Quantum dots (QDs), as novel fluorescence probes, have shown a great potential for bio-molecular labeling and cellular imaging. To stain cellular targets, the sufficient intracellular delivery of QDs is required. In this work the tat, a typical membrane-permeable carrier peptide, was conjugated with thiol-capped CdTe QDs to form CdTe Tat-QDs, and the intracellular deliveries of CdTe QDs or CdTe Tat-QDs were compared in human hepatocellular carcinoma (QGY) cells and human breast cancer (MCF7) cells in vitro by means of confocal laser scanning microscopy. Added into the cell dishes, both QDs and Tat-QDs adhered to the outer leaflet of the plasma membrane of cells within a few minutes, but the binding amount of Tat-QDs was obviously higher than that of QDs. Then both QDs and Tat-QDs can penetrate into cells, and their cellular contents increased with incubation time but both saturated after 3 hours incubation. However the cellular levels of Tat-QDs were higher than those of QDs, with the ratio of 2.1 (+/-0.3) times in QGY cells and 1.5 (+/-0.2) times in MCF7 cells, demonstrating the enhancing effect of Tat conjugation on the intracellular delivery of QDs.

SiN x films deposited on silicon in a plasma-enhanced chemical vapor deposition ͑PECVD͒ reactor from a mixture gas of SiH 4 and NH 3 are investigated as an alternative method for low-stress membrane fabrication. We verified that the stress in the silicon nitride films decreased as a function of deposition pressure. A low tensile stress in the film of 170 MPa was obtained at a pressure of 750 mTorr and the refractive index of the film was 1.8. After KOH wet etching from the back side of the silicon substrate, a flat square ͑5 ϫ 5 mm͒ membrane with thickness of 500 nm could be successfully fabricated. The chemical composition of the film was analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, with lower deposition pressures producing less Si-H bonding.Silicon nitride ͑SiN x ͒ has a wide range of applications in the microelectronic technology, including as an insulator and passivation layer on Si 1 and as a masking material for KOH etching. 2 Silicon nitride has been used in bulk micromachining, as its mechanical strength allows the fabrication of large membranes. 3 In surface micromachining, silicon nitride has been applied to devices such as interferometers, 4 where both the mechanical and the optical properties of the material are important. Most of these applications need membranes with a flat surface. This can be achieved by controlling the initial mechanical stress in films of silicon nitride, which must be tensile, but with a value sufficiently low to avoid membrane cracking after silicon substrate etching. Silicon nitride is the most common dielectric membrane material because it can be deposited with a low tensile stress by various methods and it has a very low etch rate in silicon wet anisotropic etchants. 5 The low stress state is often achieved by using low-pressure chemical vapor deposition ͑LPCVD͒ ͑Ͼ750°C͒ silicon-rich nitride films. 6,7 Low-temperature fabrication ͑Ͻ300°C͒ has many advantages over traditional, higher temperature ͑Ͼ750°C͒ deposition because a wider range of applications is made possible. Plasma-enhanced chemical vapor deposition ͑PECVD͒ is a common method of low-temperature fabrication of these films ͑Ͻ300°C͒. In this work, we succeeded in fabricating low-stress ͑Ͻ300 MPa͒ silicon nitride PECVD films, enabling realization of freestanding 5 ϫ 5 mm membranes. ExperimentalSiN x films were deposited in a radio frequency ͑rf, 13.56 MHz͒ PECVD parallel-plate reactor ͑Unaxis-Nextral D200͒ from a mixture of SiH 4 ͑20%͒, NH 3 , N 2 , and He. Those parameters which affect the stress of silicon nitride film are rf power, working pressure, flow ratio of SiH 4 /NH 3 , and temperature. In our experiments, the rf power was varied from 50 to 200 W. The ratio of silane ͑20%͒ to ammonia was varied from 0.125 to 0.625. The working pressure was varied from 600 to 800 mTorr, and the deposition temperature was varied from 160 to 280°C.Square membranes were fabricated. First the silicon nitride membrane was deposited on both sides of a cleaned p-type Si͗100͘ wafer. Squar...

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The effects of He-Ne laser irradiation on erythrocyte hemolysis were studied. Erythrocytes are prone to be easily damaged with hemolysis under laser irradiation. It was found that the power density (PD) of laser irradiation, but not the total irradiation power, is the crucial parameter for the hemolysis. Under irradiation with a PD of 5.41 mW/microm(2), erythrocytes were photohemolyzed within a few seconds, while at a PD of 0.52 mW/microm(2) the average tolerance duration (TD; from the start of irradiation to hemolysis) of erythrocytes was 110 s. The TDs of erythrocytes were also individual erythrocyte-dependent, which may be due to their different ages. The average TDs of erythrocyte samples from different donors were different, reflecting individual variations.

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