Gas injection approach for synthesis of hydroxyapatite nanorods via hydrothermal method

https://doi.org/10.1016/j.matchar.2019.110071Get rights and content

Highlights

  • The crystallinity of the hydroxyapatite nanorods was increased.

  • Dimensions of the synthesized powders are in the nanometric range.

  • Gas injection caused the growth rate to increase in all directions.

  • Gas injection increased the elastic modulus and hardness of consolidated samples.

Abstract

Hydroxyapatite nanorods were synthesized with a new strategy by mixing hydrogen (15%) and argon (85%) gas injected into hydrothermal autoclave. Calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions were used as precursors. These materials were mixed together to maintain Ca/P ratio of 1.67. The final solution pH was adjusted with ammonia solution and transferred to the autoclave for hydrothermal process. The temperature and pH were set to 180 o C and 11 respectively. Powder synthesis was carried out once without gas injection, which was 10 h. The powders synthesized at 5, 10, and 15 h by injecting the gas mixture. The synthesized powders were characterized with Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, X-ray diffraction, High-resolution transmission electron microscopy, and Raman spectroscopy. The results showed that use of injected gas increased crystallinity and crystallite size. Also, the use of gas injection has increased the hardness and elastic modulus.

Introduction

Bone and dental tissue is composed primarily of organic collagen and about 60% mineralized matrix. The mineral part consists of nanoscale Hydroxyapatite (HA) crystals [[1], [2], [3]]. HA is one of the most important and most valuable biomaterials on the market and has been widely used in medicine and dentistry for decades [4]. The chemical formula of HA in a stoichiometric state is Ca10(PO4)6(OH)2, in which the molar ratio of calcium to phosphorus is 1.67 [5]. HA crystals vary in size and morphology depending on the age and type of bones [6,7]. Synthetic HA has excellent biocompatibility due to its chemical structure being similar to hard bone tissue and HA implants have excellent integration with surrounding bone owing to its unique bioactivity [[8], [9], [10], [11]].

The applications of synthetic HA ceramics are very extensive including implant coatings [12], dentine tubule infiltration [13], hard tissue scaffolds [14], and as matrices for controlled drug release [15]. However, nanostructured HA has expanded the applications of these materials especially with regard to tissue engineering scaffolds due to the high surface to volume ratio with the degree of osteoconductivity directly related to the specific surface area [16,17]. Nanostructured HA particles can be used as building blocks for damaged enamel and osteoporosis [18]. The crystal size and crystallinity are important factors in implant applications because HA solubility decreases with increasing crystals size and crystallinity [19]. For these reasons, many studies have been carried out with various HA aspects, including rods [20,21], wires [22], ribbons [23], tubes [24,25].

Several methods have so far been reported for the synthesis of HA, including Solid-state reaction [26], sol-gel [27,28], combustion preparation [29], electrochemical deposition [30], precipitation [31,32], hydrolysis [33], multiple emulsion [34], biomimetic deposition [35], sputtering [36] and hydrothermal [[37], [38], [39]]. Common problems for these synthesis methods include agglomeration, long reaction time, uncontrolled particle size and non- stoichiometric products. Despite the plethora of synthesis methods, only a few of these methods provide sufficient morphological control. One of these is the hydrothermal technique, which uses high temperature and high pressure to achieve controlled crystal morphology [40]. So far, many studies have been done to synthesize one-dimensional HA such as ribbons, whiskers, platelets and tubes [[41], [42], [43], [44], [45], [46]] in a hydrothermal method and in some reports, organic modifiers have also been used [47,48]. Of course, this method has many other benefits [49]. In this method, precursors that are soluble in water, such as diammonium phosphate and calcium nitrate [50,51] are used, and the high pressure and temperature conditions lead to obtain the nano-sized hydroxyapatite powders with high crystallinity, which does not require post reaction calcination. The final product is HA nano-particles with accurate chemical stoichiometry and minimal agglomeration [[52], [53], [54]].

As mentioned, crystallinity of hydroxyapatite is one of the most important factors that affects biological properties and improves mechanical properties. Crystallinity increases with increasing time, pressure and hydrothermal temperature. One of the strategies for increasing pressure is the use of gas injection. Using hydrogen and argon mixed gas firstly raises pressure, and secondly, the presence of hydrogen produces hydrogen-rich water [55].

In this study, the mixture of argon and hydrogen gas was used to increase the hydrothermal pressure. This strategy has not been used before and the main purpose of this process is to increase the kinetics of hydrothermal reactions and crystallinity of synthesized powders. In this study, a traditional hydrothermal method and a new gas injection method were used to synthesize powders. First, the properties of synthesized powders were investigated and compared, and then the powders were consolidated and characterized to determine the effect of powder properties on the bulk properties.

Section snippets

Materials and methods

The chemicals used to synthesize powders, including Diammonium hydrogenphosphate ((NH4)2HPO4), Calcium nitrate tetrahydrate (Ca (NO3)2.4H2O), and ammonia solution (25%) were purchased from Sigma Aldrich.

