<s>
Organ	B-Device
printing	I-Device
utilizes	O
techniques	O
similar	O
to	O
conventional	O
3D	O
printing	O
where	O
a	O
computer	O
model	O
is	O
fed	O
into	O
a	O
printer	O
that	O
lays	O
down	O
successive	O
layers	O
of	O
plastics	O
or	O
wax	O
until	O
a	O
3D	O
object	O
is	O
produced	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
organ	B-Device
printing	I-Device
,	O
the	O
material	O
being	O
used	O
by	O
the	O
printer	O
is	O
a	O
biocompatible	O
plastic	O
.	O
</s>
<s>
The	O
ultimate	O
goal	O
of	O
organ	B-Device
printing	I-Device
is	O
to	O
create	O
organs	O
that	O
can	O
fully	O
integrate	O
into	O
the	O
human	O
body	O
as	O
if	O
they	O
had	O
been	O
there	O
all	O
along	O
.	O
</s>
<s>
Successful	O
organ	B-Device
printing	I-Device
has	O
the	O
potential	O
to	O
impact	O
several	O
industries	O
.	O
</s>
<s>
The	O
field	O
of	O
organ	B-Device
printing	I-Device
stemmed	O
from	O
research	O
in	O
the	O
area	O
of	O
stereolithography	O
,	O
the	O
basis	O
for	O
the	O
practice	O
of	O
3D	O
printing	O
that	O
was	O
invented	O
in	O
1984	O
.	O
</s>
<s>
As	O
the	O
rapid	B-Device
manufacturing	I-Device
techniques	O
entailed	O
by	O
3D	O
printing	O
become	O
increasingly	O
efficient	O
,	O
their	O
applicability	O
in	O
artificial	O
organ	O
synthesis	O
has	O
grown	O
more	O
evident	O
.	O
</s>
<s>
Organ	B-Device
printing	I-Device
using	O
3D	O
printing	O
can	O
be	O
conducted	O
using	O
a	O
variety	O
of	O
techniques	O
,	O
each	O
of	O
which	O
confers	O
specific	O
advantages	O
that	O
can	O
be	O
suited	O
to	O
particular	O
types	O
of	O
organ	O
production	O
.	O
</s>
<s>
Sacrificial	O
writing	O
into	O
function	O
tissue	O
(	O
SWIFT	O
)	O
is	O
a	O
method	O
of	O
organ	B-Device
printing	I-Device
where	O
living	O
cells	O
are	O
packed	O
tightly	O
to	O
mimic	O
the	O
density	O
that	O
occurs	O
in	O
the	O
human	O
body	O
.	O
</s>
<s>
This	O
method	O
of	O
organ	B-Device
printing	I-Device
uses	O
spatially	O
controlled	O
light	O
or	O
laser	O
to	O
create	O
a	O
2D	O
pattern	O
that	O
is	O
layered	O
through	O
a	O
selective	O
photopolymerization	O
in	O
the	O
bio-ink	O
reservoir	O
.	O
</s>
<s>
Cells	O
themselves	O
can	O
also	O
be	O
deposited	O
in	O
this	O
manner	O
with	O
or	O
without	O
polymer	B-Language
.	O
</s>
<s>
When	O
printing	O
polymer	B-Language
scaffolds	O
using	O
these	O
methods	O
,	O
each	O
drop	O
starts	O
to	O
polymerize	O
upon	O
contact	O
with	O
the	O
substrate	O
surface	O
and	O
merge	O
into	O
a	O
larger	O
structure	O
as	O
droplets	O
start	O
to	O
coalesce	O
.	O
</s>
<s>
Polymerization	O
can	O
happen	O
through	O
a	O
variety	O
of	O
methods	O
depending	O
on	O
the	O
polymer	B-Language
used	O
.	O
</s>
<s>
Recent	O
advances	O
in	O
organ	B-Device
printing	I-Device
using	O
SLS	O
include	O
3D	O
constructs	O
of	O
craniofacial	O
implants	O
as	O
well	O
as	O
scaffolds	O
for	O
cardiac	O
tissue	O
engineering	O
.	O
</s>
<s>
Materials	O
for	O
3D	O
printing	O
usually	O
consist	O
of	O
alginate	O
or	O
fibrin	O
polymers	B-Language
that	O
