Biomedical Engineering Reference
In-Depth Information
matrices for cell cultures are very important for realizing these
goals. Aliphatic polyesters, such as poly(lactic acid), poly(glycolic
acid), and their copolymers have been commonly used as matrices
for cell cultures.
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These conventional biodegradable polymers
are usually highly hydrophobic. The cell culture medium then dif-
ficultly penetrated the matrices.
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The nutrients also did not pen-
etrate these matrices. As a result, the seeded cells did not grow
in the inner portion of the matrices. To solve this problem, MPC
copolymers having enantiomeric polyesters on the side chains were
synthesized.
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Polymeric scaffolds were generated using the stere-
ocomplex formations of the side chains. The wettability of the scaf-
folds was greatly improved in comparison with that of the scaffolds
generated from conventional polyesters; cellular invasion into the
MPC copolymer scaffolds was easily observed.
Spontaneous gelation of polymers can provide the desired size
and shape for seeded and encapsulated cells. In addition, it is
useful that the cross-linking network can be dissociated by the
addition of chemical or physical stimulation. On the basis of these
requirements, recoverable hydrogels have been prepared by mixing
two kinds of aqueous polymer solutions. First, cross-linking of the
polymer chains under physiological conditions is necessary for this
purposeinordertoavoidanyreducedactivityoftheentrappedcells
and biomolecules. The cytocompatibility and nutrient permeability
of the hydrogel are important factors for the entrapped cells. Konno
et al
. prepared a new reversible hydrogel system composed of the
MPCpolymers,whichcanencapsulatethecellsandproteinsbymild
treatment with a high degree of practicability and activity.
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As the
cross-linking mechanism between the MPC polymers in an aqueous
medium, thespecificreaction betweenboronicacidandmultivalent
alcoholic compounds was used. The boronic acid in a tetrahedral
anionic structure produces stable complexes with the alcohol com-
pounds, including polyvinyl alcohol (PVA), glucose, etc.
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The
hydrogel is reversibly dissociated by the addition of low-molecular-
weight compounds such as D-glucose. They propose a new cell
maintenance system called the
cell container
on the basis of this
hydrogel. This system will be useful for maintaining the cells with
a high activity and enabling their specific functions after being
released from the hydrogel accompanied by dissociation of the
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