The materials used in cell culture include 1) Human Mesenchymal Stem cells (Lonza, PT-2501), 2) DMEM, low glucose (Invitrogen, 11880-028), 3) FBS (Gibco, 10270, lot 41F1633K), 4) l-Glutamine (Gibco, 25030-081), 5) Penicillin-Streptomycin Solution (Sigma, P0781), 6) Tissue Culture Plate, 24 well,

Results and discussion

The analyses were done in two steps. First, the characterization of hydrothermal synthesized powders was performed and in the following, the characteristics of SPS sintered bulk samples were investigated.

Conclusions

The effect of hydrogen and argon mixed gas injection with a ratio of 15 to 85 on the synthesis of hydroxyapatite nanoparticles by hydrothermal method was studied in this research. The results of the XRD and Raman spectroscopy analysis showed that the crystallinity of the hydroxyapatite nanoparticles was increased. Microscopic images showed that the dimensions of the synthesized powders are in the nanometric range. It was also found that gas injection caused the growth rate to increase and

Declaration of competing interest

The authors report no relationships that could be construed as a conflict of interest.

References (66)

  • F. Peng et al.

    In vitro cell performance on hydroxyapatite particles/poly(l-lactic acid) nanofibrous scaffolds with an excellent particle along nanofiber orientation

    Acta Biomater.

    (2011)
  • D. Tsiourvas et al.

    Biomimetic synthesis of ribbon-like hydroxyapatite employing poly (L-arginine)

    Mater Sci Eng C

    (2016)
  • B.B. Chandanshive et al.

    Synthesis of hydroxyapatite nanotubes for biomedical applications

    Mater Sci Eng C

    (2013)
  • Q. Sun et al.

    Facile preparation of hydroxyapatite nanotubes assisted by needle-like calcium carbonate

    Powder Technol.

    (2014)
  • X. Guo et al.

    Effect of calcining temperature on particle size of hydroxyapatite synthesized by solid-state reaction at room temperature

    Adv. Powder Technol.

    (2013)
  • M. Canillas et al.

    Processing of hydroxyapatite obtained by combustion synthesis

    Boletín de La Sociedad Española de Cerámica Y Vidrio

    (2017)
  • A.I. Bucur et al.

    Influence of small concentration addition of tartaric acid on the 220 °C hydrothermal synthesis of hydroxyapatite

    Mater. Charact.

    (2017)
  • H. Nosrati et al.

    Effects of hydrothermal pressure on in situ synthesis of 3D graphene/hydroxyapatite nano structured powders

    Ceram. Int.

    (2019)
  • Y. Zhang et al.

    Synthesis of nanorod and needle-like hydroxyapatite crystal and role of pH adjustment

    J. Cryst. Growth

    (2009)
  • B. Jokić et al.

    Synthesis and characterization of monetite and hydroxyapatite whiskers obtained by a hydrothermal method

    Ceram. Int.

    (2011)
  • F. Mohandes et al.

    Simple morphology-controlled fabrication of hydroxyapatite nanostructures with the aid of new organic modifiers

    Chem. Eng. J.

    (2014)
  • F. Mohandes et al.

    Particle size and shape modification of hydroxyapatite nanostructures synthesized via a complexing agent-assisted route

    Mater Sci Eng C

    (2014)
  • J.B. Liu et al.

    The influence of pH and temperature on the morphology of hydroxyapatite synthesized by hydrothermal method

    Ceram. Int.

    (2003)
  • X.M. Deng et al.

    Preparation and mechanical properties of nanocomposites of poly(d,l-lactide) with Ca-deficient hydroxyapatite nano crystals

    Biomaterials

    (2001)
  • Y. Wang

    Hydrothermal synthesis of hydroxyapatite nanopowders using cationic surfactant as a template

    Mater. Lett.

    (2006)
  • O. Akhavan et al.

    Hydrogen-rich water for green reduction of graphene oxide suspensions

    Int. J. Hydrog. Energy

    (2015)
  • O. Kaygili et al.

    Characterization of Mg-containing hydroxyapatites synthesized by combustion method

    Phys. B Condens. Matter

    (2018)
  • W.P.S.L. Wijesinghe et al.

    Facile synthesis of both needle-like and spherical hydroxyapatite nanoparticles: effect of synthetic temperature and calcination on morphology, crystallite size and crystallinity

    Mater Sci Eng C

    (2014)
  • Z.S. Stojanović et al.

    Hydrothermally processed 1D hydroxyapatite: mechanism of formation and biocompatibility studies

    Mater. Sci. Eng. C Mater. Biol. Appl.

    (2016)
  • S. Baradaran et al.

    Mechanical properties and biomedical application of a nanotube hydroxyapatite-reduced graphene oxide composite

    Carbon

    (2014)
  • H. Nosrati et al.

    In situ synthesis of three dimensional graphene-hydroxyapatite nano powders via hydrothermal process

    Mater. Chem. Phys.

    (2019)
  • N. Méndez-Lozano et al.

    Crystal growth and structural analysis of hydroxyapatite nanofibers synthesized by the hydrothermal microwave-assisted method

    Ceram. Int.

    (2017)
  • R.N. Correia et al.

    Wet synthesis and characterization of modified hydroxyapatite powders

    J. Mater. Sci. Mater. Med.

    (1996)
  • Cited by (36)

    View all citing articles on Scopus
    View full text