Kwan Soo Hong

Folate-based near-infrared fluorescent theranostic gemcitabine delivery.

A series of heptamethine cyanine (1-3) derivatives bearing a carbamate ethyl disulfide group and gemcitabine, an anticancer drug, have been newly synthesized. Their disulfide bonds are readily cleaved by various thiols including glutathione, to result in a subsequent decomposition of the carbamate into amine followed by release of the active gemcitabine, which can be monitored by the fluorescence changes. In the biological experiment, prodrug 1 is preferentially up-taken by folate-positive KB cells over folate-negative A549 cells via receptor-mediated endocytosis to release gemcitabine causing cell death and to emit fluorescence in endoplasmic reticulum. Moreover, it is selectively accumulated in the KB cells which were treated to mice by dorsal subcutaneous injection. This drug delivery system is a new theranostic agent, wherein both therapeutic effect and drug uptake can be easily monitored at the subcellular level, by in vivo and in vitro fluorescence imaging.

In Vivo Tracking of Human Mesenchymal Stem Cells in Experimental Stroke

To understand the fates of human mesenchymal stem cells (hMSCs) following transplantation into a rodent model of middle cerebral artery occlusion (MCAo), magnetic resonance imaging (MRI) techniques were employed. hMSCs were labeled with ferumoxides (Feridex®)-protamine sulfate complexes, which were visualized and examined by MRI up to 10 weeks following transplantation. Migration of the transplanted cells to the infarcted area was further confirmed by histological methods. We found that the hMSCs transplanted in MCAo models possess the capacity to migrate to the infarcted area extensively in both ipsilateral and contralateral injections, exhibiting a pathotropism. We also analyzed the detailed migration patterns of transplanted hMSCs. We speculate that the extensive migratory ability of hMSCs may represent a therapeutic potential for developing efficient cell transplantation strategies in stroke.

Cetuximab-conjugated magneto-fluorescent silica nanoparticles for in vivo colon cancer targeting and imaging

Magneto-fluorescent silica nanoparticles were conjugated with cetuximab for the targeting and imaging of colon cancer. In this study, cetuximab-conjugated magneto-fluorescent nanoparticles (MFSN-Ctx) could specifically target colon cancer cells that expressed EGFR on their cell membranes, and specific fluorescence was detected. MFSN-Ctx produced significant MRI signal changes in a human colon cancer xenograft mouse model. Intravenous injection of MFSN-Ctx resulted in faster uptake as compared to intraperitoneal injection, indicating that MFSN-Ctx had different kinetic properties in tumors based on the method of injection. The local concentration of MFSN-Ctx in a tumor was amplified by the use of an external magnetic field. These results demonstrate the potential application of MFSN-Ctx for the detection of EGFR-expressing colon cancer using in vivo imaging approaches.

Synthesis and high performance of magnetofluorescent polyelectrolyte nanocomposites as MR/near-infrared multimodal cellular imaging nanoprobes.

Here, we describe an easy but robust chemical strategy to synthesize high-performance magnetic resonance (MR)/near-infrared (NIR) multimodal imaging nanoprobes. Poly(γ-glutamic acid) was used for the convenient phase transfer of MnFe(2)O(4) nanoparticles dispersed in organic solvents into aqueous solutions and facilitated further ionic gelation with poly(l-lysine). During the gelation process, MnFe(2)O(4) nanoparticulate satellites were encapsulated in the ionic nanocomplex, which induced synergistic magnetism and resulted in huge T(2) relaxivity (r(2)). The positively charged outer surfaces were assembled with other negatively charged NIR emitting fluorescent nanocrystals and enabled the highly efficient delivery of the magnetofluorescent polyelectrolyte nanocomposites (MagFL-PEN) into cancer cells. The enhancement of negative contrast of MagFL-PEN at 2 μg/mL concentration was similar to that of Resovist at 20 μg/mL concentration. The NIR fluorescence microscopy images of the MagFL-PEN-labeled cells even at 12.5 pM were able to be clearly observed. The labeling efficiency of MagFL-PEN was approximately 65-fold higher compared to that of the commercialized fluorescent nanocrystals, only after 3 h incubation period, even at the test concentration (100 pM). Due to the high-performance capabilities both in materials properties and cell labeling efficiency, the MagFL-PEN is expected to be used as a highly efficient MR/NIR dual-modality imaging nanoprobe in the detection of cancer cells and monitoring of therapeutic cells in vivo.

