Bioactivity `Of IVb（V）`and Ta（V）一Doped

Memoirs of the Faculty of ERgineering，Okayama University，Vol．31， No． 2， pp．39−44，・March 1997
Bioactivity ’Of IVb（V）’and Ta（V）一Doped
Catcium Siticate Glasses
Naoki IMAYOSHI＊， Satoshi IIAYAKAWAt， Chikara OHTSUKI“
and Akiyoshi OSAKA＊
（Received．February 25， 1997）
Nb205−and Ta205−doped calcium si1量cate glasses were soaked fbr vadous periods in a
simulated body fluid（KQkUbo solution）up to 30 days． Apatite formation捌ity of the
surface of these glasses were inves恒gated with thin−film．X−ray diffractio且and FT−R
reflection spOctroscopy． The effects ofthese additive oxides on the bioactiVity ofCaO6SiO2
based glass were discussed． A slha11 amount of Nb205 alld Ta205 suppressed the rate of．
silica hydrogel layer fbrma廿on and th6 apatite formation on the． surface of the glasses．
The fate 6f the apatite nucleation on血e su㎡face Qf Nb205−doped calcium silicate glass
び waS slower than that on the su㎡face of Ta205−doped calc董um silicate glass． It was
concluded that the decrease in the apatite forrning ability of calcium siliCate glasses by ’
these addi廿ve oxides is a1施dbuted to the supPression of formati on of silica hydrogel layer
which plays…an impOrtant role in apatite nucl eatiOn．
1． INTRODUCTION
The essential condnion for glasses and glass−ceramics to bond to living bone is the formation of a biologically
active bone−like apatite layer on their surfaces． when they are embedded in human body． A few series of seve；al
glasses and glassrceramics containing CaO and SiO， such as Ceravital Qi）and CerabQne Q A−W‘i） have exhibited
bioactivity． The 50CaO’50SiO， glass is important for its good bioactivity and has been well studied3）’‘） ． Ohtsuki et
al．‘） have alteady suggested that the dissolution of Ca（ll） and ’SiaV） ions from 50CaO．50SiO2 glass and the silica
hydrogel layer formed on the su血ce of the glass plays an important role in aPatitp nucleation． However， it has bee血
shown． that the addition of the third component such as TiO， and Al， O， depressed the bioactivityD．， while the
addition of B，O， results in bdher bioactivityO’． Thus， those cations causes opp6site effects on the ’／bioactivity
depending oh their cohtent as they modified the chemical proper巾s of the glass． Recently， we have fbu血d that not
only silica hydrogel（Si（IV）） and titania hydrogel（Ti（IV）） but also multivalent Ta（V） species play an important role
in an apatite formationD ， We can expect that the incorporation ’of multivalent cations such as Nb’（V） and Ta（V） in
the CaO． SiO， based glass also changes its bioactivity and the mechanism of apatite formation as ’・weli as its
chemical properties． lt was・worth examining the effect of the incorporation of multivalent cations on bioactivity．
In the present study， in order to investigate fundamentally the effect of addition of Nb（V） and Ta（V） on the．
bi・aCt晦・f C・0’SiO・．b・・gd・9董・r・e・・th・・c・卿面・h・1 d・p・hd≒・ce・f・画t・脚．・ti・n・n血・・曲ce・f・91・・se・
in the system xNb， O，．（50−x／2）CaOe（50−x／2）SiO， and xTa， O，．（50Lx／2）CaO．（50−x／2）SiO， （x＝1， 2 and 5 m／olO／o） was
examined in the simulated body fluid．
“ Department of Bioscience and BiotechnologY
39
Naoki IMAYOSHI， Satoshi H’AYAKAWA， Chikara OHTSUKI and Akiyoshi OSAKA
