Gadolinium chelate coated gold nanoparticles as contrast agents for both X-ray computed tomography and magnetic resonance imaging

Storage of gold nanoclusters in muscle leads to their biphasic in vivo clearance

Ultrasmall gold nanoclusters (Au NCs) show great potential in biomedical applications. Long-term biodistribution, retention, toxicity, and pharmacokinetics profiles are pre-requisites in their potential clinical applications. Here, the biodistribution, clearance, and toxicity of one widely used Au NC species-glutathione-protected Au NCs or GSH-Au NCs-are systematically investigated over a relatively long period of 90 days in mice. Most of the Au NCs are cleared at 30 days post injection (p.i.) with a major accumulation in liver and kidney. However, it is surprising that an abnormal increase of the Au amount in the heart, liver, spleen, lung, and testis is observed at 60 and 90 days p.i., indicating that the injected Au NCs form a V-shaped time-dependent distribution profile in various organs. Further investigations reveal that Au NCs are steadily accumulating in the muscle in the first 30 days p.i., and the as-stored Au NCs gradually release into the blood in 30-90 days p.i., which induces a re-distribution and re-accumulation of Au NCs in all blood-rich organs. Further hematology and biochemistry studies show that the re-accumulation of Au NCs still causes some liver toxicity at 30 days p.i. The muscle storage and subsequent release may give rise to the potential accumulation and toxicity risk of functional nanomaterials over long periods of time.

Structural characterization, antioxidant and anticancer properties of gold nanoparticles synthesized from leaf extract(decoction)of Antigonon leptopus Hook. &Arn

Tea is an aromatic beverage prepared by pouring boiling water over alleviated leaves of the tea plant. Tea prepared from the aerial parts of Antigonon leptopus has been traditionally used as remedy for cold, diabetes and pain in many countries. The gold nanoparticles (Au NPs) synthesized from powdered leaf extract (decoction) of A. leptopus were characterized by UV–visible spectroscopy (UV–vis), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern and energy dispersive X-ray (EDX) analyses to define the formation of Au NPs. Further, the synthesized Au NPs were well characterized based on their strong surface plasmon resonance (SPR), crystalline nature, functional groups, size and dispersed shapes, purity and Bragg's reflections of face centered cubic (fcc) structure of metallic gold. The Au NPs showed higher free radical scavenging property when compared to the effect of leaf extract. Cytotoxicity study of synthesized Au NPs exhibited the growth inhibitory property at the concentration (GI50) of 257.8 μg/mL in human adenocarcinoma breast cancer (MCF-7) cells after 48 h. Thus, the Au NPs synthesized from the Mexican creeper, A. leptopus revealed the important biological properties: as a free radical as well as anticancer agent. We conclude that the A. leptopus derived biological materials have promising potential as a source for the development of anticancer drug in future.

Multifunctional dendrimer-entrapped gold nanoparticles modified with RGD peptide for targeted computed tomography/magnetic resonance dual-modal imaging of tumors

We report the use of multifunctional dendrimer-entrapped gold nanoparticles (Au DENPs) loaded with gadolinium (Gd) chelator/Gd(III) complexes and surface-modified with thiolated cyclo(Arg-Gly-Asp-Phe-Lys(mpa)) (RGD) peptide for targeted dual-mode computed tomography (CT)/magnetic resonance (MR) imaging of small tumors. In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as a nanoplatform to be covalently modified with Gd chelator, RGD via a polyethylene glycol (PEG) spacer, and PEG monomethyl ether. Then the multifunctional dendrimers were used as templates to entrap gold nanoparticles, followed by chelating Gd(III) ions and acetylation of the remaining dendrimer terminal amines. The thus-formed multifunctional Au DENPs (in short, Gd-Au DENPs-RGD) were characterized via different techniques. We show that the multifunctional Au DENPs with a Au core size of 3.8 nm are water-dispersible, stable under different pH (5-8) and temperature conditions (4-50 °C), and noncytotoxic at a Au concentration up to 100 μM. With the displayed X-ray attenuation property and the r1 relaxivity (2.643 mM(-1) s(-1)), the developed Gd-Au DENPs-RGD are able to be used as a dual-mode nanoprobe for targeted CT/MR imaging of an αvβ3 integrin-overexpressing xenografted small tumor model in vivo via RGD-mediated active targeting pathway. The developed multifunctional Gd-Au DENPs-RGD may be used as a promising dual-mode nanoprobe for targeted CT/MR imaging of different types of αvβ3 integrin-overexpressing cancer.

