Biomedical Engineering Reference
In-Depth Information
Flat Ti
5 V NT
20 V NT
20 V NT
(A)
(B)
(C)
(D)
(E)
(F)
(G)
(H)
(I)
(J)
(K)
(L)
FIGURE 17.4
Cell shape on flat Ti, 25 and 80 nm NTs cultured with 2%, 5% or 10% serum for 12 h. The insets in (B), (C),
(F), (G), (J), and (K) show the ECM deposition along the nanotopographies.
Reprinted with permission from Ref.
[2]
.
Long and thin cell fillopodia are observed on 80 nm NTs cultured in 2% serum indicating that cells
cannot form stable adhesion (
Figure 17.4D
), while strong and thick lamellipodia are observed from
cells cultured in 5% or 10% serum demonstrating stable cell adhesion (
Figures 17.4H and L
). We
have also observed many cell fragments on 80 nm NTs in 2% serum on the cell retraction path
(
Figure 17.4D
). This may partly account for cell apoptosis on the surface. In Park et al.'s
[25,35]
experiments, a low-medium serum concentration of 2% is used in cell cultures and should account
for the unfavorable effect of larger NTs on MSC functions observed by them. Since there are abun-
dant proteins in vivo, the results obtained from 10% serum should reflect the in vivo performance
of the NTs more accurately. Our results indicate the influence of protein concentration in the cul-
ture medium on the evaluated bioactivity of the NTs, which should be of concern when comparing
different reports on the NTs bioactivity.
17.3.4
Influence of protein distribution pattern on the bioactivity of the NTs
As aforementioned, the proteins adsorbed onto the biomaterials mediate cell adhesion and follow
functions on the biomaterials and play a crucial role in conveying the biological effects of the topo-
graphical cue. Besides the amount, other aspects of the adsorbed proteins such as species, confor-
mation, and orientation have also been reported to influence the cell/biomaterials interaction. We
notice that the NTs formed in an inorganic electrolyte have relatively flat top ends of NT walls
