T2-weighted Magnetic Resonance Imaging Contrast Agents Research Articles

Holmium (III)-doped multifunctional nanotheranostic agent for ultra-high-field magnetic resonance imaging-guided chemo-photothermal tumor therapy

Ultra-high-field (UHF) MRI has shown great advantages over low-field magnetic resonance imaging (MRI). Despite being the most commonly used MRI contrast agents, gadolinium chelates perform poorly in high magnetic fields, which significantly weakens their T1 intensity. In comparison, the rare element Holmium (Ho)-based nanoparticles (NPs) have demonstrated great potential as T2-weighted MRI contrast agents in UHF MRI due to their extremely short electron relaxation times (∼ 10−13s). In this study, a multifunctional nanotherapeutic probe was designed for UHF MRI-guided chemotherapy and photothermal therapy. The Ho (III)-doped mesoporous polydopamine (Ho-MPDA, HM) nanosphere was loaded with the chemotherapeutic drug mitoxantrone (MTO) and then coated with 4T1 cell membranes to enhance active targeting delivery to breast cancer. The prepared nanotherapeutic probe MTO@HMM@4T1 (HMM@T) exhibited good biocompatibility, high drug-loading capability and great potential as Ho (III)-based UHF MRI contrast agents. Moreover, the biodegradation of HMM@T in response to the intratumor pH and glutathione (GSH) promotes MTO release. Near-infrared (NIR) light irradiation of HM induced photothermal therapy and further enhanced drug release. Consequently, HMM@T effectively acted as an MRI-guided tumor-targeting chemo-photothermal therapy against 4T1 breast cancer. Statement of significanceUltra-high-field (UHF) MRI has shown great advantages over low-field magnetic resonance imaging (MRI). Although gadolinium chelates are the most commonly used MRI contrast agents in clinical practice, they exhibit a significantly decreased T1 relaxivity at UHF. Holmium exhibits outstanding UHF magnetic resonance capabilities in comparison with gadolinium chelates currently used in clinic. Herein, a theranostic nanodrug (HMM@T) was designed for UHF MRI-guided chemo-photothermal therapy. The nanodrug possessed remarkable UHF T2 MRI properties (r2 = 152.13 mM−1s−1) and high drug loading capability of 18.4 %. The biodegradation of HMM@T NPs under triple stimulations of pH, GSH, and NIR led to an efficient release of MTO in tumor microenvironment. Our results revealed the potential of a novel UHF MRI-guided multifunctional nanosystem in cancer treatment.

Theranostic Applications of an Ultra-Sensitive T1 and T2 Magnetic Resonance Contrast Agent Based on Cobalt Ferrite Spinel Nanoparticles.

Simple SummaryMagnetic nanoparticles (MNPs) represent an important class of nanomaterials that has been actively employed in multiple technological applications. The MNPs and their based composites have been intensively developed for magnetic resonance imaging, targeted drug delivery, magnetic hyperthermia, and other applications. Magnetic Resonance Imaging (MRI) has a prominent position among clinical imaging modalities as it allows for high spatial resolution and tissue specificity without harmful ionizing radiation. The aim of the study was the demonstration of the potential use of magnetic nanoparticles based on cobalt ferrite spinel as advanced MRI contrast agents that are capable of both T1-weighted positive and T2-weighted negative contrast enhancements in vitro and in vivo. Furthermore, in the present study, we combined novel physical, chemical, and biomedical approaches to develop a multifunctional MRI-detectable drug delivery system that was an efficient T1- and T2-weighted MRI contrast agent and a nanocarrier for targeted drug delivery in vivo.Nano-dimensional materials have become a focus of multiple clinical applications due to their unique physicochemical properties. Magnetic nanoparticles represent an important class of nanomaterials that are widely studied for use as magnetic resonance (MR) contrast and drug delivery agents, especially as they can be detected and manipulated remotely. Using magnetic cobalt ferrite spinel (MCFS) nanoparticles, this study was aimed at developing a multifunctional drug delivery platform with MRI capability for use in cancer treatment. We found that MCFS nanoparticles demonstrated outstanding properties for contrast MRI (r1 = 22.1 s–1mM–1 and r2 = 499 s–1mM–1) that enabled high-resolution T1- and T2-weighted MRI-based signal detection. Furthermore, MCFS nanoparticles were used for the development of a multifunctional targeted drug delivery platform for cancer treatment that is concurrently empowered with the MR contrast properties. Their therapeutic effect in systemic chemotherapy and unique MRI double-contrast properties were confirmed in vivo using a breast cancer mouse tumor model. Our study thus provides an empirical basis for the development of a novel multimodal composite drug delivery system for anticancer therapy combined with noninvasive MRI capability.