Gadolinium-based nanoparticles for theranostic MRI-radiosensitization

A rapid development of gadolinium-based nanoparticles is observed due to their attractive properties as MRI-positive contrast agents. Indeed, they display high relaxivity, adapted biodistribution and passive uptake in the tumor thanks to enhanced permeability and retention effect. In addition to these imaging properties, it has been recently shown that they can act as effective radiosensitizers under different types of irradiation (radiotherapy, neutron therapy or hadron therapy). These new therapeutic modalities pave the way to therapy guided by imaging and to personalized medicine.

Renal clearance and degradation of glutathione-coated copper nanoparticles

Degradation of inorganic nanoparticles (NPs) into small molecular complexes is often observed in the physiological environment; however, how this process influences renal clearance of inorganic NPs is largely unknown. By systematically comparing renal clearance of degradable luminescent glutathione coated copper NPs (GS-CuNPs) and their dissociated products, Cu(II)-glutathione disulfide (GSSG) complexes (Cu(II)-GSSG), we found that GS-CuNPs were eliminated through the urinary system surprisingly faster and accumulated in the liver much less than their smaller dissociation counterparts. With assistance of radiochemistry and positron emission tomography (PET) imaging, we found that the observed "nano size" effect in enhancing renal clearance is attributed to the fact that GS-CuNPs are more resistant to serum protein adsorption than Cu(II)-GSSG. In addition, since dissociation of GS-CuNPs follows zero-order chemical kinetics, their renal clearance and biodistribution also depend on initial injection doses and their dissociation processes. Quantitative understanding of size effect and other factors involved in renal clearance and biodistribution of degradable inorganic NPs will lay down a foundation for further development of renal-clearable inorganic NPs with minimized nanotoxicity.

Imaging strategies for tissue engineering applications

Tissue engineering has evolved with multifaceted research being conducted using advanced technologies, and it is progressing toward clinical applications. As tissue engineering technology significantly advances, it proceeds toward increasing sophistication, including nanoscale strategies for material construction and synergetic methods for combining with cells, growth factors, or other macromolecules. Therefore, to assess advanced tissue-engineered constructs, tissue engineers need versatile imaging methods capable of monitoring not only morphological but also functional and molecular information. However, there is no single imaging modality that is suitable for all tissue-engineered constructs. Each imaging method has its own range of applications and provides information based on the specific properties of the imaging technique. Therefore, according to the requirements of the tissue engineering studies, the most appropriate tool should be selected among a variety of imaging modalities. The goal of this review article is to describe available biomedical imaging methods to assess tissue engineering applications and to provide tissue engineers with criteria and insights for determining the best imaging strategies. Commonly used biomedical imaging modalities, including X-ray and computed tomography, positron emission tomography and single photon emission computed tomography, magnetic resonance imaging, ultrasound imaging, optical imaging, and emerging techniques and multimodal imaging, will be discussed, focusing on the latest trends of their applications in recent tissue engineering studies.

Green biochemistry approach for synthesis of silver and gold nanoparticles using Ficus racemosa latex and their pH-dependent binding study with different amino acids using UV/Vis absorption spectroscopy

Simple and eco-friendly biosynthesis approach was developed to synthesize silver nanoparticles (SNPs) and gold nanoparticles (GNPs) using Ficus racemosa latex as reducing agent. The presence of sunlight is utilized with latex and achieved the nanoparticles whose average size was in the range of 50-120 nm for SNPs and 20-50 nm for GNPs. The synthesized nanoparticles were characterized by UV/Visible absorption spectroscopy, X-ray diffraction, and field emission-scanning electron microscopy techniques toget understand the obtained nanoparticles. The pH-dependent binding studies of SNPs and GNPs with four amino acids, namely L-lysine, L-arginine, L-glutamine and glycin have been reported.

