Detection of vulnerable atherosclerosis plaques with a dual-modal single-photon-emission computed tomography/magnetic resonance imaging probe targeting apoptotic macrophages

Iron oxide nanoparticles for treatment and diagnosis of chronic inflammatory diseases: A systematic review

Chronic inflammatory conditions are among the most prevalent diseases worldwide. Several debilitating diseases such as atherosclerosis, inflammatory bowel disease, rheumatoid arthritis, and Alzheimer's are linked to chronic inflammation. These conditions often develop into complex and fatal conditions, making early detection and treatment of chronic inflammation crucial. Current diagnostic methods show high variability and do not account for disease heterogeneity and disease-specific proinflammatory markers, often delaying the disease detection until later stages. Furthermore, existing treatment strategies, including high-dose anti-inflammatory and immunosuppressive drugs, have significant side effects and an increased risk of infections. In recent years, superparamagnetic iron oxide nanoparticles (SPIONs) have shown tremendous biomedical potential. SPIONs can function as imaging modalities for magnetic resonance imaging, and as therapeutic agents due to their magnetic hyperthermia capability. Furthermore, the surface functionalization of SPIONs allows the detection of specific disease biomarkers and targeted drug delivery. This systematic review explores the utility of SPIONs against chronic inflammatory disorders, focusing on their dual role as diagnostic and therapeutic agents. We extracted studies indexed in the Web of Science database from the last 10 years (2013-2023), and applied systematic inclusion criteria. This resulted in a final selection of 38 articles, which were analyzed for nanoparticle characteristics, targeted diseases, in vivo and in vitro models used, and the efficacy of the therapeutic or diagnostic modalities. The results revealed that ultrasmall SPIONs are excellent for imaging arterial and neuronal inflammation. Furthermore, novel therapies using SPIONs loaded with chemotherapeutic drugs show promise in the treatment of inflammatory diseases. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

In Vivo Imaging of γ-Glutamyl Transferase in Cardiovascular Diseases with a Photoacoustic Probe

In this work, a photoacoustic (PA) probe, HDS-GGT, was developed for the in vivo imaging of cardiovascular diseases by monitoring the γ-glutamyl transferase (GGT) dynamics. HDS-GGT exhibited a stable PA signal with auxiliary absorbance and NIRF variation after the trigger by GGT. In all three modalities of absorbance, NIRF, and PA, HDS-GGT could quantitatively reflect the GGT level. In PA modality, HDS-GGT indicated the practical advantages including high sensitivity, high stability, and high specificity. In living oxidized low-density lipoprotein-induced RAW264.7 cells, HDS-GGT indicated proper capability for imaging the plaques by visualizing the GGT dynamics. Moreover, during imaging in living model mice, HDS-GGT was achieved to distinguish the plaques from healthy blood vessels via a multiview PA presentation. HDS-GGT could also suggest the severity of plaques in the extracted aorta from the model mice, which was consistent with the histological staining results. The information herein might be useful for future investigations on cardiovascular diseases.

Advances of nanoparticle-mediated diagnostic and theranostic strategies for atherosclerosis

Atherosclerotic plaque remains the primary cause of morbidity and mortality worldwide. Accurate assessment of the degree of atherosclerotic plaque is critical for predicting the risk of atherosclerotic plaque and monitoring the results after intervention. Compared with traditional technology, the imaging technologies of nanoparticles have distinct advantages and great development prospects in the identification and characterization of vulnerable atherosclerotic plaque. Here, we systematically summarize the latest advances of targeted nanoparticle approaches in the diagnosis of atherosclerotic plaque, including multimodal imaging, fluorescence imaging, photoacoustic imaging, exosome diagnosis, and highlighted the theranostic progress as a new therapeutic strategy. Finally, we discuss the major challenges that need to be addressed for future development and clinical transformation.

Molecularly targeted nanomedicine enabled by inorganic nanoparticles for atherosclerosis diagnosis and treatment

Atherosclerosis, a chronic cardiovascular disease caused by plaque development in arteries, remains a leading cause of morbidity and mortality. Atherosclerotic plaques are characterized by the expression and regulation of key molecules such as cell surface receptors, cytokines, and signaling pathway proteins, potentially facilitating precise diagnosis and treatment on a molecular level by specifically targeting the characteristic molecules. In this review, we highlight the recent progress in the past five years on developing molecularly targeted nanomedicine for imaging detection and treatment of atherosclerosis with the use of inorganic nanoparticles. Through targeted delivery of imaging contrast nanoparticles to specific molecules in atherogenesis, atherosclerotic plaque development at different stages could be identified and monitored via various molecular imaging modalities. We also review molecularly targeted therapeutic approaches that target and regulate molecules associated with lipid regulation, inflammation, and apoptosis. The review is concluded with discussion on current challenges and future development of nanomedicine for atherosclerotic diagnosis and treatment.

Early Assessment of Atherosclerotic Lesions and Vulnerable Plaques in vivo by Targeting Apoptotic Macrophages with AV Nanobubbles

Background

The early detection of atherosclerotic lesions is particularly important for risk prediction of acute cardiovascular events. Macrophages apoptosis was significantly associated with the degree of AS lesions and especially contributed to plaque vulnerability. In this research, we mainly sought to explore the feasibility of a home-made AV-nanobubbles (NB_AV) for visualization of apoptotic macrophages and assessment of atherosclerosis (AS) lesions by contrast-enhanced ultrasound (CEUS) imaging.

Methods

NB_AV were prepared by “Optimized Thin-Film Hydration” and “Biotin-Avidin-Biotin” methods. Then, the characterization and echogenicity of NB_AV were measured and analyzed in vitro. The targeting ability of NB_AV to ox-LDL–induced apoptotic macrophages was observed by laser scanning confocal microscope. The ApoE^−/− mice mode fed with high fat diet were observed by high-frequency ultrasound, microanatomy and oil red O staining. CEUS imaging in vivo was performed on AS plaques with NB_AV and NB_Ctrl injection through the tail vein in turn in ApoE^−/− mice. After CEUS imaging, the plaques were confirmed and analyzed by histopathological and immunological assessment.

Results

The prepared NB_AV had a nano-scale size distribution with a low PDI and a negative zeta potential. Moreover, NB_AV showed an excellent stability and exhibited a significantly echogenic signal than saline in vitro. In addition, we found that NB_AV could target apoptotic macrophages induced by ox-LDL. Compared with NB_Ctrl, CEUS imaging of NB_AV showed strong and sustained echo enhancement in plaque area of aortic arch in vivo. Further research showed that NB_AV sensitive plaques presented more significant pathological changes with several vulnerable plaque features and abundant TUNEL-positive area.

Conclusion

NB_AV displayed a sensitive indicator to evaluate apoptotic macrophages, indicating a promising CEUS molecular probe for AS lesions and vulnerable plaques identification.

Advanced targeted nanomedicines for vulnerable atherosclerosis plaque imaging and their potential clinical implications

Atherosclerosis plaques caused by cerebrovascular and coronary artery disease have been the leading cause of death and morbidity worldwide. Precise assessment of the degree of atherosclerotic plaque is critical for predicting the risk of atherosclerosis plaques and monitoring postinterventional outcomes. However, traditional imaging techniques to predict cardiocerebrovascular events mainly depend on quantifying the percentage reduction in luminal diameter, which would immensely underestimate non-stenotic high-risk plaque. Identifying the degree of atherosclerosis plaques still remains highly limited. vNanomedicine-based imaging techniques present unique advantages over conventional techniques due to the superior properties intrinsic to nanoscope, which possess enormous potential for characterization and detection of the features of atherosclerosis plaque vulnerability. Here, we review recent advancements in the development of targeted nanomedicine-based approaches and their applications to atherosclerosis plaque imaging and risk stratification. Finally, the challenges and opportunities regarding the future development and clinical translation of the targeted nanomedicine in related fields are discussed.

