Extensible chip of optofluidic variable optical attenuator.

A core chip of optofluidic variable optical attenuator (VOA) is reported. The chip, with a simple structure, utilizes microfluid and compressed air to regulate the optical attenuation, and it can be expanded to form a number of VOAs by using different microfluidic driving technologies. Three VOAs based on this chip and different driving technologies are introduced. The theoretical and experimental results show that the proposed chip possesses the advantages of large optical attenuation range (> 50dB) and low insertion loss (0.55 dB). Moreover it is a broadband optical device which can be operated in visible and near infrared wavelengths. The proposed chip provides a new method for seeking miniaturized VOAs with good performances, and it is promising to develop a number of different VOAs.

Time course effect of hypoxia on bone marrow-derived endothelial progenitor cells and their effects on left ventricular function after transplanted into acute myocardial ischemia rat.

OBJECTIVE: Ischemic heart disease is the most common cause of cardiovascular morbidity and mortality in the industrialized world, and the incidence has been increasing in developing countries. Stem cell transplantation has emerged as a potent new therapeutic strategy for acute/chronic ischemic heart disease and has been explored extensively. The present study aimed to investigate whether hypoxic preconditioning of endothelial progenitor cells (EPCs) before transplantation could ameliorate their survival and engraftment in ischemic tissue and the potential mechanisms. MATERIALS AND METHODS: EPCs extracted were subjected to increasing hypoxia for 24-72 h, survival and function of the preconditioned EPCs were assayed in both in vitro and in vivo. RESULTS: Hypoxia for 24 h caused significant enhancements in formation of tube like structure and motility of BM-EPCs (p < 0.05), as well as mRNA expressions of CXCR4, PI3K, AKT, and NF-κB, while these effects were reversed by prolonged hypoxia (48 and 72 h, p < 0.05). Hypoxia of BM-EPCs for 24 h did not result in increased apoptosis resistance, and cell apoptosis was even enhanced by prolonged hypoxia. In vivo transplantation experiments demonstrated the beneficial effect of hypoxic EPCs on left ventricular (LV) functions after acute myocardial ischemia (AMI). CONCLUSIONS: Shorter-term hypoxia showed better survival, differentiation and function of BM-EPCs in vivo, further study was still needed to optimize the hypoxic pattern of BM-EPCs so as to better protect heart from myocardial ischemic injury. The present study showed evidence suggested that hypoxic preconditioning did exert further beneficial effects of BM-EPCs on preservation of LV function after AMI. Short-term exposure to hypoxia for about 24 h provided better condition for survival and function of BM-EPCs.

Enhancement of intracellular delivery of CdTe quantum dots (QDs) to living cells by Tat conjugation.

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.