Preparation of TiO2-coated LiMn2O4 by carrier transfer method

The TiO₂-coated LiMn₂O₄ has been prepared by a carrier transfer method and investigated. This novel synthetic method involved the transfer of TiO₂ into the surface of LiMn₂O₄ with Vulcan XC-72 active carbon powders as a dispersant. The X-ray diffraction shows that spinel structure of materials does not change after the coating of TiO₂. The electrochemical performance tests show that the initial discharge capacity of TiO₂-modified LiMn₂O₄ is 111.5 mA h g⁻¹, which is better than that of pristine LiMn₂O₄ (103.8 mA h g⁻¹). The cyclic performance is significantly improved after surface modification. The TiO₂-modified LiMn₂O₄ by a carrier transfer method exhibits better discharge capability and lower resistance.     

Effect of ultrasound irradiation on bacterial internalization and bacteria-mediated gene transfer to cancer cells

The present study demonstrates that ultrasound irradiation can facilitate bacteria-mediated gene delivery (bactofection). Escherichia coli modified with avidin were employed as a vehicle for delivery of the green fluorescent protein (GFP) gene, a model heterologous gene, into the breast cancer cell line MCF-7. Avidin-mediated binding of E. coli to MCF-7 cells enhanced the internalization of E. coli by approximately 17%, irrespective of the use of ultrasound irradiation. Furthermore, the use of ultrasound irradiation increased the internalization by approximately 5%, irrespective of the presence of avidin on the E. coli cell surface. The percentages of GFP-expressing MCF-7 cells at 24 h after bactofection were below 0.5% and 2% for the case with only avidin-modification of E. coli cell surface and only ultrasound irradiation, respectively. However, combining avidin modification with the ultrasound treatment increased this value to 8%. Thus, the use of avidin-modified bacteria in conjunction with ultrasound irradiation has potential as an effective strategy for tumor-targeted bactofection.     

Subcellular impact of sonoporation on plant cells: Issues to be addressed in ultrasound-mediated gene transfer

Sonoporation (membrane perforation via ultrasonic cavitation) is known to be realizable in plant cells on a reversible basis. However, cell viability may concomitantly be affected over the process, and limited knowledge is now available on how such cytotoxic impact comes about. This work has investigated how sonoporation may affect plant cells at a subcellular level and in turn activate programmed cell death (PCD). Tobacco BY-2 cells were used as the plant model, and sonoporation was applied through a microbubble-mediated approach with 100:1 cell-to-bubble ratio, free-field peak rarefaction pressure of either 0.4 or 0.9 MPa, and 1 MHz ultrasound frequency (administered in pulsed standing-wave mode at 10% duty cycle, 1 kHz pulse repetition frequency, and 1 min duration). Fluoroscopy results showed that sonoporated tobacco cells may undergo plasma membrane depolarization and reactive oxygen species elevation (two cellular disruption events closely connected to PCD). It was also found that the mitochondria of sonoporated tobacco cells may lose their outer membrane potential over time (observed using confocal microscopy) and consequently release stores of cytochrome-c proteins (determined by Western Blotting) into the cytoplasm to activate PCD. These findings provide insight into the underlying mechanisms responsible for sonoporation-induced cytotoxicity in plant cells. They should be taken into account when using this membrane perforation approach for gene transfection applications in plant biotechnology.     

Control by osmolarity and electric field strength of electro-induced gene transfer and protein release in fission yeast cells

A high electric pulse was applied to the uptake of DNA into cells, the sterilization of cells, and the release of protein from cells. These applications to fission yeast showed a strong dependence on both the osmolarity of pulsing sorbitol solution and the intensity of the electric pulse. In electroporation, high transformation efficiency was obtained with a wide range of sorbitol (0.6–1.6 M) at 10.0 kV/cm for about 5 ms. Furthermore, the highest efficiency was achieved in 1.5 M sorbitol at a higher strength, 12.5 kV/cm, although the cell survival rate dropped. The release of protein generally increased with increasing electric field strength, due mainly to leakage from dead cells under hypotonic conditions. However, protein was released significantly in 1.5 M sorbitol at a lower strength, 7.5 kV/cm, although a high survival rate was maintained. Thus, the application of the high electric pulse to fission yeast under hypertonic conditions increased the uptake and release of macromolecules controlled by the electric field strength.     

Induction of osteoconductivity by BMP-2 gene modification of mesenchymal stem cells combined with plasma-sprayed hydroxyapatite coating

Success in bone implant depends greatly on the composition and surface features of the implant. The surface-modification measures not only favor the implant's osteoconductivity, but also promote both bone anchoring and biomechanical stability. This paper reports an approach to combine a hydroxyapatite (HA) coated substrate with a cellular vehicle for the delivery of bone morphogenetic protein-2 (BMP-2) synergistically enhancing the osteoconductivity of implant surfaces. We examined the attachment, growth and osteoinductive activity of transfected BMP-producing bone marrow mesenchymal stem cells (BMSCs) on a plasma-sprayed HA coated substrate. It was found that the HA coated substrate could allow the attachment and growth of BMP-2 gene modified BMSCs, and this combined application synergistically enhanced osteconductivity of the substrate surface. This synergistic method may be of osseointegration value in orthopedic and dental implant surgery.     

