Youn-Kyung Lee

Single-step microwave mediated synthesis of the CoS2 anode material for high rate hybrid supercapacitors

A short time microwave irradiation based synthesis method of phase pure cubic CoS2 nanoparticles is reported in this study for the first time. The energy density (ED) of hybrid supercapacitors based on CoS2 as an anode having activated carbon as a cathode has been enhanced by using the higher operating potential of organic electrolytes and by increasing the concentration of the mobile ionic species at the negative electrode, in addition to the lithium ions present in the electrolyte. The specific capacitance delivered by non-lithiated CoS2 nanoflakes was 52 F g−1 at a current rate of 0.7 A g−1 between 0 and 3 V using a LiPF6-based electrolyte. Increasing the concentration of the mobile ionic species, i.e., lithium, at the anode enhanced the performance of the hybrid supercapacitor to 119 F g−1 at a current rate of 0.7 A g−1. The hierarchical arrangement of pores in the electroactive material allowed high electrolyte access and reduced the length of the ionic pathway. Consequently, the lithiated form exhibited an ED of 37 W h kg−1 with a power density of 1 kW kg−1 at a current rate of 0.7 A g−1, compared to only 15 W h kg−1 for the non-lithiated sample. Furthermore, both samples maintained superior stability over extended cycling for 10000 cycles at a very high PD of 4 kW kg−1 with a capacitance retention of 100% for the lithiated sample and 80% for the non-lithiated sample. These results will be useful in the fabrication of high ED, high rate hybrid supercapacitors for electric vehicle applications.

Efficient revascularization by VEGF administration via heparin-functionalized nanoparticle–fibrin complex

We investigated the angiogenic bioactivity and therapeutic angiogenic effect of vascular endothelial growth factor (VEGF) administration by the heparin-functionalized nanoparticle-fibrin gel complex. The markedly increased bioactivity was observed by the VEGF-loaded nanoparticle-fibrin gel complex, compared to the VEGF-loaded fibrin gel, the nanoparticle-fibrin gel complex without VEGF, or fibrin gel (control) in terms of the capillary density in a mouse subcutaneous implantation model. Furthermore, the VEGF-loaded nanoparticle-fibrin gel complex significantly enhanced the therapeutic angiogenic effect in a rabbit ischemic hind limb model: the noticeable increase in the recovered calf blood pressure, the angiographic score, and the density of collaterals, as well as the stable maintenance of the organized collaterals, compared to the VEGF-loaded fibrin gel. These results show the enhanced angiogenic potential of VEGF administration by the proposed heparin-functionalized nanoparticle-fibrin gel complex.

Type I and II interferons enhance dendritic cell maturation and migration capacity by regulating CD38 and CD74 that have synergistic effects with TLR agonists

The major limitation for the maturation of dendritic cells (DCs) using Toll-like receptor (TLR) agonists is their decreased ability to migrate into lymph nodes compared with conventional DCs. CD38 can be used as a multifunctional marker to modulate migration, survival and Th1 responses of DCs. CD74 has been shown to negatively regulate DC migration. The goal of this study was to investigate the combinations of TLR agonists and interferons (IFNs) that most effectively regulate CD38 and CD74 expression on DCs. Synergistic TLR agonist stimulation in combination with IFN-α and IFN-γ was the best method for regulating CD38 and CD74 expression and inducing the highest secretion of IL-12p70. An in vitro migration assay showed that DCs treated with this combination had significantly enhanced migratory ability, similar to that observed in cells expressing CD38, CD74 and CCR7. The results of this study suggest that an alternative maturation protocol in which two TLR ligands are combined with type I and II IFNs generates potent DCs that have both a high migratory capacity and high IL-12p70 production.

Studies on the electrochemical intercalation/de-intercalation mechanism of NiMn2O4 for high stable pseudocapacitor electrodes

Sub-micron sized polyhedral shaped NiMn2O4 particles were successfully prepared by a glycine assisted solution combustion method. The phase purity and the presence of functional groups in NiMn2O4 were revealed through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), respectively. The formation of polyhedral shaped particles was inferred by field emission scanning electron microscopy (FE-SEM). The negative temperature coefficient of resistance (NTCR) behaviour of NiMn2O4 was observed using a solid state impedance analyser in the measured temperature range between 30 and 180 °C. Further, electrochemical studies revealed that NiMn2O4 stores the charge through intercalation rather than by a capacitive mechanism. The electrode stores 91% of the specific capacitance by intercalation and 9% by a capacitive mechanism. Also, NiMn2O4 possesses a specific capacitance of 202 F g−1 at 0.5 mA cm−2 in 1 M Na2SO4 electrolyte and exhibits excellent cyclic stability over 15 000 cycles. Similarly, the fabricated asymmetric device (FeVO4‖NiMn2O4) also delivers good specific capacitance (50 F g−1 at 1 mV s−1) and cyclic stability.

