New Hydrogel Bandages Could Boost Recovery

Piezoelectric Properties are Important for Repair

Have you ever wondered how car airbags detect a crash or how our bones stay strong just by walking and moving? These common occurrences rely on a property of certain materials called piezoelectricity; the ability to generate electricity when squeezed or stretched (mechanical stress). 

These materials, including bone and skin, have an atomic structure where the positive (+) and negative (-) electric charges are unevenly distributed. When at rest, the charges are balanced, but when they are pressed, stretched, or otherwise deformed then the charges shift and separate. This creates a distinct positive and negative end in the material - just like a battery. The separation of charges is what generates an electric current.

In our bodies, bones and collagen use piezoelectricity to promote growth and healing. Every time we walk, the pressure from our steps generates small electric signals that help keep our bones strong. Similarly, collagen in our skin is piezoelectric and produces electric currents when injured, which help to signal special cells that are responsible for skin repair.

Creating a New Hydrogel

A recent research project led by Dr. Erica Pensini, associate professor in the School of Engineering, is gaining traction in national media for developing a new type of electricity-producing “slime,” which could have far-reaching impacts. 

Conducted in collaboration with Dr. Alejandro G. Marangoni, Dr. Aicheng Chen and Dr. Stefano Gregori, the team developed novel ferroelectric hydrogels made from the amino acids lysine and arginine, oleic acid (found in olive oil), and up to 90% water content. Because the components are benign, these hydrogels are biocompatible in addition to being piezoelectric.

Pensini and colleagues analyzed their new hydrogel at the Canadian Light Source using Canada’s only synchrotron, which is like a strong microscope. They discovered the different crystal structures the hydrogel could arrange into based on its water content and applied electric fields. In the absence of water or applied electric fields, the structure was lamellar (like layers of lasagna). With 89 weight percent (wt %) water content, the structure became sponge-like in the absence of applied electric fields. However, when electric fields (up to 1 V) were applied to the 89 wt % hydrogel, the crystal structure transitioned from the sponge-like structure to the lamellar structure. 

A Repair-Promoting and Targeted Drug-Delivering Bandage 

The discovery has practical applications. Bandages and skin patches made from this material would do more than cover an injury; The electric currents generated from simply wearing the skin patch would attract special repair cells to the site of damage faster, helping to speed up the repair process. Skin patches with piezoelectric properties have been made before and demonstrated increased healing, but this is the first time they have been made from fully biocompatible materials, and the first time they have had this high of a water content, which impacts the different crystal structure forms. 
 
The unique properties of Pensini's hydrogel could also potentially be developed into skin patches that act as targeted drug delivery systems.

"If we made a hydrogel skin patch, one crystal structure could encapsulate a specific drug, and when an electric field is applied causing the crystal structure to change, the encapsulated drug would possibly be released" says Pensini.

"Further research is needed to develop a complete fundamental understanding of the correlation between hydrogel’s crystal structures and piezoelectric properties, analyzing a broader range of materials." 

This work was supported by a Natural Sciences and Engineering Research Council of Canada Discovery Grant, and through the Canadian Light Source at the University of Saskatchewan, was supported by the Canada Foundation for Innovation (CFI), the Natural Sciences and Engineering Research Council of Canada (NSERC), the National Research Council (NRC), the Canadian Institutes of Health Research (CIHR), and the Government of Saskatchewan. 
 
Pensini E., Meszaros P., Kashlan N., Marangoni A.G., Laredo, T., Gregori S., Ghazani S.M., van der Zalm J., Chen A. Ferroelectric hydrogels from amino acids and oleic acid. Iscience. 2024. doi: 10.1016/ j.isci.2024.110601 
 
Dr. Erica Pensini is currently recruiting graduate students or undergraduate research project students with backgrounds in chemistry, physics, or related areas who are interested in researching piezoelectric materials or groundwater purification methods. Graduates from the Pensini lab typically go into environmental consulting.

This story was written by Jamie Dawson as part of the Science Communicators: Research @ CEPS initiative. Jamie is an M.Sc. candidate in the Chemistry Department under Dr. Mario A. Monteiro. Her research focus is on characterizing bacterial cell-surface carbohydrate structures to ultimately develop glycoconjugate vaccines.