Macrophage-targeted nanomedicine for the diagnosis and management of atherosclerosis

Atherosclerosis is the primary cause of cardiovascular diseases, such as myocardial infarction and stroke, which account for the highest death toll worldwide. Macrophage is the major contributor to atherosclerosis progression, and therefore, macrophage-associated pathological process is considered an extremely important target for the diagnosis and treatment of atherosclerosis. However, the existing clinical strategies still have many bottlenecks and challenges in atherosclerosis’s early detection and management. Nanomedicine, using various nanoparticles/nanocarriers for medical purposes, can effectively load therapeutic agents, significantly improve their stability and accurately deliver them to the atherosclerotic plaques. In this review, we summarized the latest progress of the macrophage-targeted nanomedicine in the diagnosis and treatment of atherosclerosis, and their potential applications and clinical benefits are also discussed.

Nano-sponge-like liposomes remove cholesterol crystals for antiatherosclerosis

Atherosclerotic cardiovascular diseases remain the leading causes of morbidity and mortality worldwide. Cholesterol crystals in atherosclerotic plaques play an essential role in atherosclerosis progression. However, no clinical drugs have been used for removing cholesterol crystals from plaque to counter atherosclerosis. Previous studies identified the hydrophobic domain of lipid bilayer in liposomes acted as sinks for solubilizing hydrophobic cholesterol. Moreover, adjusting the composition of the lipid bilayer in liposomes can enhance its hydrophobic molecule loading capacity. Therefore, in this study, ginsenosides Rb1 (Rb1), one of main active components of ginseng which has a similar structure to cholesterol, is anchored into soy phospholipids bilayer with its hydrophobic region to prepare nano-sponge-like liposomes (Rb1-LPs), aiming to amplify the solubilization of cholesterol in lipid bilayer. For targeting delivery to atherosclerotic plaques, Annexin V (AnxV), a protein that can specifically recognize phosphatidylserine upregulated in atherosclerotic plaques, is applied to decorate the surface of Rb1-LPs by click reaction to obtain the final preparation of AnxV-Rb1-LPs. The in vitro studies showed that incorporating Rb1 into lipid bilayer remarkably increased the affinity of the lipid bilayer to free cholesterol and the solubilization of cholesterol crystals. Additionally, nano-sponge-like liposomes could efficiently reduce the accumulation of cholesterol crystals and improve cholesterol efflux, finally inhibiting inflammation and apoptosis in cholesterol-laden cells. Furthermore, AnxV-Rb1-LPs could efficiently accumulate in atherosclerotic plaques after intravenous injection, exert nano-sponge-like functions to remove intra- and extracellular cholesterol crystals, ultimately alleviating inflammation and apoptosis in atherosclerotic plaques for antiatherosclerosis. Therefore, AnxV-Rb1-LPs provide a potential strategy for removing cholesterol crystals in atherosclerotic plaques and can be further utilized in other diseases with excessive cholesterol accumulation.

Nanoparticles in the diagnosis and treatment of vascular aging and related diseases

Aging-induced alternations of vasculature structures, phenotypes, and functions are key in the occurrence and development of vascular aging-related diseases. Multiple molecular and cellular events, such as oxidative stress, mitochondrial dysfunction, vascular inflammation, cellular senescence, and epigenetic alterations are highly associated with vascular aging physiopathology. Advances in nanoparticles and nanotechnology, which can realize sensitive diagnostic modalities, efficient medical treatment, and better prognosis as well as less adverse effects on non-target tissues, provide an amazing window in the field of vascular aging and related diseases. Throughout this review, we presented current knowledge on classification of nanoparticles and the relationship between vascular aging and related diseases. Importantly, we comprehensively summarized the potential of nanoparticles-based diagnostic and therapeutic techniques in vascular aging and related diseases, including cardiovascular diseases, cerebrovascular diseases, as well as chronic kidney diseases, and discussed the advantages and limitations of their clinical applications.

Targeting the Microenvironment of Vulnerable Atherosclerotic Plaques: An Emerging Diagnosis and Therapy Strategy for Atherosclerosis

Atherosclerosis is considered one of the primary causes of cardiovascular diseases (CVDs). Unpredictable rupture of the vulnerable atherosclerotic plaques triggers adverse cardiovascular events such as acute myocardial syndrome and even sudden cardiac death. Therefore, assessing the vulnerability of atherosclerotic plaques and early intervention are of significance in reducing CVD mortality. Nanomedicine possesses tremendous advantages in achieving the integration of the diagnosis and therapy of atherosclerotic plaques because of its magnetic, optical, thermal, and catalytic properties. Based on the pathological characteristics of vulnerable plaques, stimuli-responsive nanoplatforms and surface-functionalized nanoagents are designed and have drawn great attention for accomplishing the precise imaging and treatment of vulnerable atherosclerotic plaques due to their superior properties, such as high bioavailability, lesion-targeting specificity, on-demand cargo release, and low off-target damage. Here, the characteristics of vulnerable plaques are generalized, and some targeted strategies for boosting the accuracy of plaque vulnerability evaluation by imaging and the efficacy of plaque stabilization therapy (including antioxidant therapy, macrophage depletion therapy, regulation of lipid metabolism therapy, anti-inflammation therapy, etc.) are systematically summarized. In addition, existing challenges and prospects in this field are discussed, and it is believed to provide new thinking for the diagnosis and treatment of CVDs in the near future.

Current Development of Nano-Drug Delivery to Target Macrophages

Macrophages are the most important innate immune cells that participate in various inflammation-related diseases. Therefore, macrophage-related pathological processes are essential targets in the diagnosis and treatment of diseases. Since nanoparticles (NPs) can be preferentially taken up by macrophages, NPs have attracted most attention for specific macrophage-targeting. In this review, the interactions between NPs and the immune system are introduced to help understand the pharmacokinetics and biodistribution of NPs in immune cells. The current design and strategy of NPs modification for specific macrophage-targeting are investigated and summarized.

Current advances in the imaging of atherosclerotic vulnerable plaque using nanoparticles

Vulnerable atherosclerotic plaques of the artery wall that pose a significant risk of cardio-cerebral vascular accidents remain the global leading cause of morbidity and mortality. Thus, early delineation of vulnerable atherosclerotic plaques is of clinical importance for prevention and treatment. The currently available imaging technologies mainly focus on the structural assessment of the vascular wall. Unfortunately, several disadvantages in these strategies limit the improvement in imaging effect. Nanoparticle technology is a novel diagnostic strategy for targeting and imaging pathological biomarkers. New functionalized nanoparticles that detect hallmarks of vulnerable plaques are promising for advance further control of this critical illness. The review aims to address the current opportunities and challenges for the use of nanoparticle technology in imagining vulnerable plaques.

CD11b-Based Pre-Targeted SPECT/CT Imaging Allows for the Detection of Inflammation in Aortic Aneurysm

Purpose

To investigate the feasibility of a pre-targeted imaging strategy based on the cycloaddition between 1,2,4,5-terazine (Tz) and trans-cyclooctene (TCO) for evaluating CD11b expression in inflammatory aortic aneurysm (AA) using single photon emission computed tomography/computed tomography (SPECT/CT).

