Synthesis of 64Cu-labeled magnetic nanoparticles for multimodal imaging

Dragon fruit-like biocage as an iron trapping nanoplatform for high efficiency targeted cancer multimodality imaging

Natural biopolymer based multifunctional nanomaterials are perfect candidates for multimodality imaging and therapeutic applications. Conventional methods of building multimodal imaging probe require either cross-linking manners to increase its in vivo stability or attach a target module to realize targeted imaging. In this study, the intrinsic photoacoustic signals and the native strong chelating properties with metal ions of melanin nanoparticle (MNP), and transferrin receptor 1 (TfR1) targeting ability of apoferritin (APF) was employed to construct an efficient nanoplatform (AMF) without tedious assembling process. Smart APF shell significantly increased metal ions loading (molar ratio of 1:800, APF/Fe(3+)) and therefore improved magnetic resonance imaging (MRI) sensitivity. Moreover, synergistic use of Fe(3+) and APF contributed to high photoacounstic imaging (PAI) sensitivity. AMF showed excellent bio-stability and presented good in vivo multimodality imaging (PET/MRI/PAI) properties (good tumor uptake, high specificity and high tumor contrast) in HT29 tumor because of its targeting property combined with the enhanced permeability and retention (EPR) effect, making it promising in theranostics and translational nanomedicine.

Stable confinement of positron emission tomography and magnetic resonance agents within carbon nanotubes for bimodal imaging

AIMS

Simultaneous positron emission tomography/MRI has recently been introduced to the clinic and dual positron emission tomography/MRI probes are rare and of growing interest. We have developed a strategy for producing multimodal probes based on a carbon nanotube platform without the use of chelating ligands.

MATERIALS & METHODS

Gd(3+) and (64)Cu(2+) ions were loaded into ultra-short single-walled carbon nanotubes by sonication. Normal, tumor-free athymic nude mice were injected intravenously with the probe and imaged over 48 h.

RESULTS & CONCLUSION

The probe was stable for up to 24 h when challenged with phosphate-buffered saline and mouse serum. Positron emission tomography imaging also confirmed the stability of the probe in vivo for up to 48 h. The probe was quickly cleared from circulation, with enhanced accumulation in the lungs. Stable encapsulation of contrast agents within ultra-short single-walled carbon nanotubes represents a new strategy for the design of advanced imaging probes with variable multimodal imaging capabilities.

Visualisation of dual radiolabelled poly(lactide-co-glycolide) nanoparticle degradation in vivo using energy-discriminant SPECT

The determination of nanoparticle (NP) stability and degradation in vivo is essential for the accurate evaluation of NP biodistribution in medical applications and for understanding their toxicological effects. Such determination is particularly challenging because NPs are extremely difficult to detect and quantify once distributed in a biological system. Radiolabelling with positron or gamma emitters and subsequent imaging studies using positron emission tomography (PET) or single-photon emission computerised tomography (SPECT) are some of the few valid alternatives. However, NPs that degrade or radionuclides that detach or are released from the NPs can cause artefact. Here, submicron-sized poly(lactide-co-glycolide) nanoparticles (PLGA-NPs) stabilised with bovine serum albumin (BSA) were dual radiolabelled using gamma emitters with different energy spectra incorporated into the core and coating. To label the core, ¹¹¹In-doped iron oxide NPs were encapsulated inside PLGA-NPs during NP preparation, and the BSA coating was labelled by electrophilic substitution using ¹²⁵I. After intravenous administration into rats, energy-discriminant SPECT resolved each radioisotope independently. Imaging revealed different fates for the core and coating, with a fraction of the two radionuclides co-localising in the liver and lungs for long periods of time after administration, suggesting that NPs are stable in these organs. Organ harvesting followed by gamma counting corroborated the SPECT results. The general methodology reported here represents an excellent alternative for visualising the degradation process of multi-labelled NPs in vivo and can be extended to a wide range of engineered NPs.

Nuclear molecular imaging with nanoparticles: radiochemistry, applications and translation

Molecular imaging provides considerable insight into biological processes for greater understanding of health and disease. Numerous advances in medical physics, chemistry and biology have driven the growth of this field in the past two decades. With exquisite sensitivity, depth of detection and potential for theranostics, radioactive imaging approaches have played a major role in the emergence of molecular imaging. At the same time, developments in materials science, characterization and synthesis have led to explosive progress in the nanoparticle (NP) sciences. NPs are generally defined as particles with a diameter in the nanometre size range. Unique physical, chemical and biological properties arise at this scale, stimulating interest for applications as diverse as energy production and storage, chemical catalysis and electronics. In biomedicine, NPs have generated perhaps the greatest attention. These materials directly interface with life at the subcellular scale of nucleic acids, membranes and proteins. In this review, we will detail the advances made in combining radioactive imaging and NPs. First, we provide an overview of the NP platforms and their properties. This is followed by a look at methods for radiolabelling NPs with gamma-emitting radionuclides for use in single photon emission CT and planar scintigraphy. Next, utilization of positron-emitting radionuclides for positron emission tomography is considered. Finally, recent advances for multimodal nuclear imaging with NPs and efforts for clinical translation and ongoing trials are discussed.

