The role of lymph nodes and their drainage in canine mammary gland tumours: Systematic review

Mammary gland tumours are the most common neoplasms in intact bitches. Over the last decades, veterinary oncology has evolved in detecting and determining the lymph nodes to be removed in these patients for an accurate staging and prognosis, as well as to achieve better disease control and higher overall survival time. Our objective was to describe recent advances related to lymphatic drainage in bitches with mammary gland tumours, focusing on surgery, diagnosis, and prognosis. Through a systematic review using PubMed as the database, a thorough multi-step search reduced 316 studies to 30 for analysis. Vital dyes appear to be crucial in reducing the overall surgery time through transoperative staining of the lymph nodes. Imaging contrasts provide information regarding specific tumour drainage; however, there is still little evidence for their use. The axillary and superficial inguinal lymph nodes are well-established as regional lymph nodes of the cranial and caudal mammary glands. In sequence, accessory axillary, medial iliac, popliteal, and sternal lymph nodes should receive attention if they demonstrate contrast drainage, even considering that the literature has not shown a relationship between drainage and metastasis in these cases. In conclusion, recent studies have provided us with more support in regional lymph node excision regarding the TNM staging system. Studies are highly heterogeneous and method comparisons do not fit due to the non-uniformity of samples, materials, and procedures. We suggest further studies with a larger sample size, complete follow-up of patients, contrast use, and lymph node morphological and immunohistochemical analysis.

Tungsten-based nanoparticles as contrast agents for liver tumor detection using dual-energy computed tomography

Dual-energy computed tomography (DECT) is a commonly used imaging technique for detecting and diagnosing liver cancer. Currently, it is performed using clinically approved iodinated small molecule contrast agents (CAs). However, these iodinated CAs have several drawbacks, including sub-optimal contrast generation and contra-indication in patients with renal insufficiency. Herein, we synthesized tungsten-based CAs (i.e., WO3-x NPs) with excellent biocompatibility and investigated their effectiveness in DECT imaging. WO3-x NPs significantly enhanced the contrast between liver tumors and normal liver tissues as indicated by in vivo DECT imaging. Furthermore, WO3-x NPs exhibited excellent biocompatibility and minimal systemic toxicity. This study introduces a novel class of CAs for DECT and presents a promising method for accurate early diagnosis of liver tumors.

Lipid Prodrug Nanoassemblies via Dynamic Covalent Boronates

Prodrug nanoassemblies combine the advantages of prodrug and nanomedicines, offering great potential in targeting the lesion sites and specific on-demand drug release, maximizing the therapeutic performance while minimizing their side effects. However, there is still lacking a facile pathway to prepare the lipid prodrug nanoassemblies (LPNAs). Herein, we report the LPNAs via the dynamic covalent boronate between catechol and boronic acid. The resulting LPNAs possess properties like drug loading in a dynamic covalent manner, charge reversal in an acidic microenvironment, and specific drug release at an acidic and/or oxidative microenvironment. Our methodology enables the encapsulation and delivery of three model drugs: ciprofloxacin, bortezomib, and miconazole. Moreover, the LPNAs are often more efficient in eradicating pathogens or cancer cells than their free counterparts, both in vitro and in vivo. Together, our LPNAs with intriguing properties may boost the development of drug delivery and facilitate their clinical applications.

Polymerization-Induced Self-Assembly for Efficient Fabrication of Biomedical Nanoplatforms

Amphiphilic copolymers can self-assemble into nano-objects in aqueous solution. However, the self-assembly process is usually performed in a diluted solution (<1 wt%), which greatly limits scale-up production and further biomedical applications. With recent development of controlled polymerization techniques, polymerization-induced self-assembly (PISA) has emerged as an efficient approach for facile fabrication of nano-sized structures with a high concentration as high as 50 wt%. In this review, after the introduction, various polymerization method-mediated PISAs that include nitroxide-mediated polymerization-mediated PISA (NMP-PISA), reversible addition-fragmentation chain transfer polymerization-mediated PISA (RAFT-PISA), atom transfer radical polymerization-mediated PISA (ATRP-PISA), and ring-opening polymerization-mediated PISA (ROP-PISA) are discussed carefully. Afterward, recent biomedical applications of PISA are illustrated from the following aspects, i.e., bioimaging, disease treatment, biocatalysis, and antimicrobial. In the end, current achievements and future perspectives of PISA are given. It is envisioned that PISA strategy can bring great chance for future design and construction of functional nano-vehicles.

