Molecular imaging

Cancer-targeted Nucleic Acid Delivery and Quantum Dot Imaging Using EGF Receptor Aptamer-conjugated Lipid Nanoparticles

Co-application of fluorescent quantum dot nanocrystals and therapeutics has recently become a promising theranostic methodology for cancer treatment. We developed a tumor-targeted lipid nanocarrier that demonstrates notable efficacy in gene delivery as well as tumor bio-imaging. Coupling of aptamer molecules against the EGF receptor (EGFR) to the distal termini of lipid nanoparticles provided the carrier with tumor-specific recognition capability. The cationic lipid component, referred to as O,O’-dimyristyl-N-lysyl glutamate (DMKE), was able to effectively complex with anionic small-interfering RNA (siRNA). The hydrophobic quantum dots (Q-dots) were effectively incorporated in hydrophobic lipid bilayers at an appropriate Q-dot to lipid ratio. In this study, we optimized the liposomal formula of aptamer-conjugated liposomes containing Q-dots and siRNA molecules (Apt-QLs). The anti-EGFR Apt-QLs exhibited remarkable EGFR-dependent siRNA delivery as well as fluorescence imaging, which were analyzed in cultured cancer cells and tumor xenografts in mice. These results imply that the formulation of Apt-QLs could be widely utilized as a carrier for tumor-directed gene delivery and bio-imaging.

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.

The value of whole-brain CT perfusion imaging and CT angiography using a 320-slice CT scanner in the diagnosis of MCI and AD patients

OBJECTIVES

To validate the value of whole-brain computed tomography perfusion (CTP) and CT angiography (CTA) in the diagnosis of mild cognitive impairment (MCI) and Alzheimer's disease (AD).

METHODS

Whole-brain CTP and four-dimensional CT angiography (4D-CTA) images were acquired in 30 MCI, 35 mild AD patients, 35 moderate AD patients, 30 severe AD patients and 50 normal controls (NC). Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP), and correlation between CTP and 4D-CTA were analysed.

RESULTS

Elevated CBF in the left frontal and temporal cortex was found in MCI compared with the NC group. However, TTP was increased in the left hippocampus in mild AD patients compared with NC. In moderate and severe AD patients, hypoperfusion was found in multiple brain areas compared with NC. Finally, we found that the extent of arterial stenosis was negatively correlated with CBF in partial cerebral cortex and hippocampus, and positively correlated with TTP in these areas of AD and MCI patients.

CONCLUSIONS

Our findings suggest that whole-brain CTP and 4D-CTA could serve as a diagnostic modality in distinguishing MCI and AD, and predicting conversion from MCI based on TTP of left hippocampus.

KEY POINTS

• Whole-brain perfusion using the full 160-mm width of 320 detector rows • Provide clinical experience of 320-row CT in cerebrovascular disorders of Alzheimer's disease • Initial combined 4D CTA-CTP data analysed perfusion and correlated with CT angiography • Whole-brain CTP and 4D-CTA have high value for monitoring MCI to AD progression • TTP in the left hippocampus may predict the transition from MCI to AD.

Functionalized graphene oxide/Fe3O4 hybrids for cellular magnetic resonance imaging and fluorescence labeling

In this work, we developed a T₂-weighted contrast agent based on graphene oxide (GO)/Fe₃O₄ hybrids for efficient cellular magnetic resonance imaging (MRI). The GO/Fe₃O₄ hybrids were obtained by combining with co-precipitation method and pyrolysis method. The structural, surface and magnetic characteristics of the hybrids were systematically characterized by transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), AFM, Raman, FT-IR and XRD. The GO/Fe₃O₄ hybrids were functionalized by modifying with anionic and cationic polyelectrolyte through layer-by-layer assembling. The fluorescence probe fluorescein isothiocyanate (FITC) was further loaded on the surface of functionalized GO/Fe₃O₄ hybrids to trace the location of GO/Fe₃O₄ hybrids in cells. Functionalized GO/Fe₃O₄ hybrids possess good hydrophilicity, less cytotoxicity, high MRI enhancement with the relaxivity (r₂) of 493mM^-1s^-1 as well as cellular MRI contrast effect. These obtained results indicated that the functionalized GO/Fe₃O₄ hybrids could have great potential to be utilized as cellular MRI contrast agents for tumor early diagnosis and monitoring.