Nanomagnetic hydrogel based on chitosan, hyaluronic acid, and glucose oxidase as a nanotheranostic platform for simultaneous therapeutic and imaging applications

Theranostic platform including therapeutic agent and diagnostics factor is of great interest in the current cancer treatment research. In this study, we constructed a pH-responsive nanomagnetic hydrogel based on chitosan, hyaluronic acid, and glucose oxidase (NMH-CsHA-GOx) as a platform, which represents good performance both as a nanomedicine and as a dual-modal magnetic resonance imaging (MRI) contrast agent. The NMH-CsHA-GOx is a hybrid catalyst that catalyzes a cascade reaction that results in the production of hydroxyl radicals. This leads to the apoptosis and death of cancer cells under the mildly acidic TME. Moreover, the ultrasmall superparamagnetic Fe3O4 NPs act as the T1-weighted and T2-weighted (dual-modal) MRI contrast agents that can be used to identify the cancer cells. The r1 = 6.37, r2 = 27.07/mM/s, and r2/r1 ratio were obtained from MRI relaxivity measurements. The NMH-CsHA-GOx was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). The morphology of the hydrogel and nanomagnetic hydrogel were characterized by Field emission scanning electron microscopy (FESEM). The size and distribution of Fe3O4NPs were studied by Transmission electron microscopy (TEM) and X-ray elemental mapping, respectively. The analysis confirmed the very small size of the Fe3O4 NPs (5–12 nm), which were dispersed uniformly. The NMH-CsHA-GOx represents high selectivity between normal cells (L929 mouse fibroblast cell line) and tumor cells (MCF-7 breast cancer cell line). The pH-sensitive NMH-CsHA-GOx, can produce a controlled amount of hydroxyl radical under the mildly acidic TME.

Fabricating Dual-Functional Plasmonic-Magnetic Au@MgFe2O4 Nanohybrids for Photothermal Therapy and Magnetic Resonance Imaging.

Bifunctional nanohybrids possessing both plasmonic and magnetic functionalities are of great interest for biomedical applications owing to their capability for simultaneous therapy and diagnostics. Herein, we fabricate a core–shell structured plasmonic–magnetic nanocomposite system that can serve as a dual-functional agent due to its combined photothermal therapeutic and magnetic resonance imaging (MRI) functions. The photothermal activity of the hybrid is attributed to its plasmonic Au core, which is capable of absorbing near-infrared (NIR) light and converting it into heat. Meanwhile, the magnetic MgFe2O4 shell exerts its ability to act as a MRI contrast agent. Our in vivo studies using tumor-bearing mice demonstrated the nanohybrids’ excellent photothermal and MRI properties. As a photothermal therapeutic agent, the nanohybrids were able to dramatically shrink solid tumors in mice through NIR-induced hyperthermia. As T2-weighted MRI contrast agents, the nanohybrids were found capable of substantially reducing the MRI signal intensity of the tumor region at 10 min postinjection. With their dual plasmonic–magnetic functionality, these Au@MgFe2O4 nanohybrids hold great promise not only in the biomedical field but also in the areas of catalysis and optical sensing.

