Jee-Hyun Cho

Graphite-Coated Magnetic Nanoparticles as Multimodal Imaging Probes and Cooperative Therapeutic Agents for Tumor Cells

An effective therapeutic approach against cancer typically requires the combination of several modalities, such as chemotherapy, radiation, and hyperthermia. In this regard, the development of multifunctional nanomaterial-based systems with combined therapeutic and molecular imaging capabilities has shown great potential but has not been fully explored. In particular, magnetic nanomaterials have been at the fore-front of cancer research as noninvasive imaging probes as well as multifunctional therapeutics. [1] For example, magnetic nanoparticles (MNPs) with appropriate surface modifications have been successfully applied to deliver therapeutic biomolecules, such as anticancer drugs, antibodies, and siRNAs, to target tumor cells or tissues. [2] Moreover, the unique physical and chemical properties of these magnetic nanostructures have enabled their wide applications in cancer imaging and therapy, including magnetic resonance imaging (MRI) and hyperthermia. [3] Promising advances have been made in synthesizing multifunctional MNPs from various materials, including metals, [4] metal oxides, [5] metal alloys, [6] and metal–graphitic-shell nanomaterials, [7] with different properties. However, current studies are mostly focused on the synthesis and characterization of materials with limited demonstration of their biomedical applications, like molecular imaging and therapy. As a result, research efforts towards developing MNP-based multimodal therapeutics to control the tumor microenvironment are highly limited and have not been fully explored. Therefore, in order to address the challenges of MNP-based therapeutics, as well as to narrow the gap between current nanoparticle-based multimodal imaging approaches and their clinical applications, there is a clear need to synthesize effective chemotherapeutic MNPs and to develop multimodal therapies for targeting specific oncogenes, thereby activating/deactivating corresponding key signaling pathways.

Europium-doped gadolinium sulfide nanoparticles as a dual-mode imaging agent for T1-weighted MR and photoluminescence imaging.

We present a facile synthesis of europium-doped gadolinium sulfide (GdS:Eu(3+)) opto-magnetic nanoparticles (NPs) via sonochemistry. Their photoluminescence and strong paramagnetic properties enable these NPs to be utilized as an in vitro cell imaging and in vivo T(1)-weighted MR imaging probe. The GdS:Eu(3+) NPs have a prominent longitudinal (r(1)) relaxivity value, which is a critical parameter for T(1)-weighted MR imaging. Here, we showed not only their strong positive contrast effect to blood vessels and organs of mice, but also blood half-life and biodistribution including clearance from organs, in order to assess the GdS:Eu(3+) NPs as a competent nanocrystal-based T(1) contrast agent. We further showed confocal images of breast cancer cells containing GdS:Eu(3+) NPs to evaluate as a photoluminescence probe. Dual-mode imaging capability obtained from the GdS:Eu(3+) NPs will allow target-oriented cellular imaging as well as the resulting disease-specific MR imaging.

Synthesis of highly magnetic graphite-encapsulated FeCo nanoparticles using a hydrothermal process

The graphite encapsulation of metal alloy magnetic nanoparticles has attracted attention for biological applications because of the high magnetization of the encapsulated particles. However, most of the synthetic methods have limitations in terms of scalability and economics because of the demanding synthetic conditions and low yields. Here, we show that well controlled graphite-encapsulated FeCo core-shell nanoparticles can be synthesized by a hydrothermal method, simply by mixing Fe/Co with sucrose as a carbon source. Various Fe/Co metal ratios were used to determine the compositional dependence of the saturation magnetization and relaxivity coefficient. Transmission electron microscopy indicated that the particle sizes were 7 nm. In order to test the capability of graphite-encapsulated FeCo nanoparticles as magnetic resonance imaging (MRI) contrast agents, these nanoparticles were solubilized in water by the nonspecific physical adsorption of sodium dodecylbenzene sulfonate.

