Tissue regeneration: A new property of mesoporous materials
Introduction
Bioactive materials play an important role in the development of biomedical technology [1] for tissue regeneration. Since the discovery of Bioglass [2], many studies have been carried out [3], [4], [5] in silica systems detecting the presence of bioactivity in contact with physiological fluids. This property encompasses the ability of a given material to form interfacial bonds with tissues when in contact with physiological fluid involving, always, the formation of a layer of hydroxycarbonoapatite. Although apatite nucleation and crystallization mechanisms are not yet completely understood, the features of both the substrate and the fluids seem to have important influences. Concerning the solution, parameters such as pH, temperature and ionic concentration determine the type of calcium phosphate formed as well as its precipitation rate [6]. On the other hand, the presence of silanol groups and porosity seems to be crucial in the apatite layer formation. In this sense, Li et al. [7] have reported that this layer is formed on silica gels, but not on dense silica glasses or quartz. Moreover, the layer formation is enhanced by the presence of pores larger than 2 nm [6], [7], [8], and a direct relation between pore size and volume and the nucleation rate has been drawn.
Mesoporous silica materials [9], [10], having pore sizes in the range of 2–90 nm and inner surface silanol and siloxane reactive groups, are promising candidates as bioactive materials. Furthermore, these pores form ordered arrangements, with high surface area, leading to biomedical applications as systems for drug delivery [11], [12], [13]. Such application was first demonstrated using MCM-41 charged with ibuprofen [11] and recently introducing amoxicillin in SBA-15 [14] and ibuprofen in MCM-48 [15].
The possibility to combine both properties, bioactivity and controlled drug release, is a very attractive goal that could be dealt with using mesoporous silica due to their intrinsic textural properties, that can induce bioactivity, together with the option of filling the pores with drugs. Therefore, the aim of this work is to study the bioactivity properties of three mesoporous materials, SBA-15, MCM-48, MCM-41, by means of in vitro assays in simulated body fluids, to evaluate their possible application in biomedical engineering for bone regeneration.
Section snippets
Experimental section
The mesoporous materials SBA-15, MCM-48 and MCM-41, were synthesized by sol–gel methods in agreement with previously reported procedures [16], [17], [18]. To perform the bioactivity assays, the three materials were compacted into disks (13 mm in diameter and 2.5 mm in height) by using uniaxial (2.75 MPa) and isostatic pressure (3 MPa). The assessment of in vitro bioactivity was carried out by soaking the disks in simulated body fluid (SBF) [19], which has a composition and ionic concentration
Results and discussion
Small-angle XRD experiments of SBA-15 and MCM-41 show well-resolved patterns with (100), (110) and (200) reflections, characteristics of the hexagonal structure of silica SBA-15 and MCM-41 with spacings of 87 and 37 Å, respectively. The pattern corresponding to MCM-48 can be indexed on the basis of a cubic mesoporous structure (Ia3d symmetry) with spacing of 38 Å. These data are in good agreement with previously reported patterns [16], [18], [24]. TEM study confirms the above
Acknowledgements
Financial support of CICYT, Spain, through research project MAT02-00025 is acknowledged. We also thank A. Rodríguez (Electron Microscopy Center, Complutense University) and F. Conde (C.A.I. X-Ray Diffraction Centre, Complutense University), for valuable technical and professional assistance.
References (26)
- et al.
Eur. J. Pharm. Biopharm.
(2004) - et al.
Solid State Ionics
(2004) - et al.
J. Solid State Chem.
(1995) - et al.
Surface Sci.
(2002) - et al.
J. Biomed. Mater. Res. Symp.
(1971) - et al.
J. Am. Ceram. Soc.
(1995) - et al.
J. Biomed. Mater. Res.
(1999) - et al.
Chem. Mater.
(2000) - et al.
J. Sol–Gel Sci. Technol.
(1996) - et al.
J. Am. Ceram. Soc.
(1992)