Quantitative assessment of binding affinities for nanoparticles targeted to vulnerable plaque

Recent successes in targeted immune and cell-based therapies have driven new directions for pharmaceutical research. With the rise of these new therapies there is an unfilled need for companion diagnostics to assess patients' potential for therapeutic response. Targeted nanomaterials have been widely investigated to fill this niche; however, in contrast to small molecule or peptide-based targeted agents, binding affinities are not reported for nanomaterials, and to date there has been no standard, quantitative measure for the interaction of targeted nanoparticle agents with their targets. Without a standard measure, accurate comparisons between systems and optimization of targeting behavior are challenging. Here, we demonstrate a method for quantitative assessment of the binding affinity for targeted nanoparticles to cell surface receptors in living systems and apply it to optimize the development of a novel targeted nanoprobe for imaging vulnerable atherosclerotic plaques. In this work, we developed sulfated dextran-coated iron oxide nanoparticles with specific targeting to macrophages, a cell type whose density strongly correlates with plaque vulnerability. Detailed quantitative, in vitro characterizations of (111)In(3+) radiolabeled probes show high-affinity binding to the macrophage scavenger receptor A (SR-A). Cell uptake studies illustrate that higher surface sulfation levels result in much higher uptake efficiency by macrophages. We use a modified Scatchard analysis to quantitatively describe nanoparticle binding to targeted receptors. This characterization represents a potential new standard metric for targeted nanomaterials.

Final step gallium-68 radiolabelling of silica-coated iron oxide nanorods as potential PET/MR multimodal imaging agents

The investigation of iron oxide-based positron emission tomography/magnetic resonance (PET/MR) multimodal imaging agents is an expanding field in which a variety of nanoparticle sizes, shapes, surface coatings and radioisotopes are open for exploration. This study develops iron oxide nanorods which are coated with various mixtures of poly(ethylene glycol) (PEG) and macrocyclic ligand (DO3A) via the formation of a silica layer on the surface. Gallium-68 radiolabelling of the nanorods was carried out in high radiochemical yields (RCY) and their stability in human serum was demonstrated for all constructs, even in the absence of the macrocyclic chelating unit. Further studies were carried out in an attempt to determine the appropriate amount of PEG coating to give optimal properties for future in vivo studies.

Long-term prevalence of NIRF-labeled magnetic nanoparticles for the diagnostic and intraoperative imaging of inflammation

Inflammation is a very common disease worldwide. In severe cases, surgery is often the method of choice. Today, there is a general need for the implementation of image-based guidance methodologies for reliable target resection. We investigated new near infrared fluorescence (NIRF)-nanoparticles (NPs) as a simple but effective bimodal magnetic resonance imaging (MRI) and optical contrast agent for diagnosis and intraoperative imaging of inflammation. Physicochemical analysis revealed that these NPs were highly fluorescent with similar characteristics like unlabeled NPs (hydrodynamic diameter about 130 nm and zeta potential about −10 mV). NP-uptake and NIR-dye labeling was biocompatible to macrophages (no impact on cellular ATP and reactive oxygen species production). These cells could successfully be tracked with MRI and NIRF-optical imaging. I.v. injection of fluorescent NPs into mice led to highly specific T₂-weighted signal of edema due to uptake by phagocytic cells and subsequent migration to the site of inflammation. NIRF signals of the edema region were well detectable for up to 4 weeks, underlining the potential of the NPs for systematic planning and flexible time scheduling in intraoperative applications. NPs were degraded over a time period of 12 weeks, which was not altered due to inflammation. Redistribution of iron might be primarily due to inflammation and not to the presence of NPs per se in a concentration suitable for imaging. Our findings highlight the potential of the NPs to be used as a suitable tool for pre- and intraoperative imaging of inflammation.

An iron oxide nanocarrier for dsRNA to target lymph nodes and strongly activate cells of the immune system

The success of nanoparticle-based therapies will depend in part on accurate delivery to target receptors and organs. There is, therefore, considerable potential in nanoparticles which achieve delivery of the right drug(s) using the right route of administration to the right location at the right time, monitoring the process by non-invasive molecular imaging. A challenge is harnessing immunotherapy via activation of Toll-like receptors (TLRs) for the development of vaccines against major infectious diseases and cancer. In immunotherapy, delivery of the vaccine components to lymph nodes (LNs) is essential for effective stimulation of the immune response. Although some promising advances have been made, delivering therapeutics to LNs remains challenging. It is here shown that iron-oxide nanoparticles can be engineered to combine in a single and small (<50 nm) nanocarrier complementary multimodal imaging features with the immunostimulatory activity of polyinosinic-polycytidylic acid (poly (I:C)). Whilst the fluorescence properties of the nanocarrier show effective delivery to endosomes and TLR3 in antigen presenting cells, MRI/SPECT imaging reveals effective delivery to LNs. Importantly, in vitro and in vivo studies show that, using this nanocarrier, the immunostimulatory activity of poly (I:C) is greatly enhanced. These nanocarriers have considerable potential for cancer diagnosis and the development of new targeted and programmable immunotherapies.

Cancer immunotherapy: nanodelivery approaches for immune cell targeting and tracking

Cancer is one of the most common diseases afflicting people globally. New therapeutic approaches are needed due to the complexity of cancer as a disease. Many current treatments are very toxic and have modest efficacy at best. Increased understanding of tumor biology and immunology has allowed the development of specific immunotherapies with minimal toxicity. It is important to highlight the performance of monoclonal antibodies, immune adjuvants, vaccines and cell-based treatments. Although these approaches have shown varying degrees of clinical efficacy, they illustrate the potential to develop new strategies. Targeted immunotherapy is being explored to overcome the heterogeneity of malignant cells and the immune suppression induced by both the tumor and its microenvironment. Nanodelivery strategies seek to minimize systemic exposure to target therapy to malignant tissue and cells. Intracellular penetration has been examined through the use of functionalized particulates. These nano-particulate associated medicines are being developed for use in imaging, diagnostics and cancer targeting. Although nano-particulates are inherently complex medicines, the ability to confer, at least in principle, different types of functionality allows for the plausible consideration these nanodelivery strategies can be exploited for use as combination medicines. The development of targeted nanodelivery systems in which therapeutic and imaging agents are merged into a single platform is an attractive strategy. Currently, several nanoplatform-based formulations, such as polymeric nanoparticles, micelles, liposomes and dendrimers are in preclinical and clinical stages of development. Herein, nanodelivery strategies presently investigated for cancer immunotherapy, cancer targeting mechanisms and nanocarrier functionalization methods will be described. We also intend to discuss the emerging nano-based approaches suitable to be used as imaging techniques and as cancer treatment options.