A highly sensitive x-ray imaging modality for hepatocellular carcinoma detection in vitro

Innovations that improve sensitivity and reduce cost are of paramount importance in diagnostic imaging. The novel x-ray imaging modality called spatial frequency heterodyne imaging (SFHI) is based on a linear arrangement of x-ray source, tissue, and x-ray detector, much like that of a conventional x-ray imaging apparatus. However, SFHI rests on a complete paradigm reversal compared to conventional x-ray absorption-based radiology: while scattered x-rays are carefully rejected in absorption-based x-ray radiology to enhance the image contrast, SFHI forms images exclusively from x-rays scattered by the tissue. In this study we use numerical processing to produce x-ray scatter images of hepatocellular carcinoma labeled with a nanoparticle contrast agent. We subsequently compare the sensitivity of SFHI in this application to that of both conventional x-ray imaging and magnetic resonance imaging (MRI). Although SFHI is still in the early stages of its development, our results show that the sensitivity of SFHI is an order of magnitude greater than that of absorption-based x-ray imaging and approximately equal to that of MRI. As x-ray imaging modalities typically have lower installation and service costs compared to MRI, SFHI could become a cost effective alternative to MRI, particularly in areas of the world with inadequate availability of MRI facilities.

One-step synthesis of surface passivated carbon microspheres for enhanced photoluminescence and their application in multifunctional magnetic-fluorescent imaging

A carbon@Gd-DTPA microspheres bifunctional contrast agent was prepared and applied for MR imaging and luminescent imaging. The primary Na₃cit molecules have been used as an intermedium to conjugate Gd-DTPA and surface passivation agents to improve photoluminescence.

Facile synthesis of hyaluronic acid-modified Fe3O4/Au composite nanoparticles for targeted dual mode MR/CT imaging of tumors

Hyaluronic acid-modified Fe₃O₄/Au composite nanoparticles can be synthesized for targeted dual mode MR/CT imaging of tumors.

Magnetic controlling of migration of DNA and proteins using one-step modified gold nanoparticles

One-step modified magnetic AuNPs coated with paramagnetic cationic surfactants were produced and used for controlling migration of DNA and proteins.

Gold nanoparticles functionalised with fast water exchanging Gd3+ chelates: linker effects on the relaxivity

Linker length has little effect on the relaxivity of Gd³⁺ chelates immobilized onto gold nanoparticles.

Large-scale synthesis of PEGylated lutetium hydroxycarbonates as nanoparticulate contrast agents for X-ray CT imaging

PEGylated lutetium hydroxycarbonate nanoparticles have been prepared via a large-scale strategy and successfully used as high-performance contrast agents for X-ray computed tomography imaging with neglectable systemic toxicity.

A new magnetic resonance imaging contrast agent loaded into poly(lacide-co-glycolide) nanoparticles for long-term detection of tumors

The incorporation of a lipophilic Gd chelate (GdDO3A-C12) in biocompatible PLGA poly(D, L-lactide-co-glycolide) nanoparticles was explored as an approach to increase the relaxivity of contrast agents for magnetic resonance imaging. By nanoprecipitation, it was possible to obtain PEGylated gadolinium nanoparticles (mean diameter of 155 nm) with high Gd loading (1.1 × 10(4) Gd centers per nanoparticle). The corresponding GdDO3AC12 ⊂ NPs nanoparticles exhibited an enhanced relaxivity (up to sixfold greater than DOTAREM® at 40 MHz) because the nanoparticle framework constrained the lipophilic Gd chelate motion and favorably impacted the Gd chelate rotational correlation time. T1-weighted imaging at 3 T on phantoms showed enhanced contrast for the GdDO3AC12 ⊂ NPs. Importantly, Gd chelate leakage was almost nonexistent, which suggested that these GdDO3AC12 ⊂ NPs could be useful for long-term MRI detection.

