488
T. Balusamy et al.
charge on the modified surface which attracts the negatively charged phosphate ions
to form amorphous calcium phosphate, which in turn promotes nucleation of calcium
apatites. After SMAT using 8 mm Ø alumina balls for 45 min, the R a of Ti is increased
from 0.15 ± 0.12 μm to 3.27 ± 0.98 μm while the water contact angle is decreased
from 64° to 43° with an increase in surface energy from 32 to 53 mJ/m
2 . In spite of a
lower water contact angle and higher surface energy, the extent of apatite formation is
decreased for Ti sample subjected to SMAT for 45 min than those treated for 30 min.
This is due to the fragmentation of the alumina balls and subsequent attachment of
the fine particles. The alumina particles incorporated on the surface of SMAT Ti
inhibit the apatite growth, which suggests that the right choice for the type of balls
for SMAT is very important.
Lai et al. [49] have compared the viability of mesenchymal stem cells (MSCs)
on untreated and SMAT Ti in terms of the extent of cell adhesion and spreading,
ALP activity, mRNA expressions of osteocalcin (OC), osteopontin (OPN), collagen
I (Col I) and bone mineralization. AFM analysis performed over a region of 2 μm
× 2 μm indicates that the average root means square (rms) roughness of untreated
Ti is 7.29 ± 1.17 nm is increased to 29.53 ± 6.97 nm after SMAT. Following this,
the water contact angle is decreased from 66.5 ± 4.1° to 51.9 ± 5.6° after SMAT.
MSCs cultured onto untreated Ti exhibits loose cell pseudopodia. However, a well
spread and intact pseudopodia are identified on SMAT Ti, suggesting that the surface
nanocrystallization of Ti by SMAT improves the adhesion and proliferation of MSCs.
When compared to its untreated counterpart, SMAT Ti shows higher cell viability,
higher ALP activity, expressed much higher levels of OC and OPN and higher mineralization. The viability of osteoblast cells on Ti and Ti6Al4V alloy before and after
SMAT is studied by Zhao et al. [20, 44]. According to them, the formation of nanostructured grains, higher surface roughness, higher surface hydrophilicity and higher
surface energy of the SMAT Ti and Ti6Al4V alloy are responsible for the improvement in adhesion and spreading of osteoblast cells when compared to its coarsegrained untreated counterpart. The morphology of the osteoblast cells attached on
the surface of untreated Ti and Ti6Al4V alloy is spherical in shape with little cell
spreading whereas those attached on the surface of SMAT Ti and Ti6Al4V alloy
exhibit a flattened shape with extensive spreading.
Huang et al. [21, 55, 56] have studied the ability of solution treated β-type Ti25Nb-3Mo-2Sn-3Zr titanium (TLM) alloy before and after SMAT using 2 mm Ø
zirconia balls at 50 Hz for 60 min to promote adhesion and proliferation of human
fetal osteoblastic (hFOB1.19) cells. During SMAT, the multidirectional impingement
of the zirconia balls on the surface of the TLM alloy has increased the surface
roughness. The water contact angle of the coarse-grained untreated TLM alloy is
67.8 ± 2.4° whereas it is decreased to 50.4 ± 1.5° after SMAT. The decrease in
water contact angle indicates better hydrophilicity of the SMAT TLM alloy. The
higher degree of hydrophilicity and higher surface energy of the SMAT TLM alloy
promotes adsorption of proteins such as fibronectin (Fn) and vitronectin (Vn). An
increase in protein adsorption is considered to exert a beneficial influence on cell
adhesion, which in turn determines cell proliferation and spreading. After 24 h of
cell culture, the hFOB1.19 cells attached to untreated TLM alloy are spherical in
T. Balusamy et al.
charge on the modified surface which attracts the negatively charged phosphate ions
to form amorphous calcium phosphate, which in turn promotes nucleation of calcium
apatites. After SMAT using 8 mm Ø alumina balls for 45 min, the R a of Ti is increased
from 0.15 ± 0.12 μm to 3.27 ± 0.98 μm while the water contact angle is decreased
from 64° to 43° with an increase in surface energy from 32 to 53 mJ/m
2 . In spite of a
lower water contact angle and higher surface energy, the extent of apatite formation is
decreased for Ti sample subjected to SMAT for 45 min than those treated for 30 min.
This is due to the fragmentation of the alumina balls and subsequent attachment of
the fine particles. The alumina particles incorporated on the surface of SMAT Ti
inhibit the apatite growth, which suggests that the right choice for the type of balls
for SMAT is very important.
Lai et al. [49] have compared the viability of mesenchymal stem cells (MSCs)
on untreated and SMAT Ti in terms of the extent of cell adhesion and spreading,
ALP activity, mRNA expressions of osteocalcin (OC), osteopontin (OPN), collagen
I (Col I) and bone mineralization. AFM analysis performed over a region of 2 μm
× 2 μm indicates that the average root means square (rms) roughness of untreated
Ti is 7.29 ± 1.17 nm is increased to 29.53 ± 6.97 nm after SMAT. Following this,
the water contact angle is decreased from 66.5 ± 4.1° to 51.9 ± 5.6° after SMAT.
MSCs cultured onto untreated Ti exhibits loose cell pseudopodia. However, a well
spread and intact pseudopodia are identified on SMAT Ti, suggesting that the surface
nanocrystallization of Ti by SMAT improves the adhesion and proliferation of MSCs.
When compared to its untreated counterpart, SMAT Ti shows higher cell viability,
higher ALP activity, expressed much higher levels of OC and OPN and higher mineralization. The viability of osteoblast cells on Ti and Ti6Al4V alloy before and after
SMAT is studied by Zhao et al. [20, 44]. According to them, the formation of nanostructured grains, higher surface roughness, higher surface hydrophilicity and higher
surface energy of the SMAT Ti and Ti6Al4V alloy are responsible for the improvement in adhesion and spreading of osteoblast cells when compared to its coarsegrained untreated counterpart. The morphology of the osteoblast cells attached on
the surface of untreated Ti and Ti6Al4V alloy is spherical in shape with little cell
spreading whereas those attached on the surface of SMAT Ti and Ti6Al4V alloy
exhibit a flattened shape with extensive spreading.
Huang et al. [21, 55, 56] have studied the ability of solution treated β-type Ti25Nb-3Mo-2Sn-3Zr titanium (TLM) alloy before and after SMAT using 2 mm Ø
zirconia balls at 50 Hz for 60 min to promote adhesion and proliferation of human
fetal osteoblastic (hFOB1.19) cells. During SMAT, the multidirectional impingement
of the zirconia balls on the surface of the TLM alloy has increased the surface
roughness. The water contact angle of the coarse-grained untreated TLM alloy is
67.8 ± 2.4° whereas it is decreased to 50.4 ± 1.5° after SMAT. The decrease in
water contact angle indicates better hydrophilicity of the SMAT TLM alloy. The
higher degree of hydrophilicity and higher surface energy of the SMAT TLM alloy
promotes adsorption of proteins such as fibronectin (Fn) and vitronectin (Vn). An
increase in protein adsorption is considered to exert a beneficial influence on cell
adhesion, which in turn determines cell proliferation and spreading. After 24 h of
cell culture, the hFOB1.19 cells attached to untreated TLM alloy are spherical in