Advanced tracers in PET imaging of cardiovascular disease

Cardiovascular disease is the leading cause of death worldwide. Molecular imaging with targeted tracers by positron emission tomography (PET) allows for the noninvasive detection and characterization of biological changes at the molecular level, leading to earlier disease detection, objective monitoring of therapies, and better prognostication of cardiovascular diseases progression. Here we review, the current role of PET in cardiovascular disease, with emphasize on tracers developed for PET imaging of cardiovascular diseases.

A sonochemical approach to the direct surface functionalization of superparamagnetic iron oxide nanoparticles with (3-aminopropyl)triethoxysilane

We report a sonochemical method of functionalizing superparamagnetic iron oxide nanoparticles (SPION) with (3-aminopropyl)triethoxysilane (APTES). Mechanical stirring, localized hot spots and other unique conditions generated by an acoustic cavitation (sonochemical) process were found to induce a rapid silanization reaction between SPION and APTES. FTIR, XPS and XRD measurements were used to demonstrate the grafting of APTES on SPION. Compared to what was reported in literature, the results showed that the silanization reaction time was greatly minimized. More importantly, the product displayed superparamagnetic behaviour at room temperature with a more than 20% higher saturation magnetization.

Advantages of gadolinium based ultrasmall nanoparticles vs molecular gadolinium chelates for radiotherapy guided by MRI for glioma treatment

AGuIX nanoparticles are formed of a polysiloxane network surrounded by gadolinium chelates. They present several characteristics. They are easy to produce, they present very small hydrodynamic diameters (<5 nm) and they are biodegradable through hydrolysis of siloxane bonds. Such degradation was evaluated in diluted conditions at physiological pH by dynamic light scattering and relaxometry. AGuIX nanoparticles are also known as positive contrast agents and efficient radiosensitizers. The aim of this paper is to compare their efficiency for magnetic resonance imaging and radiosensitization to those of the commercial gadolinium based molecular agent: DOTAREM®. An experiment with healthy animals was conducted and the MRI pictures we obtained show a better contrast with the AguIX compared to the DOTAREM® for the same amount of injected gadolinium in the animal. The better contrast obtained after injection of Aguix than DOTAREM® is due to a higher longitudinal relaxivity and a residential time in the blood circulation that is two times higher. A fast and large increase in the contrast is also observed by MRI after an intravenous injection of the AGuIX in 9 L gliosarcoma bearing rats, and a plateau is reached seven minutes after the injection.

We established a radiotherapy protocol consisting of an irradiation by microbeam radiation therapy 20 minutes after the injection of a specific quantity of gadolinium. After microbeam radiation therapy, no notable difference in median survival time was observed in the presence or absence of gadolinium chelates (38 and 44 days respectively). In comparison, the median survival time is increased to 102.5 days with AGuIX particles showing their interest in this nanomedicine protocol. This remarkable radiosensitizing effect could be explained by the persistent tumor uptake of the particles, inducing a significant nanoscale dose deposition under irradiation.

Magnetically Decorated Multi-Walled Carbon Nanotubes as Dual MRI and SPECT Contrast Agents

Carbon nanotubes (CNTs) have been proposed as one of the most promising nanomaterials to be used in biomedicine for their applications in drug/gene delivery as well as biomedical imaging. The present study developed radio-labeled iron oxide decorated multi-walled CNTs (MWNT) as dual magnetic resonance (MR) and single photon emission computed tomography (SPECT) imaging agents. Hybrids containing different amounts of iron oxide were synthesized by in situ generation. Physicochemical characterisations revealed the presence of superparamagnetic iron oxide nanoparticles (SPION) granted the magnetic properties of the hybrids. Further comprehensive examinations including high resolution transmission electron microscopy (HRTEM), fast Fourier transform simulations (FFT), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) assured the conformation of prepared SPION as γ-Fe2O3. High r2 relaxivities were obtained in both phantom and in vivo MRI compared to the clinically approved SPION Endorem®. The hybrids were successfully radio-labeled with technetium-99m through a functionalized bisphosphonate and enabled SPECT/CT imaging and γ-scintigraphy to quantitatively analyze the biodistribution in mice. No abnormality was found by histological examination and the presence of SPION and MWNT were identified by Perls stain and Neutral Red stain, respectively. TEM images of liver and spleen tissues showed the co-localization of SPION and MWNT within the same intracellular vesicles, indicating the in vivo stability of the hybrids after intravenous injection. The results demonstrated the capability of the present SPION-MWNT hybrids as dual MRI and SPECT contrast agents for in vivo use.

Potential clinical applications of bimodal PET-MRI or SPECT-MRI agents

The introduction to the clinic of positron emission tomography-magnetic resonance imaging scanners opens up the possibility to evaluate the real potential of bimodal imaging agents. In this mini-review, the limitations in the design and applications of these materials are summarised and the unique properties that may result in real clinical applications outlined.

