Integration in a multilayer microfluidic chip of 8 parallel cell sorters with flow control by sol-gel transition of thermoreversible gelation polymer.

Microfluidic systems have significant implications in the field of cell separation since they could provide platforms with inexpensive, disposable and sterile structures. Here, we present a novel strategy to integrate microfluidic sorters into a single chip for high throughput sorting. Our parallel sorter consists of a microfluidic chip with a three-dimensional channel network that utilizes flow switching by a heat-induced sol-gel transition of thermoreversible gelation polymer. The 8 parallel sheathed sample flows were realized by injecting sample and buffer solutions into only 2 inlets. The sheathed flows enabled disposal of unwanted sample waste without laser irradiation, and collection of wanted sample upon irradiation. As an application of the sorter, two kinds of fluorescent microspheres were separated with recovery ratio and purity of 70% or 90% at throughputs of about 100 or 20 particles per second, respectively. Next, Escherichia coli cells expressing green fluorescent protein were separated from those expressing DsRed with recovery ratio and purity of 90% at a throughput of about 20 cells per second.

On-chip microfluidic sorting with fluorescence spectrum detection and multiway separation.

The microfluidic platform is an important tool for diagnosis and biomedical studies because it enables us to handle precious cells and infectious materials safely. We have developed an on-chip microfluidic sorter with fluorescence spectrum detection and multiway separation. The fluorescence spectrum of specimens (495-685 nm) in the microchannels was obtained every 2 ms using a 1 x 16 arrayed photomultiplier tube. The specimen was identified by its spectrum and collected into the corresponding channel based on our previously reported thermoreversible gelation polymer technique (Y. Shirasaki, J. Tanaka, H. Makazu, K. Tashiro, S. Shoji, S. Tsukita and T. Funatsu, Anal. Chem., 2006, 78, 695-701). Four kinds of fluorescence microspheres and three kinds of Escherichia coli cells, expressing different fluorescent proteins, were successfully separated with accuracy and purity better than 90% at a throughput of about one particle per second.

A preliminary study on influence of negative air ions generated from pajamas on core body temperature and salivary IgA during night sleep.

OBJECTIVES: This study was conducted to examine whether negative air ions generated from pajamas would influence the rectal temperature and the immune system during night sleep. MATERIALS AND METHODS: Nine females (aged 18-23 years) served as participants. They slept during the night in their homes, wearing the pajamas with generation of negative air ions (1260 ions/cm3) and with normal standard (520 ions/cm3). The sequence of wearing the pajamas was: first, standard pajamas; second, pajamas with negative air ions; and third, standard pajamas again, each being worn for three consecutive days. RESULTS: Rectal temperature in the pajamas with negative air ions tended to fall more significantly during the night-time (p = 0.068). Salivary IgA tended to be higher on waking when wearing pajamas with negative air ions (p = 0.094) and its effect continued even after standard pajamas were worn again during last three days. CONCLUSION: These results suggest that the rectal temperature could possibly be more reduced and the elevation of salivary IgA more marked if the pajamas with negative air ions are worn during nocturnal sleep.