Atomically precise multi-domain GdxFe3−xO4 nanoclusters with modulated contrast properties for T2-weighted magnetic resonance imaging of early orthotopic cancer

The use of multi-domain magnetic iron oxide nanoclusters (MMIONs) as Magnetic resonance imaging (MRI) contrast agent is facing problems of strong ferromagnetism and thus weak T2 contrast ability. The doping of Gd ions holds potential to solve these problems by reducing ferromagnetism and enhancing transverse relaxivity (r2), but the exact role of doping in modulating the contrast properties remain unknown. Herein, we prepared a series of atomically precise GdxFe3−xO4 nanoclusters and systematically explored the effect of Gd doping on tuning their morphology, magnetic property, and r2 value. After the doping of Gd ions, the specific surface area of GdxFe3−xO4 nanoclusters significantly increased, and meanwhile, the magnetic property of GdxFe3-xO4 nanoclusters transformed from ferromagnetism to superparamagnetism, which led to stronger T2 contrast. Specifically, the highest r2 value was obtained at 488 mM−1s−1 (7.0 T) for Gd0.072Fe2.928O4 nanocluster, four times higher than that for pristine Fe3O4 (110 mM−1s−1). For potential applications, we validated the outstanding contrast of Gd0.018Fe2.982O4 nanocluster (r2 = 481 mM−1s−1 at 7.0 T) to diagnose early orthotopic cancer in mice. This work opens up a new avenue for the development of atomically precise Gd-doped MMIONs as efficient T2-weighted MRI contrast agents.

Hetero-Trifunctional Malonate-Based Nanotheranostic System for Targeted Breast Cancer Therapy.

Designing multifunctional linkers is crucial for tricomponent theranostic targeted nanomedicine development as they are essential to enrich polymeric systems with different functional moieties. Herein, we have obtained a hetero-trifunctional linker from malonic acid and demonstrated its implication as an amphiphilic targeted nanotheranostic system (CB DX UN PG FL). We synthesized it with varying hydrophilic segment to fine-tune the hydrophobic/hydrophilic ratio to optimize its self-assembly. pH-responsive hydrazone-linked doxorubicin was conjugated to the backbone (UN PG FL) containing folate as a targeting ligand. Cobalt carbonyl complex was used for T2-weighted magnetic resonance imaging (MRI). Electron micrographs of optimized molecule CB DX UN PG(4kDa)FL in an aqueous system have demonstrated about 50-60 nm-sized uniform micelles. The relaxivity study and the one-dimensional (1D) imaging experiments clearly revealed the effect of the nanotheranostics system on transverse relaxation (T2) of water molecules, which validated the system as a T2-weighted MRI contrast agent. The detailed in vitro biological studies validated the targeted delivery and anticancer potential of CB DX UN PG(4kDa)FL. Combining the data on transverse relaxation, folate mediated uptake, and anticancer activity, the designed molecule will have a significant impact on the development of targeted theranostic.

Preparation of Nano Materials Fe@Fe3O4 and Its Application in Magnetic Resonance Imaging for Liver Functions

The strengths of magnetic resonance imaging (MRI) lied in the strong penetrability, high resolution, no radiation, and non-invasion, while the sensitivity of MRI was too weak to distinguish the normal physiological tissue and pathological tissue. The contrast agent (CAs) was used to enhance the contrast ration of normal tissue and pathological tissue, and raise the precision of the diagnosis. The Ferric oxide with higher magnetic moment has been extensively applied in T2-weighted MRI contrast agents. In the study, the oil soluble nano materials (Fe@Fe3O4) was prepared, and its surface was modified using the large and small molecule ligands, and it was connected to F56 peptide, so as to construct the MRI-specific bimodal contrast agent (Fe–Fe NPs/HYA/F56). While the material was characterized, it can be used in clinical evaluation of liver functions. In the test, as the clad material was growing, the saturation magnetization of the material encountered a drop. The nano particle (Fe@Fe3O4) was modified with functional groups, and no obvious variation occurred to its structure and particle size. The morphology and potential were analyzed to confirm whether F56 peptide was connected to the nano particle (Fe@Fe3O4). The analysis of cell showed that the nano particle (Fe–Fe NPs/HYA/F56) had lower cytotoxicity, and the materials had better targeted performance, which had been verified in the mouse tumor model. The preparation materials were applied in evaluation of clinical studies on liver function. The quantitative analysis of the absolute enhancement value (AEV) and contrast enhancement rate (CER) of liver around the MRI-enhanced cancer was conducted. The results showed, the pathology grade of liver functions (pathological tissue and cirrhotic tissue) was related to the above indicators. The MRI contrast agent can be used to predict the pathology grade.

