Elsevier

Biomaterials

Volume 23, Issue 10, May 2002, Pages 2151-2158
Biomaterials

A novel bioactive and magnetic biphasic material

https://doi.org/10.1016/S0142-9612(01)00346-5Get rights and content

Abstract

A novel biphasic material has been synthetised from a sol–gel-derived glass (Si–Ca–P) and a glass–ceramic obtained from a melt-derived glass (Si–Ca–Fe). Both components of such a biphasic mixture are bioactive, but with different kinetics for the growth of an apatite-like layer on the surface of these materials, needing only one day for the sol–gel-derived glass and one month for the glass–ceramic. The glass–ceramic shows magnetic properties. The biphasic material, obtained from a mixture 1:1 of these components, is bioactive, and its surface is coated after 15 days of soaking in SBF. The biphasic material also exhibited magnetic behaviour, useful for hyperthermia.

Introduction

During the 1970s and 1980s, bioactive glasses were obtained only by melting and rapid cooling, getting materials with low specific surface and porosity. The research on this kind of glasses has been managed in two ways: firstly, the improvement of the mechanical properties without decreasing the bioactivity, generally carried out by the preparation of glass–ceramics [1], [2], and secondly, studying the influence of the composition on the bioactivity [3]. On the other hand, since the early 1990s, the sol–gel method has been applied to obtain bioactive glasses [4], [5], [6], [7]. The use of any sol–gel-derived glass in human clinical applications is not authorised yet but, taking into account that hydroxyapatite formation kinetics is more rapid than the kinetics for melt-derived glasses, and the rate of bone growth in animals (as preliminary assays have shown) is larger too, clinical application of sol–gel-derived glasses will probably take place in the near future. The increase of bioactivity of sol–gel-derived glasses can be explained by taking into account that the textural properties of the material (surface area, pore volume and pore size distribution) have a great influence on their reactivity [8]. Therefore, the large specific surface and porosity of sol–gel-derived glasses must play an important role in the kinetics of the hydroxyapatite formation. However, the higher reactivity of the sol–gel-derived glasses when compared with the melt-derived glasses is supported by the descriptions in the literature of bioactivity for sol–gel-derived glasses with SiO2 contents reaching 90% [9]. With such a high silica content, a melt-derived glass would be highly stable and non-bioactive.

The development of glass–ceramics started in the 1960s. They are polycrystalline ceramics with amorphous and crystalline phases, obtained by controlled crystallisation of glasses and then applying a suitable heat treatment. Around 90% of the glass crystallises, with a crystal size between 0.1 and 1 μm. The addition of metallic precipitates simplifies glass–ceramic synthesis because it improves the nucleation and growth of crystals with size below 1 μm. Glass–ceramics show excellent thermal and mechanical properties when compared with the traditional ceramics. In the field of biomaterials they started to be used in the 1980s, expecting the improvement of the mechanical properties of glasses, their predecessors, but without altering their bioactivity due to the heat treatment or the addition of metallic precipitates [10], [11].

Bioactive glasses and glass–ceramics have another application in the field of biomaterials: the elimination of cancerous cells in bones, by means of hyperthermia [12], [13], [14], [15]. This therapy consists of the selective heating of a fixed zone. Above 43°C the cancerous cells are the first to die when a heat treatment is applied. This occurs because less blood vessels and nervous ramifications are present in those zones and, therefore, they are less oxygenated. If the heat treatment is selective, that is, 43°C, and the application time is controlled, it could be possible to damage the cancerous cells without altering the healthy ones. The inclusion of magnetic aggregates in glasses or glass–ceramics of the system SiO2–CaO–P2O5 could be a solution for this application. On the one hand, it is possible to achieve the bonding of the bioactive glass and the bone and the growth of the latter, and on the other hand, it is possible to control the increase of the temperature due to the hysteresis loop of the magnetic material and the induced eddy currents when a variable external magnetic field is applied.

