Carbon nanotubes (CNTs) have been used for a plethora of biomedical applications, including their use as delivery vehicles for drugs, imaging agents, proteins, DNA, and other materials. Here, we describe the synthesis and characterization of a new CNT-based contrast agent (CA) for X-ray computed tomography (CT) imaging. The CA is a hybrid material derived from ultrashort single-walled carbon nanotubes (20–80 nm long, US-tubes) and Bi(III) oxo-salicylate clusters with four Bi(III) ions per cluster (Bi4C). The element bismuth was chosen over iodine, which is the conventional element used for CT CAs in the clinic today due to its high X-ray attenuation capability and its low toxicity, which makes bismuth a more-promising element for new CT CA design. The new CA contains 20% by weight bismuth with no detectable release of bismuth after a 48 h challenge by various biological media at 37 °C, demonstrating the presence of a strong interaction between the two components of the hybrid material. The performance of the new Bi4C@US-tubes solid material as a CT CA has been assessed using a clinical scanner and found to possess an X-ray attenuation ability of >2000 Hounsfield units (HU).Keywords: bismuth; carbon nanotubes; radiocontrast agent; X-ray CT;

Over the past few years, numerous nanotechnology-based drug delivery systems have been developed in an effort to maximize therapeutic effectiveness of conventional drug delivery, while limiting undesirable side effects. Among these, carbon nanotubes (CNTs) are of special interest as potential drug delivery agents due to their numerous unique and advantageous physical and chemical properties. Here, we show in vivo favorable biodistribution and enhanced therapeutic efficacy of cisplatin (CDDP) encapsulated within ultra-short single-walled carbon nanotube capsules (CDDP@US-tubes) using three different human breast cancer xenograft models. In general, the CDDP@US-tubes demonstrated greater efficacy in suppressing tumor growth than free CDDP in both MCF-7 cell line xenograft and BCM-4272 patient-derived xenograft (PDX) models. The CDDP@US-tubes also demonstrated a prolonged circulation time compared to free CDDP which enhanced permeability and retention (EPR) effects resulting in significantly more CDDP accumulation in tumors, as determined by platinum (Pt) analysis via inductively-coupled plasma mass spectrometry (ICP-MS).Statement of SignificanceOver the past decade, drug-loaded nanocarriers have been widely fabricated and studied to enhance tumor specific delivery. Among the diverse classes of nanomaterials, carbon nanotubes (CNTs), or more specifically ultra-short single-walled carbon nanocapsules (US-tubes), have been shown to be a popular, new platform for the delivery of various medical agents for both imaging and therapeutic purposes. Here, for the first time, we have shown that US-tubes can be utilized as a drug delivery platform in vivo to deliver the chemotherapeutic drug, cisplatin (CDDP) as CDDP@US-tubes. The studies have demonstrated the ability of the US-tube platform to promote the delivery of encapsulated CDDP by increasing the accumulation of drug in breast cancer resistance cells, which reveals how CDDP@US-tubes help overcome CDDP resistance.Download high-res image (217KB)Download full-size image

There is an ever increasing interest in developing new stem cell therapies. However, imaging and tracking stem cells in vivo after transplantation remains a serious challenge. In this work, we report new, functionalized and high-performance Gd3+-ion-containing ultra-short carbon nanotube (US-tube) MRI contrast agent (CA) materials which are highly-water-dispersible (ca. 35 mg ml−1) without the need of a surfactant. The new materials have extremely high T1-weighted relaxivities of 90 (mM s)−1 per Gd3+ ion at 1.5 T at room temperature and have been used to safely label porcine bone-marrow-derived mesenchymal stem cells for MR imaging. The labeled cells display excellent image contrast in phantom imaging experiments, and TEM images of the labeled cells, in general, reveal small clusters of the CA material located within the cytoplasm with 109 Gd3+ ions per cell.