Synthesis and characterization of PEGylated polyethylenimine-entrapped gold nanoparticles for blood pool and tumor CT imaging

The synthesis and characterization of gold nanoparticles (AuNPs) entrapped within polyethylene glycol (PEG)-modified polyethylenimine (PEI) for blood pool and tumor computed tomography (CT) imaging are reported. In this approach, partially PEGylated PEI was used as a template for AuNP synthesis, followed by acetylating the PEI remaining surface amines. The synthesized PEGylated PEI-entrapped AuNPs (Au PENPs) were characterized via different methods. Our results reveal that the synthesized Au PENPs can be tuned to have an Au core size in a range of 1.9-4.6 nm and to be water-soluble, stable, and noncytotoxic in a studied concentration range. With a demonstrated better X-ray attenuation property than that of clinically used iodinated small molecular contrast agent (e.g., Omnipaque) and the prolonged half-decay time (11.2 h in rat) confirmed by pharmacokinetics studies, the developed PEGylated Au PENPs enabled efficient and enhanced blood pool CT imaging with imaging time up to 75 min. Likewise, thanks to the enhanced permeability and retention effect, the PEGylated Au PENPs were also able to be used as a contrast agent for effective CT imaging of a tumor model. With the proven organ biocompatibility by histological studies, the designed PEGylated Au PENPs may hold great promise to be used as contrast agents for CT imaging of a variety of biological systems. The significance of this study is that rather than the use of dendrimers as templates, cost-effective branched polymers (e.g., PEI) can be used as templates to generate functionalized AuNPs for CT imaging applications.

Nanoparticle contrast agents for computed tomography: a focus on micelles

Computed tomography (CT) is an X-ray-based whole-body imaging technique that is widely used in medicine. Clinically approved contrast agents for CT are iodinated small molecules or barium suspensions. Over the past seven years there has been a great increase in the development of nanoparticles as CT contrast agents. Nanoparticles have several advantages over small molecule CT contrast agents, such as long blood-pool residence times and the potential for cell tracking and targeted imaging applications. Furthermore, there is a need for novel CT contrast agents, owing to the growing population of renally impaired patients and patients hypersensitive to iodinated contrast. Micelles and lipoproteins, a micelle-related class of nanoparticle, have notably been adapted as CT contrast agents. In this review we discuss the principles of CT image formation and the generation of CT contrast. We discuss the progress in developing nontargeted, targeted and cell tracking nanoparticle CT contrast agents. We feature agents based on micelles and used in conjunction with spectral CT. The large contrast agent doses needed will necessitate careful toxicology studies prior to clinical translation. However, the field has seen tremendous advances in the past decade and we expect many more advances to come in the next decade.

Gadolinium-enriched polyaniline particles (GPAPs) for simultaneous diagnostic imaging and localized photothermal therapy of epithelial cancer

By loading Gd(III) inside NIR-absorbing polyaniline nanostructures, a novel diagnostic and photothermal agent with enhanced MR sensitivity, targeting ability, and photothermal ability to treat epithelial cancer is developed.

Lipid-AuNPs@PDA nanohybrid for MRI/CT imaging and photothermal therapy of hepatocellular carcinoma

Multifunctional theranostic nanoparticles represent an emerging agent with the potential to offer extremely sensitive diagnosis and targeted cancer therapy. Herein, we report the synthesis and characterization of a multifunctional theranostic agent (referred to as LA-LAPNHs) for targeted magnetic resonance imaging/computed X-ray tomography (MRI/CT) dual-mode imaging and photothermal therapy of hepatocellular carcinoma. The LA-LAPNHs were characterized as having a core-shell structure with the gold nanoparticles (AuNPs)@polydopamine (PDA) as the inner core, the indocyanine green (ICG), which is electrostatically absorbed onto the surface of PDA, as the photothermal therapeutic agent, and the lipids modified with gadolinium-1,4,7,10-tetraacetic acid and lactobionic acid (LA), which is self-assembled on the outer surface as the shell. The LA-LAPNHs could be selectively internalized into the hepatocellular cell line (HepG2 cells) but not into HeLa cells due to the specific recognition ability of LA to asialoglycoprotein receptor. Additionally, the dual-mode imaging ability of the LA-LAPNH aqueous solution was confirmed by enhanced MR and CT imaging showing a shorter T1 relaxation time and a higher Hounsfield unit value, respectively. In addition, the LA-LAPNHs showed significant photothermal cytotoxicity against liver cancer cells with near-infrared irradiation due to their strong absorbance in the region between 700 and 850 nm. In summary, this study demonstrates that LA-LAPNHs may be a promising candidate for targeted MR/CT dual-mode imaging and photothermal therapy of hepatocellular carcinoma.

