Synthesis and synchrotron characterisation of novel dual-template of hydroxyapatite scaffolds with controlled size porous distribution
Introduction
In the last few years, many studies have reported the development of new calcium phosphate scaffold types with random or ordered porosity [1], [2], specifically for in-situ gradual release mechanisms of therapeutic anticancer, antibacterial and anti-inflammatory substances [3], [4]. Sophisticated methods able to combine different templates, two or three casts of different features, are grouped to obtain a single unified and consolidated template to achieve hierarchical porosity [5], [6]. Despite being efficient in obtaining mesoporous () and/or macroporous () [7], some of the methods have important limitations such as polymers with high costs or inorganic silicate templates, which lead to the formation of additional silica phases in porous calcium phosphate.
The purpose of this work is to study the synthesis of hydroxyapatite (HAP) scaffolds using an organic combination of starch/CTAB as porous dual-templates and their characterisation by means of XRD and SEM combined with SAXS/USAXS. Once the starch is able to obtain a macroporous system, CTAB was selected to produce mesoporous on hydroxyapatite by micellar distribution [2].
Section snippets
Hydroxyapatite synthesis and template preparation conditions
The dual-template was prepared as follows: 4 g of commercial cornstarch was added to 100 mL of distilled water, and the mixture was gelatinised at 74° C without agitation. The gelatinised cornstarch was added to a 60 mM CTAB boiling solution at 74 °C.
Hydroxyapatite particles synthesised with pre-nucleation solution of starch/CTAB/Calcium was called HAP-ACC sample. In this sample the hydroxyapatite pre-nucleation solution is prepared by a Ca2+ ion source at 0.167 mol Ca(NO3)24H2O dissolved into starch
Characterisation of hydroxyapatite scaffolds with dual template
Fig. 1a shows the SEM images of starch dried at 100 °C/24 h. It is possible to see the lamellar morphology promoted by the sedimentation of amylose and amylopectin microchains. The results of SAXS data in the high-angle region are shown in Fig. 1b for the dried starch sample at 100 °C/24 h. The two peaks at q(1) max = 2.41(Å−1) and q(2) max = 4.84 (Å−1) with intensity ratios confirmed the lamellar structural organisation of the dried cornstarch reported by [10]. This lamellar
Conclusions
The SEM-FEG results and USAXS data show that the nanoparticles are aggregates with a needle-like morphology. In addition, it was shown that the order of the addition of the calcium and phosphate solutions infer on the final pore size distributions for the samples synthesised in the CTAB medium. As a general conclusion, hierarchical porosity seems to be achieved via the aggregation of the resultant particles, ordered by the combination of CTAB and cornstarch gelatinisation.
Acknowledgements
This work was financial supported by the National Council for Scientific and Technological Development (CNPq) (No. 149437/2010-2). We acknowledge the CMNano-UFS (proposal #0007) infrastructure, as well as the LNLS staff during the SAXS (proposal #10980) and LNNano (proposal #13187) experiments. Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science under Contract No. DE-AC02-06CH11357 and ChemMatCARS Sector 15 under grant number NSF/CHE-0822838.
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