Chitosan coated tungsten trioxide nanoparticles as a contrast agent for X-ray computed tomography

[New contrast agents for photon-counting computed tomography]

BACKGROUND

The introduction of energy-selective photon-counting detectors into clinical practice represents the next milestone in computed tomography (CT). In addition to significantly higher resolution, these detectors allow the implicit acquisition of dual or multispectral data in a single measurement through the use of typically freely selectable thresholds. This capability reignited the interest in new contrast agents based on heavy elements, so-called high‑z elements, for clinical CT.

OBJECTIVE

The present article aims to investigate the potential suitability of different chemical elements as contrast agents and to discuss possible clinical applications, for example, K‑edge imaging or simultaneous application of different contrast agents.

CONCLUSION

First preclinical experiments as well as experiments in large animals could demonstrate potential advantages of contrast agents based on heavy elements. For example, such contrast agents promise a significant increase in image contrast compared to conventional iodine-based agents.

Tungsten-based Nanomaterials in the Biomedical Field: A Bibliometric Analysis of Research Progress and Prospects

Tungsten-based nanomaterials (TNMs) with diverse nanostructures and unique physicochemical properties have been widely applied in the biomedical field. Although various reviews have described the application of TNMs in specific biomedical fields, there are still no comprehensive studies that summarize and analyze research trends of the field as a whole. To identify and further promote the development of biomedical TNMs, a bibliometric analysis method is used to analyze all relevant literature on this topic. First, general bibliometric distributions of the dataset by year, country, institute, referenced source, and research hotspots are recognized. Next, a comprehensive review of the subjectively recognized research hotspots in various biomedical fields, including biological sensing, anticancer treatments, antibacterials, and toxicity evaluation, is provided. Finally, the prospects and challenges of TNMs are discussed to provide a new perspective for further promoting their development in biomedical research.

Hyaluronic acid-coated ultrasmall BiOI nanoparticles as a potentially targeted contrast agent for X-ray computed tomography

Commercial X-ray computed tomography (CT) contrast agents (CAs) are not appropriate for multicolor CT imaging and are limited due to a lack of tumor targeting. In this contribution, to favor the combination of high Z elements like bismuth and iodine for a broad range of X-ray photon energy, BiOI nanoparticles (NPs) are synthesized with hyaluronic acid (HA) coating to target the tumor cells with CD44 overexpression. The crystal structure of BiOI NPs is determined by X-ray powder diffraction, and the size of NPs is determined by a transmission electron microscope at about 14 ± 3 nm. The dynamic diameter of the NPs (DLS) in PBS buffer was measured at about 100 nm. Fourier transform infrared spectroscopy and thermal gravimetric analysis confirm the coating of BiOI NPs with HA. The stability of the NPs was also investigated via UV-vis spectroscopy. The immunocytochemistry process is performed to investigate the targeting ability of synthesized NPs on the human colon cancer cells with CD44 antigen. Finally, the X-ray attenuation of prepared HA-coated BiOI NPs is higher than Iohexol as the commercially available iodinated contrasting agent at the same concentrations, which can be administrated at much lower doses to achieve similar contrast to Iohexol.

Polysaccharide-Based Theranostic Systems for Combined Imaging and Cancer Therapy: Recent Advances and Challenges

Designing novel systems for efficient cancer treatment and improving the quality of life for patients is a prime requirement in the healthcare sector. In this regard, theranostics have recently emerged as a unique platform, which combines the benefits of both diagnosis and therapeutics delivery. Theranostics have the desired contrast agent and the drugs combined in a single carrier, thus providing the opportunity for real-time imaging to monitor the therapy results. This helps in reducing the hazards related to treatment overdose or underdose and gives the possibility of personalized therapy. Polysaccharides, as natural biomolecules, have been widely explored to develop theranostics, as they act as a matrix for simultaneously loading both contrast agents and drugs for their utility in drug delivery and imaging. Additionally, their remarkable physicochemical attributes (biodegradability, satisfactory safety profile, abundance, and diversity in functionality and charge) can be tuned via postmodification, which offers numerous possibilities to develop theranostics with desired characteristics. Hence, we provide an overview of recent advances in polysaccharide matrix-based theranostics for drug delivery combined with magnetic resonance imaging, computed tomography, positron emission tomography, single photon emission computed tomography, and ultrasound imaging. Herein, we also summarize the toxicity assessment of polysaccharides, associated contrast agents, and nanotoxicity along with the challenges and future research directions.

