oxygen transfer model and microfluidic encapsulation of islets
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Oxygenation in Encapsulated Islets
Jake YeungDecember 4, 2012Piret Lab Meeting
1
Native islets in pancreas are well vascularized
2(Suckale, 2011)
Encapsulated islets present new challenges
3(Vaithilingam & Tuch, 2011)
Outline
Oxygen supply and its effects on islet performance
Oxygen transfer modelling in encapsulated islets
Generating alginate beads for improved oxygen transfer
Conclusion and future work
4
Oxygen levels of transplanted rat islets
5
(Carlsson et al., 2001)
- Nondiabetic rat
- Diabetic rat
Oxygen levels and number of islets transplanted
6
(Carlsson et al., 2001)
Oxygen levels in peritoneal space
7
Method Animal pO2 (mmHg) Source Comments
Implanted tonometers
Rabbit 30 - 60(Klossner et al., 1974)
15 days in 10 rabbits
Polarographic oxygen electrode
Mouse 20 - 60(Bourdel et al., 2007)
1 hour in 6 mice
Galvanic electrode
Rabbit 15 - 55(Towell et al., 1976)
14 days in at least 7 rabbits
19F-NMR Mice 31 - 79(Goh et al., 2011)
16 days in 2 mice
Effect of hypoxia on insulin secretion
8
(Papas et al., 1996)
Outline
Oxygen supply and its effects on islet performance
Oxygen transfer modelling in encapsulated islets
Generating alginate beads for improved oxygen transfer
Conclusion and future work
9
Model geometry
10
(Greenemeier, 2008)
i Islet radius=75μm
Bead radius=250μm
Mass transport
Pressure gradient:
Four boundary conditions:a𝑡 𝑟 = 𝑅2, 𝑃2 = 𝑃𝑒𝑥𝑡
a𝑡 𝑟 = 𝑅1, 𝑃1 = 𝑃2
a𝑡 𝑟 = 𝑅1, 𝛼𝐷 1𝑑𝑃1
𝑑𝑟= 𝛼𝐷 2
𝑑𝑃2
𝑑𝑟
a𝑡 𝑟 = 𝑅0,𝑑𝑃1
𝑑𝑧= 0
11
(𝛼𝐷)𝑖
1
𝑟2𝑑
𝑑𝑟𝑟2𝑑𝑃𝑖𝑑𝑟
= 𝑉𝑖
Parameters for the model
Parameter Symbol Value Units
Oxygen consumption rate 𝑉𝑚𝑎𝑥 4 × 10−8 mol/cm3/s
Critical pO2 for cell death 𝑃𝑐 0.1 mmHg
Oxygen permeability in tissue 𝛼𝐷 1 1.24 × 10−14 mol/cm/mmHg/s
Oxygen permeability in 5%(v/v)
alginate𝛼𝐷 2 3.27 × 10−14 mol/cm/mmHg/s
12
(Johnson et al., 2009)
Oxygen and insulin secretion rate within beads
13
0 50 100 150 200 2500
20
40
60O
xyge
n p
arti
al p
ress
ure
(m
m H
g)
0 50 100 150 200 2500
0.2
0.4
0.6
0.8
1
Radial distance from centre (um)
Frac
tio
nal
insu
lin s
ecr
eti
on
rat
e
Alginate
Islets
Necrotic core
Pext=15mmHg
Pext=40mmHg
Pext=60mmHg
Pext=60mmHg
Pext=40mmHg
Pext=15mmHg
Islet diameter=150μmBead diameter=500μm
0 20 40 60 800
0.2
0.4
0.6
0.8
1
External partial pressure of oxygen (mm Hg)
Frac
tio
n o
f n
orm
al in
suli
n s
ecr
eti
on
rat
e
Fraction of normal insulin secretion rate
14
Islet diameter=150μmBead diameter=500μm
0 20 40 60 80 1000
20
40
60
80
External partial pressure of oxygen (mm Hg)
Ne
cro
tic
core
rad
ius
(um
)
Necrotic core size
15
Islet diameter=150μmBead diameter=500μm
Effect of bead size on islet performance
16
Islet diameter=150μmPext=40mmHg
200 300 400 500 600 700 800 900 10000
5
10
15
20
25
30
Bead diameter (um)
Ne
cro
tic
core
rad
ius
(um
)
200 300 400 500 600 700 800 900 10000
0.2
0.4
0.6
0.8
1
Frac
tio
n o
f n
orm
al in
suli
n s
ecr
eti
on
rat
e
Pext=40mmHgIslet diameter=150μm
Outline
Oxygen supply and its effects on islet performance
Oxygen transfer modelling in encapsulated islets
Generating alginate beads for improved oxygen transfer
Conclusion and future work
17
Microfluidic device: top view
18
Alginate
Mineral oil
Acidified oil Outlet
Courtesy of René Pedroza
Microfluidic device: side view
19
Generating alginate beads
20
Bead size distribution: t=0 to 20 minutes
21
0 3 2
72
149
247 2 0 0 0
0
5
10
15
20
25
30
0
40
80
120
160
0-1
00
10
0-2
00
20
0-3
00
30
0-4
00
40
0-5
00
50
0-6
00
60
0-7
00
70
0-8
00
80
0-9
00
90
0-1
00
0
>10
00
Nec
roti
c co
re r
adiu
s (u
m)
Bea
ds
Co
un
ted
Bead diameter (µm)
Bead size distribution: t=20 to 40 minutes
22
0
14 12
26
89
47
155 3 4 2
0
5
10
15
20
25
30
0
20
40
60
80
100
0-1
00
10
0-2
00
20
0-3
00
30
0-4
00
40
0-5
00
50
0-6
00
60
0-7
00
70
0-8
00
80