Positron emission tomography and nanotechnology: A dynamic duo for cancer theranostics

Development of novel imaging probes for cancer diagnosis is critical for early disease detection and management. The past two decades have witnessed a surge in the development and evolution of radiolabeled nanoparticles as a new frontier in personalized cancer nanomedicine. The dynamic synergism of positron emission tomography (PET) and nanotechnology combines the sensitivity and quantitative nature of PET with the multifunctionality and tunability of nanomaterials, which can help overcome certain key challenges in the field. In this review, we discuss the recent advances in radionanomedicine, exemplifying the ability to tailor the physicochemical properties of nanomaterials to achieve optimal in vivo pharmacokinetics and targeted molecular imaging in living subjects. Innovations in development of facile and robust radiolabeling strategies and biomedical applications of such radionanoprobes in cancer theranostics are highlighted. Imminent issues in clinical translation of radiolabeled nanomaterials are also discussed, with emphasis on multidisciplinary efforts needed to quickly move these promising agents from bench to bedside.

State of the art in vivo imaging techniques for laboratory animals

In recent decades, imaging devices have become indispensable tools in the basic sciences, in preclinical research and in modern drug development. The rapidly evolving high-resolution in vivo imaging technologies provide a unique opportunity for studying biological processes of living organisms in real time on a molecular level. State of the art small-animal imaging modalities provide non-invasive images rich in quantitative anatomical and functional information, which renders longitudinal studies possible allowing precise monitoring of disease progression and response to therapy in models of different diseases. The number of animals in a scientific investigation can be substantially reduced using imaging techniques, which is in full compliance with the ethical endeavours for the 3R (reduction, refinement, replacement) policies formulated by Russell and Burch; furthermore, biological variability can be alleviated, as each animal serves as its own control. The most suitable and commonly used imaging modalities for in vivo small-animal imaging are optical imaging (OI), ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and finally the methods of nuclear medicine: positron emission tomography (PET) and single photon emission computed tomography (SPECT).

Peptide-based imaging agents for cancer detection

Selective receptor-targeting peptide based agents have attracted considerable attention in molecular imaging of tumor cells that overexpress corresponding peptide receptors due to their unique properties such as rapid clearance from circulation as well as high affinities and specificities for their targets. The rapid growth of chemistry modification techniques has enabled the design and development of various peptide-based imaging agents with enhanced metabolic stability, favorable pharmacokinetics, improved binding affinity and selectivity, better imaging ability as well as biosafety. Among them, many radiolabeled peptides have already been translated into the clinic with impressive diagnostic accuracy and sensitivity. This review summarizes the current status in the development of peptide-based imaging agents with an emphasis on the consideration of probe design including the identification of suitable peptides, the chemical modification of probes and the criteria for clinical translation. Specific examples in clinical trials have been provided as well with respect to their diagnostic capability compared with other FDA approved imaging agents.

Targeting Fibronectin for Cancer Imaging and Therapy

During cancer progression, the extracellular matrix (ECM) undergoes dramatic changes, which promote cancer cell migration and invasion. In the remodeled tumor ECM, fibronectin (FN) level is upregulated to assist tumor growth, progression, and invasion. FN serves as a central organizer of ECM molecules and mediates the crosstalk between the tumor microenvironment and cancer cells. Its upregulation is correlated with angiogenesis, cancer progression, metastasis, and drug resistance. A number of FN-targeting ligands have been developed for cancer imaging and therapy. Thus far, FN-targeting imaging agents have been tested for nuclear imaging, MRI, and fluorescence imaging, for tumor detection and localization. FN-targeting therapeutics, including nuclear medicine, chemotherapy drugs, cytokines, and photothermal moieties, were also developed in cancer therapy. Because of the prevalence of FN overexpression in cancer, FN targeting imaging agents and therapeutics have the promise of broad applications in the diagnosis, treatment, and image-guided interventions of many types of cancers. This review will summarize current understanding on the role of FN in cancer, discuss the design and development of FN-targeting agents, and highlight the applications of these FN-targeting agents in cancer imaging and therapy.

