Biomedical Engineering Reference
In-Depth Information
Fig. 11 Islets with immobilized urokinase (UK-islets) were tested for the ability to dissolve fibrin.
(a) Fibrin in the plate gel medium was dissolved by UK-islets (
clear areas
). Fifty islets were
applied to each spot, and the plate was observed after incubation at 37
C for 14 h. (
1
) untreated
islets; (
2
) UK-islets treated with oligo(dT)
20
-PEG-lipid (C16), just after preparation; (
3
) UK-islets
treated with oligo(dT)
20
-PEG-lipid (C16) lost activity after 2 days in culture; (
4
) UK-islets treated
with oligo(dT)
20
-PEG-lipid (C18), just after preparation; and (
5
) UK-islets treated with oligo
(dT)
20
-PEG-lipid (C16) lost activity after 2 days in culture. (b) Morphology of UK-islets after 1
and 7 days of culture
long UK-islets can maintain the inhibition of IBMIR; however, these data
suggested that UK immobilization on islets is a promising approach for islet
transplantation.
4.3 Encapsulation of Islets with Living Cells
The histocompatibility and blood compatibility of donor islets can be significantly
improved by enclosing them inside a capsule made of the patient's vascular endothe-
lial cells. The ssDNA-PEG-lipid method was utilized to enclose islets with living
cells [
125
]. The method is schematically shown in Fig.
12a
.Oligo(dT)
20
was
introduced onto the surface of HEK293 cells with an oligo(dT)
20
-PEG-lipid, and
oligo(dA)
20
was introduced onto the surface of islets with an oligo(dA)
20
-PEG-lipid.
Then, the oligo(dA)
20
-islets were mixed with the oligo(dT)
20
-HEK293 cells. The
HEK293 cells were immobilized on the islet surface through DNA hybridization, as
shown in Fig.
12b
. Although the HEK293 cells existed as single cells on the islet just
after immobilization, the surface of islets were completely covered with a cell layer
after 3 days in culture (Fig.
12b
). No central necrosis of the islet cells was observed.
Immunostaining showed that insulin remained inside the islets after culturing for
3 days (Fig.
12b
). Furthermore, after cell encapsulation, insulin secretion in response
to glucose stimulation was well maintained (data not shown). This technique will
greatly facilitate islet transplantation for treating type 1 diabetes.