Increased Sensitivity of Computed Tomography Scan for Neoplastic Tissues Using the Extracellular Vesicle Formulation of the Contrast Agent Iohexol

Computed tomography (CT) is a diagnostic medical imaging modality commonly used to detect disease and injury. Contrast agents containing iodine, such as iohexol, are frequently used in CT examinations to more clearly differentiate anatomic structures and to detect and characterize abnormalities, including tumors. However, these contrast agents do not have a specific tropism for cancer cells, so the ability to detect tumors is severely limited by the degree of vascularization of the tumor itself. Identifying delivery systems allowing enrichment of contrast agents at the tumor site would increase the sensitivity of detection of tumors and metastases, potentially in organs that are normally inaccessible to contrast agents, such as the CNS. Recent work from our laboratory has identified cancer patient-derived extracellular vesicles (PDEVs) as effective delivery vehicles for targeting diagnostic drugs to patients' tumors. Based on this premise, we explored the possibility of introducing iohexol into PDEVs for targeted delivery to neoplastic tissue. Here, we provide preclinical proof-of-principle for the tumor-targeting ability of iohexol-loaded PDEVs, which resulted in an impressive accumulation of the contrast agent selectively into the neoplastic tissue, significantly improving the ability of the contrast agent to delineate tumor boundaries.

Spectral computed tomography with inorganic nanomaterials: State-of-the-art

Recently, spectral computed tomography (CT) technology has received great interest in the field of radiology. Spectral CT imaging utilizes the distinct, energy-dependent X-ray absorption properties of substances in order to provide additional imaging information. Dual-energy CT and multi-energy CT (Spectral CT) are capable of constructing monochromatic energy images, material separation images, energy spectrum curves, constructing effective atomic number maps, and more. However, poor contrast, due to neighboring X-ray attenuation of organs and tissues, is still a challenge to spectral CT. Hence, contrast agents (CAs) are applied for better differentiation of a given region of interest (ROI). Currently, many different kinds of inorganic nanoparticulate CAs for spectral CT have been developed due to the limitations of clinical iodine (I)-based contrast media, leading to the conclusion that inorganic nanomedicine applied to spectral CT will be a powerful collaboration both in basic research and in clinics. In this review, the underlying principles and types of spectral CT techniques are discussed, and some evolving clinical diagnosis applications of spectral CT techniques are introduced. In particular, recent developments in inorganic CAs used for spectral CT are summarized. Finally, the challenges and future developments of inorganic nanomedicine in spectral CT are briefly discussed.

(Bio)degradable and Biocompatible Nano-Objects from Polymerization-Induced and Crystallization-Driven Self-Assembly

Polymerization-induced self-assembly (PISA) and crystallization-driven self-assembly (CDSA) techniques have emerged as powerful approaches to produce a broad range of advanced synthetic nano-objects with high potential in biomedical applications. PISA produces nano-objects of different morphologies (e.g., spheres, vesicles and worms), with high solids content (∼10-50 wt %) and without additional surfactant. CDSA can finely control the self-assembly of block copolymers and readily forms nonspherical crystalline nano-objects and more complex, hierarchical assemblies, with spatial and dimensional control over particle length or surface area, which is typically difficult to achieve by PISA. Considering the importance of these two assembly techniques in the current scientific landscape of block copolymer self-assembly and the craze for their use in the biomedical field, this review will focus on the advances in PISA and CDSA to produce nano-objects suitable for biomedical applications in terms of (bio)degradability and biocompatibility. This review will therefore discuss these two aspects in order to guide the future design of block copolymer nanoparticles for future translation toward clinical applications.

Polymerization-induced self-assembly and disassembly during the synthesis of thermoresponsive ABC triblock copolymer nano-objects in aqueous solution

Polymerization-induced self-assembly (PISA) has been widely utilized as a powerful methodology for the preparation of various self-assembled AB diblock copolymer nano-objects in aqueous media. Moreover, it is well-documented that chain extension of AB diblock copolymer vesicles using a range of hydrophobic monomers via seeded RAFT aqueous emulsion polymerization produces framboidal ABC triblock copolymer vesicles with adjustable surface roughness owing to microphase separation between the two enthalpically incompatible hydrophobic blocks located within their membranes. However, the utilization of hydrophilic monomers for the chain extension of linear diblock copolymer vesicles has yet to be thoroughly explored; this omission is addressed for aqueous PISA formulations in the present study. Herein poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (G-H) vesicles were used as seeds for the RAFT aqueous dispersion polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA). Interestingly, this led to polymerization-induced disassembly (PIDA), with the initial precursor vesicles being converted into lower-order worms or spheres depending on the target mean degree of polymerization (DP) for the corona-forming POEGMA block. Moreover, construction of a pseudo-phase diagram revealed an unexpected copolymer concentration dependence for this PIDA formulation. Previously, we reported that PHPMA-based diblock copolymer nano-objects only exhibit thermoresponsive behavior over a relatively narrow range of compositions and DPs (see Warren et al., Macromolecules, 2018, 51, 8357–8371). However, introduction of the POEGMA coronal block produced thermoresponsive ABC triblock nano-objects even when the precursor G-H diblock copolymer vesicles proved to be thermally unresponsive. Thus, this new approach is expected to enable the rational design of new nano-objects with tunable composition, copolymer architectures and stimulus-responsive behavior.

