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Facile synthesis and in vitro bioactivity of radial mesoporous bioactive glasses
Materials Letters 206 (2017) 205–209
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Facile synthesis and in vitro bioactivity of radial mesoporous bioactive glasses Yudong Wang, Tianshun Liao, Miao Shi, Cong Liu, Xiaofeng Chen ⇑ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, PR China National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006, PR China
a r t i c l e
i n f o
Article history: Received 7 April 2017 Received in revised form 4 June 2017 Accepted 2 July 2017 Available online 4 July 2017 Keywords: Biomaterials Radial mesoporous Bioactive glasses Nanoparticles Microstructure
a b s t r a c t This paper reports a facile method for fabricating radial mesoporous bioactive glasses (RMBGs) using Hexadecyl trimethyl ammonium bromide (CTAB) micelle as the reaction center. The radial structure was formed with the extension of precursor dissolved in the hydrophobic solvent (cyclohexane) which gathered in the internal part of the CTAB micelle. The morphology, structure and in vitro bioactivity of RMBGs were investigated by various methods. The results indicate that the CTAB micelle could restrict the precursor-dissolved cyclohexane and was in favor of preparing the RMBGs with radial mesoporous structure, high specific surface area and good apatite-forming ability. The obtained RMBGs with the novel structure and properties may have potential application in drug delivery and hard tissue regeneration. Ó 2017 Elsevier B.V. All rights reserved.
1. Introduction Bioactive glasses (BGs) have shown a great prospect in bone and dental tissue regeneration because of their good bioactive, resorbable, osteogenesis and dentinogenesis properties [1–3]. Previous studies have suggested that the bone-bonding ability of BGs was the result of the formation of a hydroxycarbonate apatite layer on the surface when contacting the simulated body fluid (SBF) [4–6]. These years, lots of studies have been focused on the sol-gel bioactive glasses combined with the soft template technology and fabricated many kinds of bioactive glasses with different morphology and structure [7–10]. Previous studies have shown that regular spherical BGs possessed improved physicochemical and biological properties compared to the irregular BGs, exhibiting their potential applications in bone tissue regeneration and drug release systems [6,11]. However, for the aspect of drug delivery, the common bioactive glasses particles were still facing the problem of low drug-loaded capacity [10,12–14]; novel BGs particles with higher specific surface area and newly mesoporous structure were needed to improve the drug-loaded capacity. Here, we utilized the CTAB micelle as the reaction center and the extension of precursor located in the interior of the micelle
⇑ Corresponding author at: School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, PR China. E-mail address: [email protected] (X. Chen). http://dx.doi.org/10.1016/j.matlet.2017.07.021 0167-577X/Ó 2017 Elsevier B.V. All rights reserved.
contributed to the radial mesoporous structure of the novel bioactive glasses particles. The radial mesoporous structure which could be adjusted by changing the Ca concentration contributed to the high specific surface area and good apatite-forming activity; most of all, possessed a great possibility for higher drug-loaded capacity [15–17].
2. Experimental Materials: Tetraethyl orthosilicate (TEOS), triethylphosphate (TEP), calcium nitrate tetrahydrate (CN), ethanol absolute (EtOH) and ammonia solution (25 wt% NH3 in water) were purchased from Guangzhou Chemical Reagent Factory. Hexadecyl trimethyl ammonium bromide (CTAB) and cyclohexane were supplied by Aladdin (Shanghai, PR China). All chemical reagents above were analytical grade. Deionized water was obtained from a water purification system (Milipore S.A.S, France). Preparation of RMBGs: RMBGs were prepared utilizing the CTAB micelle as the reaction center. 0.6 g CTAB were added to a mixture of 62.5 ml deionized water and 37.5 ml ethanol at 35 °C to form the CTAB micelle. 1.35 ml TEOS dissolved in 18 ml cyclohexane was dropped into the solution above. Thereafter, 0.5 ml ammonia solution was added into the solution to initiate the reaction to promote TEOS hydrolysis. Then the mixture was stirring for 20 min and 0.103 ml TEP and a certain amount of CN were sequentially added to the mixture in every 30 min. After 3 h, the solution gradually turned opaque due to the formation of a white precipitate and
