Figure 1 Fabrication of nanotubes via a porous hard template such as AAO.
Figure 2 Electrochemical etching anodization set-up for the synthesis of TNT. Reproduced by permission of The Royal Society of Chemistry [41].
Figure 3 Schematic illustration of TiO2 nanotube formation [46]. Reproduced from Jin et al.
Figure 4 Human osteoblast cell attaches to nanotubular surface while filopodia penetrates into porosities as anchorage sites [10]. Reproduced with permission from John Wiley and Sons Inc.
Figure 5 Clustering of integrins, formation of focal adhesions, MSCs spreading, actin polymerization, and osteogenic differentiation are increased on a nanotubular surface with 15 nm lateral spacing, in presence of BMP-2 signaling [59]. Reproduced with permission from John Wiley and Sons Inc.
Figure 6 Schematic illustration of TiO2 nanotube formation [46]. Reproduced from Jin et al.
Figure 7 Staining actin cytoskeleton of MC3T3-E1osteoblast on: (a) smooth surface, (b) non-annealed nanotubular surface, nanotubular surfaces annealed at (c) 450 °C and (d) 550 °C. Compared with the smooth and the non-annealed nanotubular surfaces, annealed surfaces show higher regular arrangement [9]. Reproduced with permission from John Wiley and Sons Inc.
Figure 8 SEM images of TNT fabricated during varying durations [88].
Figure 9 Intercalation of drug inside the nanotubes. Reproduced by permission of The Royal Society of Chemistry [41].
Anodization Condition |
Annealing |
Cell Type |
Cell Culture Duration |
Effect of TNT Size |
Ref |
Anode:Titanium foil
|
450 °C for 3 h |
MC3T3-E1 |
2h before Cell adhesion. 24, 48, and 96h before MTT. 1, 2, and 3 weeks for ALP activity. 3 week before Alizarin R-staining. |
Diameter of 20–70 nm enhanced cell adhesion, |
[70] |
Anode:Titanium foil |
500 °C for 2 h |
MC3T3-E1 |
2h, 12h, 24h, 48h, 72h and 7d for cell counting. 24h and 48h for MTT and ALP. |
30 nmnanotubes enhanced osteoblast adhesion, while 70–100 nm nanotubes provide a lower population |
[34] |
Anode: Titanium sheet |
500 °C for 2 h |
hMSCs |
2h, 48h for Cell adhesion. 3 weeks for osteogenetic markers microscopy. |
30nm diameter nanotubes enhanced adhesion, while |
[56] |
Anode: Titanium sheet
|
|
hematopoietic stem cells (HSCs), human osteoblast-like |
2 weeks |
Diameters between 15 and 100nm were verified. 15nm supports HSCs differentiation into osteoclasts, adhesion and osteoblast proliferation. |
[57] |
Anode: Titaniumfoil |
|
Rat mesenchymal stem cells |
2weeks before analysis by immunocytochemistry. 3 and 6 days before cell counting. |
Diameter less than 30 nm with a maximum at 15 nm enhanced integrin clustering/focal contact |
[49] |
Anode: Zirconium and titanium foils |
|
Rat mesenchymal stem cells |
1 day before cell adhesion and 3 days before cell proliferation. |
Both materials provide enhanced cell adhesion and proliferationwith nanotube diameters of 15–30 nm. |
[58] |
Anode: Titanium foils |
|
mesenchymal stem cells |
24h for cell counting. 2 weeks in differentiation medium before immunocytochemistry. |
Differentiation is enhanced on 15 nm but not on 100 nmBMP-2-coated nanotubes. |
[59] |
Table1 Effect of nanotube diameter on cellular behavior
Time |
4h |
8h |
16h |
20 V |
0.589 |
1.07 |
1.39 |
40 V |
1.443 |
4.53 |
6.11 |
60 V |
5.493 |
6.75 |
10.08 |
Table2 Effect of anodization time and voltage on TNT length.