Facile Preparation of Zwitterion-Stabilized Superparamagnetic Iron Oxide Nanoparticles (ZSPIONs) as an MR Contrast Agent for in Vivo Applications

We describe a simple method for synthesizing superparamagnetic nanoparticles (SPIONs) as small, stable contrast agents for magnetic resonance imaging (MRI) based on sulfobetaine zwitterionic ligands. SPIONs synthesized by thermal decomposition were coated with zwitterions to impart water dispersibility and high in vivo stability through the nanoemulsion method. Zwitterion surfactant coating layers are formed easily on oleic acid-stabilized SPIONs via hydrophobic and van der Waals interactions. Our zwitterion-coated SPIONs (ZSPIONs) had ultrathin (∼5 nm) coating layers with mean sizes of 12.0 ± 2.5 nm, as measured by dynamic light scattering (DLS). Upon incubation in 1 M NaCl and 10% FBS, the ZSPIONs showed high colloidal stabilities without precipitating, as monitored by DLS. The T2 relaxivity coefficient of the ZSPIONs, obtained by measuring the relaxation rate on the basis of the iron concentration, was 261 mM(-1) s(-1). This value was much higher than that of the commercial T2 contrast agent because of the ultrathin coating layer. Furthermore, we confirmed that ZSPIONs can be used as MR contrast agents for in vivo applications such as tumor imaging and lymph node mapping.

The use of the fusion protein RGD-HSA-TIMP2 as a tumor targeting imaging probe for SPECT and PET.

The human serum albumin tissue inhibitor of metalloproteinase 2 (HSA-TIMP2) is known to possess antitumor activity, which has been attributed to its ability to inhibit endothelial cell proliferation by binding to integrin receptors. In this study, a fusion protein, cyclic arginine-glycine-aspartate (RGD)-HSA-TIMP2, formed by conjugating HSA-TIMP2 with a RGD peptide, and its (123)I- and (68)Ga-labeled compounds, were synthesized and evaluated with in vivo tumor imaging using single photon emission computed tomography (SPECT) and positron emission tomography (PET). RGD-HSA-TIMP2 was synthesized by covalent bonding of the RGD peptide to the side chain amino groups of HSA-TIMP2 from a two-step reaction involving from activation with N-succinimidyl iodoacetate. This conjugation improved the anticancer effect of HSA-TIMP2 in cancer cells. The (123)I- and (68)Ga-labeled fusion proteins were prepared and subsequently injected into the tail veins of mice bearing human glioblastoma cancer U87MG xenografts for SPECT and PET imaging and biodistribution studies. Tumor uptake of radioligand was high in both the PET images and in the biodistribution studies at 3 h after injection. These studies demonstrated that the new fusion protein has potential not only as an anticancer agent but also as a radioligand for the diagnosis of tumors.

In vivo 1H-MRS hepatic lipid profiling in nonalcoholic fatty liver disease: An animal study at 9.4 T

The applicability of the in vivo proton magnetic resonance spectroscopy hepatic lipid profiling (MR‐HLP) technique in nonalcoholic fatty liver disease was investigated. Using magnetic resonance spectroscopy, the relative fractions of diunsaturated (fdi), monounsaturated (fmono), and saturated (fsat) fatty acids as well as total hepatic lipid content were estimated in the livers of 8 control and 23 CCl4‐treated rats at 9.4 T. The mean steatosis, necrosis, inflammation, and fibrosis scores of the treated group were all significantly higher than those of the control group (P < 0.01). There was a strong correlation between the histopathologic parameters and the MR‐HLP parameters (r = 0.775, P < 0.01) where both steatosis and fibrosis are positively correlated with fmono and negatively correlated with fdi. Both necrosis and inflammation, however, were not correlated with any of the MR‐HLP parameters. Hepatic lipid composition appears to be changed in association with the severity of steatosis and fibrosis in nonalcoholic fatty liver disease, and these changes can be depicted in vivo by using the MR‐HLP method at 9.4 T. Thus, while it may not likely be that MR‐HLP helps differentiate between steatohepatitis in its early stages and simple steatosis, these findings altogether are in support of potential applicability of in vivo MR‐HLP at high field in nonalcoholic fatty liver disease. Magn Reson Med 70:620–629, 2013.

