effects on the adhesion and proliferation of embryonal carcinoma (EC) cells on
stent material [172].
Similar studies on angiogenesis in the frame of a joint project between material
scientists, cell biologists, and clinicians have been made by us with HUVECs and
concerned their interaction with PEC particle systems. Preliminary results on the
influence of PEC particle charge revealed that the charge sign of the PEC particles
had a crucial influence on the viability of HUVECs (unpublished results).
Interaction of PEC Particles with Osteoblast Cells
As well as the engineering of vascular tissue based on endothelial cells, there is
huge interest in the engineering of bone tissue, osseous scaffolds, or BSM based on,
e.g., osteoblasts (OB). In this framework, Nagahata reported on the development of
new scaffolds for bone regeneration based on precipitated and washed biomimetic
PEC particle films on culture dishes [173]. Analogously to endothelial cells, the
mimicking of the ECM of OB by PELs such as CHT, anionically modified (carboxyl,
phosphate, sulfate) chitin or hyaluronic acid, was aimed at. PEC films with variable
PEL compositions were prepared, and their effects on OB functions like attachment,
morphology, growth, and differentiation (as measured by alkaline phosphatase assay)
were evaluated. Use of PEL bearing carboxyl and phosphate groups resulted in
decreased OB attachment, occurrence of cell aggregation, and suppressed differentiation and proliferation. By contrast, PEC films bearing sulfated polysaccharides
showed an adhesion and proliferation performance almost similar to collagen-coated
dishes, which enables their use as scaffolds for bone regeneration (see Fig. 34a).
Additionally, these authors [173] addressed an additional effect of PEC films on
cell function, which is gap junctional intercellular communication (GJIC) allowing
OB cells to maintain homeostasis. Figure 34b shows the results of GJIC measurement by fluorescence recovery after photobleaching (FRAP) on an extracellularly
binding dye at cells in contact with at least two other cells. There was no significant
difference between PEC films and the collagen-coated dish. By contrast, OB on
pure CHT-coated dishes showed suppression of GJIC after 1 week. This suggests
that CHT disturbs homeostasis maintenance of OB, but that this effect can be
avoided by complexation with, e.g., anionic polysaccharides.
Related to this, the Abe group reported earlier on the interaction between PEC
precipitate systems consisting of anionic phosphated and carboxymethylated chitin
(PCHN and CCHN) and cationic CHT and rat OB cells in cell culture dishes [174].
OB aggregates were observed on both CHT/PCHN (4th day) and CHT/CCHN (2nd
day) to exhibit inhibited growth as compared with controls. However, OB differentiation (as shown by alkaline phosphatase assay) increased and osteocalcin mRNA
was expressed for both PEC systems, indicating the importance of OB aggregation
for bone mineralization capability.
Recently, a joint project between material scientists, cell biologists, and clinicians
was installed aiming at local and time-controlled delivery of osteoporotic drugs from
implant or bone-substituting materials. Before drug-loaded PEC particles were studied,
Sizing, Shaping and Pharmaceutical Applications of Polyelectrolyte Complex. . .
249
stent material [172].
Similar studies on angiogenesis in the frame of a joint project between material
scientists, cell biologists, and clinicians have been made by us with HUVECs and
concerned their interaction with PEC particle systems. Preliminary results on the
influence of PEC particle charge revealed that the charge sign of the PEC particles
had a crucial influence on the viability of HUVECs (unpublished results).
Interaction of PEC Particles with Osteoblast Cells
As well as the engineering of vascular tissue based on endothelial cells, there is
huge interest in the engineering of bone tissue, osseous scaffolds, or BSM based on,
e.g., osteoblasts (OB). In this framework, Nagahata reported on the development of
new scaffolds for bone regeneration based on precipitated and washed biomimetic
PEC particle films on culture dishes [173]. Analogously to endothelial cells, the
mimicking of the ECM of OB by PELs such as CHT, anionically modified (carboxyl,
phosphate, sulfate) chitin or hyaluronic acid, was aimed at. PEC films with variable
PEL compositions were prepared, and their effects on OB functions like attachment,
morphology, growth, and differentiation (as measured by alkaline phosphatase assay)
were evaluated. Use of PEL bearing carboxyl and phosphate groups resulted in
decreased OB attachment, occurrence of cell aggregation, and suppressed differentiation and proliferation. By contrast, PEC films bearing sulfated polysaccharides
showed an adhesion and proliferation performance almost similar to collagen-coated
dishes, which enables their use as scaffolds for bone regeneration (see Fig. 34a).
Additionally, these authors [173] addressed an additional effect of PEC films on
cell function, which is gap junctional intercellular communication (GJIC) allowing
OB cells to maintain homeostasis. Figure 34b shows the results of GJIC measurement by fluorescence recovery after photobleaching (FRAP) on an extracellularly
binding dye at cells in contact with at least two other cells. There was no significant
difference between PEC films and the collagen-coated dish. By contrast, OB on
pure CHT-coated dishes showed suppression of GJIC after 1 week. This suggests
that CHT disturbs homeostasis maintenance of OB, but that this effect can be
avoided by complexation with, e.g., anionic polysaccharides.
Related to this, the Abe group reported earlier on the interaction between PEC
precipitate systems consisting of anionic phosphated and carboxymethylated chitin
(PCHN and CCHN) and cationic CHT and rat OB cells in cell culture dishes [174].
OB aggregates were observed on both CHT/PCHN (4th day) and CHT/CCHN (2nd
day) to exhibit inhibited growth as compared with controls. However, OB differentiation (as shown by alkaline phosphatase assay) increased and osteocalcin mRNA
was expressed for both PEC systems, indicating the importance of OB aggregation
for bone mineralization capability.
Recently, a joint project between material scientists, cell biologists, and clinicians
was installed aiming at local and time-controlled delivery of osteoporotic drugs from
implant or bone-substituting materials. Before drug-loaded PEC particles were studied,
Sizing, Shaping and Pharmaceutical Applications of Polyelectrolyte Complex. . .
249