Methods

C57BL/6J mice were fed β-aminopropionitrile (1 g/kg/day) for 4 weeks to establish AA models. Anti-CD11b-TCO was synthesized and ^99mTc-HYNIC-PEG₁₁-Tz was designed for pre-targeted SPECT/CT. The affinity and specificity of the probe for the inflammatory cell line Raw-264.7 were investigated. Then, anti-CD11b-TCO pre-targeted and ^99mTc-HYNIC-PEG₁₁-Tz based SPECT/CT were performed to detect in vivo inflammation in AA. Finally, ex vivo aortic breast-specific gamma imaging (BSGI), Western blot assays, and immunohistochemical CD11b staining were performed to confirm the in vivo findings of SPECT/CT.

Results

In the AA models, 65.22% (15/23) had aortic lesions, including 43.48% (10/23) AA lesions. The anti-CD11b-TCO presented with a high TCO coupling ratio (7.43), and the ^99mTc-HYNIC-PEG₁₁-Tz showed high radio-purity (>95%), good in vitro stability and a rapid clearance rate. Additionally, anti-CD11b-TCO and ^99mTc-HYNIC-PEG₁₁-Tz presented high click rate (~89%). The in vitro clicked compound, ^99mTc-HYNIC-PEG₁₁-Tz/TCO-anti-CD11b, showed high affinity and specificity for Raw-264.7 cells. ^99mTc-HYNIC-PEG₁₁-Tz/TCO-anti-CD11b pre-targeting SPECT/CT successfully demonstrated inflammatory AA with a high AA-to-background ratio in AA mice, compared to AA mice that were injected with ^99mTc-HYNIC-Tz/TCO-IgG (8.13 versus 3.71, P < 0.001) and control mice injected with ^99mTc-HYNIC-Tz/TCO-anti-CD11b (8.13 versus 3.66, P < 0.001). This result was confirmed by ex vivo BSGI performed immediately after SPECT/CT and immunohistochemical CD11b staining.

Conclusion

SPECT/CT imaging using the anti-CD11b-TCO/Tz-PEG₁₁-HYNIC-^99mTc based pre-targeting imaging strategy allows for the detection of inflammation in progressive AA.

Macrophage-targeted nanomedicine for the diagnosis and treatment of atherosclerosis

Nanotechnology could improve our understanding of the pathophysiology of atherosclerosis and contribute to the development of novel diagnostic and therapeutic strategies to further reduce the risk of cardiovascular disease. Macrophages have key roles in atherosclerosis progression and, therefore, macrophage-associated pathological processes are important targets for both diagnostic imaging and novel therapies for atherosclerosis. In this Review, we highlight efforts in the past two decades to develop imaging techniques and to therapeutically manipulate macrophages in atherosclerotic plaques with the use of rationally designed nanoparticles. We review the latest progress in nanoparticle-based imaging modalities that can specifically target macrophages. Using novel molecular imaging technology, these modalities enable the identification of advanced atherosclerotic plaques and the assessment of the therapeutic efficacy of medical interventions. Additionally, we provide novel perspectives on how macrophage-targeting nanoparticles can deliver a broad range of therapeutic payloads to atherosclerotic lesions. These nanoparticles can suppress pro-atherogenic macrophage processes, leading to improved resolution of inflammation and stabilization of plaques. Finally, we propose future opportunities for novel diagnostic and therapeutic strategies and provide solutions to challenges in this area for the purpose of accelerating the clinical translation of nanomedicine for the treatment of atherosclerotic vascular disease.

Research methods for animal models of atherosclerosis (Review)

Atherosclerosis is a chronic inflammatory disease that threatens human health and lives by causing vascular stenosis and plaque rupture. Various animal models have been employed for elucidating the pathogenesis, drug development and treatment validation studies for atherosclerosis. To the best of our knowledge, the species used for atherosclerosis research include mice, rats, hamsters, rabbits, pigs, dogs, non-human primates and birds, among which the most commonly used ones are mice and rabbits. Notably, apolipoprotein E knockout (KO) or low-density lipoprotein receptor KO mice have been the most widely used animal models for atherosclerosis research since the late 20th century. Although the aforementioned animal models can form atherosclerotic lesions, they cannot completely simulate those in humans with respect to lesion location, lesion composition, lipoprotein composition and physiological structure. Hence, an appropriate animal model needs to be selected according to the research purpose. Additionally, it is necessary for atherosclerosis research to include quantitative analysis results of atherosclerotic lesion size and plaque composition. Laboratory animals can provide not only experimental tissues for in vivo studies but also cells needed for in vitro experiments. The present review first summarizes the common animal models and their practical applications, followed by focus on mouse and rabbit models and elucidating the methods to quantify atherosclerotic lesions. Finally, the methods of culturing endothelial cells, macrophages and smooth muscle cells were elucidated in detail and the experiments involved in atherosclerosis research were discussed.

Iron Oxide Nanoparticles in Regenerative Medicine and Tissue Engineering

In recent years, many promising nanotechnological approaches to biomedical research have been developed in order to increase implementation of regenerative medicine and tissue engineering in clinical practice. In the meantime, the use of nanomaterials for the regeneration of diseased or injured tissues is considered advantageous in most areas of medicine. In particular, for the treatment of cardiovascular, osteochondral and neurological defects, but also for the recovery of functions of other organs such as kidney, liver, pancreas, bladder, urethra and for wound healing, nanomaterials are increasingly being developed that serve as scaffolds, mimic the extracellular matrix and promote adhesion or differentiation of cells. This review focuses on the latest developments in regenerative medicine, in which iron oxide nanoparticles (IONPs) play a crucial role for tissue engineering and cell therapy. IONPs are not only enabling the use of non-invasive observation methods to monitor the therapy, but can also accelerate and enhance regeneration, either thanks to their inherent magnetic properties or by functionalization with bioactive or therapeutic compounds, such as drugs, enzymes and growth factors. In addition, the presence of magnetic fields can direct IONP-labeled cells specifically to the site of action or induce cell differentiation into a specific cell type through mechanotransduction.

Theranostic Applications of Nanomaterials in the Field of Cardiovascular Diseases

A large percentage of people are being exposed to mortality due to cardiovascular diseases. Convention approaches have not provided satisfactory outcomes in the management of these diseases. To overcome the limitations of conventional approaches, nanomaterials like nanoparticles, nanotubes, micelles, lipid based nanocarriers, dendrimers, carbon based nano-formulations represent the new aspect of diagnosis and treatment of cardiovascular diseases. The unique inherent properties of the nanomaterials are the major reasons for their rapidly growing demand in the field of medicine. Profound knowledge in the field of nanotechnology and biomedicine is needed for the notable translation of nanomaterials into theranostic cardiovascular applications. In this review, the authors have summarized different nanomaterials which are being extensively used to diagnose and treat the diseases such as coronary heart disease, myocardial infarction, atherosclerosis, stroke and thrombosis.

Imaging Constructs: The Rise of Iron Oxide Nanoparticles

Over the last decade, an important challenge in nanomedicine imaging has been the work to design multifunctional agents that can be detected by single and/or multimodal techniques. Among the broad spectrum of nanoscale materials being investigated for imaging use, iron oxide nanoparticles have gained significant attention due to their intrinsic magnetic properties, low toxicity, large magnetic moments, superparamagnetic behaviour and large surface area-the latter being a particular advantage in its conjunction with specific moieties, dye molecules, and imaging probes. Tracers-based nanoparticles are promising candidates, since they combine synergistic advantages for non-invasive, highly sensitive, high-resolution, and quantitative imaging on different modalities. This study represents an overview of current advancements in magnetic materials with clinical potential that will hopefully provide an effective system for diagnosis in the near future. Further exploration is still needed to reveal their potential as promising candidates from simple functionalization of metal oxide nanomaterials up to medical imaging.

