Young Mee JungDepartment of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790- 784, Korea Received August 11, 2003Key Words : Urea, 2D correlation spectroscopy, Association process, Hydrogen bondingThe denaturation of protein induced by urea has beenintensively studied.
Recently, in tissue engineering, ionizing radiation has been used as stimulation. Especially, several studies showed that low-dose ionizing radiation induced the stimulation of cell proliferation. Also, it is reported that single low dose γ-irradiation for whole-body or lymphoid-organ significantly improved the spontaneous recovery. The purpose of this study is to investigate behavior and differentiation of human adipose tissue-derived stem cells (hASCs) and rabbit bone marrow stromal cells (rBMSCs) after low dose and high dose of γ-irradiation. Cells were irradiated with γ-rays of 1, 10, 100 mGy and 1 Gy. In addition, we investigated the effects on the osteogenic differentiation of γ-irradiation. PLLA scaffolds with 90% porosity and 300-500 μm pore size were fabricated and cells were seeded onto the scaffolds. After that, cell-scaffold construct were irradiated with 1 mGy and implanted subcutaneously in nude mice for up to 10 weeks. Specimens were harvested after 10 weeks and analyzed. In the results, p-H2AX/DAPI ratio increased with time while the p-H2X expression was not found all time point in control (no irradiation) group. But, in the group radiated with low γ-ray (1 mGy), the p-H2X expression almost did not appear similar with non-radiated group. However, in the osteogenic differentiation tests, the control group and the irradiated group revealed no significant difference. In conclusion, low dose γ-irradiation could be used as stimulation for tissue engineering using specific stem cells and consequently, this system will be useful for combination technology of radiation and cell therapy. However, further studies are needed for examining the general mechanism of the effects on the low dose irradiation for stem cells.
Tumor markers play an important role in the diagnosis, treatment, and monitoring of tumors. Carcinoembryonic antigen (CEA) is a breast and rectal cancer biomarker that plays a crucial role in the early detection of cancer. Therefore, designing a suitable and ultrasensitive method for CEA analysis is very important. In this study, we demonstrated high surface-enhanced Raman scattering (SERS) performance, high reproducibility, and good biocompatibility of a polystyrene (PS)@Ag/Au chip. This chip was layer-by-layer fabricated by magnetron sputtering to generate abundant "hot spots" between the Ag and Au layers covering PS microspheres. Interestingly, the appropriate thickness of the Au layer was easily controlled. When 4-mercaptobenzoic acid (MBA) was used as a probe molecule to explore the SERS activity of the chip, the enhancement factor reached 1.12×108, with a relative standard deviation of 4.54%. A chip labeled with 5,5'-dithiobis(succinimidyl-2-nitrobenzoic acid) (DSNB) was used for CEA immunological recognition. The SERS intensity ratio I1147/I1186 exhibited a good linear relationship with the CEA concentration over a wide range from 0 to 1000 ng/mL. This chip is expected to be a novel tool in the field of cancer detection.
The effect of hydrostatic pressure (P) on the phase transitions of polystyrene-block-poly(n-pentyl methacrylate) copolymer [PS-b-PnPMA] was investigated with FTIR spectroscopy at various temperatures. The experiments were performed by using a specially designed pressure cell optimized for low-pressure regime (<100 bar) with a higher resolution (∼1 bar). The size of the closed loop consisting of both the lower disorder-to-order transition (LDOT) and the upper order-to-disorder transition (UODT) measured by FTIR spectroscopy becomes smaller with increasing P, consistent with results obtained from birefringence measurement. At lower temperatures with increasing P, the PS main chains are found to move before the PnPMA main chains. This is because the mobility of the PnPMA main chains is restricted due to the cluster formation of the alkyl side chain. At higher temperatures, the PnPMA block chains are more mobile than the PS block chains due to their larger specific volumes. The results indicate that the LDOT is mainly affected by a favorable directional interaction between PS and PnPMA blocks due to the cluster formation of the alkyl side chain, whereas the UODT depends on the combinatorial entropy.