Radiolabeled novel mAb 4G1 for immunoSPECT imaging of EGFRvIII expression in preclinical glioblastoma xenografts

Epidermal growth factor receptor mutant III (EGFRvIII) is exclusively expressed in tumors, such as glioblastoma, breast cancer and hepatocellular carcinoma, but never in normal organs. Increasing evidence suggests that EGFRvIII has clinical significance in glioblastoma prognosis due to its enhanced tumorigenicity and chemo/radio resistance, thus the development of an imaging approach to early detect EGFRvIII expression with high specificity is urgently needed. To illustrate this point, we developed a novel anti-EGFRvIII monoclonal antibody 4G1 through mouse immunization, cell fusion and hybridoma screening and then confirmed its specificity and affinity by a serial of assays. Following biodistribution and small animal single-photon emission computed tomography (SPECT/CT) imaging of 125I-4G1 in EGFRvIII positive/negative tumor-bearing mice were performed and evaluated to verify the tumor accumulation of this radiotracer. The biodistribution indicated that 125I-4G1 showed prominent tumor accumulation at 24 h post-injection, which reached maximums of 11.20 ± 0.75% ID/g and 13.98 ± 0.57% ID/g in F98npEGFRvIII and U87vIII xenografts, respectively. In contrast, 125I-4G1 had lower tumor accumulation in F98npEGFR and U87MG xenografts. Small animal SPECT/CT imaging revealed that 125I-4G1 had a higher tumor uptake in EGFRvIII-positive tumors than that in EGFRvIII-negative tumors. This study demonstrates that radiolabeled 4G1 can serve as a valid probe for the imaging of EGFRvIII expression, and would be valuable into the clinical translation for the diagnosis, prognosis, guiding therapy, and therapeutic efficacy evaluation of tumors.

In vivo detection of cucurbit[6]uril, a hyperpolarized xenon contrast agent for a xenon magnetic resonance imaging biosensor

The Hyperpolarized gas Chemical Exchange Saturation Transfer (HyperCEST) Magnetic Resonance (MR) technique has the potential to increase the sensitivity of a hyperpolarized xenon-129 MRI contrast agent. Signal enhancement is accomplished by selectively depolarizing the xenon within a cage molecule which, upon exchange, reduces the signal in the dissolved phase pool. Herein we demonstrate the in vivo detection of the cucurbit[6]uril (CB6) contrast agent within the vasculature of a living rat. Our work may be used as a stepping stone towards using the HyperCEST technique as a molecular imaging modality.

Advanced Functional Nanomaterials for Theranostics

Nanoscale materials have been explored extensively as agents for therapeutic and diagnostic (i.e. theranostic) applications. Research efforts have shifted from exploring new materials in vitro to designing materials that function in more relevant animal disease models, thereby increasing potential for clinical translation. Current interests include non-invasive imaging of diseases, biomarkers and targeted delivery of therapeutic drugs. Here, we discuss some general design considerations of advanced theranostic materials and challenges of their use, from both diagnostic and therapeutic perspectives. Common classes of nanoscale biomaterials, including magnetic nanoparticles, quantum dots, upconversion nanoparticles, mesoporous silica nanoparticles, carbon-based nanoparticles and organic dye-based nanoparticles, have demonstrated potential for both diagnosis and therapy. Variations such as size control and surface modifications can modulate biocompatibility and interactions with target tissues. The needs for improved disease detection and enhanced chemotherapeutic treatments, together with realistic considerations for clinically translatable nanomaterials will be key driving factors for theranostic agent research in the near future.

Tracking stem cells with superparamagnetic iron oxide nanoparticles: perspectives and considerations

Superparamagnetic iron oxide nanoparticles (SPIONs) have been used for diagnoses in biomedical applications, due to their unique properties and their apparent safety for humans. In general, SPIONs do not seem to produce cell damage, although their long-term in vivo effects continue to be investigated. The possibility of efficiently labeling cells with these magnetic nanoparticles has stimulated their use to noninvasively track cells by magnetic resonance imaging after transplantation. SPIONs are attracting increasing attention and are one of the preferred methods for cell labeling and tracking in preclinical and clinical studies. For clinical protocol approval of magnetic-labeled cell tracking, it is essential to expand our knowledge of the time course of SPIONs after cell incorporation and transplantation. This review focuses on the recent advances in tracking SPION-labeled stem cells, analyzing the possibilities and limitations of their use, not only focusing on myocardial infarction but also discussing other models.

Gadolinium hybrid iron oxide nanocomposites for dual T1- and T2-weighted MR imaging of cell labeling

A new generation of dual T₁- and T₂-weighted MRI contrast agents is developed for cell labeling and tracking.