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the white precipitate were collected by filtration, rinsed with ethanol and deionized water, and dried at room temperature for 24 h. Finally the RMBGs were obtained after removing organics and nitrates by calcination at 650 °C for 3 h. Besides, CN amount of 0.286 g, 0.531 g and 0.858 g were used for comparison and the corresponding RMBGs were denoted RMBGs-1, RMBGs-2 and RMBGs3 respectively. Characterization: The samples’ morphologies, microstructure and particle size distribution were determined using transmission electron microscopy (TEM, JEM-2100F, JEOL, Japan) and Zetasizer nano-ZS (Marvin, England). Specific surface area was measured using the multipoint Brumauer–Emmett–Teller(BET) N2 absorption technique at 77.3 K. The pore size and pore size distributions were calculated by the Barrett–Joyner–Halenda (BJH) method using desorption isotherm branch. The in vitro bioactivity of the obtained RMBGs was tested by immersing in SBF (Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl 147.8, HCO3 4.2, HPO24 1.0 and SO24 0.5 mmol L 1) at a concentration of 1 mg/ml at 37 °C to monitor the formation of HA on the surface of the sample [18]. Once removed from the incubation, the solids were taken out, washed with deionized water, dried in air and characterized using scanning electron microscopy (SEM, MERLIN Compact, Carl Zeiss, Germany), Fourier transform infrared spectroscopy (FT-IR, Nexus, Nicolet Co., USA) and powder X-ray diffraction (XRD, X’pert PRO, Panalytical, Netherlands) with Cu Ka (1.548 Å).
3. Results and discussion Fig. 1 shows representative TEM images and the particles size distributions of the samples prepared under different CN amount of 0.286 g, 0.531 g and 0.858 g. TEM images indicated that all the samples exhibited regularly spherical morphology and favorable dispersibility (Fig. 1A–C). TEM images in high magnification of RMBGs-1, RMBGs-2 and RMBGs-3 showed the radial structure of samples and the microstructure and particles size could be changed by adjusting the CN amount (Fig. 1D–F). RMBGs-1 showed the radial structure clearly and this microstructure turned indistinct with Ca concentration increased. Besides, the average particles diameters of RMBGs were 339 nm (RMBGs-1), 354 nm (RMBGs-2), 836 nm (RMBGs-3) and all samples exhibited relatively narrow particle size distribution as shown in Fig. 1G–I. The specific surface area and pore structure of the RMBGs samples were obtained by N2 absorption-desorption isotherm. As shown in Fig. 2A, all samples exhibited type IV isotherm patterns with H3-type hysteresis loop associated with slot-shape mesopore according to IUPAC classification [19]. The specific surface areas of RMBGs-1, RMBGs-2 and RMBGs-3 are 986.353 m2 g 1, 847.289 m2 g 1 and 750.141 m2 g 1 respectively, which is much higher than the reported BG microsphere in the literature [8,11]. As shown in Fig. 2B, the pore structure of samples exhibited a narrow mesoporous size distribution. The average pore diameters of RMBGs-1, RMBGs-2 and RMBGs-3 are 3.927 nm, 5.101 nm and 5.132 nm, respectively.
Fig. 1. TEM images and particle size distribution of RMBGs.
Y. Wang et al. / Materials Letters 206 (2017) 205–209
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Fig. 2. N2 absorption-desorption isotherm plots (A) and pore size distribution (B) of RMBGs.
The representative morphologies of RMBGs after soaking in SBF for 12 h and 24 h are shown in Fig.3A. After soaking in SBF for 12 h, the surface of RMBGs became coarser, covered by flaky apatite precipitates; the surface of RMBGs-3 had already grown the flowerlike hydroxyapatite layer. With the increase of soaking time, the flaky precipitates continued to grow and flower-like layer almost covered all the samples’ surface. Additionally, the RMBGs microspheres aggregated together and interconnected with each other by the deposit which was confirmed to be hydroxyapatite crystal according to the FT-IR and XRD results.
The FT-IR spectra of the samples before and after soaking in SBF for 24 h are summarized in Fig. 3B. Before soaking, the spectrum of RMBGs shows characteristic absorption bands corresponding to SiAOASi bonding at 1060 (stretch vibration), 798 (bending vibration) and 480 cm 1 (bending vibration). After 24 h of soaking in SBF, a double band at 562 and 603 cm 1, corresponding to the PAO bending vibrations of phosphate group in a crystalline environment could be observed [20]. The presence of absorption bands of the phosphate group at 968, 603 and 562 cm 1 demonstrated the deposition of HA on the surface of RMBGs. The formation of
Fig. 3. SEM micrographs (A), FT-IR spectra (B) and XRD patterns (C) of RMBGs after soaking in SBF for 24 h.
