One of the CaO,SiO(2)-based bioactive glasses(5OCaO･ 5OSiO (2) in mol%) were soaked for various periods in a simulated body fluid(SBF) with or without containing alcohols such as methanol, ethanol, and 1-propanol. Effect of the alcohols was investigated on the apatite formation on the glass surface with thin-film X-ray diffraction, FT-IR reflection spectroscopy and scanning electron microscopy. Under the presence of alcohols up to 0.1mol/l in the SBF an apatite layer was formed on the glass, while it consisted of crystallites similar in morphology but
larger in size than that found for the SBF without the alcohols. It was concluded that the alcohols little influenced the the apatite forming ability of the CaO,SiO(2)-based glasses

Nishiyama, Chikako

Ohtsuki, Chikara

Osaka, Akiyoshi

Tsuru, Kanji

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Effect of Alcohol on Bioactivity of Glasses

Okayama University Scientific Achievement Repository

Memoirs of the Faculty of Engineering,Okayama UniversitY,Vo1.29, No.2, pp.83-88, March 1995Effect of Alcohol on Bioactivity of GlassesKanji TSURU*, Chikako NISHIYAMA*, Chikara OHTSUKI* and Akiyoshi OSAKA*(Received January 27 , 1995)One of the CaO,Si02-based bioactive glasses(5OCaO' .5OSi02 in mol%) were soaked forvarious periods in a simulated body fluid(SBF) with or without containing alcohols such asmethanol, ethanol, and I-propanol. Effect of the alcohols was investigated on the apatiteformation on the glass surface with thin-film X-ray diffraction, Fr-IR reflection spectroscopyand scanning electron microscopy. Under the presence of alcohols up to O.lmol/l in the SBF anapatite layer was formed on the glass, while it consisted of crystallites similar in morphology butlarger in size than that found for the SBF without the alcohols. It was concluded that the alcoholslittle influenced the the apatite forming ability of the CaO,SiOTbased glasses.1. INTRODUCTIONSince discovery of Bioglass® by Hench et ai. in the early 1970s1), various types of glasses and glass-ceramicshave been developed that can bond to living bone. Some of them are already clinically used as valuable bonesubstitutes such as artificial middle ear bones, alveolar ridge maintenance implants, artificial iliac crests andvertebrae2)-4), etc. These bioactive glasses and glass-ceramics, however, can not replace a whole piece of femur andtibia, because fracture toughness is lower and Young's modulus is higher than that of the human cortical bone. Onemay consider obtaining bioactive materials with high fracture toughness by incorporating bioactive glass powdersinto an organic polymer with sol-gel methods. Bioactive composite materials prepared with the sol-gel methodswould contain residual alcohols that are used during preparation. However, the effect of alcohols on bioactivity ofglasses has not been revealed yet.It has been already confirmed5) that the essential condition for various kinds of glasses and glass-ceramics tobond to living bone is the formation of a biologically active bone-like apatite layer on their surfaces when they areembedded in the body, and that the apatite layer is reproduced on the surfaces of bioactive glasses and glass-ceramicseven in an acellular simulated body fluid(SBF). Moreover, the binary system CaO-Si02 gives the simplestcomposition showing bioactivity6),7). In the present study, in order to reveal the effect of alcohols on bioactivity ofglasses, the apatite formation on the surface of .5OCaO' .5OSi02(mol%) glass is thus investigated in the SBFcontaining alcohols.2. EXPERIMENTAL PROCEDURE2.1. Preparation of .5OCaO· .5OSi02(mol%)A glass of the nominal composition .5OCaO·.50Si02(mol%) was prepared by melting a mixture of appropriateamounts of reagent-grade chemicals Caco3 and Si02 with a 30ml platinum crucible at 1600 °C for 1 h in an MoSi2electric furnace. The melt was poured on to a stainless steel plate to be formed into a plate about Imm thick, andallowed to cool in an SiC furnace from 700 °C. Rectangular specimens of 15xlOxi mm3 were cut from the obtained*Department of Bioengineering Science8384 Kanji TSURU, Chikako NISHIYAMA, Chikara OHTSUKI and Akiyoshi OSAKAglass. Both surfaces of the specimens were polished with a diamond paste(l!-tm in diameter) and washed withacetone in an ultrasonic cleaner.2.2. Soaking in SBF containing various alcoholsThe obtained specimen was soaked in the 35 ml of SBF with and without containing various alcohols. SBFhas nearly equal ion concentrations(Na+ 142.0, K+ 5.0, Ca+ 2.5, Mg2+ 1.5, cr 147.8, HC03- 4.2, HPOi- 1.0,SOi- 0.5 mM(=10-3mol'dm-3»and pH to the human blood plasma. It was prepared by dissolving reagent-gradechemicals of NaCl, NaHC03, KCl, K2HP04·3H20, MgCl2·6H20 and N~S04 into distilled water. It wasbuffered at pH7.25 with 50 mM tris(hydroxymethyl)aminomethane«C~OH)3CNH2)and 45 mM hydrochloricacid(HCl), and its temperature was kept at 36SC. SBF is already confirmed to be able to well reproduce the apatiteformation on the surfaces of glasses and glass-ceramics in the body environment. Methanol(CH30H),ethanol(C2H50H) and 1-propanol(C3H70H) were selected as. the additives to SBE A preliminary test showed thatprecipitation was not observed till the concentration of methanol exceeded 1 mol·dm-3. Thus we fixed theconcentration of alcohols in SBF as 0.1 mol· dm-3. The examined fluids are given in Table 1.Table 1 Examined SolutionSolution Additive Concentration(mol'dm-S)SBFSBF+MeOHSBF+EtOHSBF+PrOHnomethanol(CHSOH)ethanol(C2HSOH)1-propanol(CSH70H)o0.10.10.12.3. Analysis of surface structureAfter soaking in the fluids for various periods, the glass was removed from the fluids and gently washed withacetone. The surface structure was examined with thin-film X-ray diffraction, Fourier-transform infrared(Ff-IR)reflection spectroscopy and scanning electron microscopic(SEM) observation. An X-ray diffractometer(RINT-I400,Rigaku, Japan) attached with a thin-film attachment CN2651A was used, and the glancing angle was fixed at 1°,while an infrared spectrometer(Ff-IR300, lASCO Co., Japan) was used, and the reflection angle to the normal wasset at 75°. Both techniques enabled to detect a layer about 1 !-tm thick at the surface of the specimen. In the SEMobservation, gold film was sputter-coated on the surface of the specimen and electron microscope(JSM-63oo, lEOL,Japan) was used.2.4. Measurement of ell~mentconcentrationAfter the specimen was removed from the fluids, the concentrations of calcium, silicon and phosphorus in thefluids were measured with an inductively coupled plasma(ICP) emission spectroscopy. pH of the fluids was alsomeasured.3. RESULTS AND DISCUSSIONFigure 1 shows thin-film X-ray diffraction patterns and Ff-IR reflection spectra of the surface of the glass beforeand after soaking for various periods in (a)SBF, (b)SBF+MeOH, (c)SBF+EtOH and (d)SBF+PrOH. The spectra fora apecimen without soaking are denoted as "Oh". The main peaks in Fig. 1 were assigned to as described on thebases of the data previously reported3),8). The IR reflection peaks at 500,650, 1100 and 1250 cm-1 were ascribedto Si-O bending vibration3), P-O bending vibration3), transverse optical mode of Si-O stretching vibration andlongitudinal optical mode of Si-O stretching vibration8), respectively. Fig. l(a) shows that the intensities of X-rayscattering