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Jae Park, a doctoral student in the lab of Alexandra Rutz, assistant professor of biomedical engineering, has developed a unique, dynamic platform with electricity-conducting biomaterials in which stiffness can be modulated by applying voltage. Such a platform can help researchers learn more about the potential to use conducting polymers to study mechanobiology and to study the effect of stiff environments on cells, which play a role in fibrosis and some types of cancer.
Photo Credit: Jae Park
Scientific Frontline: Extended "At a Glance" Summary: Voltage-Modulated PEDOT:PSS Platform
The Core Concept: A novel bioelectronic platform utilizes the conducting polymer PEDOT:PSS to dynamically modulate material stiffness through the application of electrical voltage. This allows researchers to subject cells to varying mechanical environments in real time.
Key Distinction/Mechanism: Unlike traditional mechanobiology tools that rely on static stiffness, this dynamic system alters its mechanical properties incrementally as applied voltage recruits ions. This enables the application of multiple, reversible stiffness states to the exact same cell or tissue sample to observe corresponding biological reactions.
Major Frameworks/Components:
- PEDOT:PSS: A bioelectronic conducting polymer capable of adopting tissue-like softness and changing mechanical properties in response to electrical stimuli.
- Ion Recruitment Mechanism: The underlying process where applied voltage draws ions into the polymer matrix, resulting in measurable, incremental changes to material stiffness.
- Dynamic Mechanical Stimulation: The methodological shift from static tissue modeling to active environmental manipulation, allowing researchers to test cellular memory and adaptability when transitioning between soft and stiff substrates.
Branch of Science: Mechanobiology, Biomedical Engineering, and Materials Science.
Future Application: The conducting material can be integrated with microelectronics to engineer high-throughput mechanobiology testing platforms for studying diverse cell types, cellular memory, and varying physiological conditions.
Why It Matters: By mimicking the dynamic mechanical shifts of living systems, this platform provides critical diagnostic and experimental insights into how stiff cellular environments drive progressive pathologies such as fibrosis and various forms of cancer.
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| Alexandra Rutz Assistant Professor Professor Rutz's research focuses on the engineering of electronic tissues using materials design and fabrication-based approaches. Our goal is to achieve robust biointerfaces and long-lived function in bioelectronics and other medical devices. Photo Credit: Courtesy of Washington University in St. Louis |
Because living systems are dynamic, biomaterials should also be dynamic in their mechanics, such as stiffness. The bioelectronic conducting material PEDOT:PSS is often used in electronics and biomedical applications. The material is capable of changing stiffness in response to applied voltage, but that has not yet been rigorously studied—until now.
Jae Park, a doctoral student in the lab of Alexandra Rutz, an assistant professor of biomedical engineering in the McKelvey School of Engineering at Washington University in St. Louis, has developed a unique, dynamic platform with electrically conducting biomaterials in which stiffness can be modulated by applying voltage. Such a platform can help researchers learn more about the potential to use conducting polymers to study mechanobiology, as well as to study the effect of stiff environments on cells, which play a role in fibrosis and some types of cancer.
In past research, Rutz’s lab has shown that it can make PEDOT:PSS very soft with tissue-like stiffness, as well as three-dimensional. The new research stems from Rutz’s National Science Foundation CAREER Award research, in which Rutz and her team are using electronically conducting polymers to create three-dimensional bioelectronic scaffolds that change stiffness in response to applied electricity.
“We've shown that this material can be great for cell-material and tissue-material interactions,” Rutz said. “Now, we are looking to use the conducting polymers in a different way to see if they can mechanically stimulate cells.”
Other researchers have used static stiffness to study how stiffness influences cells, Rutz said.
“An emerging need in mechanobiology is to move past static stiffness and have a material to which you can apply different stiffness states to the same cell or tissue because then we can ask different biological questions,” she said. “Do the cells remember if they're put back on a soft substrate after being on a stiff substrate? Do they permanently change? There are a lot of pathologies that result in higher stiffness that change cells, so we need mechanobiology tools to study that.”
Park applied voltage to observe the resulting changes in stiffness during application, as well as what occurred after the voltage was removed.
“When you apply voltage to these conducting biomaterials, it recruits ions,” Park said. “I thought stiffness would be incrementally and linearly proportional to the ions, so we could achieve incremental and multiple stiffness states.”
The maximum stiffness change the team observed upon the application of voltage over the tested range was 32.5%, with changes of 6.7% to 10.4% at 0.2-volt increments. After the voltage was removed, over a 24-hour period, the PEDOT:PSS materials lost their charge, and the stiffness changed by 2.6% to 15.2%.
“In the future, we can integrate this material with electronics or microelectronics to make high-throughput mechanical biology platforms, so we can study various kinds of cells or various kinds of conditions,” Rutz said.
Funding: This research was supported by funding from the National Science Foundation CAREER Award (2443128); the Center for Engineering MechanoBiology (CMMI 15-48571); and the Women’s Health Technologies Collaboration Initiation Grant, the Ovarian Cancer Research Innovation Fund Award, and the McDonnell International Scholars Academy (SSO) from Washington University in St. Louis.
Published in journal: Advanced Functional Materials
Title: Characterizing PEDOT: PSS for Electronic Control of Stiffness
Authors: Jae Park, Tianran Liu, Somtochukwu S. Okafor, Anna P. Goestenkors, Barbara A. Semar, Sandra K. Montgomery, Scott T. Keene, and Alexandra L. Rutz
Source/Credit: McKelvey School of Engineering | Beth Miller
Edited by: Scientific Frontline
Reference Number: bio061426_01
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