Biomimetic Nanofi brous Scaffolds for Bone Tissue Engineering Applications - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 81

revealed the increase in adsorption of proteins known to mediate cell-
surface interactions including fi bronectin, vitronectin, and laminin [102].
Later investigation with partially nanofi brous scaffolds revealed total
serum protein adsorption is directly proportional to the surface area of
the scaffolds, which was 1000X greater in nanofi brous scaffolds compared
to solid-walled scaffolds [93]. MC3T3 murine pre-osteoblasts cultured on
scaffolds for 24 h exhibited a 1.7-fold increase in cell attachment compared
to smooth-walled scaffolds, suggesting that cells more easily attached to
nanofi brous matrices, likely due to increased protein adhesion in the ini-
tial stages of cellular colonization [102].
More interesting is the capability of NF scaffolds to induce osteoblas-
tic behavior in progenitor cells. MC3T3 cells proliferated faster in smooth
scaffolds, but on nanofi brous scaffolds with the addition of ascorbic acid
to induce osteogenesis, exhibited signifi cantly higher alkaline phospha-
tase activity as well as expression of bone sialoprotein (BSP), both mark-
ers of osteogenesis. Similar results have been obtained in murine and
human embryonic stem cells [103, 104], human mesenchymal stem cells
[105], and murine osteoblasts [106]. Finally, in a calvarial defect model,
nanofi brous scaffolds resulted in signifi cantly increased bone production
at 8 weeks compared to smooth-walled scaffolds [107]. Most promising
were islands of bone production in the center of the scaffold, separate
from bone ingrowth in the periphery of the scaffold (Figure 4.4). This sug-
gests that NF scaffolds possess some osteoinductive properties in vivo ,
and further tuning of scaffold properties may allow for even faster bone
tissue nucleation and growth throughout the scaffold.

( a ) ( b ) 20

Solid Nano

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15

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4wks 8wks

Figure 4.4 Micro-computerized tomography showing bone regeneration in
a rat calvarial defect (dotted line), when using a nanofi brous PLLA scaffold
(a, bottom), compared to a smooth-walled scaffold with identical pore
microstructure (a, top). By 8 weeks a signifi cant increase in bone volume is seen
in the defect when using a nanofi brous scaffold compared to a smooth-walled
scaffold with otherwise identical microstructure (b). Adapted from Woo et al.,
2009 [107], Copyright © 2009 Mary Ann Liebert Inc.