weak or even no fluorescence when they are in free movement states but emit intensely upon the restriction of intramolecular motions. Inspired by the excellent performances of AIE molecules, a substantial number of AIE-based probes have been designed, synthesized, and applied to various fields to fulfill diverse detection tasks. According to numerous experiments, AIE probes are more practical than traditional fluorescent probes, especially when used in bioassays. To bridge bioimaging and materials engineering, this review provides a comprehensive understanding of the development of AIE bioprobes. It begins with a summary of mechanisms of the AIE phenomenon. Then, the strategies to realize accurate detection using AIE probes are discussed. In addition, typical examples of AIE-active materials applied in diagnosis, treatment, and nanocarrier tracking are presented. In addition, some challenges are put forward to inspire more ideas in the promising field of AIE-active materials.

Direct Synthesis of Water-Dispersible Magnetic/Plasmonic Heteronanostructures for Multimodality Biomedical Imaging

Magnetic/plasmonic hybrid nanoparticles are highly desirable for multimodal bioimaging and biosensing. Although the synthesis of heterodimeric nanoparticles has been reported, the products are usually hydrophobic so that post-treatment procedures are required to transfer them into water which are often difficult to perform and cause damages to the structures. Direct synthesis of hydrophilic hybrid nanostructures has remained a grand challenge albeit its immediate advantage of biocompatibility. Herein we report a general seed-mediated approach to the synthesis of hydrophilic and biocompatible M-Fe₃O₄ (M = Au, Ag, and Pd) heterodimers, in which the size of metals and Fe₃O₄ can be independently regulated in a wide range. Benefiting from the aqueous synthesis, this approach can be further extended to design more complex heterodimeric structures such as AgPt_alloy-Fe₃O₄, Au_core@Pd_shell-Fe₃O₄, and Au_shell-Fe₃O₄. The hydrophilic nature of our heterodimers makes them readily useful for biomedical applications without the need of additional ligand exchange processes in contrast to those prepared in nonpolar solvents. These nanoscale magnetic/plasmonic heterostructures were shown to be ideally suited for integrated biomedical diagnoses, such as magnetic resonance imaging, photoacoustic imaging, optical coherence tomography, and computed tomography, in virtue of their biocompatibility and combined tunable magnetic and plasmonic properties.

A modular theranostic platform for tumor therapy and its metabolic studies

Theranostic systems are able to detect and treat diseases with only one procedure, thus greatly lessening the pain of patients. Since each patient's disease can be considered as a new clinical subtype, it is essential to develop theranostic nanomaterials with changeable functions for personal treatment. In this work, a novel modular theranostic platform was designed to control the stimuli-responsive drug release. As a patch board, mesoporous silica nanoparticles (MSNs) were functionalized with a linear pH-responsive benzimidazole (Bz)-polyethylene glycol (PEG) chain containing a redox-responsive ferrocene (Fc) oxide stopper at the end. As the plug, the β-CD ring was initially located at the Bz position. In an acidic tumor microenvironment, the pH sensitive Bz was protonated and the complex formation constant between Bz and β-CD decreased. At the same time, the complex formation constant between Fc and β-CD increased remarkably. As a result, the β-CD ring would depart from the nanoparticle surface to the Fc position at pH 6.2 & 10 mM GSH, physically causing an "And" logic gate type drug release. Herein, a "plug and play" method was used to achieve changeable functions with only one platform. By plugging modified β-CD into the patch board, theranostic systems with changeable functions can be achieved easily.

Single-Irradiation Simultaneous Dual-Modal Bioimaging Using Nanostructure Scintillators as Single Contrast Agent

The rising demand for clinical diagnosis tools has led to extensive research on multimodal bioimaging systems. Unlike single-modal detection, multimodal imaging not only can provide both function and structure information but also can address the issue of sensitivity, depth, and cost. Despite enormous efforts, conventional step-by-step procedures for obtaining multimodal imaging pose a significant constraint on their practical applications. In this work, X-rays as highly penetrating radiation is proposed as a single-irradiation resource, while lanthanide-based nanostructure scintillators are employed as the single contrast agent to attenuate and convert X-rays, achieving computer tomography (CT) and optical dual-modal imaging at the same time. In other words, CT and optical dual-modal imaging are simultaneously produced via single radiation combined with single contrast agent. The function and structure information of targeted tumors in a mouse model can be clearly provided with large penetration and high sensitivity, indicating that this strategy is a simple but promising route for multimodal imaging of molecular disease and preclinical applications.

Single-Component Bismuth Nanoparticles as a Theranostic Agent for Multimodal Imaging-Guided Glioma Therapy

Single-component nanomaterials such as bismuth (Bi) based on nanoparticles (NPs) intrinsically having both diagnostic and therapeutic capabilities are widely needed in biomedical fields. However, their design and fabrication still face enormous challenges. Here, a kind of pure Bi NPs with ultrahigh X-ray attenuation coeffcient was developed and evaluated as a simple but powerful theranostic nanomaterals and potent light-to-heat conversion efficiency for photoacuostic imaging (PAI)/photothermal therapy (PTT) in this study. The prepared pure Bi NPs showed excellent photothermal performance and the temperature of NPs solution (1 mg/mL) increased to 70 °C under near-infrared light irradiation within 4 min. The pure Bi NPs showed obvious enhancement effect both in X-ray computed tomography (CT) and PA imaging modalities in vivo. In addition, the glioma growth was efficiently suppressed by the pure Bi NPs after 808 nm laser irradiation, while maintained the biosafety and low toxicity. Thus, it is notable that this type of Bi nanomaterial has great potential in multi-imaging guided cancer treatment.