40
2． EXPERIMENTAL PROCEDURE
2．1． ？reparation of Nh， O， 一 and Ta，．O， 一Doped Calcium ’Silicate Glasses
xis”）， O，’（50−x／2）CaO．（50−x／2）SiOi ahd xTa，O，’．（50−X／2）CaO．（50−xi2）SiO， （x＝1， 2 and ’5 molO／e） glaSses
were prepared． Starting material s were reagent grade SiO，， CaCO，，Nb，O， and Teq O， chemicals supplied by
Nacalai Tesque， lnc． The appropriate amp． unts of the starting materials were mixed and melted with a 30ml
platinum crucible ’ 吹f laced in「aMoSi2 electriC fUr耳ace 4t． 撃P6qO℃lbr−an hoU士．． The nie藍ts were poured onto a steel
plate ’and immediately pressed with another one to be formed into a place about l mm thick and allowed to cool in
an SiC fumace from 700eC． Rectarigular specimens of 15’×10×1 mm 3 were Cut froin the’
рb狽≠奄獅?п@glaSs． Both
surfaces of the specimens were polished with a diamond paste（lmm in diarneter） and washed with acetone in an
ultrasonic cleaner．
2．2． Soaking in SBF
The obtained specimens were soaked in 35ml of．’a simulated・body fiuid（SBF； Kokubo solution） kept at
36．50C， which had inorganic species similar in concentration to those of．the human blood plasma．・ The fiuid was
prepared by．．dissolving reagent grade ehemicals of・NaCl， NaHCOi， KCI， K， HPO，’3H， Os MgCL’6H，O， CaCl， and
Neq SO， in ． distilled water as described el sewhere8？ ． lt was・ buffered． at pH 7．25・ with 50mM trishydroxymethyl−
aminometliane （（C40H％ CN4 ） and 45TnM HCI， and its temperature was kept at 36．5“C． SBF is alteady confritmed
t・be ab1・t・w・11．・ep・qduce血・ap・亘t・f・rm・廿・n・曲・・u血・r・・f・91asse・．and・91assLce・ami・・i・止・b・dy
enwrorment．
2．3． Analysis of Surface Structure
After soaking in the SBF for various periods， specimen was rernoved from the flui d and gentiy washed with
acetone． The surface structure was examined with thin−film X−ray difftaction apd Fourier−trpmsfortn infrared（FT−IR）
refiection spectroscopy． An X−ray difftaction attached with a thin−film attachment was used．， and the glancing angle
was｝ fiXed at 1“， while an infrared spectrometer （FT−IR 300， Jasco Co．．， Japan） was Used， and the refieodon angle tq
the normal was set at 75e． Both techniques enabled to ’detect a layer’about ．1・pm’thick at the surface of the
speclmen．
2．4． Measurement of Element Concentration
After the specimen was removed from the SBF， the concentration of calcium， ．silicon and phosphorus in the
SBF rwere measured with an ．inductively coupled plasma（ICP） emission spectroscopy． pH of the fluids was also
measured：
3． RESULTS AND DISCUSSION．
Fi騨e 1・h㎝・th噴出一応lm X−ray． di缶・・知p礁・m・and・FT−R・efiec廿・n・p・㈱・f th…血ce・f
50CaO．50SiO， glasses before and after soaking up tg 30 days in the SBF． ． The X−r4y qiff；af tion pqtterps q．nq ．F． TrlR
・enecti・n・p・Ctr・・f・・a・pecim・n輔th・・t・・曲9・ar・d…綱・・“Od”・Th・’蘭・peak・i・Fig・lw・・e a・・ゆ・d t…
described on the basis of the data． preViously reported3）’e） ． lt can be seen from Fig． 1 thqt 50CaO．50SiO， glass．
Bioactiv吻Of Nわ（Ii） a”d Ta （． V）∂〔）Ped Cα嬬‘”τ∫傭α孟召ααss召s
41
forms qh ．apatite phase（X−ray diffraction near 260 and 32”） on their surfaces in the．SBF in l day The IR refiection
peaks at 500，650， H OO and 1250 cM“1 were ascribed t6 Si−O bending vibration， P−O bending． vibration， transverse
