STRATEGIES TO ENGINEER ELECTROSPUN SCAFFOLD ARCHITECTURE AND FUNCTION - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 295

15.2.3 Effect of Fiber Roughness
The incorporation of roughness/texture into the surface of elec-
trospun fibers may be an attractive means to effect biological
responses. For example, osteoblasts are very sensitive to nano-
topography, and model studies on planar surfaces have shown that
roughness affects cell shape, 26 cell attachment, 27 , 28 and expression
of the mRNA encoding the proteins alkaline phosphatase, type I col-
lagen, and the osteogenic transcription factor RUNX2. 29 One topo-
graphical feature that can be readily introduced into the surface
of electrospun fibers is nanopores. These nanopores, on the order
of 50-500 nm, can be introduced and systematically varied in size
by adjusting electrospinning conditions, such as solvent volatility,
solution concentration, and relative humidity. 30 , 31 Roughness can
also be incorporated into the fiber surface by the addition of small
particulates (e.g., ceramics, carbon nanotubes). Recently, Gupta et
al. 32 compared two approaches for incorporating hydroxyapatite
(HA) nanoparticles into electrospun fibers: combining them into
an electrospinning solution (of poly[L-lactic acid-co-caprolactone]
and gelatin) and electrospraying the HA from a separate syringe.
They found that the latter approach increased the strain-to-failure
of the meshes and enhanced alkaline phosphatase activity of adher-
ent osteoblasts. Mei et al. examined the effect of combining HA and
multiwall carbon nanotubes (MWNTs) into electrospun scaffolds. 33
In particular, they reported that HA and MWNTs together resulted
in better cell proliferation of periodontal ligament cells but poorer
proliferation of gingival epithelial cells. This result suggests that the
combination of HA and MWNTs may be attractive for guided regen-
eration of the periodontium. Finally, roughness can be incorporated
into the fiber surface by the controlled growth of a surface coating
ontheelectrospunfibers.ExamplesofthisincludethegrowthofHA
by immersion of electrospun meshes in a calcium- and phosphate-
rich solution 34 , 35 and the growth of polypyrrole by immersion
of meshes in a mixture of pyrrole, ferric chloride, and toluene
sulphate. 36 Inthesecasestheprimarygoalwastomodifythesurface
chemistry. Nevertheless, the roughness of the resultant surfaces—
which can affect cell response—was closely related to the growth
rate.