Magnetic resonance imaging (MRI) is of vast clinical utility, with tens of millions of scans performed annually. Chemical contrast agents (CAs) can greatly enhance the diagnostic potential of MRI, and ∼50% of MRI scans use CAs. However, CAs have significant limitations such as low contrast enhancement, lack of specificity, and potential toxicity. Recently developed, Gd3+-loaded ultrashort single-walled carbon nanotubes, also referred to as gadonanotubes or GNTs, exhibit ∼40 times the relaxivities of clinical CAs, representing a potential major advance in clinically relevant MRI CA materials. Although initial cytotoxicity and MRI studies have suggested great promise for GNTs, relatively little is known regarding their subcellular interactions, which are crucial for further, safe development of GNTs as CAs. In this work, we administered GNTs to a well-established human cell line (HeLa) and to murine macrophage-like cells (J774A.1). GNTs were not acutely cytotoxic and did not reduce proliferation, except for the highest exposure concentration of 27 μg/mL for J774A.1 macrophages, yet bulk uptake of GNTs occurred in minutes at picogram quantities, or millions of GNTs per cell. J774A.1 macrophages internalized substantially more GNTs than HeLa cells in a dose-dependent manner, and Raman imaging of the subcellular distribution of GNTs revealed perinuclear localization. Fluorescence intensity and lifetime imaging demonstrated that GNTs did not grossly alter subcellular compartments, including filamentous-actin structures. Together, these results provide subcellular evidence necessary to establish GNTs as a new MRI CA material.Keywords: actin; carbon nanotubes; chemical contrast agent; gadolinium; gadonanotubes; magnetic resonance imaging; Raman spectroscopy;

The present study demonstrates that highly water-dispersed graphene nanoribbons dispersed by carboxyphenylated substituents and conjugated to aquated Gd3+ ions can serve as a high-performance contrast agent (CA) for applications in T1- and T2-weighted magnetic resonance imaging (MRI) with relaxivity (r1,2) values outperforming currently-available clinical CAs by up to 16 times for r1 and 21 times for r2.

The encapsulation of bismuth as BiOCl/Bi2O3 within ultra-short (ca. 50 nm) single-walled carbon nanocapsules (US-tubes) has been achieved. The Bi@US-tubes have been characterized by high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Bi@US-tubes have been used for intracellular labeling of pig bone marrow-derived mesenchymal stem cells (MSCs) to show high X-ray contrast in computed tomography (CT) cellular imaging for the first time. The relatively high contrast is achieved with low bismuth loading (2.66% by weight) within the US-tubes and without compromising cell viability. X-ray CT imaging of Bi@US-tubes-labeled MSCs showed a nearly two-fold increase in contrast enhancement when compared to unlabeled MSCs in a 100 kV CT clinical scanner. The CT signal enhancement from the Bi@US-tubes is 500 times greater than polymer-coated Bi2S3 nanoparticles and several-fold that of any clinical iodinated contrast agent (CA) at the same concentration. Our findings suggest that the Bi@US-tubes can be used as a potential new class of X-ray CT agent for stem cell labeling and possibly in vivo tracking.

Here we demonstrate a simple, nondestructive method for the preparation of stable aqueous colloidal solutions of graphene nanoribbons and carbon nanotubes. The method includes sonication of carbon nanomaterials in hypophosphorous acid, filtration accompanied by washing the solids with water and dispersion of the solids in a fresh portion of water to form colloidal solutions.

Multi-layer graphene nanoribbons have been made highly water soluble (4.7 mg ml−1) and stable for the first time by repetitious derivatization with p-carboxyphenyldiazonium salt; similarly, single-walled carbon nanotubes (4.8 mg ml−1) and ultra-short carbon nanotubes (50 mg ml−1) can also be made highly soluble by the methodology.

In this review, the application of the Gadonanotubes (GNTs) as high-performance magnetic resonance imaging (MRI) contrast agents (CAs) is discussed. Through published and some unpublished work, we describe how the loading and nanoscale confinement of multiple Gd3+ ions within ultra-short single-walled carbon nanotubes (US-tubes) produces GNTs with MRI efficacies 40 to 90 times greater than current clinical CAs. Since there is a continuing need to increase MRI sensitivity, the molecular factors affecting the performance of Gd3+-based CAs are described and their optimization is considered for Gd3+-based agents, in general, and the GNTs in particular. The GNTs are new (ca. 2005) high-performance nanotechnology-inspired MRI CAs with promise for advanced T1-weighted MR molecular imaging applications.Graphical abstractThe Gadonanotubes are evaluated as high-performance contrast agents, exhibiting MRI efficacies far surpassing leading clinical agents, such as Magnevist®.Highlights► Basic principles underlying the Gadonanotubes as superior T1-weighted contrast agents for MRI are discussed. ► The Gadonanotubes as a new nanotechnology is emphasized. ► Applications of the Gadonanotubes as T1-weighted MRI contrast agents are reviewed and the future forecast.