Biomedical Imaging: Principles, Technologies, Clinical Aspects, Contrast Agents, Limitations and Future Trends in Nanomedicines

This review article presents the state-of-the-art in the major imaging modalities supplying relevant information on patient health by real-time monitoring to establish an accurate diagnosis and potential treatment plan. We draw a comprehensive comparison between all imagers and ultimately end with our focus on two main types of scanners: X-ray CT and MRI scanners. Numerous types of imaging probes for both imaging techniques are described, as well as reviewing their strengths and limitations, thereby showing the current need for the development of new diagnostic contrast agents (CAs). The role of nanoparticles in the design of CAs is then extensively detailed, reviewed and discussed. We show how nanoparticulate agents should be promising alternatives to molecular ones and how they are already paving new routes in the field of nanomedicine.

Bi-DTPA as a high-performance CT contrast agent for in vivo imaging

Clinically used iodinated computer tomography (CT) contrast agents suffer from low sensitivity, and the emerging lanthanide-chelates and CT imaging nanoagents raise great safety concerns. The fusion of high sensitivity and good biocompatibility is highly desired for the development of CT contrast agents. Herein, we propose a facile and green one-pot synthesis strategy for the fabrication of a small molecular CT contrast agent, Bi-diethylene triamine pentaacetate acid (DTPA) complex, for high-performance CT and spectral CT imaging. The Bi-DTPA exhibits yield of near 100%, outstanding water solubility, favorable biocompatibility, large-scale production capability, and superior X-ray attenuation ability, and is successfully applied in high-quality in vivo kidney imaging and gastrointestinal tract CT imaging and appealing spectral CT imaging. The proposed contrast agent can be rapidly excreted from body, avoiding the potential side effects caused by the long-term retention in vivo. Furthermore, our design shows great potential in developing diverse multifunctional contrast agents via chemical modification. The proposed Bi-DTPA with unique superiorities shows a bright prospect in clinic CT imaging, especially spectral CT imaging, and lays down a new way for the design of high-performance CT contrast agents with great clinical transformation potential.

Magnetite- and Iodine-Containing Nanoemulsion as a Dual Modal Contrast Agent for X-ray/Magnetic Resonance Imaging

Noninvasive diagnostic by imaging combined with a contrast agent (CA) is by now the most used technique to get insight into human bodies. X-ray and magnetic resonance imaging (MRI) are widely used technologies providing complementary results. Nowadays, it seems clear that bimodal CAs could be an emerging approach to increase the patient compliance, accessing different imaging modalities with a single CA injection. Owing to versatile designs, targeting properties, and high payload capacity, nanocarriers are considered as a viable solution to reach this goal. In this study, we investigated efficient superparamagnetic iron oxide nanoparticle (SPION)-loaded iodinated nano-emulsions (NEs) as dual modal injectable CAs for X-ray imaging and MRI. The strength of this new CA lies not only in its dual modal contrasting properties and biocompatibility, but also in the simplicity of the nanoparticulate assembling: iodinated oily core was synthesized by the triiodo-benzene group grafting on vitamin E (41.7% of iodine) via esterification, and SPIONs were produced by thermal decomposition during 2, 4, and 6 h to generate SPIONs with different morphologies and magnetic properties. SPIONs with most anisotropic shape and characterized by the highest r₂/ r₁ ratio once encapsulated into iodinated NE were used for animal experimentation. The in vivo investigation showed an excellent contrast modification because of the presence of the selected NEs, for both imaging techniques explored, that is, MRI and X-ray imaging. This work provides the description and in vivo application of a simple and efficient nanoparticulate system capable of enhancing contrast for both preclinical imaging modalities, MRI, and computed tomography.

Organic Fluorophore Coated Polycrystalline Ceramic LSO:Ce Scintillators for X-ray Bioimaging

The current effort demonstrates that lutetium oxyorthosilicate doped with 1-10% cerium (Lu₂SiO₅:Ce, LSO:Ce) radioluminescent particles can be coated with a single dye or multiple dyes and generate an effective energy transfer between the core and dye(s) when excited via X-rays. LSO:Ce particles were surface modified with an alkyne modified naphthalimide (6-piperidin-1-yl-2-prop-2-yn-1-yl-1 H-benzo[ de]isoquinoline-1,3-(2 H)-dione, AlNap) and alkyne modified rhodamine B ( N-(6-diethylamino)-9-{2-[(prop-2-yn-1-yloxy)carbonyl]phenyl}-3 H-xanthen-3-ylidene)- N-ethylethanaminium, AlRhod) derivatives to tune the X-ray excited optical luminescence from blue to green to red using Förster Resonance Energy Transfer (FRET). As X-rays penetrate tissue much more effectively than UV/visible light, the fluorophore modified phosphors may have applications as bioimaging agents. To that end, the phosphors were incubated with rat cortical neurons and imaged after 24 h. The LSO:Ce surface modified with AlNap was able to be successfully imaged in vitro with a low-output X-ray tube. To use the LSO:Ce fluorophore modified particles as imaging agents, they must not induce cytotoxicity. Neither LSO:Ce nor LSO:Ce modified with AlNap showed any cytotoxicity toward normal human dermal fibroblast cells or mouse cortical neurons, respectively.