Imaging macrophages with nanoparticles

Nanomaterials have much to offer, not only in deciphering innate immune cell biology and tracking cells, but also in advancing personalized clinical care by providing diagnostic and prognostic information, quantifying treatment efficacy and designing better therapeutics. This Review presents different types of nanomaterial, their biological properties and their applications for imaging macrophages in human diseases, including cancer, atherosclerosis, myocardial infarction, aortic aneurysm, diabetes and other conditions. We anticipate that future needs will include the development of nanomaterials that are specific for immune cell subsets and can be used as imaging surrogates for nanotherapeutics. New in vivo imaging clinical tools for noninvasive macrophage quantification are thus ultimately expected to become relevant to predicting patients' clinical outcome, defining treatment options and monitoring responses to therapy.

In situ 111In-doping for achieving biocompatible and non-leachable 111In-labeled Fe3O4 nanoparticles

The present study reports a new approach for synthesizing (111)In-radiolabeled biocompatible Fe3O4 nanoparticles. Radioactive (111)In is doped in situ into the lattice of Fe3O4 nanoparticles to achieve robust radiolabeling for accurately tracing PEGylated Fe3O4 particles in vivo.

Multifunctional iron oxide nanoparticles for diagnostics, therapy and macromolecule delivery

In recent years, multifunctional nanoparticles (NPs) consisting of either metal (e.g. Au), or magnetic NP (e.g. iron oxide) with other fluorescent components such as quantum dots (QDs) or organic dyes have been emerging as versatile candidate systems for cancer diagnosis, therapy, and macromolecule delivery such as micro ribonucleic acid (microRNA). This review intends to highlight the recent advances in the synthesis and application of multifunctional NPs (mainly iron oxide) in theranostics, an area used to combine therapeutics and diagnostics. The recent applications of NPs in miRNA delivery are also reviewed.

Multimodality PET/MRI agents targeted to activated macrophages

The recent emergence of multimodality imaging, particularly the combination of PET and MRI, has led to excitement over the prospect of improving detection of disease. Iron oxide nanoparticles have become a popular platform for the fabrication of PET/MRI probes owing to their advantages of high MRI detection sensitivity, biocompatibility, and biodegradability. In this article, we report the synthesis of dextran-coated iron oxide nanoparticles (DIO) labeled with the positron emitter (64)Cu to generate a PET/MRI probe, and modified with maleic anhydride to increase the negative surface charge. The modified nanoparticulate PET/MRI probe (MDIO-(64)Cu-DOTA) bears repetitive anionic charges on the surface that facilitate recognition by scavenger receptor type A (SR-A), a ligand receptor found on activated macrophages but not on normal vessel walls. MDIO-(64)Cu-DOTA has an average iron oxide core size of 7-8 nm, an average hydrodynamic diameter of 62.7 nm, an r1 relaxivity of 16.8 mM(-1) s(-1), and an r 2 relaxivity of 83.9 mM(-1) s(-1) (37 °C, 1.4 T). Cell studies confirmed that the probe was nontoxic and was specifically taken up by macrophages via SR-A. In comparison with the nonmodified analog, the accumulation of MDIO in macrophages was substantially improved. These characteristics demonstrate the promise of MDIO-(64)Cu-DOTA for identification of vulnerable atherosclerotic plaques via the targeting of macrophages.

Functional Imaging in Diagnostic of Orthopedic Implant-Associated Infections

Surgeries’ sterile conditions and perioperative antibiotic therapies decrease implant associated infections rates significantly. However, up to 10% of orthopedic devices still fail due to infections. An implant infection generates a high socio-economic burden. An early diagnosis of an infection would significantly improve patients’ outcomes. There are numerous clinical tests to diagnose infections. The “Gold Standard” is a microbiological culture, which requires an invasive sampling and lasts up to several weeks. None of the existing tests in clinics alone is sufficient for a conclusive diagnosis of an infection. Meanwhile, there are functional imaging modalities, which hold the promise of a non-invasive, quick, and specific infection diagnostic. This review focuses on orthopedic implant-associated infections, their pathogenicity, diagnosis and functional imaging.

Carbon-11 radiolabeling of iron-oxide nanoparticles for dual-modality PET/MR imaging

Dual-modality imaging, using Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) simultaneously, is a powerful tool to gain valuable information correlating structure with function in biomedicine. The advantage of this dual approach is that the strengths of one modality can balance the weaknesses of the other. However, success of this technique requires developing imaging probes suitable for both. Here, we report on the development of a nanoparticle labeling procedure via covalent bonding with carbon-11 PET isotope. Carbon-11 in the form of [(11)C]methyl iodide was used as a methylation agent to react with carboxylic acid (-COOH) and amine (-NH2) functional groups of ligands bound to the nanoparticles (NPs). The surface coating ligands present on superparamagnetic iron-oxide nanoparticles (SPIO NPs) were radiolabeled to achieve dual-modality PET/MR imaging capabilities. The proof-of-concept dual-modality PET/MR imaging using the radiolabeled SPIO NPs was demonstrated in an in vivo experiment.

The ubiquitous DOTA and its derivatives: the impact of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid on biomedical imaging

Over the last twenty-five years 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) has made a significant impact on the field of diagnostic imaging. DOTA is not the only metal chelate in use in medical diagnostics, but it is the only one to significantly impact on all of the major imaging modalities Magnetic Resonance (MR), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and Fluorescence imaging. This crossover of modalities has been possible due to the versatility of DOTA firstly, to complex a variety of metal ions and secondly, the ease with which it can be modified for different disease states. This has driven research over the last two decades into the chemistry of DOTA and the modification of the substituent pendant arms of this macrocycle to create functional, targeted and dual-modal imaging agents. The primary use of DOTA has been with the lanthanide series of metals, gadolinium for MRI, europium and terbium for fluorescence and neodymium for near infra-red imaging. There are now many research groups dedicated to the use of lanthanides with DOTA although other chelates such as DTPA and NOTA are being increasingly employed. The ease with which DOTA can be conjugated to peptides has given rise to targeted imaging agents seen in the PET, SPECT and radiotherapy fields. These modalities use a variety of radiometals that complex with DOTA, e.g.(64)Cu and (68)Ga which are used in clinical PET scans, (111)In, and (90)Y for SPECT and radiotherapy. In this article, we will demonstrate the remarkable versatility of DOTA, how it has crossed the imaging modality boundaries and how it has been successfully transferred into the clinic.