Plasmonic Oxygen Defects in MO3- x (M = W or Mo) Nanomaterials: Synthesis, Modifications, and Biomedical Applications

Nanomedicine is a promising technology with many advantages and provides exciting opportunities for cancer diagnosis and therapy. During recent years, the newly developed oxygen-deficiency transition metal oxides MO_{3- x} (M = W or Mo) have received significant attention due to the unique optical properties, such as strong localized surface plasmon resonance (LSPR) , tunable and broad near-IR absorption, high photothermal conversion efficiency, and large X-ray attenuation coefficient. This review presents an overview of recent advances in the development of MO_{3- x} nanomaterials for biomedical applications. First, the fundamentals of the LSPR effect are introduced. Then, the preparation and modification methods of MO_{3- x} nanomaterials are summarized. In addition, the biological effects of MO_{3- x} nanomaterials are highlighted and their applications in the biomedical field are outlined. This includes imaging modalities, cancer treatment, and antibacterial capability. Finally, the prospects and challenges of MO_{3- x} and MO_{3- x} -based nanomaterial for fundamental studies and clinical applications are also discussed.

A novel CT contrast agent for intestinal-targeted imaging through rectal administration

In this study, a novel CT contrast agent used by rectal administration is developed for targeting intestinal imaging. Iopamidol, an iodinated contrast agent, is loaded in chitosan (CS) nanospheres modified by Anti-5-HT3R (AH) antibody. The obtained AH-CS-I nanospheres (AH-CS-I Ns) would combine to 5-HT3 receptors highly expressed on the gastrointestinal mucosal, enhancing the intestinal-targeting ability of the contrast agent. The AH-CS-I Ns were administered by the rectal route for intestinal CT imaging, and FITC-labeled AH-CS-I Ns were prepared for investigating the in vivo distribution of the contrast agent. As a result, obvious contrast enhancement could still be observed at 6 h post administration because of the poorly absorption of enteral AH-CS-I Ns. Unlike the intravascularly administered agents, AH-CS-I Ns would not accumulate in the kidney and induce adverse reactions. Therefore, this technology has potential applications in the examination of intestinal diseases and could reduce the side effect of commercial iopamidol.

Surfactant-free tantalum oxide nanoparticles: synthesis, colloidal properties, and application as a contrast agent for computed tomography

With the growing interest of the medical industry in biocompatible nanoparticles (NPs), the current synthetic methods should be adapted to appropriate demands (toxicity, scalability, etc.). Most applications require colloidal systems to be stable not only in water but also in vivo, which represents a major challenge. In this study, biocompatible Ta2O5 NPs were synthesized by a solvothermal method avoiding toxic reagents, and surfactant-free stable hydrosols were obtained and used for computed tomography (CT) imaging. The small hydrodynamic size (2 nm) and colloidal stability of primary NPs were studied by dynamic light scattering (DLS). The particles were characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller analysis to confirm their structure and purity. To develop a stable hydrosol preparation protocol, the influence of pH and ultrasonication duration on the stability of Ta2O5 sols was analyzed by DLS and microelectrophoresis. To enhance the understanding of NP behavior in vivo, sol stability in conditions close to physiological (NaCl solutions) was studied in a pH range of 3-9. Hydrosols prepared by the proposed protocol were stable for at least 6 months and exhibited negligible cytotoxicity. Ta2O5 NPs also showed high CT contrast both in theoretical calculations and in vivo (rat gastrointestinal tract).

Evaluating the cytotoxicity of a large pool of metal oxide nanoparticles to Escherichia coli: Mechanistic understanding through In Vitro and In Silico studies

The toxic effect of eight metal oxide nanoparticles (MONPs) on Escherichia coli was experimentally evaluated following standard bioassay protocols. The obtained cytotoxicity ranking of these studied MONPs is Er₂O₃, Gd₂O₃, CeO₂, Co₂O₃, Mn₂O₃, Co₃O₄, Fe₃O₄/WO₃ (in descending order). The computed EC₅₀ values from experimental data suggested that Er₂O₃ and Gd₂O₃ were the most acutely toxic MONPs to E. coli. To identify the mechanism of toxicity of these 8 MONPs along with 17 other MONPs from our previous study, we employed seven classifications and machine learning (ML) algorithms including linear discriminant analysis (LDA), naïve bayes (NB), multinomial logistic regression (MLogitR), sequential minimal optimization (SMO), AdaBoost, J48, and random forest (RF). We also employed 1^st and 2^nd generation periodic table descriptors developed by us (without any sophisticated computing facilities) along with experimentally analyzed Zeta-potential, to model the cytotoxicity of these MONPs. Based on qualitative validation metrics, the LDA model appeared to be the best among the 7 tested models. The core environment of metal defined by the ratio of the number of core electrons to the number of valence electrons and the electronegativity count of oxygen showed a positive impact on toxicity. The identified properties were important for understanding the mechanisms of nanotoxicity and for predicting the potential environmental risk associated with MONPs exposure. The developed models can be utilized for environmental risk assessment of any untested MONP to E. coli, thereby providing a scientific basis for the design and preparation of safe nanomaterials.

