Biomedical subjects
Publications and source records attributed to Yong-Rok Kim.
We have newly fabricated a long one-dimensional (1D) mesoporous carbon nanofiber by using a mesoporous silica nanofiber template. The resulting mesoporous carbon nanofiber shows the unique mesoporous structure of circularly wound nanochannel alignment perpendicular to the long fiber axis and the high gas sorption property, which interestingly presents the p-type semiconducting behavior.
Unique starlike CdS particles were prepared from the lyotropic triblock copolymer solution system. The starlike CdS consists of a spherical core and dozens of the attached conical nanolobes. From the comparative studies with the spherical and rod-shaped CdS nanoparticles, the unique photophysical property is presented for the starlike CdS particle. The experimental results suggest that the photogenerated charge carriers at the tip-edge region of the conical nanolobe in the starlike CdS system diffuse into the thicker inner part including the core region, which is possibly due to the decreasing excited state potential gradient from the tip edge to the thicker inner part. This type of charge carrier diffusion dynamics from the surrounding to the thicker inner part in this anisotropic morphology of the starlike CdS semiconductor closely resembles the energy transfer dynamics in the organic dendrimers.
Large-dimension heterogeneous nanoporous membranes were obtained by the formation of CdS doped mesoporous silica within the porous channels of alumina membranes.
The mechanism of cell death by pheophorbide a (Pba) which has been established to be a potential photosensitizer was examined in experimental photodynamic therapy (PDT) on Jurkat cells, a human lymphoid tumor cell line. In 30-60 min after irradiation, Pba treated cells exhibited apoptotic features including membrane blebbing and DNA fragmentation. Pba/PDT caused a rapid release of cytochrome c from mitochondria into the cytosol. Sequentially, activation of caspase-3 and the cleavage of poly ADP-ribose polymerase (PARP) were followed. Meanwhile, no evidence of activation of caspase-8 was indicated in the cells. In experiments with caspase inhibitors, it was found that caspase-3 alone was sufficient initiator for the Pba-induced apoptosis of the cells. Pba specific emission spectra were confirmed in the mitochondrial fraction and the light irradiation caused a rapid change in its membrane potential. Thus, mitochondria were entailed as the crucial targets for Pba as well as a responsible component for the cytochrome c release to initiate apoptotic pathways. Taken together, it was concluded that the mode of Jurkat cell death by Pba/PDT is an apoptosis, which is initiated by mitochondrial cytochrome c release and caspase-3-pathways.
Aligned nanowires of organic luminescent material were prepared by introducing the organic luminants into nanochannels of variable size in an anodic aluminum oxide (AAO) membrane, and the emission spectra from these nanowire arrays exhibited novel size-dependent luminescent properties.