PET and MR imaging: the odd couple or a match made in heaven?

PET and MR imaging are modalities routinely used for clinical and research applications. Integrated scanners capable of acquiring PET and MR imaging data in the same session, sequentially or simultaneously, have recently become available for human use. In this article, we describe some of the technical advances that allowed the development of human PET/MR scanners; briefly discuss methodologic challenges and opportunities provided by this novel technology; and present potential oncologic, cardiac, and neuropsychiatric applications. These examples range from studies that might immediately benefit from PET/MR to more advanced applications on which future development might have an even broader impact.

PET/MRI: a new technology in the field of molecular imaging

BACKGROUND

The introduction of the new simultaneous PET/MRI scanner opens new opportunities in functional imaging.

SOURCES OF DATA

This article is based on the literature review and our personal experience of the first simultaneous PET/MRI scanner in the UK.

AREAS OF AGREEMENT

PET/CT is well established and a key component of management guidance in a range of diseases. MRI has superior soft tissue resolution, which is useful in the evaluation of many diseases.

AREAS OF CONTROVERSY

There are currently no guidelines regarding clinical use of PET/MRI, and those centres with a PET/MRI facility are undertaking research to look for a 'key application'.

GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH

This review briefly describes some of the technical advances, present comparisons with the diagnostic performance of current imaging modalities (PET/CT and MRI) and identifies potential indications and research directions.

Development of copper based drugs, radiopharmaceuticals and medical materials

Copper is one of the most interesting elements for various biomedical applications. Copper compounds show vast array of biological actions, including anti-inflammatory, anti-proliferative, biocidal and other. It also offers a selection of radioisotopes, suitable for nuclear imaging and radiotherapy. Quick progress in nanotechnology opened new possibilities for design of copper based drugs and medical materials. To date, copper has not found many uses in medicine, but number of ongoing research, as well as preclinical and clinical studies, will most likely lead to many novel applications of copper in the near future.

CT/fluorescence dual-modal nanoemulsion platform for investigating atherosclerotic plaques

Macrophages have become widely recognized as a key target for atherosclerosis imaging, since they contribute significantly to the progression of atherosclerosis. Dual-modal imaging contrast agents with unique X-ray computed tomography (CT) and optical imaging capabilities have great potential in disease diagnosis because of complementary combination of the high spatial resolution of CT with the high sensitivity of optical imaging. Here, a kind of quantum dots (QDs)-iodinated oil nanoemulsion of 80 nm was developed as a CT/fluorescence dual-modal contrast agent. Hydrophobic QDs were embedded in iodinated oil, which subsequently dispersed in water to form the oil-in-water nanoemulsion. The morphology and hydrodynamic size of the nanoemulsion were characterized, CT values and fluorescence properties were detected. Its cytotoxicity and affinity to three different cells were determined in vitro by MTT assay. In vitro Micro-CT and confocal microscopy cell imaging ability of the nanoemulsion were confirmed by co-incubating with murine macrophage cells and human liver cells. Then in vivo accumulation of this nanoemulsion in macrophages in atherosclerotic rabbits was investigated with clinic CT and fluorescence imaging. The results not only indicated the nanoemulsion could be served as a dual-modal contrast agent, but revealed it could specifically target to macrophages and visualize atherosclerotic plaques.

A simple and widely applicable method to 59Fe-radiolabel monodisperse superparamagnetic iron oxide nanoparticles for in vivo quantification studies

A simple, fast, efficient, and widely applicable method to radiolabel the cores of monodisperse superparamagnetic iron oxide nanoparticles (SPIOs) with (59)Fe was developed. These cores can be used as precursors for a variety of functionalized nanodevices. A quality control using filtration techniques, size-exclusion chromatography, chemical degradation methods, transmission electron microscopy, and magnetic resonance imaging showed that the nanoparticles were stably labeled with (59)Fe. Furthermore, the particle structure and the magnetic properties of the SPIOs were unchanged. In a second approach, monodisperse SPIOs stabilized with (14)C-oleic acid were synthesized, and the stability of this shell labeling was studied. In proof of principle experiments, the (59)Fe-SPIOs coated with different shells to make them water-soluble were used to evaluate and compare in vivo pharmacokinetic parameters such as blood half-life. It could also be shown that our radiolabeled SPIOs embedded in recombinant lipoproteins can be used to quantify physiological processes in closer detail than hitherto possible. In vitro and in vivo experiments showed that the (59)Fe label is stable enough to be applied in vivo, whereas the (14)C label is rapidly removed from the iron core and is not adequate for in vivo studies. To obtain meaningful results in in vivo experiments, only (59)Fe-labeled SPIOs should be used.

64Cu Core-labeled nanoparticles with high specific activity via metal-free click chemistry

A novel strategy based on metal-free "click" chemistry was developed for the copper-64 radiolabeling of the core in shell-cross-linked nanoparticles (SCK-NPs). Compared with Cu(I)-catalyzed click chemistry, this metal-free strategy provides the following advantages for Cu-64 labeling of the core of SCK-NPs: (1) elimination of copper exchange between nonradioactive Cu in the catalyst and DOTA-chelated Cu-64; (2) elimination of the internal click reactions between the azide and acetylene groups in the same NPs; and (3) increased efficiency of the click reaction because water-soluble Cu(I) does not need to reach the hydrophobic core of the NPs. When 50 mCi Cu-64 was used for the radiolabeling, the specific activity of the radiolabeled product was 975 Ci/μmol at the end of synthesis, which represents the attachment of ca. 500 Cu-64 atoms per SCK-NP, giving in essence a 500-fold amplification of specific activity of the NP over that of the Cu-64 chelate. To the best of our knowledge, this is the highest specific activity obtained for Cu-64-labeled nanoparticles.