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Fig. 4. Schematic illustration of the formation process of RMBGs.
the HA layer was also demonstrated by XRD analysis (Fig. 3C). Before soaking, only one small wide peak at around 24° was detected, indicating amorphous nature of RMBGs. After soaking for 24 h, new peaks were observed at 2h = 26°(0 0 2), 32°(2 1 1), 39°(3 1 0), 46°(2 2 2), 49°(2 1 3) and 53°(0 0 4) which corresponded to the crystallinity of HA (JCPDS 09-0432). This indicated that all the samples could induce the formation of HA after soaking in SBF for 24 h [21]. Based on the analysis of SEM, FT-IR and XRD, it was evident that all the samples possessed good apatite-forming ability. The formation mechanism of RMBGs is illustrated in Fig. 4. As we know, CTAB is a cationic surfactant which self-assembles into spherical micelles when the concentration of CTAB is above its critical concentration. The external surface of the micelles is hydrophilic while the interior is hydrophobic. When cyclohexane containing TEOS is dropped in the solution, it will gather in the internal part of the CTAB micelle at first based on the principle of the dissolution in similar material structure. When more cyclohexane is added into the solution, the internal part of the micelle cannot hold all the hydrophobic solvent and cyclohexane containing TEOS will extend out of the micelle along with the interspace of the surfactant configuration. BG sol is hydrolyzed and condensed from the interior to the out of the micelle by ammonia catalyzing when TEP and CN are added. After calcination to remove the organics and nitrate, RMBGs are obtained.
4. Conclusion RMBGs were successfully synthesized by using the CTAB micelle as reaction center and taking use of the extended precursor to create the radial mesoporous structure. The newly bioactive glasses possessed a novel radial mesoporous structure, high specific surface area and relatively homogeneous particle size which insured a great possibility for higher drug-loaded capacity. The radial structure could be infected by CN amount during the synthesis period and the radial level decreased when increasing the Ca contents. All these RMBGs with different Ca content had shown good apatite-forming ability in simulated body fluid. These novel structure and property of RMBGs may turn them into good candi-
dates as drug carriers and injectable biomaterials for hard tissue regeneration. Acknowledgments This work was supported by The Joint Funds of the National Natural Science Foundation of China (Grant No. U1501245), the Fundamental Research Funds for the Central Universities of China (2015ZP020) and the National Natural Science Foundation of China (Grant No. 51372005). References [1] L.L. Hench, J.M. Polak, Third-generation biomedical materials, Science 295 (5557) (2002) 1014–1017. [2] J.R. Jones, Review of bioactive glass: from Hench to hybrids, Acta Biomater. 9 (1) (2013) 4457–4486. [3] L.L. Hench, Biomaterials: a forecast for the future, Biomaterials 19 (16) (1998) 1419–1423. [4] L.L. Hench, N. Roki, M.B. Fenn, Bioactive glasses: importance of structure and properties in bone regeneration, J. Mol. Struct. 1073 (2014) 24–30. [5] A. Hoppe, N.S. Güldal, A.R. Boccaccini, A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics, Biomaterials 32 (11) (2011) 2757–2774. [6] B. Lei et al., Unique physical-chemical, apatite-forming properties and human marrow mesenchymal stem cells (HMSCs) response of sol-gel bioactive glass microspheres, J. Mater. Chem. 21 (34) (2011) 12725–12734. [7] O. Tsigkou et al., Monodispersed bioactive glass submicron particles and their effect on bone marrow and adipose tissue-derived stem cells, Adv. Healthc. Mater. 3 (1) (2014) 115–125. [8] Y. Li et al., Facile synthesis of mesoporous bioactive glasses with controlled shapes, Mater. Lett. 161 (2015) 605–608. [9] Q. Hu et al., Facile synthesis of hollow mesoporous bioactive glass sub-micron spheres with a tunable cavity size, Mater. Lett. 134 (2014) 130–133. [10] X.X. Yan et al., Highly ordered mesoporous bioactive glasses with superior in vitro bone-forming bioactivities, Angew. Chem. Int. Ed. 43 (44) (2004) 5980–5984. [11] H. Qing et al., Facile synthesis and in vitro bioactivity of monodispersed mesoporous bioactive glass sub-micron spheres, Mater. Lett. 106 (2013) 452– 455. [12] S. Labbaf et al., Spherical bioactive glass particles and their interaction with human mesenchymal stem cells in vitro, Biomaterials 32 (4) (2011) 1010– 1018. [13] A. El-Fiqi et al., Capacity of mesoporous bioactive glass nanoparticles to deliver therapeutic molecules, Nanoscale 4 (23) (2012) 7475–7488. [14] W. Xia, J. Chang, Well-ordered mesoporous bioactive glasses (MBG): A promising bioactive drug delivery system, J. Controlled Release 110 (3) (2006) 522–530.