Noble metal-based surface-enhanced Raman scattering (SERS)-active substrates have been developed for decades. However, the nonreproducible aggregation and photoinduced molecular degradation limit the development of SERS technology. To overcome the shortcomings of noble metal-based SERS substrates, we designed ZrO2-based nanoparticles (NPs). By doping Mg and/or Zn ions into the ZrO2 NPs, the SERS activity was significantly improved. Mg/Zn codoping of ZrO2 brought about much higher oxygen deficiency, thereby providing the surface state energy (Ess) level that enables charge transfer (CT). Upon analysis, the primary contribution for the Mg/Zn-codoped ZrO2 was determined to be from the CT resonance effect, resulting in an enhancement factor (EF) as high as 104. Most importantly, Mg/Zn-codoped ZrO2 can be used for highly sensitive antibiotic drug determination. Different kinds of antibiotic drugs can be easily identified and quantitatively analyzed with high sensitivity and reproducibility.
π-Conjugated organic semiconductors are promising materials for surface-enhanced Raman scattering (SERS)-active substrates based on the tunability of electronic structures and molecular orbitals. Herein, we investigate the effect of the temperature-mediated resonance-structure transitions of poly(3,4-ethylenedioxythiophene) (PEDOT) in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT : PSS) films on the interactions between substrate and probe molecules, thereby affecting the SERS activity. Absorption spectroscopy and density functional theory calculations show that this effect occurs mainly due to delocalization of the electron distribution in molecular orbitals, effectively promoting the charge transfer between the semiconductor and probe molecules. In this work, we investigate for the first time the effect of electron delocalization in molecular orbitals on SERS activity, which will provide new design ideas for the development of highly sensitive SERS substrates.
Poly(p-phenylene-3,6-bis(4-(n-butoxy)phenyloxy)pyromellitimide) (C4-PMDA-PDA PI), a well-defined model brush polymer composed of a rodlike polymer backbone with two bristles per repeat unit, was the first reported polyimide to align liquid crystals perpendicular to the rubbing direction at the rubbed film surface. In the present study, we used polarized infrared (IR) spectroscopy and 2D correlation analyses of the resulting IR spectra to study nanoscale films of C4-PMDA-PDA PI rubbed at various rubbing densities. The results of these studies allowed us to establish the nature and sequence of the rubbing-induced segmental reorientations that occur in the polymer molecules at the film surface. The rubbing process was found to reorient the fully rodlike polymer backbones and the n-butyl bristle end groups such that they lay parallel to the rubbing direction. In contrast, rubbing caused the phenyloxy bristle units to reorient to a direction perpendicular to the rubbing direction. These reorientations of the polymer's main chain and bristles became more pronounced with increasing rubbing density, and the rubbing process had a greater effect on the polymer's main chains than on the bristles. The rubbing-induced reorientations of the polymer segments were found to follow the sequence PDA (phenyl ring), imide ring, phenyloxy unit, imide C−N bond, and n-butyl group. It was additionally evident that the rubbing process reorients the imide rings biaxially, that is, both along the rubbing direction and out of the plane. This biaxial reorientation was found to be accompanied by a biaxial reorientation of the bristles chemically bonded to the PMDA unit that includes the imide rings. In particular, increasing the rubbing density enhanced the out-of-plane reorientation of the imide rings. In contrast, no rubbing-induced inclination of the reoriented imide rings (i.e., the polymer's main chains) was detected.
'%3e%3cg id='b'%3e%3cpath id='a' stroke='%23000' stroke-width='2' d='M-6-25H6m-12 3H6m-12 3H6'/%3e%3cuse xlink:href='%23a' y='44'/%3e%3c/g%3e%3cpath stroke='%23fff' d='M0 17v10'/%3e%3ccircle r='12' fill='%23cd2e3a'/%3e%3cpath fill='%230047a0' d='M0-12A6 6 0 0 0 0 0a6 6 0 0 1 0 12 12 12 0 0 1 0-24z'/%3e%3c/g%3e%3cg transform='rotate(-123.69)'%3e%3cuse xlink:href='%23b'/%3e%3cpath stroke='%23fff' d='M0-23.5v3M0 17v3.5m0 3v3'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)