Chain extension of linear AB diblock copolymer vesicles by seeded RAFT aqueous dispersion polymerization using a hydrophilic monomer C leads to polymerization-induced disassembly to form lower-order thermoresponsive ABC triblock copolymer nano-objects.

Polymers for Improved Delivery of Iodinated Contrast Agents

X-ray computed tomography (CT), as one of the most widely used noninvasive imaging modalities, can provide three-dimensional anatomic details with high resolution, which plays a key role in disease diagnosis and treatment assessment. However, although they are the most prevalent and FDA-approved contrast agents, iodinated water-soluble molecules still face some challenges in clinical applications, such as fast clearance, serious adverse effects, nonspecific distribution, and low sensitivity. Because of their high biocompatibility, tunable designability, controllable biodegradation, facile synthesis, and modification capability, the polymers have demonstrated great potential for efficient delivery of iodinated contrast agents (ICAs). Herein, we comprehensively summarized the applications of multifunctional polymeric materials for ICA delivery in terms of increasing circulation time, decreasing nephrotoxicity, and improving the specificity and sensitivity of ICAs for CT imaging. We mainly focused on various iodinated polymers from the aspects of preparation, functionalization, and application in medical diagnosis. Future perspectives for achieving better imaging and clinical translation are also discussed to motivate new technologies and solutions.

Organic Nanoplatforms for Iodinated Contrast Media in CT Imaging

X-ray computed tomography (CT) imaging can produce three-dimensional and high-resolution anatomical images without invasion, which is extremely useful for disease diagnosis in the clinic. However, its applications are still severely limited by the intrinsic drawbacks of contrast media (mainly iodinated water-soluble molecules), such as rapid clearance, serious toxicity, inefficient targetability and poor sensitivity. Due to their high biocompatibility, flexibility in preparation and modification and simplicity for drug loading, organic nanoparticles (NPs), including liposomes, nanoemulsions, micelles, polymersomes, dendrimers, polymer conjugates and polymeric particles, have demonstrated tremendous potential for use in the efficient delivery of iodinated contrast media (ICMs). Herein, we comprehensively summarized the strategies and applications of organic NPs, especially polymer-based NPs, for the delivery of ICMs in CT imaging. We mainly focused on the use of polymeric nanoplatforms to prolong circulation time, reduce toxicity and enhance the targetability of ICMs. The emergence of some new technologies, such as theragnostic NPs and multimodal imaging and their clinical translations, are also discussed.

Iodinated BSA Nanoparticles for Macrophage-Mediated CT Imaging and Repair of Gastritis

The development of a specific and noninvasive technology for understanding gastritic response together with efficient therapy is an urgent clinical issue. Herein, we fabricated a novel iodinated bovine serum albumin (BSA) nanoparticle based on gastritic microenvironment for computed tomography (CT) imaging and repair of acute gastritis. Derived from the characteristic mucosa defect and inflammatory cell (e.g., macrophage and neutrophil) infiltration in acute gastritis, the pH-sensitive nanoparticles can sedimentate under acidic conditions and be uniformly distributed in the defected mucosal via the phagocytosis of inflammatory cells. Hence, enhanced CT images can clearly reveal the mucosal morphology in the nanoparticle-treated gastritic rat over a long time window comparison with nanoparticle-treated healthy rats and clinical small-molecule-treated gastritic rat. In addition, we have discovered that nanoparticles can repair the atrophic gastric mucosa to a normal state. This repair process mainly stems from inflammatory immune response caused by phagocytized nanoparticles, such as the polarization of proinflammatory macrophages (M1) to anti-inflammatory macrophages (M2). The biocompatible nanoparticles that avoid the inherent defects of the clinical small molecules have great potential for accurate diagnosis and treatment of gastritis in the early stage.

