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Rewriting Life

Germ-Stabbing Particles

New type of drug kills antibiotic-resistant bacteria

Source: “Biodegradable nanostructures with selective lysis of microbial membranes”
James Hedrick et al.
Nature Chemistry 3: 409-414

Nanokiller: This infectious yeast cell has been split open by an anti­microbial nanoparticle.

Results: Nanoparticles designed to disrupt the cell membranes of a large group of pathogens, including multidrug-­resistant Staphylococcus aureus, cause the cells to burst open but don’t harm human red blood cells.

This story is part of our July/August 2011 Issue
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Why it matters: Because the nanoparticles don’t target a specific genetic pathway, researchers hope bacteria will be slow to develop resistance to them. Previous attempts to make polymers that kill microbes by poking holes in cell membranes have raised safety concerns because they tend to harm some animal cells, too, or they haven’t worked as well in the body as they did in a test tube.

Methods: Chemists at IBM Almaden Research drew on a library of previously developed polymer building blocks to make nanoparticles that would target the cell membranes of a large group of infectious agents called gram-positive bacteria. The polymers are designed to self-assemble in water or blood, forming spherical nanoparticles whose outer layer interacts with these cell membranes. They’re also tailored to be broken down by the body after a short time. In test tubes, the nanoparticles killed several kinds of bacteria—including drug-resistant staph, a major issue in hospitals—and some infectious fungi as well. The researchers also demonstrated that the nanoparticles didn’t harm human red blood cells in test tubes and had no apparent ill effects on mice that were injected with them.

Next Steps: Further tests are needed to prove that the polymers are safe. And the researchers will have to show that the drugs work in the complex environment of the human body.

Quick-Charging Batteries

A new type of ­cathode could enable cell phones to recharge in just 30 seconds

Source: “Three-dimensional bicontinuous ultrafast-charge and -discharge bulk battery electrodes”
Paul V. Braun et al.
Nature Nanotechnology online, March 20, 2011

Results: A new way of making battery electrodes from metal foams has yielded a lithium-­ion battery that recharges 50 times as fast as traditional ones, without compromising the total amount of energy stored. The prototype can recharge to 90 percent of its capacity in two minutes.

Why it matters: The main limit on recharging speeds today is the movement of electrons and ions in and out of one of the battery’s two electrodes, the cathode. The new cathode has a highly porous structure that allows ions to move in and out speedily. The metal substrate itself is highly conductive, and the structure has a large surface area, so it can be coated with enough active battery material to store a large amount of energy. The design is compatible with a range of different battery types. Cell phones incorporating this technology could recharge in 30 seconds, and electric cars could recharge in the time it takes to fill a gas tank.

Methods: Researchers at the University of Illinois at Urbana-Champaign first made the metal foam for the electrodes, starting with a matrix of tiny polymer spheres. They used a common method called electroplating to coat the spheres with nickel, then dissolved the polymer and polished the metal, leaving a spongelike nickel foam that’s 90 percent open space. Finally, they grew active battery materials on the foam and combined the finished cathode with an anode and an electrolyte to create complete cells.

Next Steps: The Illinois group will have to prove that the cathodes can be manufactured economically. They’re also working on demonstrating the cathodes with a wide range of batteries to see whether recharging times can get even faster.

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