However, the obtaining of glass–ceramics which combine bioactivity and magnetic properties, (in the proper range to be used in hyperthermia) is not an easy task. The inclusion of Fe seems to diminish the bioactivity. On the other hand, the sol–gel method is an inadequate way to obtain glass containing Fe because this element is segregated forming non-magnetic precipitates, fundamentally α-Fe2O3. As the melting and rapid cooling method allows Fe containing glasses to be obtained, this had to be the method which assures the Fe presence and, after adequate treatment, the appearance of magnetic nuclei in the material. This material could be used as a glass or, after a heat treatment, as a magnetic glass–ceramic. This option will hinder the bioactive properties. For this reason we think that the best solution would be the synthesis of a biphasic material, containing a sol–gel-derived bioactive glass, previously studied by our group [8], and which has a very high carbonatehydroxyapatite growth kinetics.

Therefore, the biphasic material will contain a highly bioactive material (sol–gel-derived glass) and another one with adequate magnetic properties (glass or glass–ceramic). This has been the aim of this work.

Section snippets

Obtaining of the melt glass (FeG)

The glass (Fe–G), had a nominal composition SiO2 45–CaO 45–Fe2O3 10 (mole %). In order to increase the reactivity and diminish the viscosity of the melting mixture [16] 3% in weight of Na2O was added. The glass was obtained by melting and rapid cooling of 8.112 g of SiO2 (Fluka), 13.5 g of CaCO3 (Fluka), 4.788 g of Fe2O3 (Philips Components) and 1.126 g of Na2CO3 (Panreac). It was introduced into a platinum crucible and heated from room temperature up to 800°C at a heating rate of 10°C/min, and

Results and discussion

Mass finer percentage and particle size distribution of sol–gel-derived (S58) and melt-derived (FeG) glasses are plotted in Fig. 1a and b, respectively. Fig. 1a shows that 80% (%wt) of FeG and S58 (sol–gel-derived) glasses were constituted by particles with a equivalent spherical diameter <52 and 29 μm, respectively. 50% of FeG and S58 mass particle was <25 and 17 μm.

Fig. 1b shows the particle size distribution of both glasses. FeG showed a broad single-mode distribution with the maximum placed

Conclusions

A bioactive and magnetic biphasic material has been obtained. In contact with SBF a nanocrystalline apatite-like layer grows over the surface and therefore, a good bone integration is expected when implanted.

Whereas its bioactive behaviour is due, fundamentally, to the sol–gel-derived glass, the presence of Fe included in the glass–ceramic phase provides magnetic properties to the biphasic material, being useful for hyperthermia treatment of cancer. These biphasic materials (sol–gel-derived

Acknowledgements

Financial support of CICYT, Spain, through research project MAT99-0466 is acknowledged. R.P. del Real is grateful to the Consejerı́a de Educación y Cultura (C.A.M.) for his postdoctoral grant.

References (19)

  • Y. Ebisawa et al.

    Bioactivity of ferrimagnetic glass–ceramics in the system FeO–Fe2O3–CaO–SiO2

    Biomaterials

    (1997)
  • T. Kokubo et al.

    Mechanical properties of a new type of apatite-containing glass–ceramic for prosthetic application

    J Mater Sci

    (1985)
  • T. Kokubo et al.

    Fatigue and life time of bioactive glass–ceramic A–W containing apatite and wollastonite

    J Mater Sci

    (1987)
  • L.L. Hench

    Bioceramicsfrom concept to clinic

    J Am Ceram Soc

    (1991)
  • R. Li et al.

    An investigation of bioactive glass powders by sol–gel proccesing

    J Appl Biomater

    (1991)
  • M. Vallet-Regı́ et al.

    XRD, SEM-EDS and FTIR studies of in vitro growth of an apatite-like layer on sol–gel glasses

    J Biomed Mater Res

    (1999)
  • M. Vallet-Regı́ et al.

    Influence of P2O5 on the crystallinity of the apatite formed in vitro on surface of bioactive glasses

    J Biomed Mater Res

    (1999)
  • J. Pérez-Pariente et al.

    Surface and chemical study of SiO2·P2O5·CaO·(MgO) bioactive glasses

    Chem Mater

    (2000)
  • M. Vallet-Regı́ et al.

    Evolution of porosity during in vitro hydroxycarbonate apatite growth in sol–gel glasses

    J Biomed Mater Res

    (2000)
There are more references available in the full text version of this article.

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