Recent advances in nanomaterial-based synergistic combination cancer immunotherapy

This review aims to summarize various synergistic combination cancer immunotherapy strategies based on nanomaterials.

X-ray-activated nanosystems for theranostic applications

X-rays are widely applied in clinical medical facilities for radiotherapy (RT) and biomedical imaging. However, the sole use of X-rays for cancer treatment leads to insufficient radiation energy deposition due to the low X-ray attenuation coefficients of living tissues and organs, producing unavoidable excessive radiation doses with serious side effects to healthy body parts. Over the past decade, developments in materials science and nanotechnology have led to rapid progress in the field of X-ray-activated tumor-targeting nanosystems, which are able to tackle even systemic tumors and relieve the burden of exposure to large radiation doses. Additionally, novel imaging contrast agents and techniques have also been developed. In comparison with conventional external light sources (e.g., near infrared), the X-ray technique is ideal for the activation of nanosystems for cancer treatment and biomedical imaging applications due to its nearly unlimited penetration depth in living tissues and organisms. In this review, we systematically describe the interaction mechanisms between X-rays and nanosystems, and provide an overview of X-ray-sensitive materials and the recent progress on X-ray-activated nanosystems for cancer-associated theranostic applications.

Water-Dispersible Bismuth-Organic Materials with Computed Tomography Contrast Properties

Two bismuth-organic network polymers were synthesized by means of a one-step polycondensation reaction between an aromatic dithiol/trithiol and triphenylbismuth. The materials were characterized by solid-state UV-vis spectroscopy, Raman spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, elemental microanalysis, and thermogravimetric analysis. Uniform dispersion of the hydrophobic and water-insoluble bismuth-containing polymers in aqueous media was achieved by the addition of 2 kDa poly(ethylene glycol) methyl ether thiol. This enabled quantitative phantom imaging experiments on a clinical computed tomography (CT) scanner, which showed that the coordination polymers possessed strong CT contrast properties. The observed X-ray attenuation properties of each coordination polymer were correlated with its bismuth payload. The X-ray opacity, thermal and chemical stabilities, and aqueous dispersibility of this novel class of bismuth-organic materials make them potentially useful as biomedical CT contrast agents and radiopaque materials.

Synthesis and Biomedical Applications of Multifunctional Nanoparticles

The accumulated knowledge of nanoparticle (NP) synthesis for the last 30 years has enabled the development of functional NPs for biomedical applications. Especially, NPs with multifunctional capabilities are gaining popularity as the demand for versatile and efficient NP agents increases. Various combinations of functional materials are integrated to form multicomponent NPs with designed size, structure, and multifunctionality. Their use as diagnostic and/or therapeutic tools is demonstrated, suggesting their application potentials in healthcare and medical practice. Here, the recent achievements in the synthesis and biomedical applications of multifunctional NPs are summarized. Starting with a brief overview regarding the advances in NP synthesis and accompanying progress in nanobiotechnology, various components to construct the multifunctional NP agents, which include polymers and mesoporous, magnetic, catalytic, and semiconducting NPs, are discussed together with their overall integration forms, such as NP assembly, hollow/porous structures, or hybrid/doped systems. Following the explanation of the features that multifunctional NP agents can offer, an outlook and a brief comment regarding the future research directions are provided.

An acidic pH/reduction dual-stimuli responsive nanoprobe for enhanced CT imaging of tumours in vivo

Computed tomography (CT) is one of the most frequently used diagnostic imaging modalities in clinics. However, the fast clearance of CT contrast agents through the kidney and short circulation time severely restrict their in vivo applications. Herein, taking advantage of the biocompatible CBT condensation reaction, we rationally designed and synthesized a new smart acidic pH/glutathione (GSH) dual-stimuli responsive nanoprobe (1) which can intermolecularly undergo condensation and form a nanoparticle assembly (I-NPs) in the tumour microenvironment. In vivo CT imaging results indicated that probe 1 could be successfully applied for enhanced CT imaging of tumours in nude mice with a low dose of 21.79 mg I per kg body weight, which may offer a promising tool for precise tumor diagnosis.

One-Step Synthesis of Iodinated Polypyrrole Nanoparticles for CT Imaging Guided Photothermal Therapy of Tumors

Theranostic materials are of great significance to a personalized precise medicine. However, conventional theranostic agents are mainly fabricated by combining presynthesized independent imaging probes and therapeutic agents, suffering from multiple synthesis procedures, poor morphological control, and time/reagent-consuming process. Herein, iodinated polypyrrole (I-PPy) nanoparticles are fabricated via a one-step synthesis strategy combining chemical oxidation and iodination for computed tomography (CT) imaging-guided photothermal therapy. Iodic acid with a high standard electrode potential enables the chemical oxidation polymerization of pyrrole monomers. Meanwhile, the iodination of PPy induced by the corresponding reduction product I₂ takes place during the polymerization process to generate I-PPy nanoparticles. The prepared I-PPy nanoparticles possess a uniform size, excellent colloidal stability, intense near-infrared absorption, strong X-ray attenuation ability, and favorable biocompatibility. The as-synthesized I-PPy nanoparticles not only guarantee remarkable contrast-enhanced CT imaging of blood pool and tumors, but also realize effective tumor suppression in vitro and in vivo by I-PPy nanoparticles-mediated CT imaging-guided photothermal therapy. To the best of the authors' knowledge, it is the first time that multifunctional PPy nanoparticles are fabricated through a one-step synthesis process. The proposed strategy opens up a new way for the fabrication of high-performance theranostic agents via a one-step strategy under mild conditions.