In vivostudy of iron oxide-calcium phosphate composite nanoparticles for delivery to atherosclerosis

Atherosclerosis is a macrophage-related inflammatory disease that remains a leading cause of death worldwide. Magnetic iron oxide (IO) nanocrystals are clinically used as magnetic resonance imaging contrast agents and their application as a detection agent for macrophages in arterial lesions has been studied extensively. We recently fabricated heparin-modified calcium phosphate (CaP) nanoparticles loaded with a large number of IO nanocrystals via coprecipitation from a supersaturated CaP solution supplemented with heparin and ferucarbotran (IO nanocrystals coated with carboxydextran). In this study, we further increased the content of IO nanocrystals in the heparin-modified IO-CaP composite nanoparticles by increasing the ferucarbotran concentration in the supersaturated CaP solution. The increase in nanoparticle IO content caused a decrease in particle diameter without impairing its dispersibility; the nanoparticles remained dispersed in water for up to 2 h due to electrostatic repulsion between particles due to the surface modification with heparin. The nanoparticles were more effectively taken up by murine RAW264.7 macrophages compared to free ferucarbotran without showing significant cytotoxicity. A preliminaryin vivostudy showed that the nanoparticles injected intravenously into mice delivered more IO nanocrystals to macrophage-rich carotid arterial lesions than free ferucarbotran. Our nanoparticles have potential as a delivery agent of IO nanocrystals to macrophages in arterial lesions.

Molecular and Nonmolecular Imaging of Macrophages in Atherosclerosis

Atherosclerosis is a major cause of ischemic heart disease, and the increasing medical burden associated with atherosclerotic cardiovascular disease has become a major public health concern worldwide. Macrophages play an important role in all stages of the dynamic progress of atherosclerosis, from its initiation and lesion expansion increasing the vulnerability of plaques, to the formation of unstable plaques and clinical manifestations. Early imaging can identify patients at risk of coronary atherosclerotic disease and its complications, enabling preventive measures to be initiated. Recent advances in molecular imaging have involved the noninvasive and semi-quantitative targeted imaging of macrophages and their related molecules in vivo, which can detect atheroma earlier and more accurately than conventional imaging. Multimodal imaging integrates vascular structure, function, and molecular imaging technology to achieve multi-dimensional imaging, which can be used to comprehensively evaluate blood vessels and obtain clinical information based on anatomical structure and molecular level. At the same time, the rapid development of nonmolecular imaging technologies, such as intravascular imaging, which have the unique advantages of having intuitive accuracy and providing rich information to identify macrophage inflammation and inform targeted personalized treatment, has also been seen. In this review, we highlight recent methods and research hotspots in molecular and nonmolecular imaging of macrophages in atherosclerosis that have enormous potential for rapid clinical application.

Targeted Molecular Imaging of Cardiovascular Diseases by Iron Oxide Nanoparticles

Cardiovascular disease is one of the major contributors to global disease burden. Atherosclerosis is an inflammatory process that involves the accumulation of lipids and fibrous elements in the large arteries, forming an atherosclerotic plaque. Rupture of unstable plaques leads to thrombosis that triggers life-threatening complications such as myocardial infarction. Current diagnostic methods are invasive as they require insertion of a catheter into the coronary artery. Molecular imaging techniques, such as magnetic resonance imaging, have been developed to image atherosclerotic plaques and thrombosis due to its high spatial resolution and safety. The sensitivity of magnetic resonance imaging can be improved with contrast agents, such as iron oxide nanoparticles. This review presents the most recent advances in atherosclerosis, thrombosis, and myocardial infarction molecular imaging using iron oxide-based nanoparticles. While some studies have shown their effectiveness, many are yet to undertake comprehensive testing of biocompatibility. There are still potential hazards to address and complications to diagnosis, therefore strategies for overcoming these challenges are required.

Employment of targeted nanoparticles for imaging of cellular processes in cardiovascular disease

Cardiovascular disease (CVD) is a leading cause of global mortality, accounting for pathologies that are primarily of atherosclerotic origin and driven by specific cell populations. A need exists for effective, non-invasive methods to assess the risk of potentially fatal major adverse cardiovascular events (MACE) before occurrence and to monitor post-interventional outcomes such as tissue regeneration. Molecular imaging has widespread applications in CVD diagnostic assessment, through modalities including magnetic resonance imaging (MRI), positron emission tomography (PET), and acoustic imaging methods. However, current gold-standard small molecule contrast agents are not cell-specific, relying on non-specific uptake to facilitate imaging of biologic processes. Nanomaterials can be engineered for targeted delivery to specific cell populations, and several nanomaterial systems have been developed for pre-clinical molecular imaging. Here, we review recent advances in nanoparticle-mediated approaches for imaging of cellular processes in cardiovascular disease, focusing on efforts to detect inflammation, assess lipid accumulation, and monitor tissue regeneration.

Radiolabeling strategies and pharmacokinetic studies for metal based nanotheranostics

Radiolabeled metal-based nanoparticles (MNPs) have drawn considerable attention in the fields of nuclear medicine and molecular imaging, drug delivery, and radiation therapy, given the fact that they can be potentially used as diagnostic imaging and/or therapeutic agents, or even as theranostic combinations. Here, we present a systematic review on recent advances in the design and synthesis of MNPs with major focuses on their radiolabeling strategies and the determinants of their in vivo pharmacokinetics, and together how their intended applications would be impacted. For clarification, we categorize all reported radiolabeling strategies for MNPs into indirect and direct approaches. While indirect labeling simply refers to the use of bifunctional chelators or prosthetic groups conjugated to MNPs for post-synthesis labeling with radionuclides, we found that many practical direct labeling methodologies have been developed to incorporate radionuclides into the MNP core without using extra reagents, including chemisorption, radiochemical doping, hadronic bombardment, encapsulation, and isotope or cation exchange. From the perspective of practical use, a few relevant examples are presented and discussed in terms of their pros and cons. We further reviewed the determinants of in vivo pharmacokinetic parameters of MNPs, including factors influencing their in vivo absorption, distribution, metabolism, and elimination, and discussed the challenges and opportunities in the development of radiolabeled MNPs for in vivo biomedical applications. Taken together, we believe the cumulative advancement summarized in this review would provide a general guidance in the field for design and synthesis of radiolabeled MNPs towards practical realization of their much desired theranostic capabilities. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Recent advances in molecular imaging of atherosclerotic plaques and thrombosis

As the complications of atherosclerosis such as myocardial infarction and stroke are still one of the leading causes of mortality worldwide, the development of new diagnostic tools for the early detection of plaque instability and thrombosis is urgently needed. Advanced molecular imaging probes based on functional nanomaterials in combination with cutting edge imaging techniques are now paving the way for novel and unique approaches to monitor the inflammatory progress in atherosclerosis. This review focuses on the development of various molecular probes for the diagnosis of plaques and thrombosis in atherosclerosis, along with perspectives of their diagnostic applications in cardiovascular diseases. Specifically, we summarize the biological targets that can be used for atherosclerosis and thrombosis imaging. Then we describe the emerging molecular imaging techniques based on the utilization of engineered nanoprobes together with their challenges in clinical translation.

