Poly(methyl methacrylate) substrates were immersed in suspensions containing bioactive 50CaO･50SiO(2) (mol%) glass particles (45 μm in diameter) and a 6:4 (volume fraction) mixture of ethanol and THF, and an ultrasonic energy was applied to the system. A layer of glass particles was implanted and covered more than 50% of the substrate surface. Thin film X-ray diffraction patterns and FT-IR reflection spectra indicated deposition of apatite on the glass-implanted substrates after they were soaked for 12 h in a simulated body fluid similar in apatite-deposition ability to the human blood plasma. Flake-like apatite crystallites formed on the substrate soaked in SBF for 3 days

Nishiyama, Chikako

Ohtsuki, Chikara

Osaka, Akiyoshi

Tsuru, Kanji

English

Okayama University Scientific Achievement Repository

Memoirs of the Faculty of Engineering,Okayama UniversitY,Vo1.29, No.2, pp.77-81, March 1995Ultrasonic Implantation of Bioactive Glass Particles intoPoly(methyl methacrylate) SubstratesKanji TSURU*, Chikako NISHIYAMA*, Chikara OHTSUKI*, and Akiyoshi OSAKA*(Received January 27 , 1995)Poly(methyl methacrylate) substrates were immersed in suspensions containing bioactive50CaO-50Si02 (mol%) glass particles (45 ~m in diameter) and a 6:4 (volume fraction) mixture ofethanol and THF, and an ultrasonic energy was applied to the system. A layer of glass particles wasimplanted and covered more than 50% of the substrate surface. Thin film X-ray diffraction patternsand Ff-IR reflection spectra indicated deposition of apatite on the glass-implanted substrates afterthey were soaked for 12 h in a simulated body fluid similar in apatite-deposition ability to the humanblood plasma. Rake-like apatite crystallites formed on the substrate soaked in SBF for 3 days.1. INTRODUCTIONA group of materials that form a direct bond to living bones1) are called bioactive. It is essential that they candeposit a layer of bone-like apatite. A few series of glasses and glass ceramics have exhibited bioactivity, such asCeravital® 2), Cerabone® A-W3), and several glasses containing CaO and Si02 including Bioglass® 4). However,almost all of metals, ceramics and organic polymers cannot form such bonds, and they are sometimes calledbiocompatible as far as they are allowed in human or mammals' bodies with forming a fibrous capsule around them.Poly(methyl methacrylate), denoted as PMMA, is one of the most important polymers that are used in medical care.It is thus significant if one could provide PMMA with bioactivity.One of the present authors used an ultrasonic energy to stimulate kinetic movements of glass or ceramic powdersin suspensions and induced bombarding a substrate immersed in them5). Such ultrasonic treatment may easilyimplant glass particles into any organic polymers when they are immersed in a suspension of a solvent capable ofswelling the polymers. In this respect the treatment is denoted as ultrasonic implantation. Then it is expectable thatthe ultrasonic implantation of bioactive powders provides polymers with bioactivity. The present paper describesthe ultrasonic implantation into PMMA of a 50Ca0e50Si02 (mol%) glass whose bioactivity was alreadyconfirmed6), and confirmation of the bioactivity of the glaSs-implanted PMMA substrate.2. EXPERIMENTALOne of the bioactive glasses of a composition 50CaO-50Si02 (mol%) was prepared by melting at 1600°C amixture of CaC03 and Si02 in a platinum crucible placed in a MoSi2-heated furnace and quenching the meltbetween two sheets of steel. The quenched glass was annealed and pulverized with a zirconia ball mill to less than45 Ilm in diameter. Several mixtures of ethanol and tetrahydrofurane (THF) in various fractions (volume %) wereprepared and tried as suspension media to find an appropriate mixing ratio. A sheet of PMMA (Sumitomo Chemical* Department of Bioengineering Science7778 Kanji TSURU, Chikako NISHIYAMA, Chikara OHTSUKI and Akiyoshi OSAKAConcentration 00-3 mol/dm3)SBF Human body plasma142.0 142.05.0 5.02.5 2.51.5 1.5147.8 103.04.2 27.01.0 1.00.5 0.5IonsNa+K+Ca2+M g2+Cl-HC03-HP042-SO 2-4Table 1. Conentrations of inorganic ions insimulated body fluid (SBF) and the human bloodplasma.examine the element distribution.Co., Ltd.) was cut into pieces with 15xlOx2 mm in size. Each piece was immersed in a suspension containing up to1 g of the glass powder dispersed in 20 or 40 ml of ethanol-THF solutions that were held in a 50 ml glass bottle.The bottle was then immersed in an ultrasonic water bath (Iuchi Co., Pasolina USC1, 65W) and was ultrasonicallystimulated