EMULSION TEMPLATING - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 671

Figure 33.4. SEM of polyHIPEs with open and closed pore structures.
Reprinted with permission from Ref. 37; copyright 2007 American Chem-
ical Society.

33.4 PolyHIPEs as Bone Scaffolds

The first polyHIPE investigated as a bone scaffold was based
on styrene and divinylbenzene. 36 However, the styrene-based
system is nonbiodegradable, which led to the investigation of
polyHIPEs based on poly(

ε

-caprolactone- co- styrene), poly(lactic
acid- co -styrene), dextran, pullulan, and gelatin. 23 , 46 − 51 Although
high-porosity polyHIPEs were prepared with these formulations,
theirapplicationtobonetissueengineeringstrategiesarerestricted
due to the limited biodegradability of the copolymer systems and
the low mechanical strength of the natural polymers. Fumarate-
based polyHIPEs were developed in the Mikos group using toluene
as a diluent to reduce viscosity su ciently to permit emulsion
formation. 37 However, osteoblast growth and mineralized matrix
production on these semi- and fully degradable polyHIPEs has yet
to beestablished.

33.4.1 Nondegradable: Styrene-Based PolyHIPEs
Akay et al . first investigated polyHIPE scaffolds to support the
growth of osteoblasts in vitro . 36 PolyHIPE foams based on styrene
with a divinylbenzene cross-linker were prepared (Fig. 33.5). Ele-
vated temperatures (up to 80 ◦ C) during emulsification were uti-
lized to generate a broader range of pore sizes. Rat osteoblasts
were seeded on polyHIPE scaffolds with three average pore sizes