Lanthanide ion-doped GdPO4 nanorods with dual-modal bio-optical and magnetic resonance imaging properties

Here, dual-modal bioprobes for combined optical and magnetic resonance (MR) imaging are reported. Gadolinium orthophosphate (GdPO(4)) nanorods co-doped with light-emitting lanthanide ions have been successfully prepared through a hydrothermal method. An efficient downconversion luminescence from Ce/Tb or Eu doped GdPO(4) nanorods and upconversion luminescence from Yb/Er co-doped GdPO(4) nanorods are observed, respectively, which offers the optical modality for the nanoprobes. Notably, we first report the upconversion phenomenon based on the GdPO(4) matrix under 980 nm near infrared irradiation. The possibility of using these nanoprobes with downconversion and upconversion luminescent emissions for optical cell imaging is also demonstrated. Furthermore, these Gd(3+)-containing nanophosphors show good positive signal-enhancement ability when performed under a 4.7 T MR imaging scanner, indicating they have potential as T(1) MR imaging contrast agents. Thus, nanoprobes based on GdPO(4) nanophosphors are shown to provide the dual modality of optical and MR imaging.

Rapid microwave-assisted synthesis of dextran-coated iron oxide nanoparticles for magnetic resonance imaging

Currently, magnetic iron oxide nanoparticles are the only nanosized magnetic resonance imaging (MRI) contrast agents approved for clinical use, yet commercial manufacturing of these agents has been limited or discontinued. Though there is still widespread demand for these particles both for clinical use and research, they are difficult to obtain commercially, and complicated syntheses make in-house preparation unfeasible for most biological research labs or clinics. To make commercial production viable and increase accessibility of these products, it is crucial to develop simple, rapid and reproducible preparations of biocompatible iron oxide nanoparticles. Here, we report a rapid, straightforward microwave-assisted synthesis of superparamagnetic dextran-coated iron oxide nanoparticles. The nanoparticles were produced in two hydrodynamic sizes with differing core morphologies by varying the synthetic method as either a two-step or single-step process. A striking benefit of these methods is the ability to obtain swift and consistent results without the necessity for air-, pH- or temperature-sensitive techniques; therefore, reaction times and complex manufacturing processes are greatly reduced as compared to conventional synthetic methods. This is a great benefit for cost-effective translation to commercial production. The nanoparticles are found to be superparamagnetic and exhibit properties consistent for use in MRI. In addition, the dextran coating imparts the water solubility and biocompatibility necessary for in vivo utilization.

Engineering the multifunctional surface on magnetic nanoparticles for targeted biomedical applications: a chemical approach

Research on multifunctional magnetic nanoparticles for biomedicines has experienced rapid growth because of the progressive advancements in nanotechnology and in modern biotechnology. However, the design of multifunctional surfaces on magnetic nanoparticles generally lacks a systematic approach. This article will try to unfold the complex chemistry in constructing a multifunctional surface, and layout a simplified guide for researchers to follow, particularly those from nonchemistry backgrounds. A number of design principles with critical rationales are to be introduced and followed by four main strategies: multifunctionality on a polymer chain, use of block copolymers, cocondensation of alkoxysilanes and of the secondary reaction on groups, with a particular reference to the use of alkoxysilanes. Nanoparticles of higher complexity are expected to be reported in the near future. These advanced systems are likely to be designed from some more logical, strategic mechanisms rather than the 'pick-and-mix' approaches we have seen in the last decade.

Rapid size-controlled synthesis of dextran-coated, 64Cu-doped iron oxide nanoparticles

Research into developing dual modality probes enabled for magnetic resonance imaging (MRI) and positron emission tomography (PET) has been on the rise recently due to the potential to combine the high resolution of MRI and the high sensitivity of PET. Current synthesis techniques for developing multimodal probes is largely hindered in part by prolonged reaction times during radioisotope incorporation--leading to a weakening of the radioactivity. Along with a time-efficient synthesis, the resulting products must fit within a critical size range (between 20 and 100 nm) to increase blood retention time. In this work, we describe a novel, rapid, microwave-based synthesis technique to grow dextran-coated iron oxide nanoparticles doped with copper (DIO/Cu). Traditional methods for coprecipitation of dextran-coated iron oxide nanoparticles require refluxing for 2 h and result in approximately 50 nm diameter particles. We demonstrate that microwave synthesis can produce 50 nm nanoparticles with 5 min of heating. We discuss the various parameters used in the microwave synthesis protocol to vary the size distribution of DIO/Cu and demonstrate the successful incorporation of (64)Cu into these particles with the aim of future use for dual-mode MR/PET imaging.

Nanoparticles labeled with positron emitting nuclides: advantages, methods, and applications

Over the past decade, positron emitter labeled nanoparticles have been widely used in and substantially improved for a range of diagnostic biomedical research. However, given growing interest in personalized medicine and translational research, a major challenge in the field will be to develop disease-specific nanoprobes with facile and robust radiolabeling strategies and that provide imaging stability, enhanced sensitivity for disease early stage detection, optimized in vivo pharmacokinetics for reduced nonspecific organ uptake, and improved targeting for elevated efficacy. This review briefly summarizes the major applications of nanoparticles labeled with positron emitters for cardiovascular imaging, lung diagnosis, and tumor theranostics.