Thermodynamic stability and kinetic inertness of a Gd-DTPA bisamide complex grafted onto gold nanoparticles

Gold nanoparticles coated by gadolinium (III) chelates (Au@DTDTPA) where DTDTPA is a dithiolated bisamide derivative of diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA), constituted contrast agents for both X-ray computed tomography and magnetic resonance imaging. In an MRI context, highly stable Gd(3+) complexes are needed for in vivo applications. Thus, knowledge of the thermodynamic stability and kinetic inertness of these chelates, when grafted onto gold nanoparticles, is crucial since bisamide DTPA chelates are usually less suited for Gd(3+) coordination than DTPA. Therefore, these parameters were evaluated by means of potentiometric titrations and relaxivity measurements. The results showed that, when the chelates were grafted onto the nanoparticle, not only their thermodynamic stability but also their kinetic inertness were improved. These positive effects were correlated to the chelate packing at the nanoparticle surface that stabilized the corresponding Gd(3+) complexes and greatly enhanced their kinetic inertness.

Polymeric-gold nanohybrids for combined imaging and cancer therapy

Here, the use of folic acid (FA)-functionalized, doxorubicin (DOXO)/superparamagnetic iron oxide nanoparticles (SPION)-loaded poly(lactic-co-glycolic acid) (PLGA)-Au porous shell nanoparticles (NPs) as potential nanoplatforms is reported for targeted multimodal chemo- and photothermal therapy combined with optical and magnetic resonance imaging in cancer. These polymeric-gold nanohybrids (PGNH) are produced by a seeded-growth method using chitosan as an electrostatic "glue" to attach Au seeds to DOXO/SPION-PLGA NPs. In order to determine their potential as theranostic nanoplatforms, their physicochemical properties, cellular uptake, and photothermal and chemotherapeutic efficiencies are tested in vitro using a human cervical cancer (HeLa) cell line. The present NPs show a near-infrared (NIR)-light-triggered release of cargo molecules under illumination and a great capacity to induce localized cell death in a well-focused region. The functionalization of the PGNH NPs with the targeting ligand FA improves their internalization efficiency and specificity. Furthermore, the possibility to guide the PGNH NPs to cancer cells by an external magnetic field is also proven in vitro, which additionally increases the cellular uptake and therapeutic efficiency.

Echographic imaging of tumoral cells through novel nanosystems for image diagnosis

Since the recognition of disease molecular basis, it has become clear that the keystone moments of medical practice, namely early diagnosis, appropriate therapeutic treatment and patient follow-up, must be approached at a molecular level. These objectives will be in the near future more effectively achievable thanks to the impressive developments in nanotechnologies and their applications to the biomedical field, starting-up the nanomedicine era. The continuous advances in the development of biocompatible smart nanomaterials, in particular, will be crucial in several aspects of medicine. In fact, the possibility of manufacturing nanoparticle contrast agents that can be selectively targeted to specific pathological cells has extended molecular imaging applications to non-ionizing techniques and, at the same time, has made reachable the perspective of combining highly accurate diagnoses and personalized therapies in a single theranostic intervention. Main developing applications of nanosized theranostic agents include targeted molecular imaging, controlled drug release, therapeutic monitoring, guidance of radiation-based treatments and surgical interventions. Here we will review the most recent findings in nanoparticles contrast agents and their applications in the field of cancer molecular imaging employing non-ionizing techniques and disease-specific contrast agents, with special focus on recent findings on those nanomaterials particularly promising for ultrasound molecular imaging and simultaneous treatment of cancer.

Solid silica nanoparticles: applications in molecular imaging

Silica and silica-based nanoparticles have been widely used for therapeutic and diagnostic applications in cancer mainly through delivery of drugs, genes and contrast agents. Development of synthesis methods has provided the possibility of fabricating silica nanoparticles with different sizes in nanometer ranges as well as silica-based multimodal nanoparticles with many innovative properties and intriguing applications in biomedicine. The surface of silica particles facilitates different methods of surface modifications and allows conjugation of various biomolecules such as proteins and nucleic acids. In this review, different methods of fabrication of silica and silica-based nanoparticles, their surface modification and the application of these nanoparticles in molecular imaging are discussed. Overall, the aim of this review is to address the development of silica and silica-based multifunctional nanoparticles that are introduced mainly for molecular imaging applications using optical, magnetic (MRI), X-ray (computed tomography) and multimodal imaging techniques.