Targeted tumor dual mode CT/MR imaging using multifunctional polyethylenimine-entrapped gold nanoparticles loaded with gadolinium

We report the construction and characterization of polyethylenimine (PEI)-entrapped gold nanoparticles (AuNPs) chelated with gadolinium (Gd) ions for targeted dual mode tumor CT/MR imaging in vivo. In this work, polyethylene glycol (PEG) monomethyl ether-modified PEI was sequentially modified with Gd chelator and folic acid (FA)-linked PEG (FA-PEG) was used as a template to synthesize AuNPs, followed by Gd(III) chelation and acetylation of the remaining PEI surface amines. The formed FA-targeted PEI-entrapped AuNPs loaded with Gd (FA-Gd-Au PENPs) were well characterized in terms of structure, composition, morphology, and size distribution. We show that the FA-Gd-Au PENPs with an Au core size of 3.0 nm are water dispersible, colloidally stable, and noncytotoxic in a given concentration range. Thanks to the coexistence of Au and Gd elements within one nanoparticulate system, the FA-Gd-Au PENPs display a better X-ray attenuation property than clinical iodinated contrast agent (e.g. Omnipaque) and reasonable r1 relaxivity (1.1 mM-1s-1). These properties allow the FA-targeted particles to be used as an efficient nanoprobe for dual mode CT/MR imaging of tumors with excellent FA-mediated targeting specificity. With the demonstrated organ biocompatibility, the designed FA-Gd-Au PENPs may hold a great promise to be used as a nanoprobe for CT/MR dual mode imaging of different FA receptor-overexpressing tumors.

Wulff in a cage gold nanoparticles as contrast agents for computed tomography and photoacoustic imaging

Nanostructures have potential for use in biomedical applications such as sensing, imaging, therapeutics, and drug delivery. Among nanomaterials, gold nanostructures are of considerable interest for biomedical research, owing to their bio-inertness, controllable surface chemistry, X-ray opacity, and optical properties. Gold nanocages are particularly attractive for imaging and therapeutic applications, because they strongly absorb light in the near infra-red region which has high light transmission in tissue. However, the X-ray attenuation of nanocages is relatively low due to their hollow structure. In this study, for the first time, we sought to combine the attractive optical properties of nanoshells with the high payloads of solid nanoparticles and investigated their biomedical applications. Here, we report the engineering of Wulff in a cage nanoparticles via converting gold Wulff-shaped seeds into gold-silver core-shell structures and then performing a galvanic replacement reaction. The structure of these nanoparticles was determined using transition electron microscopy. This morphological transformation of gold nanoparticles shaped as truncated octahedrons into a complex Wulff in a cage nanoparticles during the reaction resulted in extensive changes in their optical properties that made these unique structures a potential contrast agent for photoacoustic imaging. We found that the Wulff in a cage nanoparticles had no adverse effects on the viabilities of J774A.1, Renca, and HepG2 cells at any of the concentrations tested. In vitro and in vivo experiments showed robust signals in both photoacoustic imaging and computed tomography. To the best of our knowledge, this is the first report of Wulff in a cage nanoparticles serving as a platform for multiple imaging modalities. This unique multifunctional nanostructure, which integrates the competencies of both core and shell structures, allows their use as contrast agents for photoacoustic imaging, computed tomography and as a potential agent for photothermal therapy.

Graphene Quantum Dots-Coated Bismuth Nanoparticles for Improved CT Imaging and Photothermal Performance

By integrating high-performance CT imaging and photothermal therapy (PTT) into one nanoprobe, an effective theranostic can be achieved for clinical cancer treatment. In this study, the graphene quantum dots (GQDs)-coated bismuth (Bi) nanoparticle (NP) as a theranostic nanoprobe is synthesized and its capabilities for computed tomography (CT) imaging and PTT are investigated. Such nanotheranostic exhibits good physiological dispersity with satisfactory blood compatibility and cytotoxicity. Most importantly, the GQDs-Bi NPs offer strong and steady absorbance profile in NIR region with excellent photostability, which can remarkably convert photo-to-thermal with the photothermal efficiency of 30.0%. Thanks to the powerful PTT effect, co-delivery of GQDs-Bi NPs/NIR laser can effectively induce HeLa cells death in vitro. Cooperatively, NPs hold X-ray attenuation coefficient for high-contrast CT imaging with the corresponding CT improvement efficacy as high as 32.7[Formula: see text]HU[Formula: see text]mg[Formula: see text]. The obtained results highlight the potential of GQDs-Bi NPs as a successful theranostic nanoagent for CT imaging and cancer photothermal therapy.

Bringing Again Noble Metal Nanoparticles to the Forefront of Cancer Therapy

Nanomaterials have attracted increasing interest for their potentiality to revolutionize the diagnosis and treatment of many diseases, especially neoplasms. Interestingly, there is a huge imbalance between the number of proposed nanoplatforms and the few ones approved for clinical applications. This disequilibrium affects in particular noble metal nanoparticles (NPs), that present no-approved platform and very few candidates in clinical trials because of the issue of persistence. In this perspective, we discuss if nanomedicine is generally keeping its promises with a focus on the approach that could fill the gap between NPs and oncology in the next future: the ultrasmall-in-nano.

