Tsuyoshi Nishisaka

Detection of 1270 nm emission from singlet oxygen and photocytotoxic property of sugar-pendant 60 fullerenes.

Sugar-pendant [60] fullerene derivatives have been prepared from carbohydrate-linked azides 1a-e. Both monosugar (4a-e) and bissugar derivatives (5a-e) produce singlet oxygen ((1)O(2)) under laser irradiation (355 nm) proved by the direct observation of (1)O(2) emission at 1270 nm. Monosugar derivatives exhibit photocytotoxicity varying by the attached sugar molecule.

High-intensity pulsed laser irradiation accelerates bone formation in metaphyseal trabecular bone in rat femur

Abstract. Low-energy laser irradiation has positive effects on bone fracture healing, osteoblast proliferation, bone nodule formation, and alkaline phosphatase activity. However, the mechanism by which low-energy laser irradiation affects bone is not clearly known. It was recently found that light at a low radiation dosage is absorbed by intracellular chromophores. High-intensity pulsed laser irradiation can produce acoustic waves in the target surface by rapidly heating the tissue. We considered that the acoustic waves induced by high-intensity pulsed laser irradiation, in addition to the photochemical effects that are induced, accelerate bone formation. To clarify whether high-intensity pulsed laser irradiation accelerates bone formation, we investigated bone formation in the irradiated femur of rat, using histomorphometric analysis. Rat femurs were irradiated with a Q-switched Nd: YAG laser, which has a wavelength of 1064 nm, under two conditions: once a day, with the average fluence rate set at 100 mW/cm2 (LA1), and twice a day, i.e., every 12 h, with the average fluence rate set at 50 mW/cm2 (LA2). The mean bone volume and mineral apposition rate in the LA1 group were significantly higher than those in the nonirradiated group (control). These values were highest for the LA2 group, and were about 1.52 and 1.25-fold those of the control, respectively. These data demonstrated that the number of pulses, rather than the intensity of the laser irradiation, affects bone formation. Thus, this study indicated that high-intensity pulsed laser irradiation accelerates bone formation in the metaphysis. This bone formation induced by high-intensity pulsed laser irradiation might be due to laser-induced pressure waves.

Comparison of phototoxicity mechanism between pulsed and continuous wave irradiation in photodynamic therapy

A study has been conducted in which HeLa cells are incubated with hematoporphyrin derivative (HpD) for 1 h (1 microgram/ml of HpD in PBS) to compare the use of continuous wave (CW) and pulsed laser (10 Hz repetition rate and 7-9 ns pulse width) light for photodynamic therapy. Cytotoxic effects on the cells are evaluated by the 3-(4,5-dimethyl-2-thiazolyl)-2-5-diphenyl-2H-tetrazolium bromide (MTT) assay and the fluorescein diacetate (FDA)/propidium iodide (PI) stain method using a flow cytometer. The type of cell death is estimated by analysis of the DNA content and observation of the nuclear morphology. The cytotoxicity ratio of cells irradiated by pulsed laser light is estimated to be lower than that for CW laser light. The viability of cells that received pulsed laser light gradually decreases, whereas no significant changes are found in the cells irradiated with CW laser light with the elapse of post-irradiation time. The type of cell death differs between the pulsed and CW laser light irradiations. These findings suggest that the cytotoxic efficacy of the excitation light source is displayed by the difference in the type of cell death, namely apoptosis or necrosis.

Enhancement of cytotoxic effect of bleomycin with transient permeabilization of plasma membrane by laser-induced multiple stress waves in vitro

We investigated the effect of multiple stress waves with peak stress of less than 3 MPa on chemosensitivity of HeLa cells adhered on plastic. HeLa cells exposed to stress waves retained more than 95% of the viability found in untreated cells. The scanning electron microscopy of cells exposed to stress waves showed ruffling microvilli, indicating a change in the cell surface morphology. The cytotoxicity of bleomycin (BLM) on HeLa cells was enhanced by the stress waves exposure. Our findings demonstrated that the low-intensity stress wave would allow to deliver the BLM molecules into cytoplasm by repetition exposure.

Photoinduced hydrogen evolution with vilogen-linked water-soluble zinc porphyrins in a micellar system

Etude de la reaction dans un systeme contenant le complexe du zinc avec une porphyrine substituee, le dinucleotide nicotinamide-adenine phosphate sous sa forme reduite et une hydrogenase

Uptake and Retention of Zinc Tetrasulfophthalocyanine (ZnTSPc) in Tumor Cells

Abstract The availability of ZnTSPc as a tumor localizer was studied. ZnTSPc was administered to C3H/He mice via a tail vein (15 mg/kg), and at various intervals the tumor (transplanted MH-134 cells) as well as some organs were removed, and the fluorescence of ZnTSPc was measured. Accumulation of ZnTSPc in the tumor was higher than in other organs except for the liver at 8 hours after administration. Though ZnTSPc was detected in the liver even longer than 50 days after injection, ZnTSPc was not incorporated in the brain.