Theranostic self-assembly structure of gold nanoparticles for NIR photothermal therapy and X-Ray computed tomography imaging

The controllable self-assembly of amphiphilic mixed polymers grafted gold nanoparitcles (AuNPs) leads to strong interparticle plasmonic coupling, which can be tuned to the near-infrared (NIR) region for enhanced photothermal therapy (PTT). In this study, an improved thiolation method was adopted for ATRP and ROP polymer to obtain amphiphilic brushes of PMEO2MA-SH and PCL-SH. By anchoring PCL-SH and PMEO2MA-SH onto the 14 nm AuNPs, a smart hybrid building block for self-assembly was obtained. Increasing the PCL/PMEO2MA chain ratio from 0.8:1, 2:1 and 3:1 to 7:1, the structure of gold assemblies (GAs) was observed to transfer from vesicle to large compound micelle (LCM). Contributed to the special dense packed structure of gold nanoparticles in LCM, the absorption spectrometry of gold nanoparticles drastically red-shifted from 520 nm to 830 nm, which endowed the GAs remarkable NIR photothermal conversion ability. In addition, gold has high X-ray absorption coefficient which qualifies gold nanomaterial a potential CT contrast agent Herein, we obtain a novel gold assembly structure which can be utilized as potential photothermal therapeutic and CT contrast agents. In vitro and In vivo studies testified the excellent treatment efficacy of optimum GAs as a PTT and CT contrast agent. In vitro degradation test, MTT assay and histology study indicated that GAs was a safe, low toxic reagent with good biodegradability. Therefore, the optimum GAs with strong NIR absorption and high X-ray absorption coefficient could be used as a theranostic agent and the formation of novel gold large compound micelle might offers a new theory foundation for engineering design and synthesis of polymer grafted AuNPs for biomedical applications.

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.

Synthesis, X-ray Opacity, and Biological Compatibility of Ultra-High Payload Elemental Bismuth Nanoparticle X-ray Contrast Agents

Inorganic nanoscale X-ray contrast agents (XCAs) offer many potential advantages over currently used intravascular molecular contrast agents, including longer circulation and retention times, lower administration volumes, and greater potential for site directed imaging. Elemental bismuth nanoparticles (BiNPs) are particularly attractive candidate XCAs due to the low cost, the high atomic number and high density of bismuth, and the likelihood that BiNPs will oxidatively decompose to biocompatible bismuth(III) ions at controlled rates for renal excretion. Herein we describe the synthesis of ultrahigh payload BiNPs in 1,2-propanediol using a borane reducing agent and glucose as a biocompatible surface stabilizer. Both synthetic solvent (1,2-propanediol) and surfactant (glucose) are evident on the BiNP surfaces when analyzed by ¹H NMR and FT-IR spectroscopies. These particles contain ∼6 million Bi atoms per NP and have large inorganic cores (74 nm by TEM) compared to their hydrodynamic size (86 nm by DLS). Thus, the dense BiNP core constitutes the majority (∼60%) of each particle's volume, a necessary property to realize the full potential of nanoscale XCAs. Using quantitative computed tomography in phantom and in vitro imaging studies, we demonstrate that these BiNPs have greater X-ray opacity than clinical small molecule iodinated contrast agents at the same concentrations. We furthermore demonstrate a favorable biocompatibility profile for these BiNPs in vitro. Altogether, these studies indicate that these ultrahigh payload BiNPs, synthesized from known biocompatible components, have promising physical and cytotoxicological properties for use as XCAs.

Gold nanoshelled liquid perfluorocarbon nanocapsules for combined dual modal ultrasound/CT imaging and photothermal therapy of cancer

The integration of multimodal contrast-enhanced diagnostic imaging and therapeutic capabilities could utilize imaging guided therapy to plan the treatment strategy based on the diagnostic results and to guide/monitor the therapeutic procedures. Herein, gold nanoshelled perfluorooctylbromide (PFOB) nanocapsules with PEGylation (PGsP NCs) are constructed by oil-in-water emulsion method to form polymeric PFOB nanocapsules, followed by the formation of PEGylated gold nanoshell on the surface. PGsP NCs could not only provide excellent contrast enhancement for dual modal ultrasound and CT imaging in vitro and in vivo, but also serve as efficient photoabsorbers for photothermal ablation of tumors on xenografted nude mouse model. To our best knowledge, this is the first report of gold nanoshell serving as both CT contrast agents and photoabsorbers for photothermal therapy. The novel multifunctional nanomedicine would be of great value to offer more comprehensive diagnostic information to guide more accurate and effective cancer therapy.