Bisphosphonate Functionalized Gadolinium Oxide Nanoparticles Allow Long-Term MRI/CT Multimodal Imaging of Calcium Phosphate Bone Cement

Direct in vivo monitoring of bioconstructs using noninvasive imaging modalities such as magnetic resonance imaging (MRI) or computed tomography (CT) is not possible for many materials. Calcium phosphate-based composites (CPCs) that are applicable to bone regeneration are an example where the materials have poor MRI and CT contrast; hence, they are challenging to detect in vivo. In this study, a CPC construct is designed with gadolinium-oxide nanoparticles incorporated to act as an MRI/CT multimodal contrast agent. The gadolinium(III) oxide nanoparticles are synthesized via the polyol method and surface functionalized with a bisphosphonate (BP) derivative to give a construct (gadolinium-based contrast agents (GBCAs)-BP) with strong affinity toward calcium phosphate. The CPC-GBCAs-BP functional material is longitudinally monitored after in vivo implantation in a condyle defect rat model. The synthetic method developed produces nanoparticles that are stable in aqueous solution (hydrodynamic diameter 70 nm) with significant T₁ and T₂ relaxivity demonstrated in both clinical 3 T and preclinical 11.7 T MRI systems. The combination of GBCAs-BP nanoparticles with CPC gives an injectable material with handling properties that are suitable for clinical applications. The BP functionalization prolongs the residence of the contrast agent within the CPC to allow long-term follow-up imaging studies. The useful contrast agent properties combined with biological compatibility indicate further investigation of the novel bone substitute hybrid material toward clinical application.

Insights into 2D MXenes for Versatile Biomedical Applications: Current Advances and Challenges Ahead

Great and interdisciplinary research efforts have been devoted to the biomedical applications of 2D materials because of their unique planar structure and prominent physiochemical properties. Generally, ceramic-based biomaterials, fabricated by high-temperature solid-phase reactions, are preferred as bone scaffolds in hard tissue engineering because of their controllable biocompatibility and satisfactory mechanical property, but their potential biomedical applications in disease theranostics are paid much less attention, mainly due to their lack of related material functionalities for possibly entering and circulating within the vascular system. The emerging 2D MXenes, a family of ultrathin atomic nanosheet materials derived from MAX phase ceramics, are currently booming as novel inorganic nanosystems for biologic and biomedical applications. The metallic conductivity, hydrophilic nature, and other unique physiochemical performances make it possible for the 2D MXenes to meet the strict requirements of biomedicine. This work introduces the very recent progress and novel paradigms of 2D MXenes for state-of-the-art biomedical applications, focusing on the design/synthesis strategies, therapeutic modalities, diagnostic imaging, biosensing, antimicrobial, and biosafety issues. It is highly expected that the elaborately engineered ultrathin MXenes nanosheets will become one of the most attractive biocompatible inorganic nanoplatforms for multiple and extensive biomedical applications to profit the clinical translation of nanomedicine.

Large-Scale Synthesis and Medical Applications of Uniform-Sized Metal Oxide Nanoparticles

Thanks to recent advances in the synthesis of high-quality inorganic nanoparticles, more and more types of nanoparticles are becoming available for medical applications. Especially, metal oxide nanoparticles have drawn much attention due to their unique physicochemical properties and relatively inexpensive production costs. To further promote the development and clinical translation of these nanoparticle-based agents, however, it is highly desirable to reduce unwanted interbatch variations of the nanoparticles because characterizing and refining each batch are costly, take a lot of effort, and, thus, are not productive. Large-scale synthesis is a straightforward and economic pathway to minimize this issue. Here, the recent achievements in the large-scale synthesis of uniform-sized metal oxide nanoparticles and their biomedical applications are summarized, with a focus on nanoparticles of transition metal oxides and lanthanide oxides, and clarifying the underlying mechanism for the synthesis of uniform-sized nanoparticles. Surface modification steps to endow hydrophobic nanoparticles with water dispersibility and biocompatibility are also briefly described. Finally, various medical applications of metal oxide nanoparticles, such as bioimaging, drug delivery, and therapy, are presented.

Lanthanide phosphate (LnPO4 ) rods as bio-probes: A systematic investigation on structural, optical, magnetic, and biological characteristics

The proposed work involves an exclusive study on the synthesis protocol, crystal structure analysis, and imaging contrast features of unique lanthanide phosphates (LnPO₄ ). XRD and Raman spectra affirmed the ability of the proposed synthesis technique to achieve unique LnPO₄ devoid of impurities. The crystal structure analysis confirms the P121/c1 space setting of NdPO₄ , EuPO₄ , GdPO₄ , and TbPO₄ that all uniformly crystallizes in monoclinic unit cell. In a similar manner, the tetragonal crystal setting of DyPO₄ , ErPO₄ , HoPO₄ , and YbPO₄ that unvaryingly possess the I41/amd space setting is confirmed. Under the same synthesis conditions, the monoclinic (Eu) and tetragonal (Ho) lanthanide phosphates displayed uniform rod-like morphologies. Absorption and luminescence properties of unique LnPO₄ were determined. In vitro biological studies demonstrated low toxicity levels of LnPO₄ and clearly distinguished fluorescence of TbPO₄ and EuPO₄ in Y79, retinoblastoma cell lines. The paramagnetic response of GdPO₄ , NdPO₄ , DyPO₄ , TbPO₄ , and HoPO₄ facilitated excellent magnetic resonance imaging (MRI) contrast features. Meanwhile, GdPO₄ , DyPO₄ , HoPO₄ , and YbPO₄ possessing higher X-ray absorption coefficient than clinical contrast Omnipaque™ exhibited high computed tomography (CT) efficiency. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1372-1383, 2019.

