Scaffold Design for Bone Tissue Engineering: From Micrometric to Nanometric Level - Biologically Responsive Biomaterials for Tissue Engineering - page 12

provides several effects on the cell shape, morphology, adhesion, and proliferation.
Osteoblasts adhesion was improved when they were cultured on nanotexture sur-
faces compared to the conventional micro surfaces [ 57 ] . NIH-3T3 cells cultured
onto PGA/collagen fibers with submicrometric size scale appear fully attached,
elongated, and more fibroblastic than those seeded on micrometric fibers [ 52 ] .
SaOs-2 and BMSC showed an influence on cytoskeletal organization and cell via-
bility when cultured onto nanofibrous scaffold [ 54 ]. All these observations from
current literature have been also confirmed by the comparative studies of casted
films and PCL electrospun fibers with micro- and nano-texture [ 21 ] . Preliminary, it
has been shown that cell adhesion and viability of human MSCs are significantly
enhanced by the nanometric scale of fibers which offer a more efficacious anchor-
age to cells. Moreover, nanotopography also improves proliferation and differentia-
tion efficiency of MSCs, thus offering an active topographical signal able to influence
cell differentiation. In particular, it has been reported that fibers nanotexture is also
capable of supporting differentiation of MSCs into osteogenic phenotype, consis-
tently with others' reported literature. These concur to demonstrate the relevance of
nanotopography on guiding the fate of the osteogenic, chondrogenic, and neuro-
genic lineages of MSCs [ 25, 45 ] .

1.5.2 Chemical Cues for Cell Recognition

Cell-substrate interaction may be drastically affected by the presence of chemical
cues able to support all the main cell functions including adhesion, proliferation,
and differentiation of cells. An interesting approach for bone tissue engineering
certainly relies on the ability to geometrically and topologically reproduce the native
microenvironment of tissues, providing all the biochemical stimuli which character-
ize the extracellular matrix of natural tissues. In order to afford the effective biomi-
mesis of the natural ECM both from morphological and biochemical point of view,
a new strategy to designing micro- and nano-fibers polymers scaffolds involves the
integration of natural biopolymers able to enhance the recognition of the fiber sur-
face due to their innate hydrophilic nature.
Intrigued by their high biological recognition, natural polymers such as collagen,
gelatine, elastin, silk fibroin, fibrinogen, hyaluronan, and chitosan have been just
fabricated into three-dimensional nanofibrous scaffolds for tissue engineering appli-
cations. Based on this approach, various polymer compositions such as synthetic/
natural polymer blends were recently electrospun to produce new scaffolds with
required bioactivity and mechanical properties suitable for vascular, dermal, neural,
and cartilage tissue engineering [ 9, 33 ] .
For instance, PCL may be successfully electrospun with gelatin from a (50/50
wt/wt) polymer solution in fluorinated solvents (i.e., TFE, HFP) for obtaining a fiber
network with submicrometric sizes and random fiber distribution (Fig. 1.4 ).
In this case, nanofibers exhibited good biocompatibility of MSCs in terms of
adhesion, spreading, and proliferation. Although synthetic polymers like PCL are