Y. Wang et al. / Materials Letters 206 (2017) 205–209 [15] D.-S. Moon, J.-K. Lee, Tunable synthesis of hierarchical mesoporous silica nanoparticles with radial wrinkle structure, Langmuir 28 (33) (2012) 12341– 12347. [16] X. Du, S.Z. Qiao, Dendritic silica particles with center-radial pore channels: promising platforms for catalysis and biomedical applications, Small 11 (4) (2015) 392–413. [17] L. Xiong et al., Magnetic core-shell silica nanoparticles with large radial mesopores for siRNA delivery, Small 12 (34) (2016) 4735–4742. [18] T. Kokubo, H. Takadama, How useful is SBF in predicting in vivo bone bioactivity?, Biomaterials 27 (15) (2006) 2907–2915
209
[19] N.J. Coleman, L.L. Hench, A gel-derived mesoporous silica reference material for surface analysis by gas sorption 1 Textural features, Ceram. Int. 26 (2) (2000) 171–178. [20] I. Notingher et al., Application of FTIR and Raman spectroscopy to characterisation of bioactive materials and living cells, Spectroscopy 17 (2– 3) (2003) 275–288. [21] T.A. Ostomel et al., Spherical bioactive glass with enhanced rates of hydroxyapatite deposition and hemostatic activity, Small 2 (11) (2006) 1261–1265.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Facile synthesis and in vitro bioactivity of radial mesoporous bioactive glasses Yudong Wang, Tianshun Liao, Miao Shi, Cong Liu, Xiaofeng Chen ⇑ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, PR China National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006, PR China
a r t i c l e
i n f o
Article history: Received 7 April 2017 Received in revised form 4 June 2017 Accepted 2 July 2017 Available online 4 July 2017 Keywords: Biomaterials Radial mesoporous Bioactive glasses Nanoparticles Microstructure
a b s t r a c t This paper reports a facile method for fabricating radial mesoporous bioactive glasses (RMBGs) using Hexadecyl trimethyl ammonium bromide (CTAB) micelle as the reaction center. The radial structure was formed with the extension of precursor dissolved in the hydrophobic solvent (cyclohexane) which gathered in the internal part of the CTAB micelle. The morphology, structure and in vitro bioactivity of RMBGs were investigated by various methods. The results indicate that the CTAB micelle could restrict the precursor-dissolved cyclohexane and was in favor of preparing the RMBGs with radial mesoporous structure, high specific surface area and good apatite-forming ability. The obtained RMBGs with the novel structure and properties may have potential application in drug delivery and hard tissue regeneration. Ó 2017 Elsevier B.V. All rights reserved.
1. Introduction Bioactive glasses (BGs) have shown a great prospect in bone and dental tissue regeneration because of their good bioactive, resorbable, osteogenesis and dentinogenesis properties [1–3]. Previous studies have suggested that the bone-bonding ability of BGs was the result of the formation of a hydroxycarbonate apatite layer on the surface when contacting the simulated body fluid (SBF) [4–6]. These years, lots of studies have been focused on the sol-gel bioactive glasses combined with the soft template technology and fabricated many kinds of bioactive glasses with different morphology and structure [7–10]. Previous studies have shown that regular spherical BGs possessed improved physicochemical and biological properties compared to the irregular BGs, exhibiting their potential applications in bone tissue regeneration and drug release systems [6,11]. However, for the aspect of drug delivery, the common bioactive glasses particles were still facing the problem of low drug-loaded capacity [10,12–14]; novel BGs particles with higher specific surface area and newly mesoporous structure were needed to improve the drug-loaded capacity. Here, we utilized the CTAB micelle as the reaction center and the extension of precursor located in the interior of the micelle
⇑ Corresponding author at: School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, PR China. E-mail address: [email protected] (X. Chen). http://dx.doi.org/10.1016/j.matlet.2017.07.021 0167-577X/Ó 2017 Elsevier B.V. All rights reserved.