for 20 min. The temperature of the water rose from 20°C to 40°C.A simulated body fluid (SBF) that contained inorganic components similar in concentration to the human bloodplasma7) (Table 1) was prepared after the procedure described elsewhere8), and pH was adjusted to 7.25 by 50 mM(=10-3 mol/dm3) tris(hydroxymethyl)aminomethane and 45 mM hydrochloric acid solutions. The fluid containedno living cel1s or organic substances. It is already confirmed that SBF produces a bone-like apatite layer that wouldform in vivo on the bioactive materials9). The pieces of PMMA implanted with the glass particles were immersed inSBF held in 50 ml polyethylene bottles wliose temperature was kept at 36.5°C. After soaking up to 7 days thePMMA substrates were studied on their surface structure with. FT-IR reflection spectrometry and thin-film X-raydiffractometry. The IR reflection spectra (75° off-normal)were recorded in a JASCO FT/IR-300 spectrometer at 100scans and 4 cm-1 resolution, using a Spectra Techattachment Model 501. Thin film X-ray diffractionspectra (CuKu) were taken with a Rigaku RINT 1400diffractometer operated under 40 kV-200mA acceleration,at the incident angle of 1°. These two techniques givestructural information of an only about 1 j-tmthick surfacelayer. A scanning electron microscope (SEM, JEOL JSM-6300) equipped with an energy dispersive X-rayspectrometer (Phillips, EDX-4) was used to observemicrostructure of the surfaces and cross sections and to3. RESULTS AND DISCUSSIONIncrease in the THF fraction caused a weightloss of the specimen probably because ofchipping the swel1ed surface due toultrasonically stimulated glass particles. Notethat the suspensions with 30 mg glass powdercaused greater weight losses than the 500 mgglass-suspensions and that the latter case gaveas much weight loss as the glass-freesolutions. This indicated that the implantingrate for the 500 mg-glass suspensions waslarger than that for the 30 mg-glass ones. Fig.2 shows SEM photographs of the crosssections for the specimen that the ultrasonic8020 40 60Fraction of THF (vol%)30L. 500oGlass (mg/20mlsuspension)o 0Fig. 1. Weight change of the PMMA substrate after the ultrasonicimplantation as a function of the ethanol-THF mixing ratio in thesuspension medium..........(l) 0 W---e----B-.......""S~0>c~ -40u.j.J..c.0> -80'w~-120oFigure 1represents weight changes of the PMMA substrate after the ultrasonic implantation as a function of theethanol-THF mixing ratio in the suspension medium. The amount of glass suspended was 0, 30, and 500 mg for 20ml of the ethanol-THF solutions that were held in 30 ml glass bottles. A smal1 weight gain (1 mg) wasfound irrelevant to the amount of glass untilthe fraction of THF exceeded 30 vol%.......... 40,..-------------------....,0>EUltrasonic Implanlalian of Bioactive Glass Particles inlo PMMAimplantation was applied to with the suspensions where 1000 mg of the glass were dispersed in 40 ml of the ethanol-THF solutions different in mixing ratio. Energy dispersive X-ray analysis of Ca and Si distribution was also carriedout along the line indicated in the photographs. After the fraction of THF reached 40 vol%, glass particlesimplanted were observable on the PMMA surface as well as the strong X-ray signals of Ca and Si. Several layers ofglass particles were implanted for the suspension of 60 vol% THF while only a layer was observable for 40 voJ%79Fig. 2. SEM photographs of cross section of ultrasonically implanted PMMA. IOOOmg glass/40ml solution.THFethanol= (a)7:3, (b) 6:4, (c) 5:5, (d) 4:6., Corresponding Ca and Si distributions after electron probe micro line-analysis are also indicaated.80 Kanji TSURU, Chikako NISHIYAMA, Chikara OHTSUKI and Akiyoshi OSAKATHF. From those results a mixture of 6:4 ethanol-THFFig. 3. A SEM photograph of the surface of PMMAafter the ultrasonic implantation. looomg glass/40mL 4THF-6ethanol solution.solution was taken as the suspension medium where theweight/volume ratio of the suspending glass and the mediawas fixed at lOOO mg-glass/40 ml-solution.Fig. 3 is a SEM photograph of the surface of aspecimen after the ultrasonic implantation, showing thatthe glass particles implanted homogeneously cover morethan 50% of the surface. Fig. 4 shows thin-film X-raydiffraction patterns and Fr-IR reflection spectra of thespecimen after soaking up to 7 days in SHF. The spectrafor a specimen without soaking are denoted as "Oh". Abroad X-ray diffraction for the Oh specimen near 28=300due to the glass particles and the PMMA substrate grew inonly I h of soaking