MIT crafts bacteria-resistant films( CAMBRIDGE Mass.--Having found that w...)

CAMBRIDGE, Mass.--Having found that whether bacteria stick to surfaces depends partly on how stiff those surfaces are, MIT engineers have created ultrathin films made of polymers that could be applied to medical devices and other surfaces to control microbe accumulation.

The inexpensive, easy-to-produce films could provide a valuable layer of protection for the health care industry by helping to reduce the spread of hospital-acquired infections, which take the lives of 100,000 people and cost the United States an estimated $4.5 billion annually.

The researchers, who describe their work in an upcoming issue of the journal Biomacromolecules, found they could control the extent of bacterial adhesion to surfaces by manipulating the mechanical stiffness of polymer films called polyelectrolyte multilayers. Thus, the films could be designed to prevent accumulation of hazardous bacteria or promote growth of desirable bacteria.

All other factors being equal, mechanical stiffness of material surfaces increases bacterial adhesion, said Krystyn Van Vliet, the Thomas Lord Assistant Professor of Materials Science and Engineering and the paper's anchor author.

Van Vliet and her colleagues found the same trend in experiments with three strains of bacteria: Staphylococcus epidermidis, commonly found on skin, and two types of Escherichia coli.

Stiffness has usually been overlooked in studies of how bacteria adhere to surfaces in favor of other traits such as surface charge, roughness, and attraction to or repulsion from water. The new work shows that stiffness should also be taken into account, said Van Vliet.

The new films could be combined with current methods of repelling bacteria to boost their effectiveness, said Michael Rubner, an author of the paper and director of MIT's Center for Materials Science and Engineering.

Those methods include coating surfaces with antimicrobial chemicals or embedding metal nanopart
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