Holmium phosphate nanoparticles as negative contrast agents for high-field magnetic resonance imaging: Synthesis, magnetic relaxivity study and in vivo evaluation

The increasing use of high magnetic fields in magnetic resonance imaging (MRI) scanners demands new contrast agents, since those used in low field instruments are not effective at high fields. In this paper, we report the synthesis of a negative MRI contrast agent consisting of HoPO4 nanoparticles (NPs). Three different sizes (27 nm, 48 nm and 80 nm) of cube-shaped NPs were obtained by homogeneous precipitation in polyol medium and then coated with poly(acrylic) acid (PAA) to obtain stable colloidal suspensions of HoPO4@PAA NPs in physiological medium (PBS). The transverse relaxivity (r2) of aqueous suspensions of the resulting NPs was evaluated at both 1.44 T and 9.4 T. A positive correlation between r2 values and field strength as well as between r2 values and particle size at both magnetic field strengths was found although this correlation failed for the biggest NPs at 9.4 T, likely due to certain particles aggregation inside the magnet. The highest r2 value (489.91 mM-1s−1) was found for the 48 nm NPs at 9.4 T. Toxicity studies demonstrated that the latter NPs exhibited low toxicity to living systems. Finally, in vivo studies demonstrated that HoPO4@PAA NPs could be a great platform for next-generation T2-weighted MRI contrast agents at high magnetic field.

Manganese–Fluorouracil Metallodrug Nanotheranostic for MRI-Correlated Drug Release and Enhanced Chemoradiotherapy

For cancer therapy, drug delivery systems are often limited by insufficient drug loading capacity, which usually results in systemic toxicity and heavy metabolic burden to excrete the carriers. Her...

Microwave-Assisted Synthesis of SPION-Reduced Graphene Oxide Hybrids for Magnetic Resonance Imaging (MRI).

Magnetic resonance imaging (MRI) is a useful tool for disease diagnosis and treatment monitoring. Superparamagnetic iron oxide nanoparticles (SPION) show good performance as transverse relaxation (T2) contrast agents, thus facilitating the interpretation of the acquired images. Attachment of SPION onto nanocarriers prevents their agglomeration, improving the circulation time and efficiency. Graphene derivatives, such as graphene oxide (GO) and reduced graphene oxide (RGO), are appealing nanocarriers since they have both high surface area and functional moieties that make them ideal substrates for the attachment of nanoparticles. We have employed a fast, simple and environmentally friendly microwave-assisted approach for the synthesis of SPION-RGO hybrids. Different iron precursor/GO ratios were used leading to SPION, with a median diameter of 7.1 nm, homogeneously distributed along the RGO surface. Good relaxivity (r2*) values were obtained in MRI studies and no significant toxicity was detected within in vitro tests following GL261 glioma and J774 macrophage-like cells for 24 h with SPION-RGO, demonstrating the applicability of the hybrids as T2-weighted MRI contrast agents.

SPIO-loaded nanostructured lipid carriers as liver-targeted molecular T2-weighted MRI contrast agent.

Superparamagnetic iron oxide (SPIO) acts as a negative contrast agent in magnetic resonance imaging (MRI), and is widely used in clinical applications, including the diagnosis of hepatic diseases. Hepatocyte-targeted magnetic resonance contrast agents (MRCAs) can provide useful information for evaluating hepatic diseases. We prepared targeted magnetic nanostructured lipid carriers (MNLCs) to enhance the hepatocytes targeting efficiency. In vitro characterizations of MNLCs were determined by transmission electron microscopy (TEM). The cytotoxicity assay of the MNLCs was measured by methyl tetrazolium (MTT) method. The uptaken study was measured by confocal microscopy, flow cytometry and MRI in vitro. The enhanced liver-targeting efficiency of MNLCs was measured by fluorescence imaging and MRI in vivo. Gal-NLC-SPIO was prepared successfully. The cytotoxicity assay of the MNLCs demonstrated that the MNLC had relatively low cytotoxicity and high biocompatibility for LO2 cells. More importantly, we confirmed that Gal-NLC-SPIO had greater uptake by LO2 cells than Gal-NLC-SPIO/PEG and free Gal in vitro. A liver distribution study of MNLCs in normal mice demonstrated that the fluorescent signal values to livers of the Gal-NLC-SPIO were significantly stronger than those of NLC-SPIO and Gal-NLC-SPIO/PEG. The liver targeting efficiency of Gal-NLC-SPIO was confirmed both in vitro and in vivo. We successfully developed liver-targeting MNLCs, which showed accurate hepatocytes targeting, and thus have the potential to be a new MRI contrast agent to help the diagnosis of liver diseases.