Nanoformulations for molecular MRI

Nanoscale contrast agents have shown the ability to increase the detection sensitivity of magnetic resonance imaging (MRI) by several orders of magnitude, endowing this traditionally macroscopic modality with the ability to observe unique molecular signatures. Herein, we describe three types of nanoparticulate contrast agents: iron oxide nanoparticles, gadolinium-based nanoparticles, and bio-essential manganese, cobalt, nickel, and copper ion-containing nanoformulations. Some of these agents have been approved for clinical use, but more are still under development for medical imaging. The advantages and disadvantages of each nanoformulation, in terms of intrinsic magnetism, ease of synthesis, biodistribution, etc. are discussed.

Preparation of specific monoclonal antibodies against chelated copper ions

Copper ions are too small to elicit an immune response. Therefore, copper was conjugated to carrier proteins using S-2-(4-isothiocyanatobenzyl)-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid, a bifunctional chelator, to make artificial antigens for copper. Several mice were immunized, and monoclonal antibodies (MAbs) against chelated copper were produced. Spleen cells of immunized mice were fused with myeloma cells. The resulting hybridomas were screened using protein conjugates which were covalently bound to metal-free 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA) or Cu-DOTA. Two hybridoma cell lines (F4 and B2) that produced MAbs with high selectivity and sensitivity were expanded for further study. Cross-reactivities with other metals were below 1%. These antibodies were used to construct competitive ELISAs for copper ions. The IC(50) for F4 and B2 were 0.39 and 1.66 mg/l, respectively. The detection range and the lowest detection limit for copper using the antibody F4 was 0.019-8.22 and 0.003 mg/l, respectively. Spike recovery studies in tap water showed that the most sensitive antibody could be used for copper detection in drinking water.

Quantifying the coverage density of poly(ethylene glycol) chains on the surface of gold nanostructures

The coverage density of poly(ethylene glycol) (PEG) is a key parameter in determining the efficiency of PEGylation, a process pivotal to in vivo delivery and targeting of nanomaterials. Here we report four complementary methods for quantifying the coverage density of PEG chains on various types of Au nanostructures by using a model system based on HS-PEG-NH(2) with different molecular weights. Specifically, the methods involve reactions with fluorescamine and ninhydrin, as well as labeling with fluorescein isothiocyanate (FITC) and Cu(2+) ions. The first two methods use conventional amine assays to measure the number of unreacted HS-PEG-NH(2) molecules left behind in the solution after incubation with the Au nanostructures. The other two methods involve coupling between the terminal -NH(2) groups of adsorbed -S-PEG-NH(2) chains and FITC or a ligand for Cu(2+) ion, and thus pertain to the "active" -NH(2) groups on the surface of a Au nanostructure. We found that the coverage density decreased as the length of PEG chains increased. A stronger binding affinity of the initial capping ligand to the Au surface tended to reduce the PEGylation efficiency by slowing down the ligand exchange process. For the Au nanostructures and capping ligands we have tested, the PEGylation efficiency decreased in the order of citrate-capped nanoparticles > PVP-capped nanocages ≈ CTAC-capped nanoparticles ≫ CTAB-capped nanorods, where PVP, CTAC, and CTAB stand for poly(vinyl pyrrolidone), cetyltrimethylammonium chloride, and cetyltrimethylammonium bromide, respectively.

Layer-by-layer capsules for magnetic resonance imaging and drug delivery

Layer-by-layer (LbL) self-assembled polyelectrolyte capsules have demonstrated their unique advantages and capability in drug delivery applications. These ordered micro/nano-structures are also promising candidates as imaging contrast agents for diagnostic and theranostic applications. Magnetic resonance imaging (MRI), one of the most powerful clinical imaging modalities, is moving forward to the molecular imaging field and requires the availability of advanced imaging probes. In this review, we are focusing on the design of MRI visible LbL capsules, which incorporate either paramagnetic metal-ligand complexes or superparamagnetic iron oxide (SPIO) nanoparticles. The design criteria cover the topics of probe sensitivity, biosafety, long-circulation property, targeting ligand decoration, and drug loading strategies. Examples of MRI visible LbL capsules with paramagnetic or superparamagnetic moieties were given and discussed. This carrier platform can also be chosen for other imaging modalities.

Stabilization and functionalization of iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles (NPs) are used in a rapidly expanding number of research and practical applications in the biomedical field, including magnetic cell labeling separation and tracking, for therapeutic purposes in hyperthermia and drug delivery, and for diagnostic purposes, e.g., as contrast agents for magnetic resonance imaging. These applications require good NP stability at physiological conditions, close control over NP size and controlled surface presentation of functionalities. This review is focused on different aspects of the stability of superparamagnetic iron oxide NPs, from its practical definition to its implementation by molecular design of the dispersant shell around the iron oxide core and further on to its influence on the magnetic properties of the superparamagnetic iron oxide NPs. Special attention is given to the selection of molecular anchors for the dispersant shell, because of their importance to ensure colloidal and functional stability of sterically stabilized superparamagnetic iron oxide NPs. We further detail how dispersants have been optimized to gain close control over iron oxide NP stability, size and functionalities by independently considering the influences of anchors and the attached sterically repulsive polymer brushes. A critical evaluation of different strategies to stabilize and functionalize core-shell superparamagnetic iron oxide NPs as well as a brief introduction to characterization methods to compare those strategies is given.