Design of ProCAs (protein-based Gd(3+) MRI contrast agents) with high dose efficiency and capability for molecular imaging of cancer biomarkers

Magnetic resonance imaging (MRI) is the leading imaging technique for disease diagnostics, providing high resolution, three-dimensional images noninvasively. MRI contrast agents are designed to improve the contrast and sensitivity of MRI. However, current clinically used MRI contrast agents have relaxivities far below the theoretical upper limit, which largely prevent advancing molecular imaging of biomarkers with desired sensitivity and specificity. This review describes current progress in the development of a new class of protein-based MRI contrast agents (ProCAs) with high relaxivity using protein design to optimize the parameters that govern relaxivity. Further, engineering with targeting moiety allows these contrast agents to be applicable for molecular imaging of prostate cancer biomarkers by MRI. The developed protein-based contrast agents also exhibit additional in vitro and in vivo advantages for molecular imaging of disease biomarkers, such as high metal-binding stability and selectivity, reduced toxicity, proper blood circulation time, and higher permeability in tumor tissue in addition to improved relaxivities.

Gold nanoparticles bifunctionalized by chemiluminescence reagent and catalyst metal complexes: synthesis and unique chemiluminescence property

Despite much progress in functionalized gold nanomaterial (GNMs), chemiluminescent (CL) functionalized GNMs with high CL efficiency are far from fully developed. In this work, we report a general strategy for the synthesis of gold nanoparticles (GNPs) bifunctionalized by CL reagent and catalyst metal complexes (BF-GNPs) by taking N-(aminobutyl)-N-(ethylisoluminol) (ABEI) as a model of CL reagents. The complexes of 2-[bis[2-[carboxymethyl-[2-oxo-2-(2-sulfanylethylamino)ethyl]amino]ethyl]amino]acetic acid (DTDTPA) with various metal ions, including Co(2+), Cu(2+), Pb(2+), Ni(2+), Hg(2+), Cr(3+), Eu(3+), La(3+), Gd(3+), Sm(3+), Er(3+), Dy(3+), Ce(4+), and Ce(3+), were grafted on the surface of ABEI functionalized GNPs (ABEI-GNPs) to form a series of BF-GNPs. These BF-GNPs exhibited excellent CL activity. In particular, the CL intensity of DTDTPA/Co(2+)-ABEI-GNPs was over 3 orders of magnitude higher than ABEI-GNPs. This work demonstrates for the first time that metal complexes grafted on the surface of GNPs have unique catalytic activity on the CL reaction, superior to that in the liquid phase. Such BF-GNPs may find future applications in bioassays, microchips, and molecular/cellular imaging.

The In Vivo Radiosensitizing Effect of Gold Nanoparticles Based MRI Contrast Agents

Owing to the high atomic number (Z) of gold element, the gold nanoparticles appear as very promising radiosensitizing agents. This character can be exploited for improving the selectivity of radiotherapy. However, such an improvement is possible only if irradiation is performed when the gold content is high in the tumor and low in the surrounding healthy tissue. As a result, the beneficial action of irradiation (the eradication of the tumor) should occur while the deleterious side effects of radiotherapy should be limited by sparing the healthy tissue. The location of the radiosensitizers is therefore required to initiate the radiotherapy. Designing gold nanoparticles for monitoring their distribution by magnetic resonance imaging (MRI) is an asset due to the high resolution of MRI which permits the accurate location of particles and therefore the determination of the optimal time for the irradiation. We recently demonstrated that ultrasmall gold nanoparticles coated by gadolinium chelates (Au@DTDTPA-Gd) can be followed up by MRI after intravenous injection. Herein, Au@DTDTPA and Au@DTDTPA-Gd were prepared in order to evaluate their potential for radiosensitization. Comet assays and in vivo experiments suggest that these particles appear well suited for improving the selectivity of the radiotherapy. The dose which is used for inducing similar levels of DNA alteration is divided by two when cells are incubated with the gold nanoparticles prior to the irradiation. Moreover, the increase in the lifespan of tumor bearing rats is more important when the irradiation is performed after the injection of the gold nanoparticles. In the case of treatment of rats with a brain tumor (9L gliosarcoma, a radio-resistant tumor in a radiosensitive organ), the delay between the intravenous injection and the irradiation was determined by MRI.

