Nanoparticle contrast agents for X-ray imaging applications

The contrast agent 2,3,5-triiodobenzoic acid (TIBA) induces cell death in tumor cells through the generation of reactive oxygen species

The 2,3,5-triiodobenzoic acid (TIBA) is an iodine contrast agent used for visualization of tissue in X-ray techniques. However, TIBA induces physiological complications like increase in oxygen reactive species (ROS), and consequently, contrast-induced nephropathies. TIBA's antitumor activity was demonstrated in lung cancer, but the subcellular mechanisms involving its activity in tumor cells are still unknown. Thus, the objective of this work was evaluate whether the anti-tumor activity of TIBA involves ROS increase, in tumor lines of non-small cell lung cancer (H460), chronic myeloid leukemia (K562), and its cytotoxicity in normal renal epithelial (VERO). The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide) assay was used for evaluation of cell viability, the H₂DCFDA (cell-permeant 2',7'-dichlorodihydrofluorescein diacetate) fluorescent probe to evaluate ROS induction, cell cycle analysis was performed using flow cytometry to measure cell death, and immunofluorescence with annexin/7-AAD (7-amino-actinomycin D), to assess the association of cell death with the ROS generation. TIBA decreases cell viability in a dose-dependent manner for the H460 and K562. However, VERO cells showed less response to the drug, with 70% viable cells after 72 h of treatment in the highest concentration of the drug. While the tumor cells with only 20% viable cells. Besides, tumor cells exhibited higher DNA fragmentation, compared to the renal line (VERO with 5% of fragmented DNA, H460 with 26%, and 56% in K562). Finally, TIBA-induced ROS increase and apoptosis in all lines, which is significantly decreased after treatment with the antioxidant N-acetyl-cysteine (NAC). These data demonstrate the relationship between the increased cellular oxidative stress and the anti-tumor action of the TIBA.

Toward molecular imaging using spectral photon-counting computed tomography?

Molecular imaging is a valuable tool in drug discovery and development, early screening and diagnosis of diseases, and therapy assessment among others. Although many different imaging modalities are in use today, molecular imaging with computed tomography (CT) is still challenging owing to its low sensitivity and soft tissue contrast compared with other modalities. Recent technical advances, particularly the introduction of spectral photon-counting detectors, might allow overcoming these challenges. Herein, the fundamentals and recent advances in CT relevant to molecular imaging are reviewed and potential future preclinical and clinical applications are highlighted. The review concludes with a discussion of potential future advancements of CT for molecular imaging.

Computed tomography imaging of macrophage phagocytic activity in abdominal aortic aneurysm

Inflammation plays a major role in the pathogenesis of several vascular pathologies, including abdominal aortic aneurysm (AAA). Evaluating the role of inflammation in AAA pathobiology and potentially outcome in vivo requires non-invasive tools for high-resolution imaging. We investigated the feasibility of X-ray computed tomography (CT) imaging of phagocytic activity using nanoparticle contrast agents to predict AAA outcome. Methods: Uptake of several nanoparticle CT contrast agents was evaluated in a macrophage cell line. The most promising agent, Exitron nano 12000, was further characterized in vitro and used for subsequent in vivo testing. AAA was induced in Apoe-/- mice through angiotensin II (Ang II) infusion for up to 4 weeks. Nanoparticle biodistribution and uptake in AAA were evaluated by CT imaging in Ang II-infused Apoe-/- mice. After imaging, the aortic tissue was harvested and used from morphometry, transmission electron microscopy and gene expression analysis. A group of Ang II-infused Apoe-/- mice underwent nanoparticle-enhanced CT imaging within the first week of Ang II infusion, and their survival and aortic external diameter were evaluated at 4 weeks to address the value of vessel wall CT enhancement in predicting AAA outcome. Results: Exitron nano 12000 showed specific uptake in macrophages in vitro. Nanoparticle accumulation was observed by CT imaging in tissues rich in mononuclear phagocytes. Aortic wall enhancement was detectable on delayed CT images following nanoparticle administration and correlated with vessel wall CD68 expression. Transmission electron microscopy ascertained the presence of nanoparticles in AAA adventitial macrophages. Nanoparticle-induced CT enhancement on images obtained within one week of AAA induction was predictive of AAA outcome at 4 weeks. Conclusions: By establishing the feasibility of CT-based molecular imaging of phagocytic activity in AAA, this study links the inflammatory signal on early time point images to AAA evolution. This readily available technology overcomes an important barrier to cross-sectional, longitudinal and outcome studies, not only in AAA, but also in other cardiovascular pathologies and facilitates the evaluation of modulatory interventions, and ultimately upon clinical translation, patient management.

X-ray-Based Techniques to Study the Nano-Bio Interface

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.

Medical imaging of tissue engineering and regenerative medicine constructs

Advancement of tissue engineering and regenerative medicine (TERM) strategies to replicate tissue structure and function has led to the need for noninvasive assessment of key outcome measures of a construct's state, biocompatibility, and function. Histology based approaches are traditionally used in pre-clinical animal experiments, but are not always feasible or practical if a TERM construct is going to be tested for human use. In order to transition these therapies from benchtop to bedside, rigorously validated imaging techniques must be utilized that are sensitive to key outcome measures that fulfill the FDA standards for TERM construct evaluation. This review discusses key outcome measures for TERM constructs and various clinical- and research-based imaging techniques that can be used to assess them. Potential applications and limitations of these techniques are discussed, as well as resources for the processing, analysis, and interpretation of biomedical images.

Spectral photon-counting CT in cardiovascular imaging

Photon-counting computed tomography (PCCT) is an emerging technology promising to substantially improve cardiovascular imaging. Recent engineering and manufacturing advances by several vendors are expected to imminently launch this new technology into clinical reality. Photon-counting detectors (PCDs) have multiple potential advantages over conventional energy integrating detectors (EIDs) such as the absence of electronic noise, multi-energy capability, and increased spatial resolution. These developments will have different timescales for implementation and will affect different clinical scopes. We describe the technical aspects of PCCT, explain the current developments, and finally discuss potential advantages of PCCT in cardiovascular imaging.