optical mode of．Si−O stretching vibration and longitudial optical mpde of Si−O stretching vibration， respectively．
X−ray
IR
socao・sosiQ
o
o
socao・sosio2
o−o
30a OhO
op
2ed o￡
se d
o
o
o
oo d
o
7d
o
o
3d
oo
f凶
o
8昌58唱o
智窪35
o
。。
vv
ld
oP．
7d
op
甜
op
ld
v
12h e
12 h
Od
20
25 30 35 40
蛋｝1deg・
1600 1200 800 400
Wayenumber 1 cm“i
Fig． 1 Thin−film X−ray diffraction patterns and FT−IR reflection spectra of the surface
of 50CaO．50SiO， glasses before and after soaking up to 30 days in the SBF．
The IR reflection peaks at 1100 and 1250 cm−i
appeared after 12hours and grew in intensity and the relative
peak due to apatite was observed after immersion for l day．
Figure 2 shows changes in element concentration of
the SBF due to the immersion of 50CaO．50SiO， glass． lt can
be seen that the calcium and silicon concentration increase
and the phosphorus concentration decreases with soaking
periods． The calcium and silicon’ @cQncentration increases for
710544﹂
increasing soaking periods， This indicates that these glass
forms silica hydrogel layer on their surfaces． The 1130 cm−i
芝層＼唱O旧り儒﹄り昌①9唱09婦屋O蟹日①劇
intensity of the 1100 and 1250 cm“’ pdaks decreased with
5eCaO50SiO2
th
si
5 10 15 Ze 25 30 35
the glass soaked in the SBF until 12hours． The increase in
Time／day
calcium and silicon concentrations is due to di ssolution of
Fig． 2 Changes in element concentrations due to
Ca（II） and Si（IV） ions from the glass， After immersion for 1
immersion of 50CaO．50SiO2glass，
day the calcium and phosiphorus concentrations decreased．
This indic飢es th飢止e ap飢ite nuclei were飾㎜ed on the
surfaces of the 50CaOf50SiO， glass unti1 12hours and grew by consuming the calcium and phosphorous ions from
the SBF．
X・一ray diffraction patterns and FT−IR refiection spectra of the
Figure 3（a），（b）and（c）show that thinイilm
2 and 5 mole／o） glasses before and after soaking up to 30
surface of the xNb， O， ．（50−x／2）CaO．（50−x／2）SiO， （x＝1，
3 were assigned to as described on the basis of the data previously
days in the SBF． The main peaks in Fig．
reported3）’‘） ． lt can be seen from Fig．
3（a），（b） and （c） that only INb，O，．49．5CaO．49．5SiO， glass forms an apatite
and 32。）on their su血ces in血e SBF in 30days， while other glasses do not form it．
phase（X−ray diffraction near 26e
glass， the spectral profile did not change after soaking． On the
When x ：5 in the xNb， O，．（50−xi2）CaO．（50−x／2）SiO，
other hand， when x＝1 and 2， the IR reflection peaks at 1150 and 1250 cm’i appeared after 1 day and grew in
intensity and the．relative intensity of the 1150 and 1250 cm’ peaks decreased with increasing soaking periods．
This indicates that these glass forms silica hydrogel layer on their surfaces． ln INb，O，．49．5CaO．49．5SiO， the 1130
0rn一’ peak due to apatite was observed after immersion for 30 days． ln the 5Nb， O，．47．5CaO’47．5SiO， glass the
spectral profile did not change after soaking． Figure 3（d）， （e） and （f） show that thin−film X−ray diffraction patterns
Naoki IMAYOSHI， Satoshi HAYAKAWA， Chikara OHTSUKI and Akiyoshi OSAKA
42
Xイ ay
lmol％NlnO，
lmol％th，Ols
IR．
O
o
30d O
o
詞
oo
o oO
14d
91VO 30d
o
O AO 1ca
o
O 7d
o
y v
Y
o
’sod
o
td
od，
o
鴨ぜ枠齢
y Y
甥口8口剛
7d
lmol％Ta2（］ls
夏R
8目58唱。出
’