Squalene-based nanoparticles for the targeting of atherosclerotic lesions

Native low-density lipoproteins (LDL) naturally accumulate at atherosclerotic lesions and are thought to be among the main drivers of atherosclerosis progression. Numerous nanoparticular systems making use of recombinant lipoproteins have been developed for targeting atherosclerotic plaque. These innovative formulations often require complicated purification and synthesis procedures which limit their eventual translation to the clinics. Recently, squalenoylation has appeared as a simple and efficient technique for targeting agents to endogenous lipoproteins through a bioconjugation approach. In this study, we have developed a fluorescent squalene bioconjugate to evaluate the biodistribution of squalene-based nanoparticles in an ApoE^-/- model of atherosclerosis. By accumulating in LDL endogenous nanoparticles, the squalene bioconjugation could serve as an efficient targeting platform for atherosclerosis. Indeed, in this proof of concept, we show that our squalene-rhodamine (SQRho) nanoparticles, could accumulate in the aortas of atherosclerotic animals. Histological evaluation confirmed the presence of atherosclerotic lesions and the co-localization of SQRho bioconjugates at the lesion sites.

Biomimetic nanoparticle technology for cardiovascular disease detection and treatment

Cardiovascular disease (CVD), which encompasses a number of conditions that can affect the heart and blood vessels, presents a major challenge for modern-day healthcare. Nearly one in three people has some form of CVD, with many suffering from multiple or intertwined conditions that can ultimately lead to traumatic events such as a heart attack or stroke. While the knowledge obtained in the past century regarding the cardiovascular system has paved the way for the development of life-prolonging drugs and treatment modalities, CVD remains one of the leading causes of death in developed countries. More recently, researchers have explored the application of nanotechnology to improve upon current clinical paradigms for the management of CVD. Nanoscale delivery systems have many advantages, including the ability to target diseased sites, improve drug bioavailability, and carry various functional payloads. In this review, we cover the different ways in which nanoparticle technology can be applied towards CVD diagnostics and treatments. The development of novel biomimetic platforms with enhanced functionalities is discussed in detail.

Radiolabeling nanomaterials for multimodality imaging: New insights into nuclear medicine and cancer diagnosis

Nuclear medicine imaging has been developed as a powerful diagnostic approach for cancers by detecting gamma rays directly or indirectly from radionuclides to construct images with beneficial characteristics of high sensitivity, infinite penetration depth and quantitative capability. Current nuclear medicine imaging modalities mainly include single-photon emission computed tomography (SPECT) and positron emission tomography (PET) that require administration of radioactive tracers. In recent years, a vast number of radioactive tracers have been designed and constructed to improve nuclear medicine imaging performance toward early and accurate diagnosis of cancers. This review will discuss recent progress of nuclear medicine imaging tracers and associated biomedical imaging applications. Radiolabeling nanomaterials for rational development of tracers will be comprehensively reviewed with highlights on radiolabeling approaches (surface coupling, inner incorporation and interface engineering), providing profound understanding on radiolabeling chemistry and the associated imaging functionalities. The applications of radiolabeled nanomaterials in nuclear medicine imaging-related multimodality imaging will also be summarized with typical paradigms described. Finally, key challenges and new directions for future research will be discussed to guide further advancement and practical use of radiolabeled nanomaterials for imaging of cancers.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

A Comparison of [99mTc]Duramycin and [99mTc]Annexin V in SPECT/CT Imaging Atherosclerotic Plaques

PURPOSE

Apoptosis is a key factor in unstable plaques. The aim of this study is to evaluate the utility of visualizing atherosclerotic plaques with radiolabeled duramycin and Annexin V.

PROCEDURES

ApoE^-/- mice were fed with a high-fat diet to develop atherosclerosis, C57 mice as a control. Using a routine conjugation protocol, highly pure [^99mTc]duramycin and [^99mTc]Annexin V were obtained, which were applied for in vitro cell assays of apoptosis and in vivo imaging of atherosclerotic plaques in the animal model. Oil Red O staining, TUNEL, hematoxylin-eosin (HE), and CD68 immunostaining were used to evaluate the deposition of lipids and presence of apoptotic macrophages in the lesions where focal intensity positively correlated with the uptake of both tracers.

RESULTS

[^99mTc]duramycin and [^99mTc]Annexin V with a high radiochemical purity (97.13 ± 1.52 and 94.94 ± 0.65 %, respectively) and a well stability at room temperature were used. Apoptotic cells binding activity to [^99mTc]duramycin (Kd, 6.92 nM and Bmax, 56.04 mol/10¹⁹ cells) was significantly greater than [^99mTc]Annexin V (Kd, 12.63 nM and Bmax, 31.55 mol/10¹⁹ cells). Compared with [^99mTc]Annexin V, [^99mTc]duramycin bound avidly to atherosclerotic lesions with a higher plaque-to-background ratio (P/B was 8.23 ± 0.91 and 5.45 ± 0.48 at 20 weeks, 15.02 ± 0.23 and 12.14 ± 0.22 at 30 weeks). No plaques were found in C57 control mice. Furthermore, Oil Red O staining showed lipid deposition areas were significantly increased in ApoE^-/- mice at 20 and 30 weeks, and TUNEL and CD68 staining confirmed that the focal uptake of both tracers contained abundant apoptotic macrophages.

CONCLUSIONS

This stable, fast clearing, and highly specific [^99mTc]duramycin, therefore, can be useful for the quantification of vulnerable atherosclerotic plaques.

Sub-Micrometer Au@PDA-125 I Particles as Theranostic Embolism Beads for Radiosensitization and SPECT/CT Monitoring

Au nanoparticles (3.8 ± 0.6 nm) are assembled to sub-micrometer Au particles (186.3 ± 20.4 nm) and covered with adhesive polydopamine (PDA) as embolism beads (198.8 ± 23.2 nm). Radioactive iodine-125 is labeled to Au@PDA to introduce the function of intra-irradiation. For the therapeutic effects of Au@PDA-¹²⁵ I, Au particles sensitize the radiation to MHCC97H hepatoma cells and tumor-bearing mice. At the cellular level, after being treated with a relatively low-dose (5 Gy) γ-ray, Au-sensitized radiotherapy (RT) leads to an immediate increase of intracellular reactive oxygen species, accompanying with an increase of cell apoptosis. Due to the intra-irradiation, self-healing of RT-leaded DNA double-strand breakage is suppressed, inducing a further increase of cell apoptosis after RT treatment. Likewise, 3 cycles of sensitized RT leads to a valid control of tumor volume growth, but Au@PDA-¹²⁵ I has no harm or radioactive residual on or in the radiosensitive organs, including the thyroid, heart, lungs, liver, and spleen. Additionally, photons emitted from ¹²⁵ I and high X-ray absorption of the Au element makes the beads suitable for single photon emission computed tomography/computed tomography (SPECT/CT) imaging. Therefore, as theranostic embolism beads, Au@PDA-¹²⁵ I can both enhance the therapeutic effects of external RT, and provide a real-time SPECT/CT monitoring of therapeutic time window.