contributed to the radial mesoporous structure of the novel bioactive glasses particles. The radial mesoporous structure which could be adjusted by changing the Ca concentration contributed to the high specific surface area and good apatite-forming activity; most of all, possessed a great possibility for higher drug-loaded capacity [15–17].
2. Experimental Materials: Tetraethyl orthosilicate (TEOS), triethylphosphate (TEP), calcium nitrate tetrahydrate (CN), ethanol absolute (EtOH) and ammonia solution (25 wt% NH3 in water) were purchased from Guangzhou Chemical Reagent Factory. Hexadecyl trimethyl ammonium bromide (CTAB) and cyclohexane were supplied by Aladdin (Shanghai, PR China). All chemical reagents above were analytical grade. Deionized water was obtained from a water purification system (Milipore S.A.S, France). Preparation of RMBGs: RMBGs were prepared utilizing the CTAB micelle as the reaction center. 0.6 g CTAB were added to a mixture of 62.5 ml deionized water and 37.5 ml ethanol at 35 °C to form the CTAB micelle. 1.35 ml TEOS dissolved in 18 ml cyclohexane was dropped into the solution above. Thereafter, 0.5 ml ammonia solution was added into the solution to initiate the reaction to promote TEOS hydrolysis. Then the mixture was stirring for 20 min and 0.103 ml TEP and a certain amount of CN were sequentially added to the mixture in every 30 min. After 3 h, the solution gradually turned opaque due to the formation of a white precipitate and
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the white precipitate were collected by filtration, rinsed with ethanol and deionized water, and dried at room temperature for 24 h. Finally the RMBGs were obtained after removing organics and nitrates by calcination at 650 °C for 3 h. Besides, CN amount of 0.286 g, 0.531 g and 0.858 g were used for comparison and the corresponding RMBGs were denoted RMBGs-1, RMBGs-2 and RMBGs3 respectively. Characterization: The samples’ morphologies, microstructure and particle size distribution were determined using transmission electron microscopy (TEM, JEM-2100F, JEOL, Japan) and Zetasizer nano-ZS (Marvin, England). Specific surface area was measured using the multipoint Brumauer–Emmett–Teller(BET) N2 absorption technique at 77.3 K. The pore size and pore size distributions were calculated by the Barrett–Joyner–Halenda (BJH) method using desorption isotherm branch. The in vitro bioactivity of the obtained RMBGs was tested by immersing in SBF (Na+ 142.0, K+ 5.0, Mg2+ 1.5, Ca2+ 2.5, Cl 147.8, HCO3 4.2, HPO24 1.0 and SO24 0.5 mmol L 1) at a concentration of 1 mg/ml at 37 °C to monitor the formation of HA on the surface of the sample [18]. Once removed from the incubation, the solids were taken out, washed with deionized water, dried in air and characterized using scanning electron microscopy (SEM, MERLIN Compact, Carl Zeiss, Germany), Fourier transform infrared spectroscopy (FT-IR, Nexus, Nicolet Co., USA) and powder X-ray diffraction (XRD, X’pert PRO, Panalytical, Netherlands) with Cu Ka (1.548 Å).
