Rice University researchers report too small a dose may enhance microbes’ immunity

HOUSTON – (July 11, 2012) – Rice University researchers have settled a long-standing controversy over the mechanism by which silver nanoparticles, the most widely used nanomaterial in the world, kill bacteria.

Their work comes with a Nietzsche-esque warning: Use enough. If you don’t kill them, you make them stronger.

Scientists have long known that silver ions, which flow from nanoparticles when oxidized, are deadly to bacteria. Silver nanoparticles are used just about everywhere, including in cosmetics, socks, food containers, detergents, sprays and a wide range of other products to stop the spread of germs.

But scientists have also suspected silver nanoparticles themselves may be toxic to bacteria, particularly the smallest of them at about 3 nanometers. Not so, according to the Rice team that reported its results this month in the American Chemical Society journal Nano Letters.

In fact, when the possibility of ionization is taken away from silver, the nanoparticles are practically benign in the presence of microbes, said Pedro Alvarez, George R. Brown Professor and chair of Rice’s Civil and Environmental Engineering Department.

An international team of researchers led by University of Wisconsin-Madison Professor of Chemical and Biological Engineering Juan J. de Pablo reports in the May 3 edition of the journal Nature , the results of a computational study that shows liquid crystals, manipulated at the smallest scale, can unexpectedly induce the molecules they interact with to self-organize in ways that could lead to entirely new classes of materials with new properties.

The new study modeled the behavior of thousands of rod-shaped liquid crystal molecules packed into nano-sized liquid droplets. It showed that the confined molecules self organize as the droplets are cooled. "At elevated temperatures, the droplets are disordered and the liquid is isotropic," de Pablo explains. "As you cool them down, they become ordered and form a liquid crystal phase. The liquid crystallinity within the droplets, surprisingly, induces water and other molecules at the interface of the droplets, known as surfactants, to organize into ordered nanodomains. This is a behavior that was not known."

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Nanotextured Silica Surfaces with Robust Superhydrophobicity and Omnidirectional Broadband Supertransmissivity

A new way of creating surface textures on glass, developed at MIT, virtually eliminates reflections, producing glass that is almost unrecognizable because of its absence of glare and whose surface causes water droplets to bounce off.

The new "multifunctional" glass, based on surface nanotextures that produce an array of conical features, is self-cleaning and resists fogging and glare, the researchers say. Ultimately, they hope it can be made using an inexpensive manufacturing process that could be applied to optical devices, the screens of smartphones and televisions, solar panels, car windshields and even windows in buildings.

See http://pubs.acs.org/doi/abs/10.1021/nn301112t

Researchers at Harvard-affiliated McLean Hospital have shown a new category of "green" nanoparticles comprised of a non-toxic, protein-based nanotechnology that can non-invasively cross the blood brain barrier and is capable of transporting various types of drugs.

In an article published May 1, 2012 online in PLoS ONE, Gordana Vitaliano, MD, director of the Brain Imaging NaNoTechnology Group at the McLean Hospital Imaging Center, reported that clathrin protein, a ubiquitous protein found in human, animal, plant, bacteria and fungi cells, can been modified for use as a nanoparticle for in-vivo studies. "Clathrin has never been modified for use in vivo and offers many new and interesting possibilities for delivering drugs and medical imaging agents into the brain", said Vitaliano.

Read the full press release here...

Also, a related application of dendrimers here...