One-step preparation of nano-in-micro poly(vinyl alcohol) embolic microspheres and used for dual-modal T1/T2-weighted magnetic resonance imaging

It is crucial to develop dual or multi-modal self-imaging embolic microspheres to evaluate the effects of transcatheter arterial embolization therapy of tumor. However, the preparation of such hybrid microspheres always involved in multiple steps or complicated conditions. Here, poly(vinyl alcohol) (PVA) hybrid microspheres with dual-modal T1/T2-weighted magnetic resonance imaging (MRI) have been prepared based on microfluidic technique in one step. Gd2O3 and Fe3O4 nanoparticles with a size of ~5 nm act as T1- and T2-weighted MRI contrast agents, respectively, which are simultaneously in-situ synthesized in the PVA matrix via the reaction of metal ions and alkali with PVA chains as a soft template. Meanwhile, these metallic-oxide nanoparticles act as cross-linker to gelatinize the PVA droplets to obtain nano-in-micro PVA microspheres in one step. This procedure is simple, economic and feasible. The obtained nano-in-micro PVA microspheres show good magnetothermal effect, enhanced T1- and T2-weighted MRI and embolization effect.

Ru nanoparticles coated with γ-Fe2O3 promoting and monitoring the differentiation of human mesenchymal stem cells via MRI tracking.

Human mesenchymal stem cells (MSCs) can be successively passaged and can differentiate into multiple lineages. These attributes are important in tissue engineering, which has a great deal of attention in stem cell therapy. However, the effective labelling and tracking of MSCs in vivo remain major unresolved issues. Based on the use of iron oxides to label stem cells for magnetic resonance imaging (MRI), we synthesized nanoparticle (NPs) containing ruthenium (RuNPs), γ-Fe2O3@Ru (Fe2O3@Ru), and γ-Fe2O3@selenium (Fe2O3@Se) to label MSCs and promote osteogenic differentiation. Fe2O3@Ru and Fe2O3@Se could be used as T2-weighted MRI contrast agents. Fe2O3@Ru more effectively diffused in the cytoplasm and localized in the nuclei of MSCs, compared with Fe2O3@Se. RuNPs, Fe2O3@Ru, and Fe2O3@Se induced MSCs to differentiate into osteoblasts. Fe2O3@Ru, in particular, was a potent osteoinductive agent. Fe2O3@Ru also inhibited adipocytic differentiation. Promotion of the osteogenic differentiation of MSCs may be regulated by a Smad-dependent bone morphogenetic protein signaling pathway with reduced expression of CD44, CD73, and CD105. MSCs treated with Fe2O3@Ru NPs expressing osteoblast surface markers.

T2-Weighted Magnetic Resonance Imaging of Hepatic Tumor Guided by SPIO-Loaded Nanostructured Lipid Carriers and Ferritin Reporter Genes.