Effect of carbon coating on the electrochemical properties of Co2SnO4 for negative electrodes in Li-ion batteries

Co2SnO4 particles were synthesized by a sonochemical method under different pH conditions, followed by carbon coating by a hydrothermal method. The thermal stability and compound formation temperature were identified through thermogravimetric analysis (TGA). The X-ray diffraction (XRD) pattern elucidated the compound formation of Co2SnO4 with cubic structure. Co2SnO4 encapsulated with carbon was confirmed through the TEM and HRTEM analysis and the approximate thickness of carbon was around 20 nm. The pristine-Co2SnO4 and carbon coated Co2SnO4 provided a discharge capacity of 777 mA h g−1 and 780 mA h g−1 at the current density of 40 mA g−1 with the capacity retention of 67% and 81% respectively in the 20th cycle. The charge transfer resistance of carbon coated Co2SnO4 was low when compared to pristine Co2SnO4 which lead to good reversibility of the material. The electrochemical study revealed the excellent electrochemical performance of the carbon coated Co2SnO4 particles with superior cycling stability and electronic conductivity.

Alpha-type 1-polarized dendritic cells loaded with apoptotic allogeneic myeloma cell line induce strong CTL responses against autologous myeloma cells

To induce a potent cytotoxic T lymphocyte (CTL) response, various tumor antigens should be loaded onto dendritic cells (DCs). In multiple myeloma (MM), it is difficult to obtain a sufficient number of autologous tumor cells as a source of tumor antigens in the clinical setting. We investigated the feasibility of immunotherapy in patients with MM, using myeloma-specific CTLs generated in vitro by alpha-type 1-polarized DCs (αDC1s) loaded with the ultraviolet B-irradiated allogeneic myeloma cell line, ARH77. αDC1s significantly increased the expression of several costimulatory molecules without differences in loading with tumor antigens. αDC1s showed a high production of interleukin-12 during maturation and after subsequent stimulation with CD40L but were not significantly affected by loading tumor antigens. Myeloma-specific CTLs against autologous myeloma cells from MM patients were induced by αDC1s pulsed with apoptotic ARH77 cells. Our data indicate that autologous DCs loaded with an allogeneic myeloma cell line can generate potent myeloma-specific CTL responses against autologous myeloma cells and might provide a practical method for cellular immunotherapy in patients with MM.

Ex vivo expansion of canine cytotoxic large granular lymphocytes exhibiting characteristics of natural killer cells.

Canine NK cells still are not well-characterized due to the lack of information concerning specific NK cell markers and the fact that NK cells are not an abundant cell population. In this study, we selectively expanded the canine cytotoxic large granular lymphocytes (CLGLs) that exhibit morphologic, genetic, and functional characteristics of NK cells from normal donor PBMCs. The cultured CLGLs were characterized by a high proportion of CD5(dim) expressing cells, of which the majority of cells co-expressed CD3 and CD8, but did not express TCRαβ and TCRγδ. The phenotype of the majority of the CLGLs was CD5(dim)CD3(+)CD8(+) TCRαβ(-)TCRγδ(-)CD4(-)CD21(-)CD11c(+/-)CD11d(+/-)CD44(+). The expression of mRNAs for NK cell-associated receptors (NKG2D, NKp30, NKp44, Ly49, perforin, and granzyme B) were highly upregulated in cultured CLGLs. Specifically, NKp46 was remarkably upregulated in the cultured CLGLs compared to PBMCs. The mRNAs for the NKT-associated iTCRα gene in CLGLs was present at a basal level. The cytotoxic activity of the CLGLs against canine NK cell-sensitive CTAC cells was remarkably elevated in a dose-dependent manner, and the CLGLs produced large amounts of IFN-γ. The antitumor activity of CLGLs extended to different types of canine tumor cells (CF41.Mg and K9TCC-pu-AXC) without specific antigen recognition. These results are consistent with prior reports, and strongly suggest that the selectively expanded CLGLs represent a population of canine NK cells. The results of this study will contribute to future research on canine NK cells as well as NK cell-based immunotherapy.