have	O
been	O
integrated	O
with	O
cellular	O
adhesion	O
molecules	O
,	O
which	O
support	O
the	O
physical	O
attachment	O
of	O
cells	O
.	O
</s>
<s>
Such	O
polymers	B-Language
are	O
specifically	O
designed	O
to	O
maintain	O
structural	O
stability	O
and	O
be	O
receptive	O
to	O
cellular	O
integration	O
.	O
</s>
<s>
Hydrogel	O
alginates	O
have	O
emerged	O
as	O
one	O
of	O
the	O
most	O
commonly	O
used	O
materials	O
in	O
organ	B-Device
printing	I-Device
research	O
,	O
as	O
they	O
are	O
highly	O
customizable	O
,	O
and	O
can	O
be	O
fine-tuned	O
to	O
simulate	O
certain	O
mechanical	O
and	O
biological	O
properties	O
characteristic	O
of	O
natural	O
tissue	O
.	O
</s>
<s>
The	O
properties	O
of	O
the	O
alginate	O
or	O
mixed-polymer	O
bioink	O
are	O
tunable	O
and	O
can	O
be	O
altered	O
for	O
different	O
applications	O
and	O
types	O
of	O
organs	O
.	O
</s>
<s>
Other	O
natural	O
polymers	B-Language
that	O
have	O
been	O
used	O
for	O
tissue	O
and	O
3D	O
organ	B-Device
printing	I-Device
include	O
chitosan	O
,	O
hydroxyapatite	O
(	O
HA	O
)	O
,	O
collagen	O
,	O
and	O
gelatin	O
.	O
</s>
<s>
Gelatin	O
is	O
a	O
thermosensitive	O
polymer	B-Language
with	O
properties	O
exhibiting	O
excellent	O
wear	O
solubility	O
,	O
biodegradability	O
,	O
biocompatibility	O
,	O
as	O
well	O
as	O
a	O
low	O
immunologic	O
rejection	O
.	O
</s>
<s>
Synthetic	O
polymers	B-Language
are	O
human	O
made	O
through	O
chemical	O
reactions	O
of	O
monomers	O
.	O
</s>
<s>
However	O
,	O
their	O
lack	O
of	O
functional	O
groups	O
and	O
structural	O
complexity	O
has	O
limited	O
their	O
usage	O
in	O
organ	B-Device
printing	I-Device
.	O
</s>
<s>
Current	O
synthetic	O
polymers	B-Language
with	O
excellent	O
3D	O
printability	O
and	O
in	O
vivo	O
tissue	O
compatibility	O
,	O
include	O
polyethylene	O
glycol	O
(	O
PEG	O
)	O
,	O
poly(lactic-glycolic acid )	O
(	O
PLGA	O
)	O
,	O
and	O
polyurethane	O
(	O
PU	O
)	O
.	O
</s>
<s>
PEG	O
is	O
a	O
biocompatible	O
,	O
nonimmunogenic	O
synthetic	O
polyether	B-Application
that	O
has	O
tunable	O
mechanical	O
properties	O
for	O
use	O
in	O
3D	O
bioprinting	O
.	O
</s>
<s>
Though	O
PEG	O
has	O
been	O
utilized	O
in	O
various	O
3D	O
printing	O
applications	O
,	O
the	O
lack	O
of	O
cell-adhesive	O
domains	O
has	O
limited	O
further	O
use	O
in	O
organ	B-Device
printing	I-Device
.	O
</s>
<s>
PLGA	O
is	O
used	O
in	O
conjunction	O
with	O
other	O
polymers	B-Language
to	O
create	O
different	O
material	O
systems	O
,	O
including	O
PLGA-gelatin	O
,	O
PLGA-collagen	O
,	O
all	O
of	O
which	O
enhance	O
mechanical	O
properties	O
of	O
the	O
material	O
,	O
biocompatible	O
when	O
placed	O
in	O
vivo	O
,	O
and	O
have	O
tunable	O
biodegradability	O
.	O
</s>
<s>
An	O
application	O
of	O
PU	O
would	O
be	O
inanimate	O
artificial	O
hearts	O
;	O
however	O
,	O
using	O
existing	O
3D	O
bioprinters	O
,	O
this	O
polymer	B-Language
cannot	O
be	O
printed	O
.	O
</s>
<s>
This	O
new	O
material	O
exhibits	O
excellent	O
biocompatibility	O
,	O