A recent study published in Nano Letters documents the synthesis and performance of porous silica nanocapsules filled with magnetic nanoparticles as a controllable magnetic drug delivery vector. Under a remotely applied radiofrequency magnetic field, these nanocapsules demonstrate on-off switchable release of the internally loaded drug payload. Both in vitro and in vivo studies using MT2 mouse breast cancer cell models demonstrate that the magnetic targeting of these nanocapsules allows for deep tumor penetration and subsequent on-demand release of the drug cargo, significantly reducing tumor cell viability.

A new Rh6(CO)16-catalyzed functionalization of gadonanotube MRI probes offers the opportunity to prepare a number of amino acid and peptide derivatized gadonanotubes under RT conditions, containing, for example, the cyclic RGD peptide for the biological targeting of cancer.

With their unique nanoscalar properties, single-walled carbon nanotube (SWNT) materials are widely studied for various biological applications. Herein, we report the efficiency of full-length HiPco SWNTs and ultra-short SWNTs (US-tubes) as T2-weighted MRI contrast agents. Analysis has concluded that the superparamagnetic SWNT materials (especially US-tubes) are a new class of high-efficacy contrast agents having performance contributions from both the iron catalyst nanoparticles (originating from the synthesis of SWNT materials) and the carbon SWNT material itself. The superparamagnetic US-tubes with their short length (<100 nm), negligible metal content (<1% Fe (wt %)), and superior T2 relaxation efficiency (T2 = 31.7 ms per mg SWNT at 3 T and 37 °C) are the most promising candidates for advanced applications such as molecular and cellular imaging using MRI.

Nanotechnology offers many opportunities for enhanced diagnostic and therapeutic medicine against cancer and other diseases. In this review, the special properties that result from the nanoscale size of quantum dots, metal colloids, superparamagnetic iron oxide, and carbon-based nanostructures are reviewed and interpreted against a background of the structural and electronic detail that gives rise to their nanotechnologic behavior. The detection and treatment of cancer is emphasized, with special attention paid to the biologic targeting of the disease. The future of nanotechnology in cancer research and clinical practice is projected to focus on ‘theranostic’ nanoparticles that are both diagnostic and therapeutic by design.

The first fullerene (C60) immunoconjugates have been prepared and characterized as an initial step toward the development of fullerene immunotherapy (FIT).

We report the nanoscale loading and confinement of aquated Gd3+n-ion clusters within ultra-short single-walled carbon nanotubes (US-tubes); these Gd3+n@US-tube species are linear superparamagnetic molecular magnets with Magnetic Resonance Imaging (MRI) efficacies 40 to 90 times larger than any Gd3+-based contrast agent (CA) in current clinical use.

A facile synthesis for derivatizing fullerenes with diphosphonate groups based on the Bingel reaction has been explored. Five different bisadduct isomers of C60 with tetraethyl methylenediphosphonate, CH2(PO3Et2)2, have been synthesized, separated and characterized by MALDI-TOF mass spectrometry and 31P{1H} and 13C NMR spectroscopy. Hydrolysis of the C60[C(PO3Et2)2]2 isomers generates water-soluble diphosphonic acids, C60[C(PO3H2)2]2 for future in vitro and in vivo studies in which mineralized bone tissue will be selectively targeted.

A tissue-vectored bisphosphonate fullerene, C60(OH)16AMBP [4,4-bisphosphono-2-(polyhydroxyl-1,2-dihydro-1,2-methanofullerene[60]-61-carboxamido)butyric acid], designed to target bone tissue has been synthesized and evaluated in vitro. An amide bisphosphonate addend, in conjunction with multiple hydroxyl groups, confers a strong affinity for the calcium phosphate mineral hydroxyapatite of bone. Constant composition crystal growth studies indicate that C60(OH)16AMBP reduces hydroxyapatite mineralization by 50% at a concentration of 1 μM, following a non-Langmuirian mechanism. Parallel studies with C60(OH)30 also indicate an affinity for hydroxyapatite, but at a reduced level (28% crystal growth rate reduction at 1 μM) compared with C60(OH)16AMBP. This study is the first to demonstrate that a fullerene-based material can be successfully targeted to a selected tissue as a step toward the development of such materials for medical purposes, in general.Graphic