Ultra‐small, Uniform, and Single bcc‐Phased FexCo1‐x/Graphitic Shell Nanocrystals for T1 Magnetic Resonance Imaging Contrast Agents

We have synthesized ultra-small and uniform Fe(x)Co(1-x)/graphitic carbon shell (Fe(x)Co(1-x)/GC) nanocrystals (x=0.13, 0.36, 0.42, 0.50, 0.56, and 0.62, respectively) with average diameters of <4 nm by thermal decomposition of metal precursors in approximately 60 nm MCM-41 and methane CVD. The composition of the Fe(x)Co(1-x)/GC nanocrystals can be tuned by changing the Fe:Co ratios of the metal precursors. The Fe(x)Co(1-x)/GC nanocrystals show superparamagnetic properties at room temperature. The Fe(0.50)Co(0.50)/GC, Fe(0.56)Co(0.44)/GC, and Fe(0.62)Co(0.38)/GC nanocrystals have a single bcc FeCo structure, whereas the Fe(0.13)Co(0.87)/GC, Fe(0.36)Co(0.64)/GC, and Fe(0.42)Co(0.58)/GC nanocrystals have a mixed structure of bcc FeCo and fcc Co. The single bcc-phased Fe(x)Co(1-x)/GC nanocrystals functionalized with phospholipid-poly(ethylene glycol) (PL-PEG) in phosphate buffered saline (PBS) are demonstrated to be excellent T(1) MRI contrast agents.

Feasibility of FAIR imaging for evaluating tumor perfusion

To evaluate the feasibility of flow‐sensitive alternating inversion recovery (FAIR) for measuring blood flow in tumor models.

Detection of iron-labeled single cells by MR imaging based on intermolecular double quantum coherences at 14 T.

To evaluate the efficiency and feasibility of intermolecular multiple quantum coherence (iMQC) magnetic resonance (MR) imaging for single cell detection, we obtained intermolecular double quantum coherence (iDQC) and conventional gradient echo (GE) images of macrophage cells labeled by contrast agents in gel. The iDQC images obtained with echo-planar readout visualized the labeled cells effectively and with a higher contrast than seen in conventional GE images, especially at low planar resolutions and with thick slices. This implies that iDQC imaging with contrast agents could be a good alternative to conventional MR imaging for detecting labeled single cells or cell tracking under favorable conditions.

Manganese-enhanced MR imaging of brain activation evoked by noxious peripheral electrical stimulation

As imaging technology develops, magnetic resonance imaging (MRI) has furthered our understanding of brain function by clarifying the anatomical structure and generating functional imaging data related to information processing in pain conditions. Recent studies have reported that manganese (Mn(2+))-enhanced MRI (MEMRI) provides valuable information about the functions of the central nervous system. The aim of this study was to identify specific brain regions activated during noxious electric stimulation using high-resolution MEMRI. Male Sprague Dawley rats were divided into three groups: naïve, sham electrical stimulation, and noxious electric stimulation. Under urethane with α-chloralose mixture anesthesia, a catheter was placed in the external carotid artery to administrate 20% mannitol and manganese chloride (25mM MnCl2). Noxious electric stimulation (2Hz, 10V) was applied to the hind paw with a needle electrode. Stimulation-induced neuronal activation was detected using 4.7-T MRI. In response to noxious electrical stimulation, remarkable Mn(2+)-enhanced signals were observed in the agranular insular cortex, auditory cortex, primary somatosensory cortex of the hind limb, and granular and dysgranular insular cortex, which correspond to sensory tactile electric stimulus to the hindpaws. These results indicate that the combination of MEMRI with activity-induced Mn(2+)-dependent contrast can delineate functional areas in the rat brain.