Oハ︻O
y 一 ．．．．v
lca．e
8目58唱o
咽旨9霞
伽藪署軍挫ω
o
lmolTa201s
X−ray
7d
su eY
v
ld
．0 3岨
v
ld
12h
・12h
oa
oa
oo
40
25 30 35
2e 1 dag．
X−ray
1600 1200 800 400
−1
（a）
20
IR
2mol％NbjO，
20／deg．
（d）
7d
v
Yn sa
o
o9 sod
o
ぺん遂▼
@r Y
甥口3震一
▼’▼
”、詞幽皿価ω
甥口8震一
8躍ε8唱。
Y一． 14d
2rmol％Ta201s
9 30d
oo目88唱①出
略画
O＾O
Y 30d Y
v
IR
2mol％TstiOs
X−ray
2me1％Nb20s
y’
oo 1600 1200 800 400
Wavenumber （em−i）
25 ’so 35
Wayenumber 1 cm
o
14d
o
7d
v
Y． ld
卸
oa
ld
14d oo
e
7d
v
銅
v
ld
12h
Y
ee
v
oa
oo
25 30 35
40 1600 1200 800 400
（b） Wavenumber （ciii’i）’
2e ldeg．
X−ray
IR
Smol％NtttOs
20
40 1600 1200 800 400
Wavenumber （cm’i）
25 30 35
2e／dag L
（e）
5uro1％NbA
X−ray
5mo且Ta凸
夏R
v
v
sod
30d
3d ・・
v
7d
v
su
30d
14d
7d
v
ld
銅
v
ld
ld
oa
14k葦
rv
7d
v
鍼
v
ld
v
ca
1600 1200 800 400
Wa▼・皿mber（・㎡1）
op・
，20
．2S． ．so ．35
2ef deg．
（c）
40 1600 1200 800 400
W・…m晩・画∼
︵b
25 30 35
2e ldag．
v
Od
−od
20
8纈88唱。
唱旨8三
7d
30d
v
魯日野8三
8口88唱o
14d
14d
5nrol％Ta20s
Fig． 3 Thin−film X−ray diffraction patterns and FT−IR reflection spectra of the surface of the xNb，O，．（50−
Xi2）C・0・（5・一x／2）SiO・（（の・一1・（b）・＝2・and（・）x＝5岬％）a・d・T…O・1（5・一身C・0・（5・一Xi2）SiO・（（d）・一1・（・）・一2．・・nd
（Dx＝”5 mole／o） glasses before and after Soaking up to 30 days in the SBF．
働α6励伽（ゾNわ（の侃4Tα（γ）一D（）Ped Cal伽隅∫弼。伽αα55召3
43
and．FT−R reflection spectra of．the surface of xTa205．・（50−x／2）caO・．（50−x／2）siQ2（xs 1，2and 5血．ol％）91asses
before and’after soaking up to 30 days in the SBF， lt can be seen from Fig． 3（d） and （e） that’XTa， O，’（50−
x／2）CaOf（50−x／2）SiO2（x＝1 and 2 mo1％）glasses forrn an apatite phase on their surfaces in the SBF in 3 and 7 days，
respectively， while 5Ta，O，．47．5CaO147．5 SiO， glass does not form it． ・ln the 5Ta，O，．47．5CaO．47．5SiO， glass the
spectral profile did not change after soakdng． On the other hand， when xニ1 and 2， the皿く reflection peaks at l 100
and 1250 cm−i appeared after 12h． This indicates that these glass forms silica hydrogel layer on their surfaces． in
the I Ta， O，’49．5CaO’49．5SiO，． and 2Ta， O，．49CaO．49SiO， glasses the 540 cm” peak grew and finally split into
two peaks at 570 and 610 cm−i due to apatite after 7 days． ln the 2Ta，O，．49CaO．49SiO， glass the 540 cmri peak
grew and finally split into two peaks at 570 and 610 cm一’ due to apatite after 14 days．
Figure 4（a）， （b） and （c） show changes in element concentration of the SBF due to the immersion of the
）（Nb，O， e（50−x／2）CaO．（50−x／2）SiO，（x＝1， 2 and 5 molO／o） glasses． lt can be seen from Fig． 4（a） and （b） that the
calcium and silicon concentration increase and the phosphorus concentration decreases with soaking periods． The
increase in calcium and silicon concentrations is due to dissolution of Ca（il）．and Si（IV） ions from the glass． Figure
4（d）， （e） and （O show changes in element concentration of the SBF due to the immersion of thg xTeq O，’（50−
x／2）CaO．（50−x／2）SiO，（x＝1， 2 and 5 molO／o） glasses． lt can’be seen that the calcium concentration increases for the
glass ． soaked in the SBF unti1 3 days． After immersion for 3 days the calcium and phosphorus concentrations
1皿o亘％
Ca
P
5
10
15
20
25
30
ThOs lmo190
Ca
醐P
r重
7 6 5 4 3 ゴ 現
N賜D5
薯黒目、昌O冒“﹄一口OU自09一目O目O
6 5 4 3
目、8言﹄ヨ8口8霜。日￡
7
5 10 15 20 25 30 35
Time／day
Time l day
（a）
（d）
7 6 5 4 3 2 功