Hybrid Decorated Core@Shell Janus Nanoparticles as a Flexible Platform for Targeted Multimodal Molecular Bioimaging of Cancer

In the recent years, targeted cancer theranosis, the concomitant therapeutic treatment and selective visualization of cancerous tissue, has become a powerful strategy to improve patient prognosis. In this context, targeted multimodal molecular imaging, the combination of different imaging modalities overcoming their individual limitations, has attracted great attention. Due to their unique properties, advanced nanomaterials have taken center stage in the development of theranostics. In this work, we report a novel Janus nanoplatform by combining an Fe₃O₄ NPs/mesoporous silica core@shell face together with an Au nanoparticle face. Due to its anisotropy, this hybrid nanomaterial enabled the orthogonal site-selective modification of each face permitting the incorporation of a targeting peptide for cancer detection (cRGD) and a fluorescent dye. Due to the intrinsic characteristics of this Janus nanoplatform together with those selectively generated on their surfaces, the resulting hybrid nanocarrier successfully promoted the in vivo tumor-targeted multimodal imaging by magnetic resonance (Fe₃O₄ core), computed tomography (AuNP face), and fluorescent tracking (fluorescent dye loading) in a fibrosarcoma-bearing mouse model. The achieved results endorse these hybrid Janus nanoparticles as a powerful and flexible platform with integrated imaging and carrier functionalities to be equipped with therapeutic features to generate an advanced multifunctional nanocarrier for targeted cancer theranosis.

CT Imaging of Enzymatic Activity in Cancer Using Covalent Probes Reveal a Size-Dependent Pattern

X-ray CT instruments are among the most available, efficient, and cost-effective imaging modalities in hospitals. The field of CT molecular imaging is emerging which relies mainly on the detection of gold nanoparticles and iodine-containing compounds directed to tagging a variety of abundant biomolecules. Here for the first time we attempted to detect enzymatic activity, while the low sensitivity of CT scanners to contrast reagents made this a challenging task. Therefore, we developed a new class of nanosized cathepsin-targeted activity-based probes (ABPs) for functional CT imaging of cancer. ABPs are small molecules designed to covalently modify enzyme targets in an activity-dependent manner. Using a CT instrument, these novel probes enable detection of the elevated cathepsin activity within cancerous tissue, thus creating a direct link between biological processes and imaging signals. We present the generation and biochemical evaluation of a library of ABPs tagged with different sized gold nanoparticles (GNPs), with various ratios of cathepsin-targeting moiety and a combination of different polyethylene glycol (PEG) protective layers. The most potent and stable GNP-ABPs were applied for noninvasive cancer imaging in mice. Surprisingly, detection of CT contrast from the tumor had reverse correlation to GNP size and the amount of targeting moiety. Interestingly, TEM images of tumor sections show intercellular lysosomal subcellular localization of the GNP-ABPs. In conclusion, we demonstrate that the covalent linkage is key for detection using low sensitive imaging modalities and the utility of GNP-ABPs as a promising tool for enzymatic-based CT imaging.

Small, Long Blood Half-Life Iodine Nanoparticle for Vascular and Tumor Imaging

Standard clinical X-ray contrast agents are small iodine-containing molecules that are rapidly cleared by the kidneys and provide robust imaging for only a few seconds, thereby limiting more extensive vascular and tissue biodistribution imaging as well as optimal tumor uptake. They are also not generally useful for preclinical microCT imaging where longer scan times are required for high resolution image acquisition. We here describe a new iodine nanoparticle contrast agent that has a unique combination of properties: 20 nm hydrodynamic diameter, covalent PEG coating, 40 hour blood half-life, 50% liver clearance after six months, accumulation in tumors, and well-tolerated to at least 4 g iodine/kg body weight after intravenous administration in mice. These characteristics are unique among the other iodine nanoparticles that have been previously reported and provide extended-time high contrast vascular imaging and tumor loading. As such, it is useful for preclinical MicroCT animal studies. Potential human applications might include X-ray radiation dose enhancement for cancer therapy and vascular imaging for life-threatening situations where high levels of contrast are needed for extended periods of time.

Ultrafast synthesis of ultrasmall polyethylenimine-protected AgBiS2 nanodots by "rookie method" for in vivo dual-modal CT/PA imaging and simultaneous photothermal therapy

Developing a biocompatible nanotheranostic platform integrating diagnostic and therapeutic functions is a great prospect for cancer treatment. However, it is still a great challenge to synthesize nanotheranostic agents using an ultra-facile method. In the research reported here, ultrasmall polyethylenimine-protected silver bismuth sulfide (PEI-AgBiS2) nanodots were successfully synthesized using an ultra-facile and environmentally friendly strategy (1 min only at room temperature), which could be described as a "rookie method". PEI-AgBiS2 nanodots show good monodispersity and biocompatibility. For the first time, PEI-AgBiS2 nanodots were reported as a powerful and safe nanotheranostic agent for cancer treatment. PEI-AgBiS2 nanodots exhibit excellent computed tomography (CT) and photoacoustic (PA) dual-modal imaging ability, which could effectively guide photothermal cancer therapy. Furthermore, PEI-AgBiS2 nanodots exhibit a high photothermal conversion efficiency (η = 35.2%). The photothermal therapy (PTT) results demonstrated a highly efficient tumor ablation ability. More importantly, the blood biochemistry and histology analyses verify that the PEI-AgBiS2 nanodots have negligible long-term toxicity. This work highlights that PEI-AgBiS2 nanodots produced using this extremely effective method are a high-performance and safe PTT agent. These findings open a new gateway for synthesizing nanotheranostic agents by using this ultra-facile method in the future.

