Patching up weak hearts with gold nanowires

Heart of goldHeart of an average person beats about 2 billion times in their lifetimes. Unfortunately, hearts of some 32 million people worldwide start skipping their beats each year. More than 50 % of these people; 17.5 million, don’t live to fight another day. Statistics are shocking! Heart disease, more specifically, coronary heart disease is the number one killer in the world. The death toll due to heart diseases itself exceed the number of deaths by HIV/AIDS , diabetes, lung cancer, road accidents and diarrheal diseases combined.  However, statistics looked hopeless about ten years back. Fortunately, due to great advances in detection techniques, surgical techniques, drugs and fast response tools, significant number of lives are saved each year at least in some countries.

Death of heart cells with heart attack

Saving a life of heart patient from imminent death is only avoiding the tip of the iceberg. People who have heart disease or that have suffered a heart attack are left with damaged and weakened hearts, which presents a much deeper problem. Unlike other organs in the body, heart has no or has very little capacity to heal itself through tissue regeneration.  The minor forms of heart diseases usually not require a major heart surgery. The heart that progressively get weakened due to heart attacks or from other diseases may require surgery or sometimes heart transplant.  Thanks to advances in tissue engineering and bionanotechnology new strategies are developed for heart tissue regeneration and initiate heart repair in patients who have weaker hearts.

The “Heart Patch”

There have been significant advances in a heart repair strategy called “heart patch” over the years pioneered mostly by Duke University and MIT. As the name would suggests the heart patch is a polymeric matrix made typically from biocompatible naturel polymers like alginate and synthetic polymers like polylactic acid. The material is extremely porous and exhibits sponge like structure. These structures are referred to as scaffolds and used as structural support and to organize the individual cells in to functioning tissues. Scaffolds are then seeded with heart cells and kept at conditions where the growth of the heart cells is most optimum. These patches are applied to the damaged sites of the hearts of the patients to accelerate tissue regeneration. This presents the conventional (if such word can be used) approach to heart repair.

Cardiac patch demonstrated

Bridging the gap with silver nanowires

Unfortunately, the procedure was not as effective as doctors would like them to be. Later it was discovered that the scaffold tissue engineering itself would not be sufficient to control complex arrangement of heart tissues. The polymeric scaffolds themselves presented the first problem. Due to the poor conductive nature of the scaffolds, electrical signals that trigger contraction of cardiomyocytes simply didn’t passed through. This disturbed the newly patched cells to attain a smooth and continuous contraction of heart cells which would in turn mean cardiac arrhythmia and may trigger more heart problems than the ones it has already. The ideal heart patch would mean getting the perfect combination of cells, scaffolds and signaling molecules, which still a challenge with available heart tissue engineering techniques.

A group of scientists from the most elite, Harvard medical school and Massachusetts Institute of Technology joined hands to solve this problem. Their approach was to incorporate trillions of nanowires in to the alginate scaffold before culturing it with the heart cells. The gold nanowires used in the research are 20 nanometers thick and about 2-3 microns in length. Gold nanowires can be easily fabricated and biocompatible. These highly conductive nanowires bridged the electrically insulating pore walls of alginate scaffold and improved electrical communication between adjacent cardiac cells. Compared to conventional scaffolds, gold nanowire incorporated scaffolds show better alignment and increased growth. When electrically simulated gold nanowire containing scaffolds showed synchronous contraction which in phase with the other heart tissues (watch video). Furthermore, heightened levels of proteins were observed in these improved scaffolds which would further assist the tissue regeneration and heart repair function.

Gold nanowire scaffold make electrical connections between heart cells

Many experts believe that the first commercial cardiac patches would enter in to the market in the near future as some companies are already given clearance to human trials.

More reading

  1. Lakshmanan, Rajesh, Uma Maheswari Krishnan, and Swaminathan Sethuraman. “Living cardiac patch: the elixir for cardiac regeneration.” Expert opinion on biological therapy12, no. 12 (2012): 1623-1640.

  2. Dvir, Tal, Brian P. Timko, Mark D. Brigham, Shreesh R. Naik, Sandeep S. Karajanagi, Oren Levy, Hongwei Jin, Kevin K. Parker, Robert Langer, and Daniel S. Kohane. “Nanowired three-dimensional cardiac patches.” Nature nanotechnology6, no. 11 (2011): 720-725.

  3. Yang, Shoufeng, Kah-Fai Leong, Zhaohui Du, and Chee-Kai Chua. “The design of scaffolds for use in tissue engineering. Part I. Traditional factors.” Tissue engineering7, no. 6 (2001): 679-689.

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4 thoughts on “Patching up weak hearts with gold nanowires

    • Hi ALI, there are number of ways to prepare gold nanowires. Usually, gold nanowires are grown in a liquid medium starting from a seed crystal. Growth solution is usually added with special capping agents to cover only some specific faces of the crystal. And the solution is then subjected to a hydrothermal treatment. Since only few faces are open for the growth, a nanowire formation can be achieved.
      Following is a link to a good paper that describes gold nanowire synthesis and I myself used this method to grow gold nanowires.

      Kim, Franklin, Kwonnam Sohn, Jinsong Wu, and Jiaxing Huang. “Chemical synthesis of gold nanowires in acidic solutions.” Journal of the American Chemical Society 130, no. 44 (2008): 14442-14443.

      Like

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