Team shapes cell behavior research

A team led by James Henderson, assistant professor of biomedical and chemical engineering in Syracuse University's L.C. Smith College of Engineering and Computer Science (LCS) and researcher in the Syracuse Biomaterials Institute, has used shape memory polymers to provide greater insight into how cells sense and respond to their physical environment.

Most cell biomechanics research has examined cell behavior on unchanging, flat surfaces. "Living cells are remarkably complex, dynamic and versatile systems, but the material substrates currently used to culture them are not," says Henderson (at right in photo). "What motivated our work was the need for cell culture technologies that would allow dynamic control of cell-material interactions. We wanted to give a powerful new tool to biologists and bioengineers."

The goal of the current research was to develop a temperature-sensitive shape memory polymer substrate that could be programmed to change shape under cell-compatible conditions. Shape memory polymers (SMPs) are a class of "smart" materials that can switch between two shapes on command, from a fixed (temporary) shape to a pre-determined permanent shape, via a trigger such as a temperature change.

The breakthrough needed to achieve the research goal was made by Kevin Davis, a third-year Ph.D. student in the Henderson lab. Davis was able to develop a SMP with a transition temperature that worked within the limited range required for cells to live. He observed greater than 95 percent cell viability before and after topography and temperature change. This is the first demonstration of this type of cell-compatible, programmable topography change. Davis' and Henderson's work collaboration with Kelly Burke of Case Western Reserve University and Patrick T. Mather, Milton and Ann Stevenson Professor of Biomedical and Chemical Engineering at Syracuse University, is highlighted in the January issue of the journal Biomaterials, the leading journal in biomaterials research.

After confirming that cells remained viable on the substrate, Davis then investigated the changes in cell alignment on the surface that results from topography change. Davis programmed a SMP substrate that transitioned from a micron-scale grooved surface to a smooth surface. When the cells were seeded on the grooved sample at 30oC, the cells lined up along the grooves of the surface. The substrates were then placed in a 37oC incubator, which was the transition temperature for the substrate to recover to a smooth surface. Following shape memory recovery, the cells were observed to be randomly oriented on the substrate.

This research project aimed to determine if cells could remain viable with a change in substrate topography and determine whether cells responded to the change. The next phase of this research is to move from a 2D substrate to a 3D substrate and examine cell viability. Additionally, Henderson's team will be looking at what is going on inside the cells as a result of topography changes.

The application of shape memory principles offers potential solutions for current limitations of static substrate research in bioengineering research, such as medical devices and tissue engineering scaffolds. "For the first time, we've shown that this general concept can be used successfully with cells, which suggests that it can be extended to a number of biomaterials that could be used for scaffolds and many other applications," says Davis. Since most scaffolding is made out of polymers, Henderson envisions one day using SMPs to create scaffolds that can expand inside the body, allowing for less invasive surgical procedures.

Provided by Syracuse University

New method for infectious diseases research

 Infectious diseases researchers at Umea University in Sweden are studying the surface properties of bacteria together with materials scientists. Studies of the outermost parts of the cell walls of bacteria yield new information about the chemical composition of structures that are important for the capacity of bacteria to infect organisms. The findings are now being reported in the Journal of Biological Chemistry.

When bacteria infect a host organism, they usually attach to tissue cells. Infectious diseases scientists at Umea University are studying structural details of the outermost layer of bacterial cells in order to find new substances that can prevent bacterial infections. In collaboration with materials researchers at the Department of Chemistry, they describe new methods that facilitate and speed up their studies.

Chemist Madeleine Ramstedt is pursuing research on a material with new properties that prevent bacteria from attaching to its surface. The new material would be optimal for equipment in health care, where biofilms of bacteria can be a source of infection. In her research, Madeleine Ramstedt uses spectroscopic methods, among others, that she is now making available to her colleagues in the research consortium Umea Centre for Microbial Research, UCMR.

Microbiologists Sun Nyunt Wai, Ryoma Nakao, and Bernt Eric Uhlin, together with chemists Jean-François Boily and Madeleine Ramstedt, were investigating whether new physiochemical analysis methods could also be used for microbial studies. The scientists combined so-called cryo-x-ray photoelectron spectroscopy with multivariate analysis. This analysis yields specific patterns of intensity curves depending on the chemical composition of the surface of the material being studied.

"We've succeeded also in analyzing the cell surfaces of bacteria with our x-ray spectroscopy. We found strong patterns that we could clearly relate to different compositions in lipids, sugar, protein, and the polymer peptidoglycan in the cell wall of the bacterium that can affect the capacity of a bacterium to infect an organism," explains Madeleine Ramstedt. "The method makes it possible to analyze the outermost layer, about 10 nanometers from the surface."

"Our method is relatively simple in comparison with other methods in which the extraction of various cell components is needed. This means that with our method the surface of the bacteria can be examined under more natural conditions in an intact bacterial cell."

X-ray photoelectron spectroscopy has previously been used to study bacteria, but only to a limited extent. The Umea scientists have managed to optimize the method. "We shock freeze the bacteria and keep them frozen throughout the analysis. This allows us to assume that they do not change during the examination. Now it's possible to compare the cell walls in similar bacteria that have been treated in different ways or that have changed, for example by developing resistance. With our method we can now compare structures in cell walls in pathogenic bacteria with those of non-pathogenic bacteria, all on a larger scale. Hopefully this new method of analysis will yield more rapid results and provide infectious diseases researchers with new clues for finding new antibiotics," says Madeleine Ramstedt.

UCMR is one of Umea University's strong research environments. The centre is an interdisciplinary research consortium that brings together a number of research teams in microbial research with participation from chemistry, medical and clinical microbiology, molecular biology, physics, and bioinformatics.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Umea universitet, via AlphaGalileo.

Journal Reference:

M. Ramstedt, R. Nakao, S. N. Wai, B. E. Uhlin, J.-F. Boily. Monitoring surface chemistry changes in the bacterial cell wall - multivariate analysis of Cryo-X-ray photoelectron spectroscopy data. Journal of Biological Chemistry, 2011; DOI: 10.1074/jbc.M110.209536