0-9
00
90
0-1
00
0
>10
00
Nec
roti
c co
re r
adiu
s (u
m)
Bea
ds
Co
un
ted
Bead diameter (µm)
Bead size distribution: t=40 to 60 minutes
23
0 4 10
165
67 69
32
7 3 0 10
5
10
15
20
25
30
0
40
80
120
160
200
0-1
00
10
0-2
00
20
0-3
00
30
0-4
00
40
0-5
00
50
0-6
00
60
0-7
00
70
0-8
00
80
0-9
00
90
0-1
00
0
>10
00
Nec
roti
c co
re r
adiu
s (u
m)
Bea
ds
Co
un
ted
Bead diameter (µm)
Viability of MIN6 cells versus time in syringe
24
0%
20%
40%
60%
80%
100%
0 20 40 60 80 100
Ce
ll vi
abili
ty (
%)
Time spent in syringe (minutes)
Bead size: microfluidic chip versus spinner flask
25
From microfluidic chip From spinner flask
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0-1
00
10
0-2
00
20
0-3
00
30
0-4
00
40
0-5
00
50
0-6
00
60
0-7
00
70
0-8
00
80
0-9
00
90
0-1
00
0
>1
00
0
Vo
lum
etri
c Fr
acti
on
Bead diameter (µm)
0-100 100-200
200-300
300-400
400-500
500-600
600-700
700-800
800-900
900-1000
>1000
Bead diameter (µm)
Microfluidic chip versus spinner flask
+ Narrower distribution
+ Reduced shear stress
+ No entrapped bubbles or oil
– Coalescence of beads
– Losses inside tubing
– Transient effects on viability
26
Outline
Oxygen supply and its effects on islet performance
Oxygen transfer modelling in encapsulated islets
Generating alginate beads for improved oxygen transfer
Conclusion and future work
27
Conclusion
28
(Greenemeier, 2008)
i Islet radius=75μm
Bead radius=250μm
Literature review Modelling Microfluidics
Future work
29
Analyzing islets after transplantation
Process optimization
Courtesy of Blanche Lo
Acknowledgements
Piret lab
Ali Nazari
Blanche Lo
Chris Sherwood
René Pedroza
30
Cheung lab
Linfen Yu
Works cited
31
Bourdel, N., Matsuzaki, S., Bazin, J.-E., Pouly, J.-L., Mage, G., and Canis, M. (2007). Peritoneal tissue-oxygen tension during a carbon
dioxide pneumoperitoneum in a mouse laparoscopic model with controlled respiratory support. Hum. Reprod. 22, 1149–1155.
Suckale, J. (2011). Mouse pancreatic islet: Wikipedia.
Carlsson, P.-O., Palm, F., Andersson, A., and Liss, P. (2001). Markedly Decreased Oxygen Tension in Transplanted Rat Pancreatic Islets
Irrespective of the Implantation Site. Diabetes 50, 489–495.
Goh, F., Long, R., Simpson, N., and Sambanis, A. (2011). Dual perfluorocarbon method to noninvasively monitor dissolved oxygen
concentration in tissue engineered constructs in vitro and in vivo. Biotechnology Progress 27, 1115–1125.
Greenemeier, L. (2008). Pigs Could Be the Salvation of Diabetes Sufferers: Scientific American.
Klossner, J., Kivisaari, J., and Niinikoski, J. (1974). Oxygen and carbon dioxide tensions in the abdominal cavity and colonic wall of the
rabbit. The American Journal of Surgery 127, 711–715.
Liu, E.H., Rother, K.I., and Harlan, D.M. (2009). Islet Transplantation and the Challenges of Treating Type 1 Diabetes. Discovery
Medicine 5, 43–49.
Papas, K.K., Long Jr., R.C., Constantinidis, I., and Sambanis, A. (1996). Effects of oxygen on metabolic and secretory activities of βTC3
cells. Biochimica Et Biophysica Acta (BBA) - General Subjects 1291, 163–166.
Towell, M.E., Lysak, I., Layne, E.C., and Bessman, S.P. (1976). Tissue oxygen tension in rabbits measured with a galvanic electrode. J
Appl Physiol 41, 245–250.
Vaithilingam, V., and Tuch, B.E. (2011). Islet Transplantation and Encapsulation: An Update on Recent Developments. Rev Diabet Stud 8,
51–67.
Batch effects?
32
0
200
400
600
800
1000
1200
0 100 200 300 400
Bea
d d
iam
eter
(u
m)
Bead rank
t=0 to 20 min
t=20 to 40 min
t=40 to 60 min
2 4 6 8 100
10
20
30
40
50
60
70
Percentage of Alginate (%v/v)
Ne
cro
tic
core
siz
e (
um
)
2 4 6 8 100
0.2
0.4
0.6
0.8
1
Frac
tio
n o
f n
orm
al in
suli
n s
ecr
eti
on
rat
e
Effect of alginate concentration
33
Pext=40mmHgIslet diameter=150μmBead diameter=500 μm
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