A new tough and flexible hybrid made from carbon nanotubes (CNTs) embedded in a polymer fiber could improve the treatment of damaged heart tissue.
After a heart attack, the organ is unable to regenerate or repair itself, so there have been significant research efforts into developing biomimetic scaffolds to engineer replacement functioning cardiac tissue. While considerable progress has been made in creating cardiac patches that mimic the architecture of natural myocardial tissue, these scaffold materials have tended to be either electrically insulating or insufficiently mechanically robust to withstand cardiac contractions – or too stiff to allow them at all.
Now, however, researchers from Brigham and Women’s Hospital and Harvard Medical School in Boston have created a hybrid scaffold material that could overcome these challenges [Kharaziha, M., et al., Biomaterials 35 (2014), 7346-7354, DOI: 10.1016/j.biomaterials.2014.05.014]. The material is composed of different concentrations (0-1.5%) of multi-walled CNTs embedded in an aligned arrangement in poly(-glycerol sebacate):gelatin nanofibers produced by electrospinning. The nanotubes are first coated with methacrylated gelatin (GelMA) to ensure an even dispersion in the polymer fibers.
Schematic drawing showing the interactions of CNTs with PG scaffold upon cross-linking with EDC/NHS.“We noticed that the incorporation of CNTs significantly enhanced the toughness of the scaffolds and improved their electrical properties,” explains Ali Khademhosseini, director of the Harvard-affiliated Biomaterials Innovations Research Center, who led the research. “Increasing the CNT content resulted in improved fiber orientation, mimicking the anisotropic structure of native myocardium.”
But not only does the CNT-polymer hybrid mimic the tough and flexible character of cardiac tissue, the nanotubes bring electrical conductivity too. This combination of properties appears to suit cardiac muscle cells (cardiomyocytes), which the researchers found could be seeded onto scaffolds made out of the new hybrid material. The cells retain their viability and alignment on the scaffold, and their contractile behavior.
“Most notably, the contractile properties of the cardiomyocytes seeded on the fabricated scaffolds [are] significantly increased as a function of CNT content,” says Khademhosseini.
The researchers observed that cardiomyocytes seeded onto the new CNT-polymer hybrid showed stronger and more synchronized beating behavior than on polymer-only scaffolds.
“Due to ease of handling, ability to suture and the notable electrical and mechanical characteristics, these patches may one day be used for cardiac repair and regeneration,” Khademhosseini told Materials Today.
The researchers now intend to stack layers of the CNT-polymer hybrid to create thick cardiac tissue scaffolds that can also house vascular networks. But Khademhosseini cautions that they do not yet know of the potential cytotoxicity of introducing CNTs into the body over the long term.
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