3. Results and discussion Fig. 1 shows representative TEM images and the particles size distributions of the samples prepared under different CN amount of 0.286 g, 0.531 g and 0.858 g. TEM images indicated that all the samples exhibited regularly spherical morphology and favorable dispersibility (Fig. 1A–C). TEM images in high magnification of RMBGs-1, RMBGs-2 and RMBGs-3 showed the radial structure of samples and the microstructure and particles size could be changed by adjusting the CN amount (Fig. 1D–F). RMBGs-1 showed the radial structure clearly and this microstructure turned indistinct with Ca concentration increased. Besides, the average particles diameters of RMBGs were 339 nm (RMBGs-1), 354 nm (RMBGs-2), 836 nm (RMBGs-3) and all samples exhibited relatively narrow particle size distribution as shown in Fig. 1G–I. The specific surface area and pore structure of the RMBGs samples were obtained by N2 absorption-desorption isotherm. As shown in Fig. 2A, all samples exhibited type IV isotherm patterns with H3-type hysteresis loop associated with slot-shape mesopore according to IUPAC classification [19]. The specific surface areas of RMBGs-1, RMBGs-2 and RMBGs-3 are 986.353 m2 g 1, 847.289 m2 g 1 and 750.141 m2 g 1 respectively, which is much higher than the reported BG microsphere in the literature [8,11]. As shown in Fig. 2B, the pore structure of samples exhibited a narrow mesoporous size distribution. The average pore diameters of RMBGs-1, RMBGs-2 and RMBGs-3 are 3.927 nm, 5.101 nm and 5.132 nm, respectively.
Fig. 1. TEM images and particle size distribution of RMBGs.
Y. Wang et al. / Materials Letters 206 (2017) 205–209
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Fig. 2. N2 absorption-desorption isotherm plots (A) and pore size distribution (B) of RMBGs.
The representative morphologies of RMBGs after soaking in SBF for 12 h and 24 h are shown in Fig.3A. After soaking in SBF for 12 h, the surface of RMBGs became coarser, covered by flaky apatite precipitates; the surface of RMBGs-3 had already grown the flowerlike hydroxyapatite layer. With the increase of soaking time, the flaky precipitates continued to grow and flower-like layer almost covered all the samples’ surface. Additionally, the RMBGs microspheres aggregated together and interconnected with each other by the deposit which was confirmed to be hydroxyapatite crystal according to the FT-IR and XRD results.
The FT-IR spectra of the samples before and after soaking in SBF for 24 h are summarized in Fig. 3B. Before soaking, the spectrum of RMBGs shows characteristic absorption bands corresponding to SiAOASi bonding at 1060 (stretch vibration), 798 (bending vibration) and 480 cm 1 (bending vibration). After 24 h of soaking in SBF, a double band at 562 and 603 cm 1, corresponding to the PAO bending vibrations of phosphate group in a crystalline environment could be observed [20]. The presence of absorption bands of the phosphate group at 968, 603 and 562 cm 1 demonstrated the deposition of HA on the surface of RMBGs. The formation of
Fig. 3. SEM micrographs (A), FT-IR spectra (B) and XRD patterns (C) of RMBGs after soaking in SBF for 24 h.
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Fig. 4. Schematic illustration of the formation process of RMBGs.
the HA layer was also demonstrated by XRD analysis (Fig. 3C). Before soaking, only one small wide peak at around 24° was detected, indicating amorphous nature of RMBGs. After soaking for 24 h, new peaks were observed at 2h = 26°(0 0 2), 32°(2 1 1), 39°(3 1 0), 46°(2 2 2), 49°(2 1 3) and 53°(0 0 4) which corresponded to the crystallinity of HA (JCPDS 09-0432). This indicated that all the samples could induce the formation of HA after soaking in SBF for 24 h [21]. Based on the analysis of SEM, FT-IR and XRD, it was evident that all the samples possessed good apatite-forming ability. The formation mechanism of RMBGs is illustrated in Fig. 4. As we know, CTAB is a cationic surfactant which self-assembles into spherical micelles when the concentration of CTAB is above its critical concentration. The external surface of the micelles is hydrophilic while the interior is hydrophobic. When cyclohexane containing TEOS is dropped in the solution, it will gather in the internal part of the CTAB micelle at first based on the principle of the dissolution in similar material structure. When more cyclohexane is added into the solution, the internal part of the micelle cannot hold all the hydrophobic solvent and cyclohexane containing TEOS will extend out of the micelle along with the interspace of the surfactant configuration. BG sol is hydrolyzed and condensed from the interior to the out of the micelle by ammonia catalyzing when TEP and CN are added. After calcination to remove the organics and nitrate, RMBGs are obtained.