Radiopaque and uniform alginate microspheres loaded with tantalum nanoparticles for real-time imaging during transcatheter arterial embolization

One restriction to the development and application of transcatheter arterial chemoembolization (TACE) therapy is the lack of an inherently radiopaque embolic whose location and distribution can be precisely visualized in real time and be used for non-invasive examination after surgery. Methods: A one-step electrospray method was developed to fabricate calcium alginate microspheres loaded with tantalum nanoparticles (Ta@CaAlg). The parameters of electrospraying were assessed. The in vivo X-ray imaging capability and embolic effect of Ta@CaAlg microspheres were evaluated in the renal arteries of normal rabbits by digital radiography and computed tomography. Doxorubicin hydrochloride (Dox) was chosen as a model drug, and the drug loading capacity and release behavior of these microspheres was valuated in vitro.Results: Spherical Ta@CaAlg microspheres with monodisperse sizes ranging from 150 to 1200 μm were fabricated by electrospraying. The results of an in vivo study showed that Ta@CaAlg microspheres possessed the qualities of both embolic agents and contrast media. They could not only feed back the real-time location and distribution of the embolic microspheres but also maintained clear X-ray imaging of embolized sites for up to 4 weeks as assessed by digital radiography and computed tomography. Digital subtraction angiography showed that they had an excellent embolic effect. Ta@CaAlg microspheres could be loaded with Dox to form "3-in-1" embolic microspheres. The maximum Dox loading was 97.3 mg Dox per mL beads and loaded microspheres exhibited pH-dependent release profiles. Conclusion: The X-ray opacity and drug-loading capability of Ta@CaAlg microspheres offers great promise in direct, real-time, in vivo investigation for TACE and long-term non-invasive re-examination.

Mitochondria-Targeted Artificial "Nano-RBCs" for Amplified Synergistic Cancer Phototherapy by a Single NIR Irradiation

Phototherapy has emerged as a novel therapeutic modality for cancer treatment, but its low therapeutic efficacy severely hinders further extensive clinical translation and application. This study reports amplifying the phototherapeutic efficacy by constructing a near-infrared (NIR)-responsive multifunctional nanoplatform for synergistic cancer phototherapy by a single NIR irradiation, which can concurrently achieve mitochondria-targeting phototherapy, synergistic photothermal therapy (PTT)/photodynamic therapy (PDT), self-sufficient oxygen-augmented PDT, and multiple-imaging guidance/monitoring. Perfluorooctyl bromide based nanoliposomes are constructed for oxygen delivery into tumors, performing the functions of red blood cells (RBCs) for oxygen delivery ("Nano-RBC" nanosystem), which can alleviate the tumor hypoxia and enhance the PDT efficacy. The mitochondria-targeting performance for enhanced and synergistic PDT/PTT is demonstrated as assisted by nanoliposomes. In particular, these "Nano-RBCs" can also act as the contrast agents for concurrent computed tomography, photoacoustic, and fluorescence multiple imaging, providing the potential imaging capability for phototherapeutic guidance and monitoring. This provides a novel strategy to achieve high therapeutic efficacy of phototherapy by the rational design of multifunctional nanoplatforms with the unique performances of mitochondria targeting, synergistic PDT/PTT by a single NIR irradiation (808 nm), self-sufficient oxygen-augmented PDT, and multiple-imaging guidance/monitoring.

Acetylated Polyethylenimine-Entrapped Gold Nanoparticles Enable Negative Computed Tomography Imaging of Orthotopic Hepatic Carcinoma

Developing an effective computed tomography (CT) contrast agent is still a challenging task for precise diagnosis of hepatic carcinoma (HCC). Here, we present the use of acetylated polyethylenimine (PEI)-entrapped gold nanoparticles (Ac-PE-AuNPs) without antifouling modification for negative CT imaging of HCC. PEI was first linked to fluorescein isothiocyanate (FI) and then utilized as a vehicle for the entrapment of AuNPs. The particles were then acetylated to reduce its positive surface potential. The designed Ac-PE-AuNPs were characterized by various techniques. We find that the Ac-PE-AuNPs with a uniform size distribution (mean diameter = 2.3 nm) are colloidally stable and possess low toxicity in the studied range of concentration. Owing to the fact that the particles without additional antifouling modification were mainly gathered in liver, the Ac-PE-AuNPs could greatly improve the CT contrast enhancement of normal liver, whereas poor CT contrast enhancement appeared in liver necrosis region caused by HCC. As a result, HCC could be easily and precisely diagnosed. The designed Ac-PE-AuNPs were demonstrated to have biocompatibility through in vivo biodistribution and histological studies, hence holding an enormous potential to be adopted as an effective negative CT contrast agent for diagnosis of hepatoma carcinoma.