Successful cross-presentation of allogeneic myeloma cells by autologous alpha-type 1-polarized dendritic cells as an effective tumor antigen in myeloma patients with matched monoclonal immunoglobulins

AbstractsFor wide application of a dendritic cell (DC) vaccination in myeloma patients, easily available tumor antigens should be developed. We investigated the feasibility of cellular immunotherapy using autologous alpha-type 1-polarized dendritic cells (αDC1s) loaded with apoptotic allogeneic myeloma cells, which could generate myeloma-specific cytotoxic T lymphocytes (CTLs) against autologous myeloma cells in myeloma patients. Monocyte-derived DCs were matured by adding the αDC1-polarizing cocktail (TNFα/IL-1β/IFN-α/IFN-γ/poly-I:C) and loaded with apoptotic allogeneic CD138+ myeloma cells from other patients with matched monoclonal immunoglobulins as a tumor antigen. There were no differences in the phenotypic expression between αDC1s loaded with apoptotic autologous and allogeneic myeloma cells. Autologous αDC1s effectively took up apoptotic allogeneic myeloma cells from other patients with matched subtype. Myeloma-specific CTLs against autologous target cells were successfully induced by αDC1s loaded with allogeneic tumor antigen. The cross-presentation of apoptotic allogeneic myeloma cells to αDC1s could generate CTL responses between myeloma patients with individual matched monoclonal immunoglobulins. There was no difference in CTL responses between αDC1s loaded with autologous tumor antigen and allogeneic tumor antigen against targeting patients myeloma cells. Our data indicate that autologous DCs loaded with allogeneic myeloma cells with matched immunoglobulin can generate potent myeloma-specific CTL responses against autologous myeloma cells and can be a highly feasible and effective method for cellular immunotherapy in myeloma patients.

Dendritic cells loaded with myeloma cells pretreated with a combination of JSI-124 and bortezomib generate potent myeloma-specific cytotoxic T lymphocytes in vitro

Signal transducer and activator of transcription 3 (STAT3) is highly activated in multiple myeloma. Activated STAT3 promotes survival and proliferation of cancer cells, suppresses Th1 immune response, and induces dysfunction of immune cells. We investigated whether pretreating myeloma cells with a phosphor (p)-STAT3 inhibitor (JSI-124) and/or bortezomib before loading into dendritic cells (DCs) can affect DC function. The combination treatment with JSI-124 and bortezomib resulted in the highest expression of heat shock protein (HSP) 90 and the lowest expression of p-STAT3 in dying myeloma cells. DCs loaded with dying myeloma cells treated by JSI-124 and bortezomib produced the least amount of p-STAT3 compared to other treatments. The DCs were recovered from abnormal cytokine secretions of interleukin (IL)-10, IL-6, and IL-23 without any effect on production of IL-12p70. DCs loaded with JSI-124 and bortezomib treated, dying myeloma cells most potently generated myeloma-specific cytotoxic T lymphocytes (CTLs). The data suggest that pretreatment of myeloma cells with JSI-124 and bortezomib can recover DC function through the up-regulation of HSP90 and the down-regulation of p-STAT3 and inhibitory cytokines, and that these DCs can potently generate myeloma-specific CTLs.

Optimal culture conditions for the generation of natural killer cell-induced dendritic cells for cancer immunotherapy

Dendritic cell (DC)-based vaccines continue to be considered an attractive tool for cancer immunotherapy. DCs require an additional signal from the environment or other immune cells to polarize the development of immune responses toward T helper 1 (Th1) or Th2 responses. DCs play a role in natural killer (NK) cell activation, and NK cells are also able to activate and induce the maturation of DCs. We investigated the types of NK cells that can induce the maturation and enhanced function of DCs and the conditions under which these interactions occur. DCs that were activated by resting NK cells in the presence of inflammatory cytokines exhibited increased expression of several costimulatory molecules and an enhanced ability to produce IL-12p70. NK cell-stimulated DCs potently induced Th1 polarization and exhibited the ability to generate tumor antigen-specific cytotoxic T lymphocyte responses. Our data demonstrate that functional DCs can be generated by coculturing immature DCs with freshly isolated resting NK cells in the presence of Toll-like receptor agonists and proinflammatory cytokines and that the resulting DCs effectively present antigens to induce tumor-specific T-cell responses, which suggests that these cells may be useful for cancer immunotherapy.