4. Conclusion RMBGs were successfully synthesized by using the CTAB micelle as reaction center and taking use of the extended precursor to create the radial mesoporous structure. The newly bioactive glasses possessed a novel radial mesoporous structure, high specific surface area and relatively homogeneous particle size which insured a great possibility for higher drug-loaded capacity. The radial structure could be infected by CN amount during the synthesis period and the radial level decreased when increasing the Ca contents. All these RMBGs with different Ca content had shown good apatite-forming ability in simulated body fluid. These novel structure and property of RMBGs may turn them into good candi-
dates as drug carriers and injectable biomaterials for hard tissue regeneration. Acknowledgments This work was supported by The Joint Funds of the National Natural Science Foundation of China (Grant No. U1501245), the Fundamental Research Funds for the Central Universities of China (2015ZP020) and the National Natural Science Foundation of China (Grant No. 51372005). References [1] L.L. Hench, J.M. Polak, Third-generation biomedical materials, Science 295 (5557) (2002) 1014–1017. [2] J.R. Jones, Review of bioactive glass: from Hench to hybrids, Acta Biomater. 9 (1) (2013) 4457–4486. [3] L.L. Hench, Biomaterials: a forecast for the future, Biomaterials 19 (16) (1998) 1419–1423. [4] L.L. Hench, N. Roki, M.B. Fenn, Bioactive glasses: importance of structure and properties in bone regeneration, J. Mol. Struct. 1073 (2014) 24–30. [5] A. Hoppe, N.S. Güldal, A.R. Boccaccini, A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics, Biomaterials 32 (11) (2011) 2757–2774. [6] B. Lei et al., Unique physical-chemical, apatite-forming properties and human marrow mesenchymal stem cells (HMSCs) response of sol-gel bioactive glass microspheres, J. Mater. Chem. 21 (34) (2011) 12725–12734. [7] O. Tsigkou et al., Monodispersed bioactive glass submicron particles and their effect on bone marrow and adipose tissue-derived stem cells, Adv. Healthc. Mater. 3 (1) (2014) 115–125. [8] Y. Li et al., Facile synthesis of mesoporous bioactive glasses with controlled shapes, Mater. Lett. 161 (2015) 605–608. [9] Q. Hu et al., Facile synthesis of hollow mesoporous bioactive glass sub-micron spheres with a tunable cavity size, Mater. Lett. 134 (2014) 130–133. [10] X.X. Yan et al., Highly ordered mesoporous bioactive glasses with superior in vitro bone-forming bioactivities, Angew. Chem. Int. Ed. 43 (44) (2004) 5980–5984. [11] H. Qing et al., Facile synthesis and in vitro bioactivity of monodispersed mesoporous bioactive glass sub-micron spheres, Mater. Lett. 106 (2013) 452– 455. [12] S. Labbaf et al., Spherical bioactive glass particles and their interaction with human mesenchymal stem cells in vitro, Biomaterials 32 (4) (2011) 1010– 1018. [13] A. El-Fiqi et al., Capacity of mesoporous bioactive glass nanoparticles to deliver therapeutic molecules, Nanoscale 4 (23) (2012) 7475–7488. [14] W. Xia, J. Chang, Well-ordered mesoporous bioactive glasses (MBG): A promising bioactive drug delivery system, J. Controlled Release 110 (3) (2006) 522–530.
Y. Wang et al. / Materials Letters 206 (2017) 205–209 [15] D.-S. Moon, J.-K. Lee, Tunable synthesis of hierarchical mesoporous silica nanoparticles with radial wrinkle structure, Langmuir 28 (33) (2012) 12341– 12347. [16] X. Du, S.Z. Qiao, Dendritic silica particles with center-radial pore channels: promising platforms for catalysis and biomedical applications, Small 11 (4) (2015) 392–413. [17] L. Xiong et al., Magnetic core-shell silica nanoparticles with large radial mesopores for siRNA delivery, Small 12 (34) (2016) 4735–4742. [18] T. Kokubo, H. Takadama, How useful is SBF in predicting in vivo bone bioactivity?, Biomaterials 27 (15) (2006) 2907–2915
209
[19] N.J. Coleman, L.L. Hench, A gel-derived mesoporous silica reference material for surface analysis by gas sorption 1 Textural features, Ceram. Int. 26 (2) (2000) 171–178. [20] I. Notingher et al., Application of FTIR and Raman spectroscopy to characterisation of bioactive materials and living cells, Spectroscopy 17 (2– 3) (2003) 275–288. [21] T.A. Ostomel et al., Spherical bioactive glass with enhanced rates of hydroxyapatite deposition and hemostatic activity, Small 2 (11) (2006) 1261–1265.