Abstract
Nanosized hydroxyapatite (HA) is a promising candidate for a substitute for apatite in bone in biomedical applications. Furthermore, due to its excellent bone bioactivity, nanosized strontium-substituted HA (SrHA) has aroused intensive interest. However, the size effects of these nanoparticles on cellular bioactivity should be considered. In this study, nanosized HA and SrHA with different dimensions and crystallization were synthesized by hydrothermal methods. The phase, crystallization and chemical composition were analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), respectively. The morphology was observed under field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The degradation behaviors of the samples were monitored by determining the ions release profile with inductively coupled plasma mass spectrometry (ICP-MS). The releasing behavior of Ca2+ and Sr2+ showed that the degradation rate was proportional to the specific surface area and inversely proportional to crystallization. The in vitro experiment evaluated by MG63 cells showed that SrHA nanorods with a length greater than 100 nm had the best biological performance both in cell proliferation and differentiation (* p < 0.05 compared with HA-1 and SrHA-1; * p < 0.01 compared with HA-2). In addition, HA nanoparticles with a lower aspect ratio had better bioactivity than higher ones (* p < 0.05). This study demonstrated that nanosized HA and SrHA with subtle differences (including dimensions, crystallization, specific surface area, and degradation rate) could affect the cellular growth and thus might have an impact on bone growth in vivo. This work provides a view of the role of nano-HAs as ideal biocompatible materials in future clinical applications.
Highlights
Due to its good biocompatibility, bioactivity, and osteoconductivity with human body constituents, hydroxyapatite (HA, Ca10 (PO4 )6 (OH)2 ), which is the main inorganic constituent of human bones and teeth, has been widely used in biomedical applications, such as tissue engineering systems [1], Nanomaterials 2017, 7, 38; doi:10.3390/nano7020038 www.mdpi.com/journal/nanomaterialsNanomaterials 2017, 7, 38 replacements for bony and periodontal defects [2], bioactive coating on metallic osseous implants [3], and dental materials [4]
Studies have shown that nanosized HA possesses a significant capability of improving osteogenesis-related cell proliferation and differentiation [16,17]
There were no significant differences between HA-1 and HA-2 with respect to the diffraction peaks
Summary
Due to its good biocompatibility, bioactivity, and osteoconductivity with human body constituents, hydroxyapatite (HA, Ca10 (PO4 ) (OH)2 ), which is the main inorganic constituent of human bones and teeth, has been widely used in biomedical applications, such as tissue engineering systems [1], Nanomaterials 2017, 7, 38; doi:10.3390/nano7020038 www.mdpi.com/journal/nanomaterials. Studies have shown that nanosized HA possesses a significant capability of improving osteogenesis-related cell proliferation and differentiation [16,17]. Many studies have proved that Sr enhances the proliferation of osteogenesis-related cells and bone matrix synthesis and reduces the osteoclast activity [22,23,24]. Sr has been shown to stimulate bone formation and decrease bone resorption in both animal studies and clinical trials [25,26]. For these reasons, Sr-substituted HA (SrHA) has attracted considerable interest from researchers and clinicians. It is necessary to research the biological properties of nanosized HA and SrHA with subtle differences in dimensions
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