biodegradability	O
,	O
bioprintability	O
,	O
and	O
biostability	O
for	O
use	O
in	O
complex	O
bioartificial	O
organ	B-Device
printing	I-Device
and	O
manufacturing	O
.	O
</s>
<s>
Due	O
to	O
high	O
vascular	O
and	O
neural	O
network	O
construction	O
,	O
this	O
material	O
can	O
be	O
applied	O
to	O
organ	B-Device
printing	I-Device
in	O
a	O
variety	O
of	O
complex	O
ways	O
,	O
such	O
as	O
the	O
brain	O
,	O
heart	O
,	O
lung	O
,	O
and	O
kidney	O
.	O
</s>
<s>
Natural-synthetic	O
hybrid	O
polymers	B-Language
are	O
based	O
on	O
the	O
synergic	B-Language
effect	O
between	O
synthetic	O
and	O
biopolymeric	O
constituents	O
.	O
</s>
<s>
Hyaluronic	O
acid	O
(	O
HA	O
)	O
-PEG	O
is	O
another	O
natural-synthetic	O
hybrid	O
polymer	B-Language
that	O
has	O
proven	O
to	O
be	O
very	O
successful	O
in	O
bioprinting	O
applications	O
.	O
</s>
<s>
HA	O
combined	O
with	O
synthetic	O
polymers	B-Language
aid	O
in	O
obtaining	O
more	O
stable	O
structures	O
with	O
high	O
cell	O
viability	O
and	O
limited	O
loss	O
in	O
mechanical	O
properties	O
after	O
printing	O
.	O
</s>
<s>
Lastly	O
,	O
a	O
series	O
of	O
biodegradable	O
polyurethane	O
(	O
PU	O
)	O
-gelatin	O
hybrid	O
polymers	B-Language
with	O
tunable	O
mechanical	O
properties	O
and	O
efficient	O
degradation	O
rates	O
have	O
been	O
implemented	O
in	O
organ	B-Device
printing	I-Device
.	O
</s>
<s>
All	O
of	O
the	O
polymers	B-Language
described	O
above	O
have	O
the	O
potential	O
to	O
be	O
manufactured	O
into	O
implantable	O
,	O
bioartificial	O
organs	O
for	O
purposes	O
including	O
,	O
but	O
not	O
limited	O
to	O
,	O
customized	O
organ	O
restoration	O
,	O
drug	O
screening	O
,	O
as	O
well	O
as	O
metabolic	O
model	O
analysis	O
.	O
</s>
<s>
However	O
,	O
the	O
ability	O
of	O
some	O
tissues	O
to	O
self-organize	O
into	O
differentiated	O
structures	O
may	O
provide	O
a	O
way	O
to	O
simultaneously	O
construct	O
the	O
tissues	O
and	O
form	O
distinct	O
cell	O
populations	O
,	O
improving	O
the	O
efficacy	O
and	O
functionality	O
of	O
organ	B-Device
printing	I-Device
.	O
</s>
<s>
The	O
types	O
of	O
printers	O
used	O
for	O
organ	B-Device
printing	I-Device
include	O
:	O
</s>
<s>
3D	O
organ	B-Device
printing	I-Device
has	O
the	O
potential	O
to	O
remove	O
both	O
these	O
issues	O
;	O
if	O
organs	O
could	O
be	O
printed	O
as	O
soon	O
as	O
there	O
is	O
need	O
,	O
there	O
would	O
be	O
no	O
shortage	O
.	O
</s>
<s>
In	O
the	O
field	O
of	O
organ	B-Device
printing	I-Device
,	O
applications	O
can	O
be	O
applied	O
for	O
patients	O
and	O
surgeons	O
.	O
</s>
<s>
3D	O
organ	B-Device
printing	I-Device
technology	O
permits	O
the	O
fabrication	O
of	O
high	O
degrees	O
of	O
complexity	O
with	O
great	O
reproducibility	O
,	O
in	O
a	O
fast	O
and	O
cost-effective	O
manner	O
.	O
</s>
<s>
Also	O
,	O
organ	B-Device
printing	I-Device
has	O
been	O
used	O
as	O
a	O
transformative	O
tool	O
for	O
in	O
vitro	O
testing	O
.	O
</s>
<s>
Organ	B-Device
printing	I-Device
technology	O
can	O
also	O
be	O
combined	O
