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valve is that it lasts a long time after it's implanted. However, a mechanical
valve can trigger blood clots that break off and migrate into the brain. That's
why people with a mechanical heart valve must take blood thinning medicine,
causing a cascade of yet another set of medical challenges, as well as occupa-
tional and lifestyle limitations.
Heart values transplanted from an animal, typically a pig, don't require
blood thinners but they don't last as long. Transplanted animal valves aren't
durable enough to survive for long in the active bodies of younger patients.
Finally, neither mechanical nor biologically derived prosthetic valves can grow
in tandem with their living host, requiring that recipients receive repeat open
heart surgeries to implant increasingly larger valves.
Jonathan explained that someday surgeons will save human lives by tak-
ing an entirely new approach: 3D printing a new heart valve that's implanted
directly inside a young child suffering from a congenital defect. Jonathan
believes that a critical part of such a solution lies in unlocking the mystery
of how the stem cells in an embryo develop into mature heart valve cells. If
he can gain insight into this maturation process, Jonathan believes he will
be one step closer to someday bioprinting a functioning artiicial heart valve.
Jonathan's research aims to crack three parts of the bioprinting puzzle.
First, he's addressing the old tough love problem. To function property, printed
heart valves, like joint cartilage, need to be beaten up a bit in an incubator
called a bioreactor.
Jonathan is working on methods to perfect the bioprinting of many different
types of stem cells in a single “print job.” To mimic nature's ability to swirl
together lots of different types of cells into precise, mission-critical patterns,
Jonathan 3D prints in living ink using several printing nozzles at one time.
To bioprint different types of stem cells at once, Jonathan modiied a Fab@
Home bioprinter with multiple syringes.
Finally, since bioprinting is by deinition multi-material printing, Jonathan
is developing software that can choreograph the movements of several print
heads that each contains a different cell type. “A 3D printer can follow instruc-
tions from a design ile to print just one type of material. So we had to invent
a software algorithm that enables a single design ile to manage a multi-nozzle
3D printer to enable us to print several different types of cells at once,” he said.
Much of Jonathan's focus is on deining the optimal shape for the deposit of
bioprinted stem cells. Since cells on a heart valve must be densely packed in a
particular placement to function, cell placement is critical. Stem cells are like