Development of new PTK7-targeting aptamer-fluorescent and -radiolabelled probes for evaluation as molecular imaging agents: Lymphoma and melanoma in vivo proof of concept

Aptamers are single-stranded oligonucleotides that recognize molecular targets with high affinity and specificity. Aptamer that selectively bind to the protein tyrosine kinase-7 (PTK7) receptor, overexpressed on many cancers, has been labelled as probes for molecular imaging of cancer. Two new PTK7-targeting aptamer probes were developed by coupling frameworks from the fluorescent dye AlexaFluor647 or the 6-hydrazinonicotinamide (HYNIC) chelator-labelled to ^99mTc. The derivatizations via a 5'-aminohexyl terminal linker were done at room temperature and under mild buffer conditions. Physicochemical and biological controls for both imaging agents were performed verifying the integrity of the aptamer-conjugates by HPLC. Recognition of melanoma (B16F1) and lymphoma (A20) mouse cell lines by the aptamer was studied using cell binding, flow cytometry and confocal microscopy. Finally, in vivo imaging studies in tumour-bearing mice were performed. The new probes were able to bind to melanoma and lymphoma cell lines in vitro, the in vivo imaging in tumour-bearing mice showed different uptake behaviours showing for the fluorescent conjugate good uptake by B cell lymphoma while the radiolabelled conjugate did not display tumour uptake due to its high extravascular distribution, and both showed rapid clearance properties in tumour-bearing mice.

Novel Imaging Methods for Analysis of Tissue Resident Cells in HIV/SIV

The use of advanced tissue-imaging methodologies has greatly facilitated the study of molecular mechanisms and cellular interactions in humans and animal models of disease. Particularly, in HIV research, there is an ever-increasing demand for a comprehensive analysis of immune cell dynamics at tissue level stemming from the need to advance our understanding of those interactions that regulate the generation of adaptive antigen-specific immune responses. The latter is critical for the development of vaccines to elicit broadly neutralizing antibodies as well as for the discovery of novel targets for immuno-therapies to strengthen the cytolytic arm of the immune system at local level. In this review, we focus on current and emerging imaging technologies, discuss their strengths and limitations, and examine how such technologies can inform the development of new treatments and vaccination strategies. We also present some perspective on the future of the technology development.

Targeted Contrast-Enhanced Ultrasound for Inflammation Detection

Molecular imaging is a form of nanotechnology that enables the noninvasive examination of biological processes in vivo. Radiopharmaceutical agents are used to target biochemical markers, permitting their detection and evaluation. Early visualization of molecular variations indicative of pathophysiological processes can aid in patient diagnoses and management decisions. Molecular imaging is performed by introducing into the body molecular probes, which are often contrast agents that have been nanoengineered to target and tether to molecules, thus enabling their radiologic identification. Through a nanoengineering process, ultrasound contrast agents can be targeted to specific molecules, extending ultrasound’s capabilities from the tissue to molecular level. Molecular ultrasound, or targeted contrast-enhanced ultrasound (TCEUS), has recently emerged as a popular molecular imaging technique due to its ability to provide real-time anatomic and functional information without ionizing radiation. However, molecular ultrasound represents a novel form of molecular imaging and consequently remains largely preclinical. This review explores the commonalities of TCEUS across several molecular targets and points to the need for standardization of kinetic behavior analysis. The literature underscores evidence gaps and the need for additional research. The application of TCEUS is unlimited but needs further standardization to ensure that future research studies are comparable.

Ionizing Radiation Impairs Endogenous Regeneration of Infarcted Heart: An In Vivo 18F-FDG PET/CT and 99mTc-Tetrofosmin SPECT/CT Study in Mice

Epidemiological studies have suggested that ionizing radiation increases cardiovascular disease risk, but the relevant mechanism is poorly understood. We recently demonstrated that adult mice exposed to whole-body irradiation with 3 Gy gamma rays significantly decreases the number and quality of cardiac stem cells. To further determine if radiation impairs myocardial regenerative potency, a myocardial infarction model was established in adult C57BL/6 mice by ligating the left anterior descending artery approximately 6 h after sham- or whole-body gamma irradiation (0 or 3 Gy). To evaluate the regenerative potency of the infarcted heart, we measured the myocardial perfusion and remodeling by ¹⁸F-FDG PET/CT and ^99mTc-tetrofosmin SPECT/CT at 1-2 days (baseline) and 14-15 days (end point) after infarction, respectively. Mice were sacrificed at day 15 after infarction, and heart tissue was collected for histological analysis. The infarct area of the left ventricle was significantly larger in irradiated mice than healthy controls 14 days after infarction, although it was similar between the groups at the baseline. However, histological analysis showed that the infarct size and left ventricle wall thickness were not significantly different among the groups. Compared to the healthy controls, irradiated mice had significantly less c-kit-positive stem cells, less Sca-1-positive stem cells, less proliferating cells, more apoptotic cells and lower vessel density within the infarcted heart. The results of this study suggest that whole-body irradiation with 3 Gy gamma rays impairs the endogenous regeneration of infarcted heart, which may indirectly predict future cardiovascular disease risk.

