Hydrothermal Synthesis and Biocompatibility Study of Highly Crystalline Carbonated Hydroxyapatite Nanorods

Abstract

(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Highly crystalline carbonated hydroxyapatite (CHA) nanorods with different carbonate contents were synthesized by a novel hydrothermal method. The crystallinity and chemical structure of synthesized nanorods were studied by Fourier transform infrared spectroscopy (FTIR), X-ray photo-electronic spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The biocompatibility of synthesized CHA nanorods was evaluated by cell viability and alkaline phosphatase (ALP) activity of MG-63 cell line. The biocompatibility evaluation results show that these CHA nanorods are biologically active apatites and potentially promising bone-substitute biomaterials for orthopedic application.Keywords: Hydroxyapatite; Carbonated hydroxyapatite; Nanorods; Cell viability; Alkaline phosphatase activity; MG-63 cell BackgroundHydroxyapatite (HA) is the main inorganic component of human bone mineral, and the content of carbonate in human bone mineral is about 5-8 wt % [1, 2]. Carbonate ions in carbonated hydroxyapatites (CHA) substitute both the phosphate and hydroxyl sites of the HA structure and each is called A-type CHA and B-type CHA, respectively. Predominantly, the carbonate ions are present as B-type carbonates in natural bone minerals [3]. Synthetic CHAs have been widely used in a variety of biomedical applications including osteoconductive coatings [4][5][6], bone-substitute biomaterials [7], and vehicles for drug delivery [ 8]. Recently, hydoxyapatite nanorods have been prepared by an ethanol-induced method [9], liquid crystals [10], sonochemical synthesis [11], sol-gel method [12], and hydrothermal reaction [13,14]. However, few methods have been reported for the preparation of carbonated hydroxyapatite nanorods with different carbonate contents. Since carbonate ion substitution in the apaptite lattice plays a major role in the biochemistry and physical properties of biological apatites, it is important to develop convenient ways for the synthesis of CHA nanorods with different carbonate contents and understand how various carbonate contents affect the crystal structure and biocompatibility of CHA nanorods. Table 1 Synthesizing materials for preparing HA and CHA nanorods SamplesCaThe hydrothermal method is a typical process which has been widely used in synthesis of inorganic materials for its good repeatability and crystallinity control [15][16][17]. In this study, we developed a hydrothermal process to synthesize carbonated hydroxyapatite nanorods with different carbonate contents, using ethylene diamine tetraacetic aci...

Development of multisubstituted hydroxyapatite nanopowders as biomedical materials for bone tissue engineering applications

“…All CHA calcined powders regardless of the calcination temperature produced bands corresponding to the B‐type CHA at about 870–875, 1410–130, and 1450–1470 cm −1 . For SiCHA‐1 and SiCHA‐2 calcined powders, a missing band of CO 3 at 870–875 cm −1 was observed and only two main bands of CO 3 were found at 1410–1430 and 1450–1470 cm −1 .…”

“…Although, stoichiometric HA, composed of calcium (Ca), phosphates (PO 4 ), and hydroxyl (OH) groups [Ca 10 (PO 4 ) 6 (OH) 2 ], the chemical composition of biological apatites differs from the stoichiometric HA . The biological apatites are uniquely similar in that they all comprise carbonate (CO 3 ) in varying amounts of 2–8 wt %, preferentially substituting the PO 4 site (B‐type) compared with OH (A‐type) ions in the apatite lattice . The composition of CO 3 depends on bone age, site, sex, and health of the individual …”

Is THP‐1 viability affected by the crystallinity of nanostructured carbonated hydroxyapatites?

“…Although the HA cytocompatibility has been well‐established by various studies, changes in its structure can strongly impact the biocompatibility of new biomaterials that must be evaluated in vitro before their in vivo and clinical practice 20,26 to avoid unnecessary tests in animals (ISO 10993‐1)and negative outcomes. An essential aspect of developing new biomaterials is preclinical testing, and in vitro evaluation of single parameters of biocompatibility shall be avoided 26,27 .…”

“…Given these drawbacks, some studies have sought improvements in the characteristics of this compound (i.e., crystallinity and bioabsorption) by providing biomaterials that can mimic natural bone with better clinical results to optimize bone repair 10 . Another alternative is the incorporation of different chemical elements, such as strontium, 3,11 zinc, 7,9,12 carbon, 9,13,14 or changing the particle size, shape, 15‐18 or crystallinity 19,20 …”

“…Nanostructured carbonated hydroxyapatite (cHA) represents an alternative to conventional HA in regenerative medicine due to its biocompatibility, bioactivity, and osteoconductivity 7,10,14,18,20‐22 along with proper tissue absorption 7,13,19,20 . This biomaterial is more similar to the mineral phase of bone than HA 23 due to the presence of carbonate (CO 3 ) −2 in its composition.…”