Gold Nanoparticles as a Computed Tomography Marker for Stem Cell Tracking

Stem cell tracking is an essential prerequisite for effective stem cell therapy. Computed tomography (CT) imaging technique is an emerging quantitative tool to detect real time distribution of transplanted cells. Most of CT labels based on the high atomic number (Z) materials have concern over biocompatibility. The present book chapter describes a protocol for the use of biocompatible gold nanoparticles as a CT marker for efficient labeling of mesenchymal stem cells (MSCs) and subsequent cell tracking in rodent models.

PVP-stabilized tungsten oxide nanoparticles: pH sensitive anti-cancer platform with high cytotoxicity

Photochromic tungsten oxide (WO₃) nanoparticles stabilized by polyvinylpyrrolidone (PVP) were synthesized to evaluate their potential for biomedical applications. PVP-stabilized tungsten oxide nanoparticles demonstrated a highly selective cytotoxic effect on normal and cancer cells in vitro. WO₃ nanoparticles were found to induce substantial cell death in osteosarcoma cells (MNNG/HOS cell line) with a half-maximal inhibitory concentration (IC50) of 5 mg/mL, while producing no, or only minor, toxicity in healthy human mesenchymal stem cells (hMSc). WO₃ nanoparticles induced intracellular oxidative stress, which led to apoptosis type cell death. The selective anti-cancer effects of WO₃ nanoparticles are due to the pH sensitivity of tungsten oxide and its capability of reactive oxygen species (ROS) generation, which is expressed in the modulation of genes involved in reactive oxygen species metabolism, mitochondrial dysfunction, and apoptosis.

Evaluation of X-ray tomography contrast agents: A review of production, protocols, and biological applications

X-ray computed tomography is a strong tool that finds many applications both in medical applications and in the investigation of biological and nonbiological samples. In the clinics, X-ray tomography is widely used for diagnostic purposes whose three-dimensional imaging in high resolution helps physicians to obtain detailed image of investigated regions. Researchers in biological sciences and engineering use X-ray tomography because it is a nondestructive method to assess the structure of their samples. In both medical and biological applications, visualization of soft tissues and structures requires special treatment, in which special contrast agents are used. In this detailed report, molecule-based and nanoparticle-based contrast agents used in biological applications to enhance the image quality were compiled and reported. Special contrast agent applications and protocols to enhance the contrast for the biological applications and works to develop nanoparticle contrast agents to enhance the contrast for targeted drug delivery and general imaging applications were also assessed and listed.

Advantages and Limitations of Current Techniques for Analyzing the Biodistribution of Nanoparticles

Nanomedicines are typically submicrometer-sized carrier materials (nanoparticles) encapsulating therapeutic and/or imaging compounds that are used for the prevention, diagnosis and treatment of diseases. They are increasingly being used to overcome biological barriers in the body to improve the way we deliver compounds to specific tissues and organs. Nanomedicine technology aims to improve the balance between the efficacy and the toxicity of therapeutic compounds. Nanoparticles, one of the key technologies of nanomedicine, can exhibit a combination of physical, chemical and biological characteristics that determine their in vivo behavior. A key component in the translational assessment of nanomedicines is determining the biodistribution of the nanoparticles following in vivo administration in animals and humans. There are a range of techniques available for evaluating nanoparticle biodistribution, including histology, electron microscopy, liquid scintillation counting (LSC), indirectly measuring drug concentrations, in vivo optical imaging, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine imaging. Each technique has its own advantages and limitations, as well as capabilities for assessing real-time, whole-organ and cellular accumulation. This review will address the principles and methodology of each technique and their advantages and limitations for evaluating in vivo biodistribution of nanoparticles.

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.