The Multifaceted Uses and Therapeutic Advantages of Nanoparticles for Atherosclerosis Research

Nanoparticles are uniquely suited for the study and development of potential therapies against atherosclerosis by virtue of their size, fine-tunable properties, and ability to incorporate therapies and/or imaging modalities. Furthermore, nanoparticles can be specifically targeted to the atherosclerotic plaque, evading off-target effects and/or associated cytotoxicity. There has been a wealth of knowledge available concerning the use of nanotechnologies in cardiovascular disease and atherosclerosis, in particular in animal models, but with a major focus on imaging agents. In fact, roughly 60% of articles from an initial search for this review included examples of imaging applications of nanoparticles. Thus, this review focuses on experimental therapy interventions applied to and observed in animal models. Particular emphasis is placed on how nanoparticle materials and properties allow researchers to learn a great deal about atherosclerosis. The objective of this review was to provide an update for nanoparticle use in imaging and drug delivery studies and to illustrate how nanoparticles can be used for sensing and modelling, for studying fundamental biological mechanisms, and for the delivery of biotherapeutics such as proteins, peptides, nucleic acids, and even cells all with the goal of attenuating atherosclerosis. Furthermore, the various atherosclerosis processes targeted mainly for imaging studies have been summarized in the hopes of inspiring new and exciting targeted therapeutic and/or imaging strategies.

Atherosclerosis imaging to refine cardiovascular risk assessment in diabetic patients: Computed tomography and positron emission tomography applications

The lifetime cardiovascular risk of a diabetic patient is approximately 4-5 times higher than that of an age and sex matched individual without diabetes mellitus. Despite the well-publicized cardiovascular risk equivalence of diabetes mellitus, it has become apparent that not all diabetic patients are equally at high-risk and many patients may have a level of risk similar to that of the general population. Cardiovascular imaging has been employed to address the dilemma of a more accurate risk stratification of diabetic patients. Two randomized clinical trials aiming at uncovering the presence of unknown obstructive coronary artery disease (CAD) gave disappointing results. In fact, the number of patients with inducible myocardial ischemia and/or severe obstructive disease was lower than expected and the overall outcome was not improved after having brought the existence of CAD to light. Other techniques that may help identify a diabetic patient susceptible to suffer future events have therefore being explored. In this review we discuss two imaging tools that provide anatomical and functional information on pre-clinical coronary atherosclerosis: computed tomography for calcium scoring, and plaque characterization and myocardial ischemia detection and positron emission tomography using tracers to identify functionally unstable plaques. Despite the availability of several imaging techniques there remain numerous questions as to the utility of imaging to define risk in diabetes mellitus and an optimal approach has yet to be found.

pH-Responsive Charge-Conversional and Hemolytic Activities of Magnetic Nanocomposite Particles for Cell-Targeted Hyperthermia

Magnetic nanocomposite particle (MNP)-induced hyperthermia therapy has been restricted by inefficient cellular targeting. pH-responsive charge-conversional MNPs can enhance selective cellular uptake in acidic cells like tumors by sensing extracellular acidity based on their charge alteration. We have synthesized new, pH-induced charge-conversional, superparamagnetic, and single-cored Fe₃O₄ nanocomposite particles coated by N-itaconylated chitosan (NICS) cross-linked with ethylene glycol diglycidyl ether (EGDE) (Fe₃O₄-NICS-EGDE) using a simple, one-step chemical coprecipitation-coating process. The surface of the Fe₃O₄-NICS-EGDE nanocomposite particles was modified with ethanolamine (EA) via aza-Michael addition to enhance their buffering capacity, aqueous stability, and pH sensitivity. The designed Fe₃O₄-NICS-EGDE-EA nanocomposite particles showed pH-dependent charge-conversional properties, colloidal stability, and excellent hemocompatibility in physiological media. By contrast, the charge-conversional properties enabled microwave-induced hemolysis only under weakly acidic conditions. Therefore, the composite particles are highly feasible for magnetically induced and targeted cellular thermotherapeutic applications.

Recent Advances in Managing Atherosclerosis via Nanomedicine

Atherosclerosis, driven by chronic inflammation of the arteries and lipid accumulation on the blood vessel wall, underpins many cardiovascular diseases with high mortality rates globally, such as stroke and ischemic heart disease. Engineered bio-nanomaterials are now under active investigation as carriers of therapeutic and/or imaging agents to atherosclerotic plaques. This Review summarizes the latest bio-nanomaterial-based strategies for managing atherosclerosis published over the past five years, a period marked by a rapid surge in preclinical applications of bio-nanomaterials for imaging and/or treating atherosclerosis. To start, the biomarkers exploited by emerging bio-nanomaterials for targeting various components of atherosclerotic plaques are outlined. In addition, recent efforts to rationally design and screen for bio-nanomaterials with the optimal physicochemical properties for targeting plaques are presented. Moreover, the latest preclinical applications of bio-nanomaterials as carriers of imaging, therapeutic, or theranostic agents to atherosclerotic plaques are discussed. Finally, a mechanistic understanding of the interactions between bio-nanomaterials and the plaque ("athero-nano" interactions) is suggested, the opportunities and challenges in the clinical translation of bio-nanomaterials for managing atherosclerosis are discussed, and recent clinical trials for atherosclerotic nanomedicines are introduced.

Fe3+-Enhanced NIR-to-NIR upconversion nanocrystals for tumor-targeted trimodal bioimaging

Fe³⁺-Enhanced NIR-to-NIR multifunctional upconversion luminescence nanocrystals were synthesized for excellent tumor-targeted UCL/MRI/X-ray trimodal bioimaging.

A review of molecular imaging of atherosclerosis and the potential application of dendrimer in imaging of plaque

Despite the fact that technological advancements have been made in diagnosis and treatment, cardiovascular diseases (CVDs) remain the leading cause of mortality and morbidity worldwide. Early detection of atherosclerosis (AS), especially vulnerable plaques, plays a crucial role in the prevention of acute coronary syndrome (ACS). Targeting the critical cytokines and molecules that are upregulated during the biological process of AS by in vivo molecular imaging has been widely used in plaque imaging. With their three-dimensional architecture, composition, and abundant terminal functional groups, dendrimers provide a platform for multitargeting and multimodal imaging. Thus, modified dendrimers with the key molecules upregulated in AS plaques will be an innovative attempt to achieve targeted imaging of AS plaques specifically and efficiently. This review was aimed to address some recent works on imaging of AS plaques using various types of image technology and further discuss the applications of dendrimers, an innovative yet seldom used method in imaging of AS plaques due to some limitations and challenges, and we highlight the bright future of the modified dendrimers in characterizing AS plaques.

Magnetic iron oxide nanoparticles as novel and efficient tools for atherosclerosis diagnosis

Cardiovascular complications derivate from atherosclerosis are the main cause of death in western world. An early detection of vulnerable atherosclerotic plaques is primordial for a better care of patients suffering the pathology. In this context nanotechnology has emerged as a promising tool to achieve this goal. Nanoparticles based on magnetic iron oxide (MNPs) have been extensively studied in cardiovascular diseases diagnosis, as well as in the treatment and diagnostic of other pathologies. The present review aims to describe and analyze the most current literature regarding to this topic, offering the level of detail required to reproduce the experimental tasks providing a critical input of the latest available reports. The current diagnostic features are presented and compared, highlighting their advantages and disadvantages. Information on novel technology intended to this purpose is also recompiled and in deep analyzed. Special emphasis is placed in magnetic nanotechnology, remarking the possibility to assess selective and multifunctional systems to the early detection of artherosclerotic pathologies. Finally, in view of the state of the art, the future perspectives about the trends on MNPs in artherosclerorsis diagnostic and treatment have also been addressed.

