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 nanoparticles into the surface, which disrupt the bacterial cell walls.
“For those bacteria that readily form biofilms, we have no delusions that we can prevent bacterial films from starting to form. However, if we can limit how much growth occurs, these existing methods can become much more effective,” Rubner said.Jenny Lichter, graduate student in materials science and engineering, and Todd Thompson, a graduate student in the Harvard-MIT Division of Health Sciences and Technology, are joint lead authors of the paper.
They note that the films could also be used on medical devices that go inside the body, such as stents and other cardiac implants.
“Once a foreign object enters into the body, if you can limit the number of bacteria going in with it, this may increase the chances that the immune system can defend against that infection,” said Thompson.
Another possible application for the films is to promote growth of so- called “good bugs” by tuning the mechanical stiffness of the material on which these bacteria are cultured. These films could stimulate growth of bacteria needed for scientific study, medical testing, or industrial uses such as making ethanol.
The researchers built their films, which are about 50 nanometers (billionths of a meter) thick, with layers of polyelectrolytes (a class of charged polymer). Alternating layers are added at different pH (acidity) levels, which determines how stiff the material is when hydrated at near-neutral pH, such as water. Polymer films assembled at higher pH (up to 6) are stiffer because the polymer chains crosslink readily and the polymers do not swell too much; those added at lower, more acidic pH (down to 2.5) are more compliant.
Van Vliet says the team's results could be explained by the relationship between surfaces and tiny projections from the bacterial cell walls, known as pili. Stiffer surfaces may reinforce stronger, more stable bonds with the bacterial pili. The researchers are now working on figuring out this mechanism.
The research was funded by the National Science Foundation, National Institutes of Health and the Arnold and Mabel Beckman Foundation Young Investigator Program.
Maricela Delgadillo, a senior in materials science and engineering, and Takehiro Nishikawa, a former postdoctoral researcher at MIT, now at the Advanced Medical Engineering Center in Osaka, Japan, are also authors of the paper.
Written by Anne Trafton, MIT News Office
Elizabeth A. Thomson | MIT News Office
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences