3D Bioprinting is one of the emerging technologies in the field of regenerative medicine. By using it, we can create a live tissue that resembles the native tissue in form and function. In this presentation, the important topics in 3D bioprinting are discussed briefly...

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3D Bioprinting
Done By; Rawan Abdulwali Alakwaa

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IN THIS LECTURE:
• Justification
• 3D Bioprinting concept.
• 3D Bioprinting process:
• Generating printing paths.
• Selecting Bioinks.
• Start Bioprinting.
• Current advances in 3D Bioprinting.

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JUSTIFICATION
• Organ failure is drastically increasing. Often, clinical
treatments are limited by a paucity of available donors and
immune rejection of donated tissue. In the search for
alternatives for the repair or replacement of malfunctioning
human tissues and organs, tissue 3D Bioprinting is being
explored as a promising solution.

5. 3D BIOPRINTING
• Bioprinting is the layer-by-layer
deposition of cells to create 3D
tissue that closely resembles
native tissue in form and
function from basic biological
building blocks.
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BIOPRINTING PROCESS
• To successfully create bioprinted
tissues, it is necessary to:
• Generate the printing paths
• Select appropriate bioinks
• Control the bioprinter and
perform quality control after
printing.
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GENERATING THE
PRINTING PATHS
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8. 1. CREATING THE 3D MODEL
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The correct anatomical shape of
the desired tissue construct is
achieved by:
representing clinical imaging (CT or
MRI) data as a computer 3D model
 STL file format as an
intermediate between model and
print path generation.

9. 2. SLICING
In a process analogous to
histological sectioning, printing
paths are created by “slicing”
these STL model into layers and
creating bioprinter tool paths
that trace out the perimeter and
interior features of each slice.

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SELECTING THE
APPROPRIATE BIOINK
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11. BIOINK
• The Bioink is the bioprintable
material consisting of living cells
and biomaterials that resemble
the ECM to support cells.
• An ideal bioink
should possess proper
mechanical, rheological, and
biological properties of the
target tissues.

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BIOINK
CLASSIFICATION OF BIOINKS
Scaffold Based Bioinks
• Consist of cells dispersed
within biomaterials that help
to create a conducive
environment for cell
proliferation as well as
providing structural support.
Scaffold Free Bioinks
• Cells are bioprinted without a
supporting hydrogel and
therefore cells are loaded in
higher concentrations which
then deposit their own ECM.
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SCAFFOLD BASED BIOINKS
•Hydrogel:
• Natural: including collagen, fibrin, chitosan, and alginate.
• Synthetic: including methacrylated gelatin, Pluronic, and
polyethylene glycol.
• Hybrid.
•Decellularized matrix components obtained by
chopping tissue into small fragments, lysing the cells,
and extracting the remaining ECM.
TYPES OF BIOINKS USED

14. SCAFFOLD BASED BIOINKS
•Microcarriers have recently
been used in bioprinting to
increase the cell density in
bioinks. They are porous
particles designed to
promote cell attachment,
survival, and expansion.
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16. CELL SOURCE
• The cell component of the bioink
should be autologous and patient
specific.
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17. STEM CELLS
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STEM CELLS IN 3D BIOPRINTING
• Stem cells have the properties of self-renewal and potency,
representing an unlimited cell source for 3D bioprinting and
regenerative medicine. However, autologous adult stem cells
have to be obtained invasively through bone marrow
harvesting, adipose tissue extraction by liposuction or least
invasively using blood apheresis.

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STEM CELLS IN 3D BIOPRINTING
• In 2006, with the discovery of human induced pluripotent
stem cells (iPSCs) , patient-specific stem cell lines can now be
created from mature cell types, such as peripheral blood
mononuclear cells by venipuncture, or dermal skin fibroblasts
by skin biopsy. This ability to reprogram patient-specific cells
also allows for the creation of stem cells containing heritable
mutations, which can then be bioprinted and studied.

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STEM CELLS IN 3D BIOPRINTING
• This has the potential to improve current understanding of
disease mechanisms and phenotypic variability, while
minimizing rejection when transplanted back into the host for
the purposes of tissue regeneration.

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START TO BIOPRINT
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25. INKJET 3D BIOPRINTING
• Bioink is stored in the ink cartridge
which is connected to a printer head
and acts as the source during the
electronically controlled printing
process. During printing, the printer
heads are squeezed by a thermal or
piezoelectric actuator to generate
droplets of a controllable size.
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• (1) low cost due to similar structure
with commercial printers
• (2) high printing speed
• (3) relatively high cell viability
(usually from 80% to 90%).
The advantages of inkjet printing include:
INKJET 3D BIOPRINTING
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27. EXTRUSION BASED BIOPRINTING
• Extrusion printing is a
modification of inkjet printing.
In order to print the viscous
materials inkjet printers cannot
deposit, extrusion printing uses
either an air-force pump, piston
or a mechanical screw plunger
to dispense bioinks.
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28. LASER ASSISTED BIOPRINTING
• A focused laser pulse is applied
to stimulate a small area of the
absorbing layer. This laser pulse
vaporizes a portion of the donor
layer, creating a high-pressure
bubble at the interface of the
bioink layer and propelling the
suspended bioink.
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29. CURRENT ADVANCES
3D BIOPRINTING

30. CARDIOVASCULAR TISSUE
CURRENT ADVANCES
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• Creating 3D cardiovascular tissue
constructs, using different proliferative
cell types. These tissue constructs
exhibit synchronous macroscopic
beating and self-assembly of vessel-like
conduits when co-cultured with
endothelial cells.

31. MUSCULOSKELETAL TISSUE
CURRENT ADVANCES
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• Fabricating 3D skeletal muscle
constructs that are precisely
patterned. The bioprinted cells had
high viability and responded
synchronously to electric pulses.

32. NEURONAL TISSUE
CURRENT ADVANCES
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• Neurons have been bioprinted with
high cell viability, and they
maintained basic cellular phenotypes
and functionality for over two weeks
post-printing, with successful
development of voltage-gated
potassium and sodium channels.

33. HEPATIC TISSUE
CURRENT ADVANCES
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• The bioprinted cells were
positive for hepatic markers
and they were phenotypically
similar to native hepatocytes,
as demonstrated by albumin
secretion capability and
morphological analysis.

34. HEPATIC TISSUE
CURRENT ADVANCES
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• One of the bioprinted constructs
showed morphological organization
that recapitulated the native liver
environment and high levels of liver-
specific gene expression, metabolic
product secretion, and cytochrome
P450 induction.

35. SKIN
CURRENT ADVANCES
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• Printing full-thickness skin
equivalents, using alternating
layers of bioink and a dermal
fibroblast cell suspension that
showed high viability after
printing.

36. SKIN
CURRENT ADVANCES
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• The cells were bioprinted directly
over the wound site, and the
bioprinted construct enhanced
wound closure as well as re-
epithelialization as compared to
controls treated with only the
fibrin-collagen hydrogel.

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3D bioprinting using stem cells have shown
much research progress in multiple organ
systems.
Common challenges faced in multiple organ
systems include vascularization, viability and
scalability.

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Tissue engineering using
3D bioprinting technology has
promising clinical potential for
organ regeneration.

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References
• 1. Ashley N. et al. Bioprinting of stem cells for transplantable tissue fabrication. Stem
cells translational medicine 2017; 6:1940-1948.
• 2. Ong et al. 3D bioprinting using stem cells. Pediatric Research 2018; 83:223–231.
• 3. Christian Mandrycky et al. 3D Bioprinting for Engineering Complex Tissues.
Biotechnol Adv. 2016 Jul-Aug; 34(4): 422–434.
• 4. Gungor-Ozkerim PS et al. Bioinks for 3D bioprinting: an overview. Biomaterials
Science 2018 May 1;6(5):915-946.
• 5. Kang HW et al. A 3D bioprinting system to produce human-scale tissue constructs
with structural integrity. Nature Biotechnology 2016 Mar;34(3):312-9
• 6. 3D Bioprinting: bioinks selection guide. www.sigmaaldrich.com

40. Thank You
Rawan Abdulwali Alakwaa