Concentration dependence of nitroxyl spin probes in liposomal solution: electron spin resonance and overhauser-enhanced magnetic resonance studies

In this work, the detailed studies of electron spin resonance (ESR) and overhauser-enhanced magnetic resonance imaging (OMRI) were carried out for permeable nitroxyl spin probe, MC-PROXYL as a function of agent concentration in liposomal solution. In order to compare the impermeable nature of nitroxyl radical, the study was also carried out only at 2 mM concentration of carboxy-PROXYL. The ESR parameters were estimated using L-band and 300 MHz ESR spectrometers. The line width broadening was measured as a function of agent concentration in liposomal solution. The estimated rotational correlation time is proportional to the agent concentration, which indicates that less mobile nature of nitroxyl spin probe in liposomal solution. The partition parameter and permeability values indicate that the diffusion of nitroxyl spin probe distribution into the lipid phase is maximum at 2 mM concentration of MC-PROXYL. The dynamic nuclear polarization (DNP) parameters such as DNP factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for 2 mM MC-PROXYL in 400 mM liposomal dispersion. The spin lattice relaxation time was shortened in liposomal solution, which leads to the high relaxivity. Reduction in coupling factor is due to less interaction between the electron and nuclear spins, which causes the reduction in enhancement. The leakage factor increases with increasing agent concentration. The increase in DNP enhancement was significant up to 2 mM in liposomal solution. These results paves the way for choosing optimum agent concentration and OMRI scan parameters used in intra and extra membrane water by loading the liposome vesicles with a lipid permeable nitroxyl spin probes in OMRI experiments.

Imaging techniques: new avenues in cancer gene and cell therapy

Cancer is one of the world's most concerning health problems and poses many challenges in the range of approaches associated with the treatment of cancer. Current understanding of this disease brings to the fore a number of novel therapies that can be useful in the treatment of cancer. Among them, gene and cell therapies have emerged as novel and effective approaches. One of the most important challenges for cancer gene and cell therapies is correct monitoring of the modified genes and cells. In fact, visual tracking of therapeutic cells, immune cells, stem cells and genetic vectors that contain therapeutic genes and the various drugs is important in cancer therapy. Similarly, molecular imaging, such as nanosystems, fluorescence, bioluminescence, positron emission tomography, single photon-emission computed tomography and magnetic resonance imaging, have also been found to be powerful tools in monitoring cancer patients who have received therapeutic cell and gene therapies or drug therapies. In this review, we focus on these therapies and their molecular imaging techniques in treating and monitoring the progress of the therapies on various types of cancer.

ESR line width and line shape dependence of Overhauser-enhanced magnetic resonance imaging

Electron spin resonance and Overhauser-enhanced magnetic resonance imaging studies were carried out for various concentrations of ¹⁴ N-labeled 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl in pure water. Overhauser-enhancement factor attains maxima in the range of 2.5-3 mm concentration. The leakage factor showed an asymptotic increase with increasing agent concentration. The coupling parameter showed the interaction between the electron and nuclear spins to be mainly dipolar in origin. The electron spin resonance parameters, such as the line width, line shape and g-factor, were determined. The line width analysis confirms that the line broadening is proportional to the agent concentration, and also the agent concentration is optimized in the range of 2.5-3 mm. The line shape analysis shows that the observed electron spin resonance line shape is a Voigt line shape, in which the Lorentzian component is dominant. The contribution of Lorentzian component was estimated using the winsim package. The Lorentzian component of the resonance line attains maxima in the range of 2.5-3 mm concentration. Therefore, this study reveals that the agent concentration, line width and Lorentzian component are the important factors in determining the Overhauser-enhancement factor. Hence, the agent concentration was optimized as 2.5-3 mm for in vivo/in vitro electron spin resonance imaging and Overhauser-enhanced magnetic resonance imaging phantom studies. Copyright © 2016 John Wiley & Sons, Ltd.