Multiplexed imaging of therapeutic cells with multispectrally encoded magnetofluorescent nanocomposite emulsions.

Here, we describe the fabrication of multispectrally encoded nanoprobes, perfluorocarbon (PFC)/quantum dots (QDs) nanocomposite emulsions, which could provide both multispectral MR and multicolor optical imaging modalities. Our strategy exploited the combination of the multispectral MR properties of four different PFC materials and the multicolor emission properties of three different colored CdSe/ZnS QDs. The PFC/QDs nanocomposite emulsions were fabricated by exchanging hydrophobic ligands coated onto CdSe/ZnS QDs using 1H,1H,2H,2H-perfluorooctanethiol, which renders the QDs to be dispersible in the PFC liquids. To provide biocompatibility, the PFC liquids containing QDs were emulsified into aqueous solutions with the aid of phospholipids. The distinct (19)F-based MR images of PFC/QDs nanocomposite emulsions were obtained by selective excitation of the nanocomposite emulsions with magnetic resonance frequency of each PFC, while a specific fluorescence image of them could be selected using appropriate optical filters. The uptake of PFC/QDs nanocomposite emulsions was high in phagocytic cells such as macrophages (90.55%) and dendritic cells (85.34%), while it was low in nonphagocytic T cells (33%). We have also shown that the nanocomposite emulsions were successfully applied to differentially visualize immunotherapeutic cells (macrophages, dendritic cells, and T cells) in vivo. The PFC/QDs nanocomposite emulsions are expected to be a promising multimodality nanoprobe for the multiplexed detection and imaging of therapeutic cells both in vitro and in vivo.

In vivo and ex vivo evidence for ketamine-induced hyperglutamatergic activity in the cerebral cortex of the rat: Potential relevance to schizophrenia.

Subanesthetic doses of ketamine, a noncompetitive N‐methyl‐D‐aspartate (NMDA) receptor antagonist, impair prefrontal cortex (PFC) function in the rat and produce symptoms in humans similar to those observed in patients with schizophrenia. In the present study, in vivo 1H‐MRS and ex vivo 1H high‐resolution magic angle spinning (HR‐MAS) spectroscopy was used to examine the brain metabolism of rats treated with subanesthetic doses of ketamine (30 mg/kg) for 6 days. A single voxel localization sequence (PRESS, TR/TE = 4000/20 ms and NEX = 512) was used to acquire the spectra in a 30‐µl voxel positioned in the cerebral cortex (including mainly PFC) of the rats (ketamine group: n = 12; saline group: n = 12) anesthetized with isoflurane. After the in vivo 1H‐MRS acquisition, the animals were sacrificed and the cerebral cortex tissues were extracted (ketamine group: n = 7; saline group: n = 7) for ex vivo 1H HR‐MAS spectroscopy (CPMG sequence, 2.0‐s presaturation delay, 2.0‐s acquisition time, 128 transients and 4‐ms inter‐pulse delay) using a 500‐MHz NMR spectrometer. All proton metabolites were quantified using the LCModel. For the in vivo spectra, there was a significant increase in glutamate concentration in the cerebral cortex of the ketamine group compared with the controls (p < 0.05). For the ex vivo HR‐MAS spectra, there was a significant increase in the glutamate/total creatine ratio, and a decrease in the glutamine/total creatine and glutamine/glutamate ratios in the cerebral cortex tissue of the ketamine group compared with the controls. The results of the present study demonstrated that administration of subanesthetic doses of ketamine in the rat may exert at least part of their effect in the cerebral cortex by activation of glutamatergic neurotransmission. Copyright

Therapeutic potential of human induced pluripotent stem cells in experimental stroke.

Ischemic stroke mainly caused by middle cerebral artery occlusion (MCAo) is a major type of stroke, but there are currently very limited therapeutic options for its cure. Neural stem cells (NSCs) or neural precursor cells (NPCs) derived from various sources are known to survive and improve neurological functions when they are engrafted in animal models of stroke. Induced pluripotent stem cells (iPSCs) generated from somatic cells of patients are novel cells that promise the autologous cell therapy for stroke. In this study, we successfully differentiated iPSCs derived from human fibroblasts into NPCs and found their robust therapeutic potential in a rodent MCAo stroke model. We observed the significant graft-induced behavioral recovery, as well as extensive neural tissue formation. Animal MRI results indicated that the majority of contralaterally transplanted iPSC-derived NPCs migrated to the peri-infarct area, showing a pathotropism critical for tissue recovery. The transplanted animals exhibited the significant reduction of stroke-induced inflammatory response, gliosis and apoptosis, and the contribution to the endogenous neurogenesis. Our results demonstrate that iPSC-derived NPCs are effective cells for the treatment of stroke.

