Biomedical Engineering Reference
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(B)
(A)
500 nm
100 nm
100 nm
1 µ m
200 nm
100 nm
500 nm
(C)
(D)
100 nm
200 nm
300 nm
10 µ m
300 nm
1 µ m
10 µ m
FIGURE 7.2
Scanning electron microscopy (SEM) images showing TiO 2 nanotube layers grown by different anodization
processes of Ti. (A) Typical morphology obtained in acidic fluoride or HF electrolytes, (B) glycerol/fluoride
electrolytes, (C) ethylene glycol/fluoride electrolytes. The insets show top views (open tubes), bottom
views (closed ends), and side walls in detail. (D) Tubes grown by a different approach: rapid breakdown
anodization (RBA); these tubes grow in disordered bundles within seconds at comparably high anodic
potentials. The upper inset in (D) shows a side view of the layer, the lower inset shows a low magnification
of the surface [11] .
when compared with clinically used hydroxy apatite-β tricalcium phosphate (HA-βTCP) inserts [35] .
It was shown that the presence of chemically modified TiO 2 nanotubes have significantly acceler-
ated the kinetics of hydroxyapatite growth by 7 times. Chemical modification of TiO 2 nanotubes with
sodium hydroxide (NaOH) has resulted in surface with bioactive nanoscale sodium titanate [36] ,
which can enhance osteogenesis ( Figure. 7.4 ). A recent study on osteoblast adhesion on TiO 2 nano-
tubes (30-100 nm diameter) concluded that large diameter nanotubes, in the approximately 100 nm
regime induced extremely elongated cellular shapes, which resulted in substantially enhanced upregu-
lation of alkaline phosphatase activity, suggesting greater bone-forming ability than nanotubes with
smaller diameters (30 nm) [37] . These nanotubes stimulate calcium phosphate crystal formation and
deposition when exposed to 20 cycles of alternating immersion in saturated Ca(OH) 2 and 0.02 M
(NH 4 ) 2 HPO 4 ( Figure. 7.5 ). Such approaches prove that calcium phosphate coatings can be fabricated
 
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