Advances in Molecular Imaging Strategies for In Vivo Tracking of Immune Cells

Tracking of immune cells in vivo is a crucial tool for development and optimization of cell-based therapy. Techniques for tracking immune cells have been applied widely for understanding the intrinsic behavior of immune cells and include non-radiation-based techniques such as optical imaging and magnetic resonance imaging (MRI), radiation-based techniques such as computerized tomography (CT), and nuclear imaging including single photon emission computerized tomography (SPECT) and positron emission tomography (PET). Each modality has its own strengths and limitations. To overcome the limitations of each modality, multimodal imaging techniques involving two or more imaging modalities are actively applied. Multimodal techniques allow integration of the strengths of individual modalities. In this review, we discuss the strengths and limitations of currently available preclinical in vivo immune cell tracking techniques and summarize the value of immune cell tracking in the development and optimization of immune cell therapy for various diseases.

Multispectral Emissions of Lanthanide-Doped Gadolinium Oxide Nanophosphors for Cathodoluminescence and Near-Infrared Upconversion/Downconversion Imaging

Comprehensive imaging of a biological individual can be achieved by utilizing the variation in spatial resolution, the scale of cathodoluminescence (CL), and near-infrared (NIR), as favored by imaging probe Gd₂O₃ co-doped lanthanide nanophosphors (NPPs). A series of Gd₂O₃:Ln3+/Yb3+ (Ln3+: Tm3+, Ho3+, Er3+) NPPs with multispectral emission are prepared by the sol-gel method. The NPPs show a wide range of emissions spanning from the visible to the NIR region under 980 nm excitation. The dependence of the upconverting (UC)/downconverting (DC) emission intensity on the dopant ratio is investigated. The optimum ratios of dopants obtained for emissions in the NIR regions at 810 nm, 1200 nm, and 1530 nm are applied to produce nanoparticles by the homogeneous precipitation (HP) method. The nanoparticles produced from the HP method are used to investigate the dual NIR and CL imaging modalities. The results indicate the possibility of using Gd₂O₃ co-doped Ln3+/Yb3+ (Ln3+: Tm3+, Ho3+, Er3+) in correlation with NIR and CL imaging. The use of Gd₂O₃ promises an extension of the object dimension to the whole-body level by employing magnetic resonance imaging (MRI).

Targeting T1 and T2 dual modality enhanced magnetic resonance imaging of tumor vascular endothelial cells based on peptides-conjugated manganese ferrite nanomicelles

Tumor angiogenesis plays very important roles for tumorigenesis, tumor development, metastasis, and prognosis. Targeting T₁/T₂ dual modality magnetic resonance (MR) imaging of the tumor vascular endothelial cells (TVECs) with MR molecular probes can greatly improve diagnostic sensitivity and specificity, as well as helping to make an early diagnosis of tumor at the preclinical stage. In this study, a new T₁ and T₂ dual modality nanoprobe was successfully fabricated. The prepared nanoprobe comprise peptides CL 1555, poly(ε-caprolactone)-block-poly(ethylene glycol) amphiphilic copolymer shell, and dozens of manganese ferrite (MnFe₂O₄) nanoparticle core. The results showed that the hydrophobic MnFe₂O₄ nanoparticles were of uniform spheroidal appearance and narrow size distribution. Due to the self-assembled nanomicelles structure, the prepared probes were of high relaxivity of 281.7 mM⁻¹ s⁻¹, which was much higher than that of MnFe₂O₄ nanoparticles (67.5 mM 1 s⁻¹). After being grafted with the targeted CD105 peptide CL 1555, the nanomicelles can combine TVECs specifically and make the labeled TVECs dark in T₂-weighted MR imaging. With the passage on, the Mn²⁺ ions were released from MnFe₂O₄ and the size decreased gradually, making the signal intensity of the second and third passage of labeled TVECs increased in T₁-weighted MR imaging. Our results demonstrate that CL-poly(ethylene glycol)-MnFe₂O₄ can conjugate TVECs and induce dark and bright contrast in MR imaging, and act as a novel molecular probe for T₁- and T₂-enhanced MR imaging of tumor angiogenesis.