Σ目、口㊤胃尉﹄一自Q9目0りω蕾碧
Ca
P
S
＝自日、唱O嘱︸呵﹄曽塁Oり口Oり一鎖O自日〇一国︻
7654﹁3
NbzOs 2mo19e
5 10 15 20 25 30 35
TNOs 2mol 90
C
P
5 10 15 20 25 30 35
T薩melday
．Time／day
（b）
（e）
25 3’e 35
7
−b 5 ﹂6 3
コ S 10 15 20
Σ自日、個O嘱り“﹄一目09員0り︸員O田口〇一国︻
Ca
PS
9箱O目〇一
7 6 5 41 3
薯目一、昌O咽一曜﹄一塁りり昌O
Nb20s 5mel 9e
Ta2q5 5mo塁％
a
o
Si
5
10
15
20
25
30
Time／day
Time I day
（c）
（D
Fig．4Changes in element concentrtitions due to immersion of Nb205−and Ta205−doped calcium silicate 91asses．
Naoki IMAYOSHI， Satoshi HAYAKAWA， Chikara OHTSUKI and Akiyoshi OSAKA
44
decreased． This indicates that the apatite nuclei were formed on the surfaces of the I Ta， O，．49．5CaO．49．5SiO，
glass unti1 3 days and grow by consuming the caleium ’and phosphorous ions from the SBF． Figure 2（e） and （O
show that the calcium and phosphorus concentration decrease with soaking periods and the silicon cpncentration is
not be’ detected． The rate of dissolUtion of Ca（II） and Si（IV） ions decreases with increasing Nb20， and Ta20s
content． The change in element concentration due to immersion of Nb，O，一doped glasses were similar to that of
Ta， O，一doped glasses． The present results indicates that the incorporation of Nb，O， and Ta， O， in CaO．SiO， based
glass suppressed the formation of silicq hydrogel layer which plays an important role in apatite nucleation．
4． SUMMARY
We examined the apatite formation on the surface of Nb，O，一 and Ta，Os−doped calcium silicate glasses in
order to investigate fundamentally the effect of addition of Nb（V） and Ta（V） on the bioactivity of CaO’SiO， based
glasses． Nb，O，一 and Ta， O，一doped calcium silicate glasses were soaked for various periods in a simulated body
fluid（Kokubo solution） up to 30 days． A sma11 amount of additive oxides， Nb， O， and Ta， O， suppressed the rate of
silica hydrogel layer forrnation qnd the apatite formation on the surface of the glasses． The rate of the apatite
nUcleation on the suffaoe of Nb， O， 一doped calCium siiicate glass was slower than that on the surface of Ta，O，一doped
calcium silicate glass． The decrease in the apatite forming ability of calcium silicate glasses by these additive
oxides is attributed to the suppression of formation of silica hydrogel layer which plays an important role in apatite
nucleation．
Acknowledgement
This work was supported by a GTant−in−Aid of Ilhe Asahi Glass Foundation For lndustrial Technology．
REFER｝l NCES
［1］
C．Ohtsuki， H． Kushitぬ， T． Kokubo， S． K：otani and T． Yamamuro，工Biomed。 Mat． Res．s 25（1991）1363−70．
［2］
T． Kokptbo， Biomaterials， 12（1991）155−63．
［3］
C．Ohtsuki， T． K：okubo−and T． Yamamuro， J． Non−Crystl． Solids，143（1992）84−92．
［4］
T． Kokubo， H． Kushitani，，C． Ohtsuki， S． Sakl［a and T． Yamamuro， J． Mater． Sci．： Materials in Medicine， 3
（1992）79−83．
［5］
C． Ohtsuki， A． Osaka and T． Kokubo， in Bioceramics， Vol． 7， ed． by O． H． Andersson and A， Yli−Urpo，
Butterwonh−Heinemann Ltd， Oxford， 1994， pp． 73−78．
［6］
C． Ohtsuki， Y． Kobayashi， K． Tsuru and A． Osakeq J． Soc， Mat． Sci．， Japan， 44［501］（1995）693−699．
［刀
C． Ohtsuki， H． lida， S． Hayakawa and A． Osaka， J． Biomed． Mat． Res．， 33（1997） in press
［8］
C． Ohtsuki， Y． Aoki， T． Kokubo， Y． Bando， M． Neo and T． Nakamura， J． Ceram． Soc． Japan，． 103［5］，
（1995）449454．