Single-Photon Emission Computed Tomography/Computed Tomography Imaging in a Rabbit Model of Emphysema Reveals Ongoing Apoptosis In Vivo

Evaluation of lung disease is limited by the inability to visualize ongoing pathological processes. Molecular imaging that targets cellular processes related to disease pathogenesis has the potential to assess disease activity over time to allow intervention before lung destruction. Because apoptosis is a critical component of lung damage in emphysema, a functional imaging approach was taken to determine if targeting apoptosis in a smoke exposure model would allow the quantification of early lung damage in vivo. Rabbits were exposed to cigarette smoke for 4 or 16 weeks and underwent single-photon emission computed tomography/computed tomography scanning using technetium-99m-rhAnnexin V-128. Imaging results were correlated with ex vivo tissue analysis to validate the presence of lung destruction and apoptosis. Lung computed tomography scans of long-term smoke-exposed rabbits exhibit anatomical similarities to human emphysema, with increased lung volumes compared with controls. Morphometry on lung tissue confirmed increased mean linear intercept and destructive index at 16 weeks of smoke exposure and compliance measurements documented physiological changes of emphysema. Tissue and lavage analysis displayed the hallmarks of smoke exposure, including increased tissue cellularity and protease activity. Technetium-99m-rhAnnexin V-128 single-photon emission computed tomography signal was increased after smoke exposure at 4 and 16 weeks, with confirmation of increased apoptosis through terminal deoxynucleotidyl transferase dUTP nick end labeling staining and increased tissue neutral sphingomyelinase activity in the tissue. These studies not only describe a novel emphysema model for use with future therapeutic applications, but, most importantly, also characterize a promising imaging modality that identifies ongoing destructive cellular processes within the lung.

Annexin V-Conjugated Mixed Micelles as a Potential Drug Delivery System for Targeted Thrombolysis

To alleviate the hemorrhagic side effect of thrombolysis therapy, a thrombus targeted drug delivery system based on the specific affinity of Annexin V to phosphatidylserine exposed on the membrane surface of activated platelet was developed. The amphiphilic and biodegradable biomaterial, polycaprolactone-block-poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-hydroxyethyl methacrylate) (PCL-b-PDMAEMA-b-PHEMA (PCDH)) triblock polymer, was synthesized via ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) to use as the nanocarriers of thrombolytic drug. In order to conjugate Annexin V to the polymer, PCDH was modified by succinic anhydride via ring-opening reaction to introduce the carboxyl group (PCDH-COOH). After preparation of PCDH/PCDH-COOH (9/1, m/m) mixed micelles, Annexin V was coupled with the micelles using carbodiimide chemistry. The blood clot lysis assay in vitro confirmed that lumbrokinase-loaded targeted micelles (LKTM) had stronger thrombolysis potency than free lumbrokinase (LK) and LK-loaded nontargeted micelles (LKM, P < 0.05). In vivo thrombolytic assay, multispectral, optoacoustic tomography (MSOT) was used to assess the target ability of LKTM. The results of MSOT images indicated the fluorescence intensity of the LKTM group located in the blood clot position were significantly stronger than the LKM group. A 5 mm of carotid artery containing blood clot was cut out 24 h later after administration to assess the degree of thrombolysis. The results of thrombolytic assay in vivo were consistent with the assay in vitro, which the differences between LK, LKM, and LKTM groups were both statistically significant. All the results of thrombolysis assays above proved that the capacity of thrombolysis in the LKTM group was optimal. It suggested that Annexin V-conjugated micelles will be a potential drug delivery system for targeted thrombolysis.

H2O2-Depleting and O2-Generating Selenium Nanoparticles for Fluorescence Imaging and Photodynamic Treatment of Proinflammatory-Activated Macrophages

Macrophages have a pivotal role in chronic inflammatory diseases (CIDs), so imaging and controlling activated macrophage is critical for detecting and reducing chronic inflammation. In this study, photodynamic selenium nanoparticles (SeNPs) with photosensitive and macrophage-targeting bilayers were developed. The first layer of the photosensitive macromolecule was composed of a conjugate of a photosensitizer (rose bengal, RB) and a thiolated chitosan (chitosan-glutathione), resulting in a plasmonic coupling-induced red shift and broadening of RB absorption bands with increased absorption intensity. Electron paramagnetic resonance (EPR) and diphenylanthracene (DPA) quenching studies revealed that the SeNPs that were coated with the photosensitive layer were more effective than RB alone in producing singlet oxygen (¹O₂) under photoirradiation. The second layer of the activated macrophage-targetable macromolecule was synthesized by conjugation of hyaluronic acid with folic acid using an ethylenediamine linker. Proinflammatory-activated macrophages rapidly internalized the SeNPs that were covered with the targeting ligand, exhibiting a much stronger fluorescence signal of the SeNPs than did the nonactivated macrophages. Since proinflammatory-activated macrophage was known to generate a substantial amount of H₂O₂ while the inflamed site generally caused inflammation-associated tissue hypoxia, the SeNPs were further modified with O₂ self-sufficient function for photodynamic therapy. Catalase was immobilized on the SeNPs by the formation of disulfide bonds. Intracellular reduction of disulfide bonds induced the subsequent release of catalase, which catalyzed the decomposition of H₂O₂. The H₂O₂-depleting and O₂-generating photodynamic SeNPs efficiently killed activated macrophages and quenched the intracellular H₂O₂ and NO that are associated with inflammation. The SeNPs may have potential as a theranostic nanomaterial to image and control the activation of macrophages.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.

Feasibility of USPIOs for T1-weighted MR molecular imaging of tumor receptors

USPIOs having a superior T₁ contrast effect could only be used for T₂-weighted, but not for T₁-weighted MR tumor receptor imaging.

Radiolabeled theranostics: magnetic and gold nanoparticles

Introduction: Growing advances in nanotechnology have facilitated the applications of newly emerged nanomaterials in the field of biomedical/pharmaceutical sciences. Following this trend, the multifunctional nanoparticles (NPs) play a significant role in development of advanced drug delivery systems (DDSs) such as diapeutics/theranostics used for simultaneous diagnosis and therapy. Multifunctional radiolabeled NPs with capability of detecting, visualizing and destroying diseased cells with least side effects have been considered as an emerging filed in presentation of the best choice in solving the therapeutic problems. Functionalized magnetic and gold NPs (MNPs and GNPs, respectively) have produced the potential of nanoparticles as sensitive multifunctional probes for molecular imaging, photothermal therapy and drug delivery and targeting.

Methods: In this study, we review the most recent works on the improvement of various techniques for development of radiolabeled magnetic and gold nanoprobes, and discuss the methods for targeted imaging and therapies.

Results: The receptor-specific radiopharmaceuticals have been developed to localized radiotherapy in disease sites. Application of advanced multimodal imaging methods and related modality imaging agents labeled with various radioisotopes (e.g., ¹²⁵I, ¹¹¹In, ⁶⁴Cu, ⁶⁸Ga, ⁹⁹mTc) and MNPs/GNPs have significant effects on treatment and prognosis of cancer therapy. In addition, the surface modification with biocompatible polymer such as polyethylene glycol (PEG) have resulted in development of stealth NPs that can evade the opsonization and immune clearance. These long-circulating agents can be decorated with homing agents as well as radioisotopes for targeted imaging and therapy purposes.

Conclusion: The modified MNPs or GNPs have wide applications in concurrent diagnosis and therapy of various malignancies. Once armed with radioisotopes, these nanosystems (NSs) can be exploited for combined multimodality imaging with photothermal/photodynamic therapy while delivering the loaded drugs or genes to the targeted cells/tissues. These NSs will be a game changer in combating various cancers.

