Sustainable Energy

From the Labs: Materials

New publications, experiments and breakthroughs in materials science–and what they mean.

Cell Programmer
A polymer implant signals cells to combat cancer.

Cell trainer: Immune cells attracted to nooks in this porous, biodegradable polymer implant are stimulated to attack cancer.

Source: “Infection-Mimicking Materials to Program Dendritic Cells In Situ”
David Mooney et al.
Nature Materials
8: 151-158

This story is part of our May/June 2009 Issue
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Results: A new implant attracts immune cells and exposes them to molecules that stimulate them to attack cancerous tumors. When tested in mice that normally die of cancer within 25 days, the implants allowed 90 percent of the mice to survive. Similar experimental therapies based on transplanting immune cells are only about 60 percent effective.

Why it matters: The implants could eventually be used to treat human cancers that don’t respond to other therapies, and they could also be used to treat immune disorders such as type 1 diabetes and arthritis. Other approaches that involve stimulating immune cells haven’t proved successful in clinical trials. Those techniques require the cells to be removed from the body and then reimplanted; many are damaged in the process and die, while survivors often fail to trigger attacks on cancerous tumors. The new implant stimulates cells inside the body, without subjecting them to stressful procedures.

Methods: The spongelike implant is made of a biodegradable polymer that releases chemical signals called cytokines. In mice with melanoma, these signals attract immune cells called dendritic cells to the nooks and crannies of the implant. There the cells are exposed to a cancer antigen that stimulates them to attack tumors. When tissues from the mice were analyzed, the researchers found that dendritic cells had migrated to the lymph nodes and activated other immune cells, and the animals’ tumors had shrunk.

Next steps: Before proceeding to clinical trials, the implants must pass safety tests in large animals. Long-term studies will then establish whether the immune system will attack cancer that may recur years after the implant has degraded.

Ethanol Fuel Cell
A new catalyst could make the technology usable in portable electronics.

Source: “Ternary Pt/Rh/SnO2 Electrocatalysts for Oxidizing Ethanol to CO2”
Radoslav Adzic et al.
Nature Materials
8: 325-330

Results: A new catalyst efficiently breaks the strong carbon-carbon bond at the center of ethanol molecules, converting ethanol to carbon dioxide in a process that releases protons and electrons. It generates electrical currents 100 times greater than those produced with other catalysts that oxidize ethanol.

Why it matters: Ethanol-powered fuel cells based on the catalyst could open the way for portable electronics that can be refueled faster than battery-powered devices can be recharged. The technology would also be safer than portable fuel cells that use toxic methanol. Previous catalysts used to free electrons from ethanol were inefficient: either they used a great deal of energy to break the carbon-carbon bond or they broke only the molecule’s weaker bonds, releasing just a few electrons per molecule. The new catalyst efficiently frees 12 electrons per molecule without requiring much energy.

Methods: To make the catalyst, researchers at Brookhaven National Laboratory in New York deposited tiny clusters of platinum and rhodium on tin oxide nanoparticles. Rhodium had been shown to break bonds between carbon atoms, but only at high temperatures–200 to 300 °C. Combining the rhodium and platinum with tin oxide allowed it to break these bonds at room temperature, making the catalyst more practical for portable fuel cells.

Next steps: The catalyst will be incorporated into fuel cells to determine whether the current produced can be increased from the 7.5 milli­amps per square centimeter seen in initial tests to the hundreds of milliamps needed for most applications.

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