Synthesis and characterization of functional multicomponent nanosized gallium chelated gold crystals

Multicomponent nanomaterials containing Au, Ga, and a biomolecule have been synthesized. Compositional analysis of these nanoparticles was performed by using STEM-HAADF and EELS spectroscopy.

Synthesis, Characterization, In Vitro Phantom Imaging, and Cytotoxicity of A Novel Graphene-Based Multimodal Magnetic Resonance Imaging - X-Ray Computed Tomography Contrast Agent

Graphene nanoplatelets (GNPs), synthesized using potassium permanganate-based oxidation and exfoliation followed by reduction with hydroiodic acid (rGNP-HI), have intercalated manganese ions within the graphene sheets, and upon functionalization with iodine, show excellent potential as biomodal contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT). Structural characterization of rGNP-HI nanoparticles with low- and high-resolution transmission electron microscope (TEM) showed disc-shaped nanoparticles (average diameter, 200 nm, average thickness, 3 nm). Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of intercalated manganese. Raman spectroscopy and X-ray diffraction (XRD) analysis of rGNP-HI confirmed the reduction of oxidized GNPs (O-GNPs), absence of molecular and physically adsorbed iodine, and the functionalization of graphene with iodine as polyiodide complexes (I₃^- and I₅^-). Manganese and iodine content were quantified as 5.1 ± 0.5 and 10.54 ± 0.87 wt% by inductively-coupled plasma optical emission spectroscopy and ion-selective electrode measurements, respectively. In vitro cytotoxicity analysis, using absorbance (LDH assay) and fluorescence (calcein AM) based assays, performed on NIH3T3 mouse fibroblasts and A498 human kidney epithelial cells, showed CD₅₀ values of rGNP-HI between 179-301 µg/ml, depending on the cell line and the cytotoxicity assay. CT and MRI phantom imaging of rGNP-HI showed high CT (approximately 3200% greater than HI at equimolar iodine concentration) and MRI (approximately 59% greater than equimolar Mn²⁺ solution) contrast. These results open avenues for further in vivo safety and efficacy studies towards the development of carbon nanostructure-based multimodal MRI-CT contrast agents.

Biocompatible folate-modified Gd3+/Yb3+-doped ZnO nanoparticles for dualmodal MRI/CT imaging

Folate-modified ZnO:Gd,Yb nanoprobes with good stability and biocompatibility can efficiently induce positive contrast enhancement in T₁-weighted MRI and CT imaging.

A 5-(difluorenyl)-1,10-phenanthroline-based Ru(ii) complex as a coating agent for potential multifunctional gold nanoparticles

The photophysical properties of new gold nanoparticles surface functionalized by substituted-1,10-phenanthroline-ligand based Ru(ii) complexes are described. Nonlinear optical properties were determinedviaZ-scan measurements between 600 and 1300 nm and applications can be anticipated.

Highly stable intrinsically radiolabeled indium-111 quantum dots with multidentate zwitterionic surface coating: dual modality tool for biological imaging

A highly stable bimodal indium(111) radiolabeled indium QDs were synthesized for in vivo SPECT/fluorescence imaging.

Multicolor computed tomographic molecular imaging with noncrystalline high-metal-density nanobeacons

Computed tomography (CT) is one of the most frequently pursued radiology technologies applied in the clinics today and in the preclinical field of biomedical imaging. Myriad advances have been made to make this technique more powerful with improved signal sensitivity, rapid image acquisition and faster reconstruction. Synergistic development of novel nanoparticles has been adopted to produce the next-generation CT contrasts agents for imaging specific biological markers. Nanometer-sized agents are anticipated to play a critical part in the prospect of medical diagnostics owing to their capabilities of targeting specific biological markers, extended blood circulation time and defined biological clearance. This review paper introduces the readers to the fundamental design principles of nanoparticulate CT contrast agents with a special emphasis on molecular imaging with noncrystalline high-metal-density nanobeacons.