NOVEL MICROSPHERES FOR PROLONGED CELL SURVIVAL - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 657

instance, a comparison of cell density for culture seeded under nor-
moxic (21% O 2 ,5%CO 2 ) and hypoxic ( < 1% O 2 ) conditions in the
presence and absence of microspheres over a period of time can be
made. Any significant density differences of cells between the cul-
tures will contribute towards the effort in drawing conclusions over
the oxygen-releasing phenomena. Theoretically, under hypoxic con-
dition, the oxygen level is very low and cells usually will not sur-
vive long under such conditions. With the addition of microspheres
under such conditions, if the cells can survive, this gives an indi-
cation that oxygen is supplied by the microspheres. In contrast, if
cellsfailtosurviveandshowthesameresultasthecultureswithout
microspheres, this indicates a failure. In this type of a comparison
study, all conditionsset between the control and the sample need to
be identical and well controlled. Such kind of an evaluation method
has been practically used in the work by Oh etal. 44
32.4 ORMs in Applications for E cient Cell Survival
Despite the success in developing ORMs, the next important aspect
is to utilize the microspheres for e cient cell survival effectively in
applications.Themicrospheresshouldbeabletoreleasetheoxygen
to cells at the targeted place and time, without being wasted or tar-
geted on the wrong area. Thus, this reflects the need for designing
elegant delivery mechanisms, integrated on a suitable platform that
actsasabridgetomergethemicrospheresintoarealbiologicalsys-
tem. Based on the literature, there are several potential options that
can be employed and further modified in achieving this task. This
section will discuss some of the methods with suggestions based on
the authors' opinions.
32.4.1 Direct Integration in Scaffolds
The integration of microspheres encapsulated with active agents
into scaffolds for tissue engineering purposes has been widely
reported. 12 , 78 - 80 The motivation is to combine the strengths
and advantages, both of conventional scaffolds and encapsulated
microspheres, into a new class of a composite biomaterial in