Among the many applications for carbon nanotubes (CNTs), their use in medicine has drawn special attention due to their potential for a variety of therapeutic and diagnostic applications. As progress toward clinical applications continues, monitoring CNTs in vivo will be essential to evaluate their biodistribution, potential toxicity, therapeutic activity, and any physiological changes that the material may induce in specific tissues. There are many different imaging modalities to visualize and track CNTs in vivo, yet only a few are full-body penetrating, a central characteristic that widens their clinical utility. In order to visualize CNTs, chemical modification is often required for the material to be used as a platform to carry imaging agents compatible with one or more of the clinical imaging techniques. Here, we focus on the most recent work involving the use of CNTs as imaging agents for the non-invasive, full-body penetrating clinical modalities of MRI, PET, SPECT, and X-ray CT. The synthesis and modification of the CNT materials are discussed, as well as relevant preclinical studies.

Among the many applications for carbon nanotubes (CNTs), their use in medicine has drawn special attention due to their potential for a variety of therapeutic and diagnostic applications. As progress toward clinical applications continues, monitoring CNTs in vivo will be essential to evaluate their biodistribution, potential toxicity, therapeutic activity, and any physiological changes that the material may induce in specific tissues. There are many different imaging modalities to visualize and track CNTs in vivo, yet only a few are full-body penetrating, a central characteristic that widens their clinical utility. In order to visualize CNTs, chemical modification is often required for the material to be used as a platform to carry imaging agents compatible with one or more of the clinical imaging techniques. Here, we focus on the most recent work involving the use of CNTs as imaging agents for the non-invasive, full-body penetrating clinical modalities of MRI, PET, SPECT, and X-ray CT. The synthesis and modification of the CNT materials are discussed, as well as relevant preclinical studies.

Fullerene (C60)-monoclonal antibody (mAb) immunoconjugates have been determined to internalize into target cells using water-soluble Gd3+ ion-filled metallofullerenes (Gd@C60[OH]x). Two separate conjugations of Gd@C60(OH)x with the antibody ZME-018 and a murine antibody mixture (MuIgG) were performed in a 1:5 mAb/Gd@C60 ratio. Characterization of the immunoconjugates was established using inductively coupled plasma mass spectrometry (ICP-MS) for Gd3+ and UV-Vis spectrometry (for Gd@C60 + C60). Once conjugated, enzyme-linked immunosorbent assays showed little change in the specific binding of ZME-018. Each immunoconjugate was exposed to two cancer cell lines, A375m (antigen positive), and T24, bladder carcinoma (antigen negative). Internalization levels of the immunoconjugate were determined at various time points during 24 hours by harvesting and digesting the cells with 70% HNO3 for Gd3+ ion analysis by ICP-MS. These results are the first to demonstrate the practicality of a targeted cancer therapy based on fullerene immunotherapy.

The encapsulation of bismuth as BiOCl/Bi2O3 within ultra-short (ca. 50 nm) single-walled carbon nanocapsules (US-tubes) has been achieved. The Bi@US-tubes have been characterized by high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Bi@US-tubes have been used for intracellular labeling of pig bone marrow-derived mesenchymal stem cells (MSCs) to show high X-ray contrast in computed tomography (CT) cellular imaging for the first time. The relatively high contrast is achieved with low bismuth loading (2.66% by weight) within the US-tubes and without compromising cell viability. X-ray CT imaging of Bi@US-tubes-labeled MSCs showed a nearly two-fold increase in contrast enhancement when compared to unlabeled MSCs in a 100 kV CT clinical scanner. The CT signal enhancement from the Bi@US-tubes is 500 times greater than polymer-coated Bi2S3 nanoparticles and several-fold that of any clinical iodinated contrast agent (CA) at the same concentration. Our findings suggest that the Bi@US-tubes can be used as a potential new class of X-ray CT agent for stem cell labeling and possibly in vivo tracking.

Multi-layer graphene nanoribbons have been made highly water soluble (4.7 mg ml−1) and stable for the first time by repetitious derivatization with p-carboxyphenyldiazonium salt; similarly, single-walled carbon nanotubes (4.8 mg ml−1) and ultra-short carbon nanotubes (50 mg ml−1) can also be made highly soluble by the methodology.

Here we demonstrate a simple, nondestructive method for the preparation of stable aqueous colloidal solutions of graphene nanoribbons and carbon nanotubes. The method includes sonication of carbon nanomaterials in hypophosphorous acid, filtration accompanied by washing the solids with water and dispersion of the solids in a fresh portion of water to form colloidal solutions.