Illustration of the cardiomyocyte-laden conductive nanofibrous sheets and formation of folding and tubular bioactuators.
Illustration of the cardiomyocyte-laden conductive nanofibrous sheets and formation of folding and tubular bioactuators.

Heart attacks are the major cause of death worldwide and while treatments exist, repair of damaged heart tissue is severely limited by its inability to regenerate. Tissue engineering can help heart tissue regenerate by providing a supportive environment for regrowing heart cells or cardiomyocytes to flourish. Various materials are being explored for cardiac tissue scaffolds, but researchers from Xi’an Jiaotong University in China and the University of Michigan think that they have hit on a winning formula [Wang et al., Acta Biomaterialia (2017), doi: 10.1016/j.actbio.2017.06.036].

Led by Baolin Guo and Peter X. Ma, the researchers developed a fibrous structure from two common polymers, poly(L-lactic acid) (PLA) and polyaniline (PANI), that mimics the nanofibrous and conductive properties of natural extracellular matrix. Both polymers are biocompatible and PLA is already FDA-approved for use as a biomaterial in medical applications.

“These nanofibrous sheets were developed by the electrospinning technique,” explains Guo. “By incorporating of varying contents of PANI from 0 wt% to 3 wt% into the PLA polymer, we can vary the conductivity in these sheets while maintaining the same fiber diameter.”

The electrospinning technique, whereby a solution of the two polymers is ejected out through a charged nozzle, is tightly controlled so that all the produced fibers have a diameter of 500 nm. This limits the effects of diameter variation on the conductivity of the resulting nanofibrous structure.

The conductive nanofibrous sheets enhanced the differentiation of rat cardiac cell line and maturation of rat primary cardiomyocytes. Samples of the cell-laden PANI/PLA scaffold material started to beat spontaneously after just a few days of culturing and continued for up to 21 days.

“The maturation, spontaneous beating, and calcium transients of primary cardiomyocytes demonstrates the great potential of these conductive nanofibrous sheets in cardiac tissue engineering,” Guo told Materials Today.

But as well as creating a material that could be a useful cardiac tissue engineering scaffold, the researchers used the same material to create a bioactuator – a muscle-like artificial device that can flex and contract spontaneously.

The team took sheets of the cell-laden PANI/PLA scaffold material and shaped it into folded or rolled tubular actuators that contract synchronously and spontaneously.

“We plan to investigate these conductive nanofibrous sheets further for applications in three-dimensional bioactuators by reinforcing their actuation performance,” says Guo.

This option could prove easier to realize sooner than cardiac tissue engineering scaffolds, since PANI requires regulatory approval for in vivo use in the body.