Nowadays, there is a high demand for supersensitive contrast agents for the early diagnostics of hepatocarcinoma. It has been recognized that accurate imaging information is able to be achieved by constructing hepatic tumor specific targeting probes, though it still faces challenges. Here, a AGKGTPSLETTP peptide (A54)-functionalized superparamagnetic iron oxide (SPIO)-loaded nanostructured lipid carrier (A54-SNLC), which can be specifically uptaken by hepatoma carcinoma cell (Bel-7402) and exhibited ultralow imaging signal intensity with varied Fe concentration on T2-weighted imaging (T2WI), was first prepared as an effective gene carrier. Then, an endogenous ferritin reporter gene for magnetic resonance imaging (MRI) with tumor-specific promoter (AFP-promoter) was designed, which can also exhibit a decrease in signal intensity on T2WI. At last, using protamine as a cationic mediator, novel ternary nanoparticle of A54-SNLC/protamine/DNA (A54-SNPD) as an active dual-target T2-weighted MRI contrast agent for imaging hepatic tumor was achieved. Owing to the synergistic effect of A54-SNLC and AFP-promoted DNA targeting with Bel-7402 cells, T2 imaging intensity values of hepatic tumors were successfully decreased via the T2 contrast enhancement of ternary nanoparticles. It is emphasized that the novel A54-SNPD ternary nanoparticle as active dual-target T2-weighted MRI contrast agent were able to greatly increase the diagnostic sensitivity and specificity of hepatic cancer.

TbF3 nanoparticles as dual-mode contrast agents for ultrahigh field magnetic resonance imaging and X-ray computed tomography

Considering the development of magnetic resonance imaging (MRI) under ultrahigh magnetic field (>3 T), the exploration of novel contrast agents (CAs) for ultrahigh field MRI is urgently needed. Herein, we report polyethyleneimine (PEI)-coated TbF3 nanoparticles (NPs), which were synthesized by a facile solvothermal method, as potential dual-mode CAs for ultrahigh field MRI and X-ray computed tomography (CT). Owing to their strong paramagnetism, the TbF3 NPs showed excellent transverse relaxivity (395.77 mM–1·s–1) and negligible longitudinal relaxivity under an ultrahigh magnetic field (7 T) with a great potential as a T 2-weighted MRI contrast agent. Furthermore, by comparison with the clinically used CT CAs (iohexol), the TbF3 NPs showed superior X-ray attenuation ability. The practical application for T 2-weighted MRI and CT imaging was demonstrated with an animal model. Moreover, cell cytotoxicity and in vivo toxicity assessments implied the low toxicity of TbF3 NPs. In summary, the above results indicate that TbF3 NPs are promising candidates for ultrahigh field MRI and CT dual-mode imaging.

Superstable Magnetic Nanoparticles in Conjugation with Near-Infrared Dye as a Multimodal Theranostic Platform.

Near-infrared (NIR) dyes functionalized magnetic nanoparticles (MNPs) have been widely applied in magnetic resonance imaging (MRI), NIR fluorescence imaging, drug delivery, and magnetic hyperthermia. However, the stability of MNPs and NIR dyes in water is a key problem to be solved for long-term application. In this study, a kind of superstable iron oxide nanoparticles was synthesized by a facile way, which can be used as T1 and T2 weighted MRI contrast agent. IR820 was grafted onto the surface of nanoparticles by 6-amino hexanoic acid to form IR820-CSQ-Fe conjugates. Attached IR820 showed increased stability in water at least for three months and an enhanced ability of singlet oxygen production of almost double that of free dyes, which will improve its efficiency for photodynamic therapy. Meanwhile, the multispectral optoacoustic tomography (MSOT) and NIR imaging ability of IR820-CSQ-Fe will greatly increase the accuracy of disease detection. All of these features will broaden the application of this material as a multimodal theranostic platform.

Theranostic Application of Mixed Gold and Superparamagnetic Iron Oxide Nanoparticle Micelles in Glioblastoma Multiforme.