Muon catalyzed fusion and muon to 3He transfer in solid T2 studied by X-ray and neutron detection

X-ray and neutron measurements were carried out for muon catalyzed fusion and related phenomena in solid T₂. The X-ray originated from the μ^- to α sticking in muon catalyzed fusion; t + t + μ ^- → (μ ^- α) + 2n was measured for the first time, yielding K _α X-ray intensity of (μα) atom and the intensity ratio of K _β to K _α . Utilizing the phenomena of ³He accumulation in solid T₂, the X-ray in the μ^- transfer process from (tμ) to ³He was detected, providing a formation rate and radiative decay branching-ratio of (t ³Heμ) molecule. From fusion neutron measurements, estimated values were obtained for (ttμ) molecular formation rate as well as sticking probability ω_t in ttμ fusion. A possible new insight in t + t fusion reaction process at a low energy limit is also obtained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Photon down-shifting by energy transfer from Sm3+ to Eu3+ ions in sol-gel SiO2-LaF3 nano-glass-ceramics for photovoltaics

95SiO₂?C5LaF₃ sol-gel derived nano-glass-ceramics single doped with Eu³⁺ or Sm³⁺ and codoped with both of them were successfully obtained. XRD measurements confirm the precipitation of LaF₃ nanocrystals after the ceramming process, with mean size ranging from 10 to 20?nm which increases with the thermal treatment temperature. The incorporation of rare-earth ions into precipitated LaF₃ nanocrystals was confirmed from luminescence spectra. Intense yellow-red emissions were detected under UV and blue light excitation in single and codoped samples. The effect of codoping with Eu³⁺ and Sm³⁺ ions and the energy transfer mechanism between them have been analyzed in order to increase the yellow-red emissions.     

Selective stimulation of catecholamine release from bovine adrenal chromaffin cells by an ionotropic purinergic receptor sensitive to 2-methylthio ATP

Background  

2-Methylthioadenosine 5'-triphosphate (2-MeSATP), formerly regarded as a specific P2Y (metabotropic) purinergic receptor agonist, stimulates Ca²⁺ influx and evokes catecholamine release from adrenal chromaffin cells. These cells express P2Y and P2X (ionotropic) purinoceptors, with the latter providing an important Ca²⁺ influx pathway. Using single cell calcium imaging techniques, we have determined whether 2-MeSATP might be a specific P2X receptor agonist in bovine chromaffin cells and assessed the relative role of P2X and P2Y receptors on catecholamine secretion from these cells.     

Converting of the 2D graphene to its 3D by chicken red blood cells as sheets separator for construction supercapacitor electrode

Here, we report on a facile green and scalable method for the fabrication of porous 3D graphene as a well-known carbon-based material used in many energy storage devices. Chicken red blood cells were used as sheets spacer and heteroatom sources in the construction of 3D graphene. First, the red blood cells were separated from the blood and mixed with graphene oxide. Then, the mixture was freeze-dried and carbonized at 700 °C. The resulted 3D graphene containing heteroatoms was used as a supercapacitor electrode modifier on a glassy carbon electrode and tested with various electrochemical techniques. The supercapacitor electrode showed a specific capacitance of 330 F g⁻¹ at a current density of 1 A g⁻¹, maximum power density of 1958 W kg⁻¹, and maximum energy density of 85 Wh kg⁻¹. Furthermore, the supercapacitive performances were tested in a two-electrode symmetrical system which exhibited a specific capacitance of 238 F g⁻¹ for 1 A g⁻¹. It also showed a power density of 2200 W kg⁻¹ and an appreciable energy density of 160 Wh kg⁻¹. The excellent electrochemical behavior of 3D graphene indicates the promising abilities of the composite for other applications such as biosensors, batteries, electrocatalysts, etc.     

Quantitative liver iron measurement by magnetic resonance imaging: in vitro and in vivo assessment of the liver to muscle signal intensity and the R2* methods

Purpose

To evaluate the liver-to-muscle signal intensity and R2* methods to gain a transferable, clinical application for liver iron measurement.

Materials and Methods

Sixteen liver phantoms and 33 human subjects were examined using three 1.5-T MRI scanners from two different vendors. Phantom-to-muscle and liver-to-muscle signal intensity ratios were analyzed to determine MRI estimated phantom and hepatic iron concentration (M-PIC and M-HIC, respectively). R2* was calculated for the phantoms and the liver of human subjects. Seven patients' biochemical hepatic iron concentration was obtained.

Results

M-PIC and R2* results of three scanners correlated linearly to phantom iron concentrations (r=0.984 to 0.989 and r=0.972 to 0.981, respectively), and no significant difference between the scanners was found (P=.482 and P=.846, respectively) in vitro. The patients' R2* correlated linearly to M-HIC of the standard scanner (r=0.981). M-HIC values did not differ from those obtained from the biopsy specimens (P=.230). The difference in M-HIC was significant, but the difference in R2* was not significant between the scanners (P<.0001 and P=.505, respectively) in vivo.

Conclusion

Both methods, M-HIC and R2*, are reliable iron concentration indicators with linear dependence on iron concentration in vivo and in vitro. The R2* method was found to be comparable among different scanners. Transferability testing is needed for the use of the methods at various scanners.     

Quantum cutting downconversion by cooperative energy transfer from Bi3+ to Yb3+ in Y2O3 phosphor

Bi~(3+) and Yb~(3+) codoped cubic Y2O3 phosphors are prepared by pechini sol-gel method.Strong near-infrared (NIR) emission around 980 nm from Yb~(3+)(2F5/2 → 2F7/2) is observed under ultraviolet light excitation.A broad excitation band ranging from 320 to 360 nm,owing to the 6s 2 →6s6p transition of Bi~(3+) ions,is recorded when the Yb~(3+) emission is monitored,which suggests a very efficient energy transfer from Bi~(3+) ions to Yb~(3+) ions.The Yb~(3+) concentration dependences of both the Bi~(3+) and the Yb~(3+) emissions are investigated.The decay curve of Bi ~(3+) emission under the excitation of 355 nm pulse laser is used to explore the Bi~(3+) →Yb~(3+) energy transfer process.Cooperative energy transfer (CET) is discussed as a possible mechanism for the near-infrared emission.