Targeted Nanocarriers for Imaging and Therapy of Vascular Inflammation

Vascular inflammation is a common, complex mechanism involved in pathogenesis of a plethora of disease conditions including ischemia-reperfusion, atherosclerosis, restenosis and stroke. Specific targeting of imaging probes and drugs to endothelial cells in inflammation sites holds promise to improve management of these conditions. Nanocarriers of diverse compositions and geometries, targeted with ligands to endothelial adhesion molecules exposed in inflammation foci are devised for this goal. Imaging modalities that employ these nanoparticle probes include radioisotope imaging, MRI and ultrasound that are translatable from animal to human studies, as well as optical imaging modalities that at the present time are more confined to animal studies. Therapeutic cargoes for these drug delivery systems include diverse anti-inflammatory agents, anti-proliferative drugs for prevention of restenosis, and antioxidants. This article reviews recent advances in the area of image-guided translation of targeted nanocarrier diagnostics and therapeutics in nanomedicine.

Biodistribution study of nanometric hybrid gadolinium oxide particles as a multimodal SPECT/MR/optical imaging and theragnostic agent

Nanometric hybrid gadolinium oxide particles (Gado-6Si-NP) for diagnostic and therapeutic applications (mean diameter 3-4 nm) were obtained by encapsulating Gd(2)O(3) cores within a polysiloxane shell, which carries organic fluorophore (Cy 5) and is derivatized by a hydrophilic carboxylic layer. As residency time in the living body and methods of waste elimination are crucial to defining a good nanoparticle candidate and moving forward with steps for validation, this study was aimed at evaluating the biodistribution of these multimodal Gado-6Si-NP in rodents. Gado-6Si-NP were imaged following intravenous injection in control Wistar rats and mice using MRI (7 T), optical fluorescent imaging, and SPECT. A clear correlation was observed among MRI, optical imaging, and SPECT regarding the renal elimination. Quantitative biodistribution using gamma-counting of each sampled organ confirmed that these nanoparticles circulated freely in the blood pool and were rapidly cleared by renal excretion without accumulation in liver and RES uptake. These results demonstrate that Gado-6Si-NP display optimal biodistribution properties, enabling them to be developed as multimodal agents for in vivo imaging and theragnostics, especially in oncological applications.

Nanomaterials: applications in cancer imaging and therapy

The application of nanomaterials (NMs) in biomedicine is increasing rapidly and offers excellent prospects for the development of new non-invasive strategies for the diagnosis and treatment of cancer. In this review, we provide a brief description of cancer pathology and the characteristics that are important for tumor-targeted NM design, followed by an overview of the different types of NMs explored to date, covering synthetic aspects and approaches explored for their application in unimodal and multimodal imaging, diagnosis and therapy. Significant synthetic advances now allow for the preparation of NMs with highly controlled geometry, surface charge, physicochemical properties, and the decoration of their surfaces with polymers and bioactive molecules in order to improve biocompatibility and to achieve active targeting. This is stimulating the development of a diverse range of nanometer-sized objects that can recognize cancer tissue, enabling visualization of tumors, delivery of anti-cancer drugs and/or the destruction of tumors by different therapeutic techniques.

Multifunctional nanoparticles for dual imaging

For imaging with different modalities, labels, which provide contrast for all modalities, are required. Colloidal nanoparticles composed out of an inorganic core and a polymer shell offer progress in this direction. Both, the core and the polymer shell, can be synthesized to be fluorescent, magnetic, or radioactive. When different cores are combined with different polymer shells, different types of particles for dual imaging can be obtained, as for example, fluorescent cores with radioactive polymer shells. Properties and perspectives of such nanoparticles for multimodal imaging are discussed.

(⁹⁹m)Tc-bisphosphonate-iron oxide nanoparticle conjugates for dual-modality biomedical imaging

The combination of radionuclide-based imaging modalities such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) with magnetic resonance imaging (MRI) is likely to become the next generation of clinical scanners. Hence, there is a growing interest in the development of SPECT- and PET-MRI agents. To this end, we report a new class of dual-modality imaging agents based on the conjugation of radiolabeled bisphosphonates (BP) directly to the surface of superparamagnetic iron oxide (SPIO) nanoparticles. We demonstrate the high potential of BP-iron oxide conjugation using (⁹⁹m)Tc-dipicolylamine(DPA)-alendronate, a BP-SPECT agent, and Endorem/Feridex, a liver MRI contrast agent based on SPIO. The labeling of SPIOs with (⁹⁹m)Tc-DPA-alendronate can be performed in one step at room temperature if the SPIO is not coated with an organic polymer. Heating is needed if the nanoparticles are coated, as long as the coating is weakly bound as in the case of dextran in Endorem. The size of the radiolabeled Endorem (⁹⁹m)Tc-DPA-ale-Endorem) was characterized by TEM (5 nm, Fe₃O₄ core) and DLS (106 ± 60 nm, Fe₃O₄ core + dextran). EDX, Dittmer-Lester, and radiolabeling studies demonstrate that the BP is bound to the nanoparticles and that it binds to the Fe₃O₄ cores of Endorem, and not its dextran coating. The bimodal imaging capabilities and excellent stability of these nanoparticles were confirmed using MRI and nanoSPECT-CT imaging, showing that (⁹⁹m)Tc and Endorem co-localize in the liver and spleen In Vivo, as expected for particles of the composition and size of (⁹⁹m)Tc-DPA-ale-Endorem. To the best of our knowledge, this is the first example of radiolabeling SPIOs with BP conjugates and the first example of radiolabeling SPIO nanoparticles directly onto the surface of the iron oxide core, and not its coating. This work lays down the basis for a new generation of SPECT/PET-MR imaging agents in which the BP group could be used to attach functionality to provide targeting, stealth/stability, and radionuclides to Fe₃O₄ nanoparticles using very simple methodology readily amenable to GMP.