with	O
microfluidic	O
technology	O
to	O
develop	O
organs-on-chips	O
.	O
</s>
<s>
Organ	B-Device
printing	I-Device
,	O
on	O
the	O
other	O
hand	O
,	O
is	O
a	O
novel	O
industry	O
that	O
utilizes	O
biological	O
components	O
to	O
develop	O
therapeutic	O
applications	O
for	O
organ	O
transplants	O
.	O
</s>
<s>
Organ	B-Device
printing	I-Device
can	O
assist	O
in	O
diminishing	O
the	O
imbalance	O
between	O
supply	O
and	O
demand	O
by	O
printing	O
patient-specific	O
organ	O
replacements	O
,	O
all	O
of	O
which	O
is	O
unfeasible	O
without	O
regulation	O
.	O
</s>
<s>
Due	O
to	O
the	O
complexity	O
of	O
this	O
therapeutic	O
approach	O
,	O
the	O
location	O
of	O
organ	B-Device
printing	I-Device
on	O
the	O
spectrum	O
has	O
not	O
been	O
discerned	O
.	O
</s>
<s>
From	O
an	O
ethical	O
standpoint	O
,	O
there	O
are	O
concerns	O
with	O
respect	O
to	O
the	O
availability	O
of	O
organ	B-Device
printing	I-Device
technologies	O
,	O
the	O
cell	O
sources	O
,	O
and	O
public	O
expectations	O
.	O
</s>
<s>
Organ	B-Device
printing	I-Device
can	O
decrease	O
or	O
eliminate	O
animal	O
studies	O
and	O
trials	O
,	O
but	O
also	O
raises	O
questions	O
on	O
the	O
ethical	O
implications	O
of	O
autologous	O
and	O
allogenic	O
sources	O
.	O
</s>
<s>
Overall	O
,	O
the	O
ethical	O
considerations	O
of	O
organ	B-Device
printing	I-Device
are	O
similar	O
to	O
those	O
of	O
general	O
ethics	O
of	O
bioprinting	O
,	O
but	O
are	O
extrapolated	O
from	O
tissue	O
to	O
organ	O
.	O
</s>
<s>
Altogether	O
,	O
organ	B-Device
printing	I-Device
possesses	O
short	O
-	O
and	O
long-term	O
legal	O
and	O
ethical	O
consequences	O
that	O
need	O
to	O
be	O
considered	O
before	O
mainstream	O
production	O
can	O
be	O
feasible	O
.	O
</s>
<s>
Organ	B-Device
printing	I-Device
for	O
medical	O
applications	O
is	O
still	O
in	O
the	O
developmental	O
stages	O
.	O
</s>
<s>
Thus	O
,	O
the	O
long	O
term	O
impacts	O
of	O
organ	B-Device
printing	I-Device
have	O
yet	O
to	O
be	O
determined	O
.	O
</s>
<s>
Researchers	O
hope	O
that	O
organ	B-Device
printing	I-Device
could	O
decrease	O
the	O
organ	O
transplant	O
shortage	O
.	O
</s>
<s>
An	O
additional	O
impact	O
of	O
organ	B-Device
printing	I-Device
includes	O
the	O
ability	O
to	O
rapidly	O
create	O
tissue	O
models	O
,	O
therefore	O
increasing	O
productivity	O
.	O
</s>
<s>
The	O
challenges	O
faced	O
in	O
the	O
organ	B-Device
printing	I-Device
field	O
extends	O
beyond	O
the	O
research	O
and	O
development	O
of	O
techniques	O
to	O
solve	O
the	O
issues	O
of	O
multivascularization	O
and	O
difficult	O
geometries	O
.	O
</s>
<s>
Before	O
organ	B-Device
printing	I-Device
can	O
become	O
widely	O
available	O
,	O
a	O
source	O
for	O
sustainable	O
cell	O
sources	O
must	O
be	O
found	O
and	O
large-scale	O
manufacturing	O
processes	O
need	O
to	O
be	O
developed	O
.	O
</s>
<s>
While	O
many	O
developments	O
have	O
been	O
made	O
in	O
the	O
field	O
of	O
organ	B-Device
printing	I-Device
,	O
more	O
research	O
must	O
be	O
conducted	O
.	O
</s>
