Materials meet bioelectrical and -mechanical demands of the heart
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Materials meet bioelectrical and -mechanical demands of the heart By Andy Tay
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ardiovascular disease is the largest single cause of death worldwide. The World Economic Forum estimates total global costs from cardiovascular diseases (2010–2030) to be USD$20 trillion. The primary treatment for cardiovascular diseases is routinely taking a combination of drugs to reduce blood clotting and cholesterol levels. Unfortunately, this only alleviates symptoms in 50–70% of patients and has adverse side effects, such as unexplained muscle weakness, occasional pain, and weight loss. To improve the understanding of cardiac physiology and drug screening, researchers want to create better heart models, even patient-specific ones. Another solution to treat heart disease is to develop biomaterials such as cardiac patches that can meet the biochemical/ electrical/mechanical demands of the heart simultaneously to promote regeneration following cardiac infarction (more commonly known as heart attack) when blood stops flowing to some regions of the heart. Cardiac patches are formed from a mesh of biocompatible polymers with seeded cells and/or chemicals such as growth factors. They can be attached onto the surface of heart tissue to provide biochemical cues for regeneration. Also, the seeded cells in
the patches may form electrical junctions with native cardiac cells to generate bioelectrical signals essential for growth.
Piezoelectric scaffolds for drug screening The predominant heart model for drug testing is to culture cardiac cells in two-dimensional (2D) polystyrene plates, a material commonly used in plastic packaging. In reality, cardiac cells grow by integrating biochemical/electrical cues from neighboring cells in three-dimensional (3D) spaces that flat polystyrene plates cannot emulate. These limitations motivated the research group led by Lino Ferreira at the University of Coimbra, Portugal, to engineer a piezoelectric scaffold environment for cardiac cells. They published the results of their work last fall in Biomaterials (doi:10.1016/j.biomaterials.2017.05.048). Pedro Gouveia, the first author of this article, says that their idea for the scaffold came from the “use of piezoelectric materials in mobile devices and how they can produce energy by exploiting environmental cues.” The research group coated micropoly(vinylidene fluoride-trifluoroethylene), or PVF, onto their scaffolds. PVF exhibits
piezoelectrical properties, as discovered in 1969 by scientist Heiji Kawai, who was then at the Kobayashi Institute of Physical Research (Japanese Journal of Applied Physics, doi:10.1143/JJAP.8.975). By analyzing confocal images and quantifying expression levels of connexin 43, a protein that indicates whether cells are forming electrical gap junctions to allow cell–cell communications and have healthy rhythmic contractions, the research group found that cardiac cells preferentially grew and aligned much better on their piezoelectric scaffolds than on the 2D polystyrene plate (Figure 1). The cardiac cells grew so well on the pie
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