at small angles increases and IR reflection peak at 1250 cm-1 appears in the first day of immersion in SBEEffect of Alcohol on Bioactivity of Glasses 85(a) (b)X-ray IR X-ray IRo20 30 40 1600 1200 800 400 20 30 40 1600 1200 800 4002 eI deg. Wavenumber I cm-1 2 eI deg. Wavenumber I cm-1(c) (d)X-ray IR X-ray IR00 0 00 020 302 eI deg.40 1600 1200 800 400 20Wavenumber I cm-1302 e I deg.40 1600 1200 800 400Wavenumber I cm-1Fig. 1 Thin-film X-ray diffraction patterns and FT-IR reflection spectra of the surface of the glass soakedin (a)SBF, (b)SBF+MeOH, (c)SBF+EtOH and (d)SBF+PrOH for various periods.0: apatite, .: P-O bending Vibration, .:Si-O bending vibration, \7: transverse optical mode of Si-Ostretching vibration, ....: longitudinal optical mode of Si-O stretching vibration.86 Kanji TSURU. Chikako NISHIYAMA. Chikara OHTSUKI and Akiyoshi OSAKAThis indicates that a silica hydrogel layer is fonned on the surface of the glass. The IR reOection peak at 6.50 cm- Isimultaneously grew. This suggests that a type of amorphous phosphate such as a calcium phosphate is fonned onthe surface of the silica gel layer. Both the X-ray diffraction patterns and IR reflection spectra in Fig. I(a) show thatan apatite layer is fonned by I day and it grows with increasing soaking time. The same results of the surfacestructural changes of the glass were observed for the glass soaked in SBF containing methanol, ethanol or 1-propanol(Fig. l(b)-(d)). These results indicates that the glass fonns an apatite layer on its surface even if the alcoholsare present in SBE Figure 2 shows SEM photographs of the surface of the glass soaked for 7 days in (a)SBF and(b)SBF+PrOH. Fine flake-like particles are observed, while the size of crystallites fonned in SBF+PrOH is largerthan that fonned in SBE These particles are the crystals of apatite after Fig. I. Similar flake-like particles are alsoobserved on the glass soaked in SBF+MeOH and SBF+EtOH. That is, the morphology of the apatite crystal did notchange wi th coexistence of the alcohol.Figure 3 shows changes in concentration of the calcium, silicon and phosphorus as well as in pH of (a)SBF,(b)SBF+MeOH, (c)SBF+EtOH and (d)SBF+PrOH due to immersion of the glass. Fig. 3(a) shows that the calciumand silicon concentration increase for the glass soaked in the SBF until 12 hours. After immersion for I day, thecalcium concentration decreased, accompanied by an appreciable decrease in the phosphorus concentration. Increasein the calcium and silicon concentration is due to dissolution of Ca(H) and Si(IV) ions from the glass. Then decreasein the calcium and phosphorus concentrations is due to fonnation of calcium phosphate on the glass. Similar changesin element concentrations were observed for the SBF+MeOH, SBF+EtOH and SBF+PrOH. From the results, it isconcluded that the alcohols did not influence on the rate of dissolution of the glass.The mechanism of apatite fonnation on CaO,SiOTbased glasses is reported as follows9): The calcium iondissolved fonn CaO,SiOTbased glasses increases the degree of supersaturation of the surrounding body fluid withrespect to apatite, and the hydrated silica fonned on their surfaces provides specific sites favorable to the apatitenucleation. As a result, the apatite nuclei are easily fonned on the surfaces of the CaO,SiOTbased glasses and growspontaneously by consuming the calcium and phosphate ions from the surrounding body fluid. We also reported inprevious papers that a specific structural unit of the hydrated silica is required for inducing the apatite nucleation 10),and that the apatite nucleation ability of the hydrated silica is suppressed by only a small amounts