Molecular, Functional, and Structural Imaging of Major Depressive Disorder

Major depressive disorder (MDD) is a significant cause of morbidity and mortality worldwide, correlating with genetic susceptibility and environmental risk factors. Molecular, functional, and structural imaging approaches have been increasingly used to detect neurobiological changes, analyze neurochemical correlates, and parse pathophysiological mechanisms underlying MDD. We reviewed recent neuroimaging publications on MDD in terms of molecular, functional, and structural alterations as detected mainly by magnetic resonance imaging (MRI) and positron emission tomography. Altered structure and function of brain regions involved in the cognitive control of affective state have been demonstrated. An abnormal default mode network, as revealed by resting-state functional MRI, is likely associated with aberrant metabolic and serotonergic function revealed by radionuclide imaging. Further multi-modal investigations are essential to clarify the characteristics of the cortical network and serotonergic system associated with behavioral and genetic variations in MDD.

Fluoridated hydroxyapatite: Eu(3+) nanorods-loaded folate-conjugated D-α-tocopheryl polyethylene glycol succinate (vitamin E TPGS) micelles for targeted imaging of cancer cells

In this study, fluoridated hydroxyapatite: Eu(3+) nanorod-loaded folate-conjugated TPGS micelles were prepared by thin-film hydration. The findings in this study demonstrate that micelles show improved dispersion, high stability, and excellent fluorescent property in aqueous solutions, suitable for targeted imaging of cancer cells with over-expressing folate receptors on their surface. The micelles designed in this study will be a promising tool for early detection of cancer.

Dual delivery of biological therapeutics for multimodal and synergistic cancer therapies

Cancer causes >8.2 million deaths annually worldwide; thus, various cancer treatments have been investigated over the past decades. Among them, combination drug therapy has become extremely popular, and treatment with more than one drug is often necessary to achieve appropriate anticancer efficacy. With the development of nanoformulations and nanoparticulate-based drug delivery, researchers have explored the feasibility of dual delivery of biological therapeutics to overcome the current drawbacks of cancer therapy. Compared with the conventional single drug therapy, dual delivery of therapeutics has provided various synergistic effects in addition to offering multimodality to cancer treatment. In this review, we highlight and summarize three aspects of dual-delivery systems for cancer therapy. These include (1) overcoming drug resistance by the dual delivery of chemical drugs with biological therapeutics for synergistic therapy, (2) targeted and controlled drug release by the dual delivery of drugs with stimuli-responsive nanomaterials, and (3) multimodal theranostics by the dual delivery of drugs and molecular imaging probes. Furthermore, recent developments, perspectives, and new challenges regarding dual-delivery systems for cancer therapy are discussed.

The Utility of Molecular Imaging in Prostate Cancer

Prostate cancer is the commonest solid-organ cancer diagnosed in males and represents an important source of morbidity and mortality worldwide. Imaging plays a crucial role in diagnosing prostate cancer and informs the ongoing management of the disease at all stages. Several novel molecular imaging technologies have been developed recently that have the potential to revolutionise disease diagnosis and the surveillance of patients living with prostate cancer. These innovations include hyperpolarised MRI, choline PET/CT and PSMA PET/CT. The major utility of choline and PSMA PET/CT currently lies in their sensitivity for detecting early recurrence after radical treatment for prostate cancer and identifying discrete lesions that may be amenable to salvage therapy. Molecular imaging is likely to play a future role in characterising genetic and biochemical signatures in individual tumours, which may be of particular significance as cancer therapies move into an era of precision medicine.

Labeling Human Melanoma Cells With SPIO: In Vitro Observations

Objectives:

To use the superparamagnetic iron oxide (SPIO) contrast agent Resovist (±transfection agent) to label human melanoma cells and determine its effects on cellular viability, microstructure, iron quantity, and magnetic resonance imaging (MRI) detectability.

Materials and Methods:

Human SK-Mel28 melanoma cells were incubated with Resovist (±liposomal transfection agent DOSPER). The cellular iron content was measured, and labeled cells were examined at 1.5 T and 3.0 T. The intracellular and extracellular distributions of the contrast agent were assessed by light and electron microscopy.

Results:

The incubation of melanoma cells with SPIO does not interfere with cell viability or proliferation. The iron is located both intracellularly and extracellularly as iron clusters associated with the exterior of the cell membrane. Despite thorough washing, the extracellular SPIO remained associated with the cell membrane. The liposomal transfection agent does not change the maximum achievable cellular iron content but promotes a faster iron uptake. The MRI detectability persists for at least 7 days.