Cu2+-Responsive Bimodal (Optical/MRI) Contrast Agent for Cellular Imaging

A water-soluble T1 magnetic resonance imaging contrast agent (1) has been synthesized. The bimodal contrast agent 1 responds to the Cu(2+) ion in living cells by enhancing the MRI modality signal whereas the optical signal gradually drops. This dual modality probe response depends on the cellular free copper ions in RAW 264.7 cells even at the micromolar level.

Therapeutic effect of BDNF-overexpressing human neural stem cells (HB1.F3.BDNF) in a rodent model of middle cerebral artery occlusion.

Ischemic stroke mainly caused by middle cerebral artery occlusion (MCAo) represents the major type of stroke; however, there are still very limited therapeutic options for the stroke-damaged patients. In this study, we evaluated the neurogenic and therapeutic potentials of human neural stem cells (NSCs) overexpressing brain-derived neurotrophic factor (HB1.F3.BDNF) following transplantation into a rodent model of MCAo. F3.BDNF human NSCs (F3.BDNF) were transplanted into the contralateral side of striatum at 7 days after MCAo, and the transplanted animals were monitored up to 8 weeks using animal MRI and various behavioral tests before they were sacrificed for immunohistochemical analysis. Interestingly, animal MRI results indicate that the majority of contralaterally transplanted neural stem cells were migrated to the peri-infarct area, showing a pathotropism. Transplanted animals exhibited significant behavioral improvements in stepping, rotarod, and modified neurological severity score (mNSS) tests. We also found that the transplanted human cells were colocalized with nestin, DCX, MAP2, DARPP-32, TH, GAD65/67-positive cells, of which results can be correlated with neural regeneration and behavioral recovery in the transplanted animals. More importantly, we were able to detect high levels of human BDNF protein expression, presumably derived from the transplanted F3.BDNF. Taken together, these results provide strong evidence that human neural stem cells (F3.BDNF) are effective in treating stroke animal models.

Noninvasive Assessment of Myocardial Inflammation by Cardiovascular Magnetic Resonance in a Rat Model of Experimental Autoimmune Myocarditis

Background— Limited availability of noninvasive and biologically precise diagnostic tools poses a challenge for the evaluation and management of patients with myocarditis. Methods and Results— The feasibility of cardiovascular magnetic resonance (CMR) imaging with magneto-fluorescent nanoparticles (MNPs) for detection of myocarditis and its effectiveness in discriminating inflammation grades were assessed in experimental autoimmune myocarditis (EAM) (n=65) and control (n=10) rats. After undergoing CMR, rats were administered with MNPs, followed by a second CMR 24 hours later. Head-to-head comparison of MNP-CMR with T2-weighted, early and late gadolinium enhancement CMR was performed in additional EAM (n=10) and control (n=5) rats. Contrast-to-noise ratios were measured and compared between groups. Flow cytometry and microscopy demonstrated that infiltrating inflammatory cells engulfed MNPs, resulting in altered myocardial T2* effect. Changes in contrast-to-noise ratio between pre- and post-MNP CMR were significantly greater in EAM rats (1.08±0.10 versus 0.48±0.20; P<0.001). In addition, contrast-to-noise ratio measurement in MNP-CMR clearly detected the extent of inflammation (P<0.001) except for mild inflammation. Compared with conventional CMR, MNP-CMR provided better image contrast (CNR change 8% versus 46%, P<0.001) and detectability of focal myocardial inflammation. Notably, MNP-CMR successfully tracked the evolution of myocardial inflammation in the same EAM rats. Conclusions— Magneto-fluorescent nanoparticle CMR permitted effective visualization of myocardial inflammatory cellular infiltrates and distinction of the extent of inflammation compared with conventional CMR in a preclinical model of EAM. Magneto-fluorescent nanoparticle CMR performs best in EAM rats with at least moderate inflammatory response.