Biocompatible piezoelectric materials promote neural regeneration

LAURA LEAY: Welcome to MRS Bulletin’s Materials News Podcast, providing breakthrough news & interviews with researchers on the hot topics in materials research. My name is Laura Leay. Piezoelectric materials have a variety of applications and one of them is in tissue engineering. Electrical stimulation is an effective way of promoting neural regeneration in relation to spinal cord injuries and usually requires the use of wired connections. A new fabrication process can produce biocompatible piezoelectric materials which can provide wireless electrical stimulation in response to mechanical action.

HAMIDEH KHANBAREH: We came across this new application for using piezoelectric materials in tissue engineering and we started looking into how we can design these materials specifically for tissue engineering applications.

LAURA LEAY: That was Dr. Hamideh Khanbareh from the University of Bath in the UK. Her research has previously shown that two processes can be combined to both activate piezoelectric particles and to get the particles to align. While the matrix is in the liquid uncured state, she applied an alternating current which leads to dielectrophoretic structuring, as well as a direct current to induce poling. The composite’s piezoelectric properties can be tailored simply by changing the dc poling field during in situ poling-dielectrophoresis. This in situ method was first developed by Dr. Khanbareh during her own PhD and has been further refined by Dr. Vlad Jarkov, supervised by Dr. Khanbereh during his studies at the University of Bath, so that consistent batches of the material can be produced.

VLAD JARKOV: We wanted a consistent 10–20 samples because cells are very sensitive so you want samples that are the same in terms of surface topology, thickness, modulus: different kinds of mechanical properties. The way that we scaled up the process is also pretty unique in that we can now make loads of consistent materials so you don’t really have to worry about variation between samples. That’s particularly important in cell work.

LAURA LEAY: Potassium-sodium-niobate is a piezoelectric material compatible with cell lines that are similar to neurons. Combining this with polydimethylsiloxane resulted in a composite with a softness similar to that of neurons. The ratio of these two components was optimized to produce a material of the required stiffness. Vlad worked with researchers at Keele University in the UK to understand how the composite material would interact with neural stem cells. He saw that the stem cells bound to the surface of the material but also noticed that activation of the piezoelectric component had an interesting effect.

VLAD JARKOV: In the inactive composites—so the un-poled—we saw balling of cells which meant that the cells preferred to bind to each other rather than to spread out on the surface which is kind of an indicator that the surface is not ideal. But with the poled composites, they actually spread nicely which meant that the piezolectrically activated composites did something. We assume it’s the piezoelectric surface charge that allowed them to better spread across the surface.  

LAURA LEAY: Vlad looked at three different types of cell lines: neurons and two types of cells that act as supports. 

VLAD JARKOV: Particularly in the positively poled materials we saw an increase in the amount of neurons that were being produced without actually decreasing the amount of the supporting oligodendrocytes and astrocytes. 

LAURA LEAY: Usually the use of piezoelectric materials in tissue engineering requires mechanical stimulation from either movement of the body or the application of ultrasound. In this research, no additional mechanical stimulation was required.

VLAD JARKOV: The fact that we saw this residually happening on the surface was either because there’s some sort stimulation from the cells moving on the surface or during culture. It kind of implies that mild mechanical stimulation might even be sufficient.

LAURA LEAY: These initial results are encouraging and further work can test out these ideas. The next stage for Dr. Khanbareh’s research group is to look at other methods to regenerate the central nervous system including topological structuring and the inclusion of growth factors. She also has on open PhD position to conduct in vivo work and will also look to add antimicrobial properties to the piezoelectric composite. What is striking about this already published work is the close collaboration between disciplines which led to some really strong research.

HAMIDEH KHANBAREH: We were lucky enough to get in touch with neuroscientists that enabled this project.

VLAD JARKOV: It’s always exciting to collaborate with people in different fields and get a different perspective because it makes for much stronger research. Working with Chris Adams and Imman in Keele meant that not only was the materials side great in the paper, but the biological side was also great because we always had that feedback.

LAURA LEAY: This work was published in a recent issue of Advanced Engineering Materials. My name is Laura Leay from the Materials Research Society. For more news, log onto the MRS Bulletin website at mrsbulletin.org and follow us on twitter, @MRSBulletin. Don’t miss the next episode of MRS Bulletin Materials News – subscribe now. Thank you for listening.