of impurities suchas A1 20.3 and Ti021!). The present results have indicated that the presence of alcohols in SBF up to 0.1 mol'dm-3do not influence the increasing rate of degree of the supersaturation of the surrounding body fluid with respect to theapatite. Furthennore, the apatite nucleation ability of silica hydrogel fonned on the glass is not depressed by thepresence of alcohols with a low molecular weight. This suggests that CaO,Si02-based bioactive glasses are usefulfor designing various kinds of bioactive composites utilizing sol-gel methods.Fig 2 SEM photographs of the surface of the glass soaked in (a)SBF and (b)SBF+PrOH for 7daysEffect of Alcohol on Bioactivity of Glasses 87~ 4 ...------/\--------"-p..,..,,H7.5E (b) pH~-l'> /- .6 ~ 7.45 3~ CaO--.o-o--°___.OC_ 7.3~2 Io 0-I:: 7.2~1~ -. P--....._ _ _ P 7.1E io-~Si~ 0 dI:I;;;)!iJ:::::!:l4"'~:L-L--IL..-..L-....l.-L..-.......:::...J 7.0036 12 1 2 3 4 5 6 7Time I hour Time Iday7.2P 7.1·Si7.06 753~1:~2I::81: 1_...--.(J) Pe~ SiO=:-- ~ _!===-[jJ 0 d:H;;;1:£il::~ I-'----L_..L-....L.........L.---L_..L-....I036 12 1 2 3 4 5Time I hour Time I day~4E (a)-- ~~ 7.1I::(J) .~~iE(J) 0[jJ 7.0036 12 2 3 4 5 6 7Time I hour Time I day7.3I0-7.2~ 4 r----------------,,..,, 7 5E (d) pH .PHls-.6_.6 / 7.4ccP :!::s. oC1::3o~1:2~I::~ 1~ ...............-j. Pe--______ 7.1E &0 ~~~ OlSQi:Ul=:::ltd.j I-'-----'_..L...-........---L_~.....L_ ......w 036 12 2 3 4 5 6 7 7.0Time I hour Time I day-7.2~ 4 r--------------...,7 5E (c) 6........ .6PH .pH.6-{', /""A ~ ---~ 7.4Cao_~o--oC7.3I0-I:: 3o~1: 2(J)oc::8-Fig. 3 Changes in element concentrations and pH of (a)SBF, (b)SBF+MeOH, (c)SBF+EtOH and(d)SBF+PrOH due to immersion of the glass.4. SUMMARYIn order to investigate the effect of alcohols on bioactivity of glasses, we examined the apatite formation on thesurface of 5OCaO" 5OSi02 (mol%) glass in SBF containing methanol, ethanol or I-propanol. The apatite formationability of the glass was not influenced by coexistence of the alcohols up to 0.1 mol'dm-3 in SBF. CaO,Si02-basedbioactive glasses show bioactivity even in the presence of alcohols with low molecular weight in the bodyenvironment.AcknowledgmentThis work was supported by a Grant-in-Aid of The Kazuchika Okura Memorial Foundation.REFERENCES1) L. L. Hench, R. J. Splinter, W. C. Allen and T. K. Greenlee, J. Biomed. Mater. Res. Symp., No.2, (part 1)117-43 (1972).2) J. Wilson, "Glass-Current Issues", Ed. by A. F. Wright and J. Dupuy, Martinus Nijhoff Publishers,Dordrecht (1985) pp. 662-69.3) L. L. Hench, J. Am. Ceram. Soc., 74, 1487-510 (1991).88 Kanji TSURU, Chikako NISHIYAMA, Chikara OHTSUKI and Akiyoshi OSAKA4) T. Yamamuro, "Introduction to bioceramics", Ed. by L. L. Hench and J. Wilson, World Scientific, Singapore(1993) pp. 89-103.5) T. Kokubo, Semmikkusu Ronbunshi, 99,965-73 (1991).6) C. Ohtsuki, T. Kokubo, K. Takatsuka and T. Yamamuro, Semmikkusu Ronbunshi, 99, 1-6 (1991).7) K. Ohura, T. Nakamura, T. Yamamuro, T. Kokubo, Y. Ebisawa, Y. Kotoum and M. Oka, J. Biomed. Mater.Res., 25, 357-65 (1991).8) R. M. Almeida, T. A. Guiton and C. G. Pantano, J. Non-Cryst. Solids, 119, 238-41 (1990).9) C. Ohtsuki, T. Kokubo and T. Yamamuro, J. Non-Cryst. Solids, 143, 84-92 (1992).10) T. Kokubo, S. B. Cho, K. Nakanishi, N. Soga, C. Ohtsuki, T. Kitsugi, T. Yamamuro and T. Nakamura"Bioceramics", vol. 7, ed. by O. H. Apdersson ~d A. Yli-Urpo, Butterworth-Heinemann Ltd, Oxford (1994)pp.49-54.11) C. Ohtsuki, A. Osaka and T. Kokubo, "Bioceramics", vol: 7, Ed. by O. H. Andersson and A. Yli-Urpo,Butterworth-Heinemann Ltd, Oxford (1994) pp. 73-78.

Effect of Alcohol on Bioactivity of Glasses

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