The treatment of glioblastoma multiforme, the most prevalent and lethal form of brain cancer in humans, has been limited in part by poor delivery of drugs through the blood-brain barrier and by unclear delineation of the extent of infiltrating tumor margins. Nanoparticles, which selectively accumulate in tumor tissue due to their leaky vasculature and the enhanced permeability and retention effect, have shown promise as both therapeutic and diagnostic agents for brain tumors. In particular, superparamagnetic iron oxide nanoparticles (SPIONs) have been leveraged as T2-weighted MRI contrast agents for tumor detection and imaging; and gold nanoparticles (AuNP) have been demonstrated as radiosensitizers capable of propagating electron and free radical-induced radiation damage to tumor cells. In this study, we investigated the potential applications of novel gold and SPION-loaded micelles (GSMs) coated by polyethylene glycol-polycaprolactone (PEG-PCL) polymer. By quantifying gh2ax DNA damage foci in glioblastoma cell lines, we tested the radiosensitizing efficacy of these GSMs, and found that GSM administration in conjunction with radiation therapy (RT) led to ~2-fold increase in density of double-stranded DNA breaks. For imaging, we used GSMs as a contrast agent for both computed tomography (CT) and magnetic resonance imaging (MRI) studies of stereotactically implanted GBM tumors in a mouse model, and found that MRI but not CT was sufficiently sensitive to detect and delineate tumor borders after administration and accumulation of GSMs. These results suggest that with further development and testing, GSMs may potentially be integrated into both imaging and treatment of brain tumors, serving a theranostic purpose as both an MRI-based contrast agent and a radiosensitizer.

Gd-doped BNNTs as T2-weighted MRI contrast agents

This work describes, for the first time, doping of boron nitride nanotubes (BNNTs) with gadolinium (Gd@BNNTs), a stable functionalization that permits non-invasive BNNT tracking via magnetic resonance imaging (MRI). We report the structure, Gd loading, and relaxometric properties in water suspension at 7 T of Gd@BNNTs, and show the behaviour of these nanostructures as promising T2-weighted contrast agents. Finally, we demonstrate their complete biocompatibility in vitro on human neuroblastoma cells, together with their ability to effectively label and affect contrast in MRI images at 7 T.

Magnetic PEGylated Pt3Co nanoparticles as a novel MR contrast agent: in vivo MR imaging and long-term toxicity study

Magnetic resonance (MR) imaging using magnetic nanoparticles as the contrast agent has been extensively explored in biomedical imaging and disease diagnosis. Herein, we develop biocompatible polymer coated ultra-small Pt3Co magnetic nanoparticles as a new T2-weighted MR imaging contrast agent. A unique class of alloy Pt3Co nanoparticles is synthesized through a thermal decomposition method. After being modified with polyethylene glycol (PEG), the obtained Pt3Co-PEG nanoparticles exhibit an extremely high T2-weighted relaxivity rate (r2) up to 451.2 mM s(-1), which is much higher than that of Resovist®, a commercial T2-MR contrast agent used in the clinic. In vitro experiments indicate no obvious cytotoxicity of Pt3Co-PEG nanoparticles to various cell lines. After intravenous injection of Pt3Co-PEG nanoparticles, in vivo T2-weighted MR imaging of tumor-bearing mice reveals strong tumor contrast, which is much higher than that offered by injecting Resovist®. We further study the long-term biodistribution and toxicology of this new type of MR contrast nanoparticles after intravenous injection into healthy mice. Despite the significant retention of Pt3Co-PEG nanoparticles in the mouse liver and spleen, no appreciable toxicity of these nanoparticles to the treated animals has been noted in our detailed histological and hematological analysis over a course of 60 days. Our work demonstrates that functionalized Pt3Co nanoparticles may be a promising new type of T2-weighted MR contrast agent potentially useful in biomedical imaging and diagnosis.

Synthesis of water-soluble FeOOH nanospindles and their performance for magnetic resonance imaging

Water soluble FeOOH nanospindles with small size were synthesized by a simple hydrolysis method of inorganic salts and water bath treatment with different incubation time. The morphology, microstructure, magnetic resonance imaging (MRI) performance and cytotoxicity of the as-prepared FeOOH nanospindles were investigated, respectively. The results showed that the longitudinal length of FeOOH nanospindles was about 40–50nm, and the incubation time had important effect for the morphology and production rate of FeOOH nanospindles. MRI test showed that the longitudinal and transverse relaxivities (r1 and r2 values) of FeOOH nanospindles were about 3.06mM−1s−1 and 5.06mM−1s−1, respectively. Furthermore, the experimental results of the Prussian Blue staining showed the clusters of FeOOH nanospindles in the cytoplasm of the labeled cells, and the cytotoxicity characterization indicated that FeOOH nanospindles have low cytotoxicity. Therefore, the as-prepared FeOOH nanospindles will have potential applications as T1- and T2-weighted MRI contrast agents.