An Intravascular Tantalum Oxide-based CT Contrast Agent: Preclinical Evaluation Emulating Overweight and Obese Patient Size

Purpose To compare the CT imaging performance of a carboxybetaine zwitterionic-coated tantalum oxide (TaCZ) nanoparticle CT contrast agent with that of a conventional iodinated contrast agent in a swine model meant to simulate overweight and obese patients. Materials and Methods Four swine were evaluated inside three different-sized adipose-equivalent encasements emulating abdominal girths of 102, 119, and 137 cm. Imaging was performed with a 64-detector row CT scanner at six scan delays after intravenous injection of 240 mg element (Ta or I) per kilogram of body weight of TaCZ or iopromide. For each time point, contrast enhancement of the aorta and liver were measured by using regions of interest. Two readers independently recorded the clarity of vasculature using a five-point Likert scale. Findings were compared by using paired t tests and Wilcoxon signed-rank tests. Results Mean peak enhancement was higher for TaCZ than for iopromide in the aorta (270 HU [σ = 24.5] vs 199 HU [σ = 10.2], P < .001) and liver (61.3 HU [σ = 11.7] vs 45.2 HU [σ = 8], P < .001). Vascular clarity was higher for TaCZ than for iopromide in 63% (132 of 208), 82% (170 of 208), and 86% (178 of 208) of the individual vessels at the 102-, 119-, and 137-cm girths, respectively (P < .01). Arterial clarity scores were higher for TaCZ than for iopromide in 62% (208 of 336) of vessels. Venous clarity scores were higher for TaCZ than for iopromide in 89% (128 of 144) of the veins in the venous phase and in 100% (144 of 144) of veins in the delayed phase (P < .01). No vessel showed higher clarity score with iopromide than with TaCZ. Conclusion An experimental tantalum nanoparticle-based contrast agent showed greater contrast enhancement compared with iopromide in swine models meant to simulate overweight and obese patients. © RSNA, 2018.

Improved Calcium Scoring at Dual-Energy Computed Tomography Angiography Using a High-Z Contrast Element and Novel Material Separation Technique

OBJECTIVES

The aim of this study was to compare the accuracy of existing dual-energy computed tomography (CT) angiography coronary artery calcium scoring methods to those obtained using an experimental tungsten-based contrast material and a recently described contrast material extraction process (CMEP).

METHODS

Phantom coronary arteries of varied diameters, with different densities and arcs of simulated calcified plaque, were sequentially filled with water, iodine, and tungsten contrast materials and scanned within a thorax phantom at rapid-kVp-switching dual-energy CT. Calcium and contrast density images were obtained by material decomposition (MD) and CMEP. Relative calcium scoring errors among the 4 reconstructed datasets were compared with a ground truth, 120-kVp dataset.

RESULTS

Compared with the 120-kVp dataset, tungsten CMEP showed a significantly lower mean absolute error in calcium score (6.2%, P < 0.001) than iodine CMEP, tungsten MD, and iodine MD (9.9%, 15.7%, and 40.8%, respectively).

CONCLUSIONS

Novel contrast elements and material separation techniques offer improved coronary artery calcium scoring accuracy and show potential to improve the use of dual-energy CT angiography in a clinical setting.

Synthesis of highly stable and biocompatible gold nanoparticles for use as a new X-ray contrast agent

This work reports a novel reduction procedure for the synthesis of Gum Arabic (GA) capped-gold nanoparticles (AuNPs) in glucosammonium formate as a new ionic liquid. The GA coated AuNPs show good stability in physiological media. The synthesized AuNPs were characterized by UV-Vis spectroscopy, transmission electron microscopy, dynamic light scattering and X-ray diffraction analysis. These stable AuNPs are introduced as a new contrast agent for X-ray Computed Tomography (X-ray CT). These nanoparticles have higher contrasting properties than the commercial contrast agent, Visipaque. The precursors used (Gum Arabic and glucose based-ionic liquid) for synthesis of AuNPs are biocompatible and non-toxic.

Structural, Mechanical, Imaging and in Vitro Evaluation of the Combined Effect of Gd3+ and Dy3+ in the ZrO2-SiO2 Binary System

Mechanical strength and biocompatibility are considered the main prerequisites for materials in total hip replacement or joint prosthesis. Noninvasive surgical procedures are necessary to monitor the performance of a medical device in vivo after implantation. To this aim, simultaneous Gd³⁺ and Dy³⁺ additions to the ZrO₂-SiO₂ binary system were investigated. The results demonstrate the effective role of Gd³⁺ and Dy³⁺ to maintain the structural and mechanical stability of cubic zirconia ( c-ZrO₂) up to 1400 °C, through their occupancy of ZrO₂ lattice sites. A gradual tetragonal to cubic zirconia ( t-ZrO₂ → c-ZrO₂) phase transition is also observed that is dependent on the Gd³⁺ and Dy³⁺ content in the ZrO₂-SiO₂. The crystallization of either ZrSiO₄ or SiO₂ at elevated temperatures is delayed by the enhanced thermal energy consumed by the excess inclusion of Gd³⁺ and Dy³⁺ at c-ZrO₂ lattice. The addition of Gd³⁺ and Dy³⁺ leads to an increase in the density, elastic modulus, hardness, and toughness above that of unmodified ZrO₂-SiO₂. The multimodal imaging contrast enhancement of the Gd³⁺ and Dy³⁺ combinations were revealed through magnetic resonance imaging and computed tomography contrast imaging tests. Biocompatibility of the Gd³⁺ and Dy³⁺ dual-doped ZrO₂-SiO₂ systems was verified through in vitro biological studies.