Conclusion:

The transfection agent DOSPER facilitates the efficient labeling of human metastatic melanoma cells with Resovist. Our findings raise the possibility that other Resovist-labeled cells may collect associated extracellular nanoparticles. The SPIO may be available to other iron-handling cells and not completely compartmentalized during the labeling procedure.

Insight into the Molecular Imaging of Alzheimer's Disease

Alzheimer's disease is a complex neurodegenerative disease affecting millions of individuals worldwide. Earlier it was diagnosed only via clinical assessments and confirmed by postmortem brain histopathology. The development of validated biomarkers for Alzheimer's disease has given impetus to improve diagnostics and accelerate the development of new therapies. Functional imaging like positron emission tomography (PET), single photon emission computed tomography (SPECT), functional magnetic resonance imaging (fMRI), and proton magnetic resonance spectroscopy provides a means of detecting and characterising the regional changes in brain blood flow, metabolism, and receptor binding sites that are associated with Alzheimer's disease. Multimodal neuroimaging techniques have indicated changes in brain structure and metabolic activity, and an array of neurochemical variations that are associated with neurodegenerative diseases. Radiotracer-based PET and SPECT potentially provide sensitive, accurate methods for the early detection of disease. This paper presents a review of neuroimaging modalities like PET, SPECT, and selected imaging biomarkers/tracers used for the early diagnosis of AD. Neuroimaging with such biomarkers and tracers could achieve a much higher diagnostic accuracy for AD and related disorders in the future.

Molecular imaging and therapy targeting copper metabolism in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. Significant efforts have been devoted to identify new biomarkers for molecular imaging and targeted therapy of HCC. Copper is a nutritional metal required for the function of numerous enzymatic molecules in the metabolic pathways of human cells. Emerging evidence suggests that copper plays a role in cell proliferation and angiogenesis. Increased accumulation of copper ions was detected in tissue samples of HCC and many other cancers in humans. Altered copper metabolism is a new biomarker for molecular cancer imaging with position emission tomography (PET) using radioactive copper as a tracer. It has been reported that extrahepatic mouse hepatoma or HCC xenografts can be localized with PET using copper-64 chloride as a tracer, suggesting that copper metabolism is a new biomarker for the detection of HCC metastasis in areas of low physiological copper uptake. In addition to copper modulation therapy with copper chelators, short-interference RNA specific for human copper transporter 1 (hCtr1) may be used to suppress growth of HCC by blocking increased copper uptake mediated by hCtr1. Furthermore, altered copper metabolism is a promising target for radionuclide therapy of HCC using therapeutic copper radionuclides. Copper metabolism has potential as a new theranostic biomarker for molecular imaging as well as targeted therapy of HCC.

SPECT/NIRF Dual Modality Imaging for Detection of Intraperitoneal Colon Tumor with an Avidin/Biotin Pretargeting System

We describe herein dual-modality imaging of intraperitoneal colon tumor using an avidin/biotin pretargeting system. A novel dual-modality probe, ^99mTc-HYNIC-lys(Cy5.5)-PEG₄-biotin, was designed, synthesized and characterized. Single-photon emission computed tomography/ computed tomography (SPECT/CT) imaging and near infrared fluorescence (NIRF) imaging were developed using intraperitoneal LS180 human colon adenocarcinoma xenografts. Following avidin preinjection for 4 hours, ^99mTc-HYNIC-lys(Cy5.5)-PEG₄-biotin could successfully detect colon tumors of different sizes inside the abdominal region using both modalities, and the imaging results showed no differences. Biodistribution studies demonstrated that the tumors had a very high uptake of the probe ^99mTc-HYNIC-lys(Cy5.5)-PEG₄-biotin (12.74 ± 1.89% ID/g at 2 h p.i.), and the clearance from blood and other normal tissues occured very fast. The low tumor uptake in the non-pretargeted mice (1.63 ± 0.50% ID/g at 2 h p.i.) and tumor cell staining results showed excellent tumor binding specificity of the pretargeting system. The ability of the novel probe to show excellent imaging quality with high tumor-to-background contrast, a high degree of binding specificity with tumors and excellent in vivo biodistribution pharmacokinetics should prove that the avidin/biotin based dual-modality pretargeting probe is a promising imaging tool during the entire period of tumor diagnosis and treatment.

Mini-review: fluorescence imaging in cancer cells using dye-doped nanoparticles

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