Gold nanoparticles-based SPECT/CT imaging probe targeting for vulnerable atherosclerosis plaques

In order to realize accurate localization and precise evaluation of vulnerability of atherosclerotic plaques via dual-modal imaging, gold nanoparticles (GNPs) were firstly caped with a thin amino-PEGs cover and then conjugated with the targeting molecular Annexin V and radionuclide Tc-99m simultaneously to form SPECT/CT imaging probe targeting apoptotic macrophages. The as-synthesized (99m)Tc-GNPs-Annexin V was with uniform size (30.2 ± 2.9 nm) and high labeling rate (98.9 ± 0.5%) and stability. Targeting ability of Annexin V for apoptotic macrophages was kept and enhanced. For macrophages with 30% apoptosis, cellular uptakes of 3.52 ± 0.35% for (99m)Tc-GNPs-Annexin V, 2.41 ± 0.53% for (99m)Tc-GNPs and 1.68 ± 0.36% for (99m)Tc-Annexin V were achieved after 2 h incubation. ApoE knock out mice with high fat diet-induced atherosclerosis were scanned via (99m)Tc-GNPs-Annexin V SPECT/CT. With the introduction of targeting molecules, imaging probe was more efficient in accumulating in apoptotic macrophages. In practical evaluation, CT helps to restrict the lesions depiction more accurately, meanwhile, SPECT imaging intensity correlated with pathological changes tightly. In conclusion, Annexin V-modified hybrid gold nanoparticles were successfully synthesized, and this imaging system helped to better localize and diagnose those vulnerable AS plaques via specific targeting the apoptotic macrophages.

Detection and treatment of atherosclerosis using nanoparticles

Atherosclerosis is the key pathogenesis of cardiovascular disease, which is a silent killer and a leading cause of death in the United States. Atherosclerosis starts with the adhesion of inflammatory monocytes on the activated endothelial cells in response to inflammatory stimuli. These monocytes can further migrate into the intimal layer of the blood vessel where they differentiate into macrophages, which take up oxidized low-density lipoproteins and release inflammatory factors to amplify the local inflammatory response. After accumulation of cholesterol, the lipid-laden macrophages are transformed into foam cells, the hallmark of the early stage of atherosclerosis. Foam cells can die from apoptosis or necrosis, and the intracellular lipid is deposed in the artery wall forming lesions. The angiogenesis for nurturing cells is enhanced during lesion development. Proteases released from macrophages, foam cells, and other cells degrade the fibrous cap of the lesion, resulting in rupture of the lesion and subsequent thrombus formation. Thrombi can block blood circulation, which represents a major cause of acute heart events and stroke. There are generally no symptoms in the early stages of atherosclerosis. Current detection techniques cannot easily, safely, and effectively detect the lesions in the early stages, nor can they characterize the lesion features such as the vulnerability. While the available therapeutic modalities cannot target specific molecules, cells, and processes in the lesions, nanoparticles appear to have a promising potential in improving atherosclerosis detection and treatment via targeting the intimal macrophages, foam cells, endothelial cells, angiogenesis, proteolysis, apoptosis, and thrombosis. Indeed, many nanoparticles have been developed in improving blood lipid profile and decreasing inflammatory response for enhancing therapeutic efficacy of drugs and decreasing their side effects. WIREs Nanomed Nanobiotechnol 2017, 9:e1412. doi: 10.1002/wnan.1412 For further resources related to this article, please visit the WIREs website.

99mTc-labelled anti-CD11b SPECT/CT imaging allows detection of plaque destabilization tightly linked to inflammation

It remains challenging to predict the risk of rupture for a specific atherosclerotic plaque timely, a thrombotic trigger tightly linked to inflammation. CD11b, is a biomarker abundant on inflammatory cells, not restricted to monocytes/macrophages. In this study, we fabricated a probe named as ^99mTc-MAG₃-anti-CD11b for detecting inflamed atherosclerotic plaques with single photon emission computed tomography/computed tomography (SPECT/CT). The ApoE-knockout (ApoE^−/−) mice were selected to establish animal models, with C57BL/6J mice used for control. A higher CD11b⁺-cell recruitment with higher CD11b expression and more serious whole-body inflammatory status were identified in ApoE^−/− mice. The probe showed high in vitro affinity and specificity to the Raw-264.7 macrophages, as well as inflammatory cells infiltrated in atherosclerotic plaques, either in ex vivo fluorescent imaging or in in vivo micro-SPECT/CT imaging, which were confirmed by ex vivo planar gamma imaging, Oil-Red-O staining and CD11b-immunohistochemistry staining. A significant positive relationship was identified between the radioactivity intensity on SPECT/CT images and the CD11b expression in plaques. In summary, this study demonstrates the feasibility of anti-CD11b antibody mediated noninvasive SPECT/CT imaging of inflammatory leukocytes in murine atherosclerotic plaques. This imaging strategy can identify inflammation-rich plaques at risk for rupture and evaluate the effectiveness of inflammation-targeted therapies in atheroma.

Tumor Angiogenesis Targeted Radiosensitization Therapy Using Gold Nanoprobes Guided by MRI/SPECT Imaging

Gold nanoparticles (AuNPs) have recently garnered great interest as potential radiosensitizers in tumor therapy. However, major challenges facing their application in this regard are further enhancement of tumor accumulation of the particles in addition to enhanced permeability retention (EPR) effect and an understanding of the optimal particle size and time for applying radiotherapy after the particle administration. In this study, we fabricated novel cyclic c(RGDyC)-peptide-conjugated, Gd- and 99 mTc-labeled AuNPs (RGD@AuNPs-Gd99 mTc) probes with different sizes (29, 51, and 80 nm) and evaluated their potential as radiosensitization therapy both in vitro and in vivo. We found that these probes have a high specificity for αvβ3 integrin positive cells, which resulted in their high cellular uptake and thereby enhanced radiosensitization. Imaging in vivo with MRI and SPECT/CT directly showed that the RGD@AuNPs-Gd99 mTc probes specifically target tumors and exhibit greater accumulation within tumors than the RAD@AuNPs-Gd99 mTc probes. Interestingly, we found that the 80 nm RGD@AuNPs-Gd99 mTc probes exhibit the greatest effects in vitro; however, the 29 nm RGD@AuNPs-Gd99 mTc probes were clearly most efficient in vivo. As a result, radiotherapy of tumors with the 29 nm probe was the most potent. Our study demonstrates that RGD@AuNPs-Gd99 mTc probes are highly useful radiosensitizers capable of guiding and enhancing radiation therapy of tumors.

Nanoparticle uptake by macrophages in vulnerable plaques for atherosclerosis diagnosis

The composition of atherosclerotic (AS) plaques is crucial concerning rupture, thrombosis and clinical events. Two plaque types are distinguished: stable and vulnerable plaques. Vulnerable plaques are rich in inflammatory cells, mostly only M1 macrophages, and are highly susceptible to rupture. These plaques represent a high risk particularly with the standard invasive diagnosis by coronary angiography. So far there are no non-invasive low-risk clinical approaches available to detect and distinguish AS plaque types in vivo. The perspective review introduces a whole work-flow for a novel approach for non-invasive detection and classification of AS plaques using the diffusion reflection method with gold nanoparticle loaded macrophages in combination with flow and image cytometric analysis for quality assurance. Classical biophotonic methods for AS diagnosis are summarized. Phenotyping of monocytes and macrophages are discussed for specific subset labelling by nanomaterials, as well as existing studies and first experimental proofs of concept for the novel approach are shown. In vitro and in vivo detection of NP loaded macrophages (MΦ). Different ways of MΦ labelling include (1) in vitro labelling in suspension (whole blood or buffy coat) or (2) labelling of short-term MΦ cultures with re-injection of MΦ-NP into the animal to detect migration of the cells in the plaques and (3) in vivo injection of NP into the organism.