Multifunctional Magnetic Nanoagents for Bioimaging and Therapy

Multifunctional magnetic nanoagents (MMNs) have drawn increasing attention in cancer precision therapy, attributed to their good biocompatibility and the potential applications for multimodal imaging and multidisciplinary therapy. The noble metal or isotopes contained in MMNs could not only perform superparamagnetism, providing an outstanding magnetic targeting property for drug delivery, but also endow the MMNs with a magnetocaloric effect, photothermal performance, and radiotherapy sensitization, arriving at a multimode combination therapy for cancer. Also, the composite component can endow MMNs with various imaging performance, such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), and single-photon emission computed tomography (SPECT), thereby achieving accurate image-guided therapy for cancer. However, the joint function of MMNs is closely correlated with their functional nanocomponents and nanostructures. In this article, we will systematically discuss the design, synthesis, and structure optimization of MMNs, as well as their potential in multimodal diagnosis and therapy, scientifically providing an integrated diagnosis and treatment of nanomedicine for the future cancer therapy.

Facile Hydrothermal Synthesis of an Iodine-Doped Computed Tomography Contrast Agent Using Insoluble Triiodobenzene

Carbonized iodine-doped particles (CIPs) were developed to overcome the disadvantages of computed tomography (CT) contrast agents, such as high osmolality and the radiodensity dilution of monomolecular contrast agents and low solubility and high toxicity of polymeric contrast agents. The CIPs were synthesized via a hydrothermal synthesis for 8 h using ATIPA (5-amino-2,4,6-triiodoisophthalic acid), glycerol, and tromethamine in the presence of D.W. (deionized water)-insoluble ATIPA converted into CIPs through a hydrothermal synthesis, showing high solubility and low osmotic pressure. The in vitro contrast effect determined for the resulting CIPs demonstrated a 57.6% enhancement compared to iohexol, and the osmotic pressure of the resulting CIPs was lower than that of iohexol. In addition, the CIPs demonstrated no dilution-induced contrast decrease in plasma and, therefore, demonstrated high contrast strength in vivo. Cytotoxicity tests, hemolysis assays, and histological analyses were conducted to verify the biocompatibility of the CIP product; however, no toxicity was observed. Furthermore, the CIP demonstrated a much higher contrast effect than iohexol at low concentrations. These results indicate that the CIP we have produced may be used as an effective blood pool agent for CT imaging.

A Dendrimer-Based Dual Radiodense Element-Containing Nanoplatform for Targeted Enhanced Tumor Computed Tomography Imaging

The exploration of original computed tomography (CT) imaging contrast agents with enhanced sensitivity and specificity is currently one of the major challenging tasks for precision medicine. Herein, we develop an innovative nanoprobe of dendrimer-stabilized gold nanoparticles (Au DSNs) linked with folic acid (FA) as a targeting ligand and diatrizoic acid (DTA) for specific enhanced tumor CT imaging. In current work, poly(amidoamine) (PAMAM) dendrimers of generation 5 (G5) with amine termini were adopted to entrap Au NPs through a stepwise complexation/reduction method to achieve a higher Au loading than the conventional one-step complexation/reduction method. The prepared [(Au⁰)₁₂₀-G5.NH₂] NPs were sequentially functionalized with diatrizoic acid (DTA), a typical CT contrast agent based on iodine(I), FA through a poly(ethylene glycol) (PEG) spacer, and carboxylated PEG monomethyl ether (mPEG-COOH), ended with complete acetylation of the leftover dendrimer amine termini. The generated Au DSNs-DTA-FA (Au core diameter = 5.9 nm) were thoroughly characterized. Our data reveal that the Au DSNs-DTA-FA containing Au and I dual radiodense elements are stable, display enhanced CT imaging performance, much higher than the single-radiodense elemental material solely based on Au or I, and possess a quite good cytocompatibility. With the demonstrated FA-rendered specific targeting, the developed Au DSNs-DTA-FA can be employed as a highly efficient nanoprobe for targeted enhanced CT imaging of cancer cells and a subcutaneous tumor model. Overall, the created Au DSNs-DTA-FA may be a powerful nanoprobe for specific enhanced CT imaging of various kinds of FA receptor-expressing tumors or biosystems.

cRGD-modified and disulfide bond-crosslinked polymer nanoparticles based on iopamidol as a tumor-targeted CT contrast agent

The disulfide bond-crosslinked polymer nanoparticles based on iopamidol were prepared and then surface-modified with cRGD peptide through the linkages of PEG to acquire a CT contrast agent for breast cancer-targeted imaging.

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.