The effect of ellagic acid on photodynamic therapy in leukemia cells.

Ellagic acid (EA) is a naturally phenolic acid presented in different foods. It has a variety of biological activities including antioxidant, anti-inflammatory, anti-microbiological and anti-cancer properties. On account of its antioxidant activity, EA might protect cancer cells from free radical damage in photodynamic therapy (PDT) during which reactive oxygen species (ROS) production was stimulated leading to irreversible tumor cell injury. In this study, the influence of EA on K562 cells in 5-aminolevulinic acid (ALA)-based PDT is demonstrated. Cell apoptosis was assayed by flow cytometry. Oxidative damage induced by PDT was investigated by measurement of malondialdehyde (MDA). Comet assay was used to evaluate the potential genotoxic effect induced by PDT on the cells. The results showed that EA supplementation alone did not affect the lipid peroxidation, DNA damage and apoptosis in K562 cells. It increases the lipid peroxidation, DNA damage, apoptosis and decreases the survival rate in K562 cells induced by ALA-PDT. The singlet oxygen quencher sodium azide suppresses apoptosis, lipid peroxidation and DNA damage induced by EA in PDT. In conclusion, EA consumption during PDT did not decrease the effectiveness of cancer therapy on malignant cells. The effect of antioxidants on PDT maybe was determined by its sensitization ability to singlet oxygen.

Research on the effect of formononetin on photodynamic therapy in K562 cells.

At the present time, many cancer patients combine some forms of complementary and alternative medicine therapies with their conventional therapies. The most common choice of these therapies is the use of antioxidants. Formononetin is presented in different foods. It has a variety of biological activities including antioxidant and anti-cancer properties. On account of its antioxidant activity, formononetin might protect cancer cells from free radical damage in photodynamic therapy (PDT) during which reactive oxygen species (ROS) production was stimulated leading to irreversible tumor cell injury. In this study, the influence of formononetin on K562 cells in PDT was demonstrated. The results showed that formononetin supplementation alone did not affect the lipid peroxidation, DNA damage and apoptosis in K562 cells. It increases the lipid peroxidation, DNA damage and apoptosis in K562 cells induced by PDT. The singlet oxygen quencher sodium azide suppresses the apoptosis induced by PDT with formononetin. In conclusion, formononetin consumption during PDT increases the effectiveness of cancer therapy on malignant cells. The effect of antioxidants on PDT maybe was determined by its sensitization ability to singlet oxygen.

Fabrication of nanopores for biomacromolecule detection.

Nanopores embedded in a thin membrane with diameter below 10 nm are suitable for the biomacromolecule detection. For such purpose, in this study, we developed a technique of how to obtain small nanopores in silicon nitride films using a focused-ion-beam (FIB) system. By changing the process parameters, such as the beam current, the film thickness of the membrane and the ion beam exposure time, the diameter of the nanopore can be tuned. Under an optimized condition, high quality nanopores with diameter as low as 6 nm was fabricated on a 7 nm thick membrane. Our result suggests that FIB direct writing technique might be a suitable approach for biomacromolecule detector fabrication.

Nanofluidic channel fabrication and manipulation of DNA molecules.

Confining DNA molecules in a nanofluidic channel, particularly in channels with cross sections comparable to the persistence length of the DNA molecule (about 50 nm), allows the discovery of new biophysical phenomena. This sub-100 nm nanofluidic channel can be used as a novel platform to study and analyze the static as well as the dynamic properties of single DNA molecules, and can be integrated into a biochip to investigate the interactions between protein and DNA molecules. For instance, nanofluidic channel arrays that have widths of approximately 40 nm, depths of 60 nm, and lengths of 50 mum are created rapidly and exactly by a focused-ion beam milling instrument on a silicon nitride film; and the open channels are sealed with anodic bonding technology. Subsequently, lambda phage DNA (lambda-DNA; stained with the fluorescent dye, YOYO-1) molecules are introduced into these nanoconduits by capillary force. The movements of the DNA molecules, e.g. stretching, recoiling, and transporting along channels, are studied with fluorescence microscopy.

The morphology of DNA solution in an open fluidic channel studied by non-contact AFM.

The morphologies of pure buffer solution and DNA-containing solution in an open fluidic channel with rectangle cross section (1 microm in width and 150 nm in depth) have been explored using non-contact AFM. A remarkable feature is that a uniform nano-scale trench (approximately 15 nm deep and 14 microm long) on the surface of the DNA solution has been observed. The presence of two neighboring stretched DNA molecules near the solution surface may be responsible for the configuration of the nanotrench. This new phenomenon of partially stretched DNA molecules is likely to be useful for the future designing of fluidic devices, and for the manipulation and study of single DNA molecules.