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← How to 3D print human tissue - Taneka Jones

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Showing Revision 4 created 10/14/2019 by lauren mcalpine .

  1. There are currently hundreds of thousands
    of people on transplant lists,
  2. waiting for critical organs like kidneys,
    hearts, and livers
  3. that could save their lives.
  4. Unfortunately,
  5. there aren’t nearly enough donor organs
    available to fill that demand.
  6. What if instead of waiting,

  7. we could create brand-new, customized
    organs from scratch?
  8. That’s the idea behind bioprinting,
  9. a branch of regenerative medicine
    currently under development.
  10. We’re not able to print complex
    organs just yet,
  11. but simpler tissues including blood
    vessels and tubes
  12. responsible for nutrient
    and waste exchange
  13. are already in our grasp.
  14. Bioprinting is a biological
    cousin of 3-D printing,

  15. a technique that deposits layers of
    material on top of each other
  16. to construct a three-dimensional object
    one slice at a time.
  17. Instead of starting with metal, plastic,
    or ceramic,
  18. a 3-D printer for organs and
    tissues uses bioink:
  19. a printable material that
    contains living cells.
  20. The bulk of many bioinks are water-rich
    molecules called hydrogels.

  21. Mixed into those are
    millions of living cells
  22. as well as various chemicals that
    encourage cells to communicate and grow.
  23. Some bioinks include a
    single type of cell,
  24. while others combine several different
    kinds to produce more complex structures.
  25. Let’s say you want to print a meniscus,

  26. which is a piece of cartilage in the knee
  27. that keeps the shinbone and thighbone
    from grinding against each other.
  28. It’s made up of cells called chondrocytes,
  29. and you’ll need a healthy supply of
    them for your bioink.
  30. These cells can come from donors whose
    cell lines are replicated in a lab.
  31. Or they might originate from a
    patient’s own tissue
  32. to create a personalized meniscus less
    likely to be rejected by their body.
  33. There are several printing techniques,
  34. and the most popular is extrusion-based
  35. In this, bioink gets loaded into a
    printing chamber
  36. and pushed through a round nozzle
    attached to a printhead.
  37. It emerges from a nozzle that’s rarely
    wider than 400 microns in diameter,
  38. and can produce a continuous filament
  39. roughly the thickness
    of a human fingernail.
  40. A computerized image or file guides the
    placement of the strands,

  41. either onto a flat surface or into a
    liquid bath
  42. that’ll help hold the structure in place
    until it stabilizes.
  43. These printers are fast, producing the
    meniscus in about half an hour,
  44. one thin strand at a time.
  45. After printing, some bioinks
    will stiffen immediately;

  46. others need UV light or an additional
    chemical or physical process
  47. to stabilize the structure.
  48. If the printing process is successful,
  49. the cells in the synthetic tissue
  50. will begin to behave the same way
    cells do in real tissue:
  51. signaling to each other, exchanging
    nutrients, and multiplying.
  52. We can already print relatively simple
    structures like this meniscus.

  53. Bioprinted bladders have also been
    successfully implanted,
  54. and printed tissue has promoted facial
    nerve regeneration in rats.
  55. Researchers have created lung tissue,
    skin, and cartilage,
  56. as well as miniature, semi-functional
    versions of kidneys, livers, and hearts.
  57. However, replicating the complex
    biochemical environment
  58. of a major organ
    is a steep challenge.
  59. Extrusion-based bioprinting may destroy
  60. a significant percentage of cells in the
    ink if the nozzle is too small,
  61. or if the printing pressure is too high.
  62. One of the most formidable challenges
  63. is how to supply oxygen and nutrients
    to all the cells in a full-size organ.
  64. That’s why the greatest successes so far
  65. have been with structures
    that are flat or hollow—
  66. and why researchers are busy
    developing ways
  67. to incorporate blood vessels
    into bioprinted tissue.
  68. There’s tremendous potential to use

  69. to save lives and advance our
  70. of how our organs function
    in the first place.
  71. And the technology opens up a dizzying
    array of possibilities,
  72. such as printing tissues with
    embedded electronics.
  73. Could we one day engineer organs that
    exceed current human capability,
  74. or give ourselves features like
    unburnable skin?
  75. How long might we extend human life
    by printing and replacing our organs?
  76. And exactly who—and what—
  77. will have access to this technology
    and its incredible output?