in SHF. This suggested some changein surface structure took place on the glass surface at soearly a stage of soaking in SHF. The 12 h specimen showed faint X-ray diffraction peaks near 260 and 320 due tothe (002) plane and an envelope of (211), (112) and (300) planes of apatite (JCPDS: 9-432), respectively, and theygrew to distinct ones in a longer period of soaking. AlO30 cm-1 IR reflection peak observed for the Oh specimenwas assigned to a Si-O stretching band for the 50Ca0e50Si02 glass as well as weak 900 and 8lO cm-1 peaks. Aweaker band near 480 cm-1 was due to Si-O deformation. After 1 h soaking in SHF several bands newly appearedat about 1240 and 1130 cm-1 that were already assigned to a longitudinal optical mode and transverse optical one ofSi-O stretchingl -4, 6,8,9) after Almeida et al. lO) For longer soaking periods, 1130 and 1040 cm-1 peaks grew ino Apatite o Apatite(002) (211 ) T Si-O optical0 0 modes 007d 7d3d 3d>- 1d 1d+-'(J)c cQ) 0+-' 12h +-' 12hc uQ)>- 'i=co 6h Q)I- ~I 6hX3h 3hT1h 1hOh20 40 1600 400Fig. 4. Thin-film X-ray diffraction patterns (left) and Fr-IR reflection spectra(right) of the specimen after ultrasonicimplantation (1000 mg glass/40 mL 4THF-6ethanol solution) and soaking up to 7 days in SHF.0: apatite,~ : Si-O optical modes.Ultrasonic Implantation of Bioa£live Glass Particles into PMMA 81Fig. 5. A SEM photograph of PMMA soaked inSBF for 3 days after ultrasonic implantation (\000mg glass/4O mL 4THF-6ethanol solution).4. SUMMARYPieces of PMMA were immersed in suspensions thatcontained particles (45 !!m in diameter) of bioactive glassof composition 5OCaa.5OSi02 in a 6:4 (volume fraction)mixture of ethanol and THF, and an ultrasonic energywas applied to the system. With a mixture of 40 vol% ofTHF a layer of glass particles was implanted in thesurface of PMMA while several layers were implantedfor the 60 vol% THF suspension. A scanning electronmicrograph indicated that more than 50% of the surfacearea were covered with the glass particles when the 40vol% THF suspension was used for the ultrasonicimplantation. The surface structure was examined for thespecimen with glass implanted in the 6:4 ethanol-THF suspension after soaking in SBF up to 7 days. Thin film X-ray diffraction patterns indicated trace (002) and (211) peaks of apatite for the specimen soaked for 12 h. Theybecame distinct in a longer period of soaking. FT-IR renection spectra showed Si-O bands before growth of apatitelR bands. Flake-like crystallites of apatite were observed in SEM photographs for the specimen soaked in SBF formore than I day.intensity whereas the relative intensity of the 1240 and 1180 cm- 1 bands decreased as well as that of 900-750 cm- 1ones until they disappeared after soaking for 7 days. Moreover, the 540 cm- 1 peak grew and finally split into twopeaks at 6\0 and 570 em-I. The 1130, 1040,6\0 and 570 cm- I peaks were due to apatite l -3 ,9). This supports theprevious assignment of the X-ray diffraction near 26° and 32° in Fig. 4.Fig. 5 shows the SEM photograph of the specimen soaked in SBF for 3 days. Flake-like crystallites composedhemispherical agglomerates <2 flmin diameter to cover the surface of the PMMA substrate. The morphology of thecrystallites was the same as apatite crystals found for bulk glasses and glass ceramics 1-4,6,8,9). Again deposition ofapatite was confirmed on the glass-implanted PMMA, and it was concluded that the present ultrasonic implantationwas applicable to provide PMMA with bioactivity.5. REFERENCESI) T. Kokubo, J. Non-Cryst. Solids, 120, 138-51 (1990).2) e. Ohtsuki, H. Kushitani, T. Kokubo, S. Kotani, and T. Yamamuro, J Biomed. Mat. Res., 25, 1363-70( 1991).3} T. Kokubo, Biomaterials, 12, 155-63 (1991).4) M. Ogino and L.L. Hench, J. Non-Cryst. Solids, 38 & 39, 673-78 (1980).S) Y. Ding, A. Osaka, and Y. Miura, J. Am. Ceram. Soc., 77, 749-52 (1994).6) Y. Ebisawa, T. Kokubo, K. Ohura, and T. Yamamuro, 1. Mat. Sci.: Materials in Medicine, 1,239-44 (1990).7) J. Gamble, in "Chemical Anatomy, Physiology and Pathology of Extracellular Fluid," 6th ed., HarvardUniversity Press, Cambridge, 1967, p. I.8) e. Ohtsuki, T. Kokubo, and T. Yamamuro, J. Non-Cryst. Solids, 143,84-92 (1992).9) T. Kokubo, S. Ito, Z.T. Huang, T. Hayashi, S. Sakka, S. Kitsugi, and T. Yamamuro, J. Biomed. Mat. Res.,24,331-43 (1990).10) R.M. Almeida, T.A. Guiton, and e.G. Pantano, 1. Non-Cryst. Solids, 119,238-41 (1990).

Ultrasonic Implantation of Bioactive Glass Particles into Poly(methyl methacrylate) Substrates

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