Biomedical Engineering Reference
In-Depth Information
UV-induced PCL-g-poly(methyl acrylate) (PMA) is 70°, while Ma et al. [57]
found that for chondrocytes on PLLA-g-poly(methyl methal acrylate) (PMAA) it
is 76°. Even further, when Fe
2+
was used to initiate grafting polymerization, the
chrondrocytes on PLLA-g-PMMA favored the surface with a water contact angle
of 52° [57]. These results show there is no clear rule of thumb when it comes to
polymer surface hydrophilicity, protein adsorption, and subsequent integrin-
mediated cell adhesion.
Surface Charge
: Modulating surface charge is yet another way to influence
proteins adsorption and cell adhesion and spreading. Electrostatically driven
protein adsorption is mainly directed by global charges on proteins and surfaces
[41]. Since proteins are generally positively charged to attract negatively charged
cell membranes, negatively charging biomaterial surfaces have been shown to
enhance protein adsorption [41]. There are also instances when negatively
charged proteins are attracted to negatively charged surfaces. This takes place
when positively charged patches on the protein are exposed and oriented towards
the negatively charged surface, resulting in electrostatic attraction and protein
adsorption. Negative charges can be introduced to biomaterial surfaces in a
number of ways, including but not limited to grafting, hydrolysis, and electrical
stimulation [64-66]. Mayingi and colleagues [64] functionalized oxidized
titanium (Ti) surfaces by the covalent grafting of sodium styrene sulfonate NaSS.
The anionic groups of polyNaSS enhanced osteoblast-like cell adhesion to the
surface modified metallic substrate, showing a 19% increase in mineralization as
compared to unmodified surfaces. Similarly, Bisson et al. [65] induced an
electrostatic attraction between poly(acrylic acid) (PAA) grafted poly(ethylene
terephthalate) (PET) to spur the interaction between the negatively charged
surface and positively charged collagen proteins to coat the PET surface. Human
bladder SMCs cultured on this surface exhibited 100% confluence within one
week. Lastly, Kotwal and Schmidt [66] found that the electrical stimulation of
polymer polypyrrole (PP) increases FN adsorption from purified FN and serum-
containing solutions, resulting in longer neurite expression from PC-12 cells.
Surface Topography
: The effect of surface topology on cell behavior such as
morphology, migration, protein synthesis and gene expression has long been
recognized in the literature [67]. Whether texture is inherently incorporated in a
biomaterial's topology, unconsciously introduced during material processing, or
intentionally fabricated into scaffold materials (physically and chemically
patterned surfaces), it is generally perceived to have a tunable effect on cell
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