Abstract
Bacteria are one of the significant causes of infection in the body after scaffold implantation. Effective use of nanotechnology to overcome this problem is an exciting and practical solution. Nanoparticles can cause bacterial degradation by the electrostatic interaction with receptors and cell walls. Simultaneously, the incorporation of antibacterial materials such as zinc and graphene in nanoparticles can further enhance bacterial degradation. In the present study, zinc-doped hydroxyapatite/graphene was synthesized and characterized as a nanocomposite material possessing both antibacterial and bioactive properties for bone tissue engineering. After synthesizing the zinc-doped hydroxyapatite nanoparticles using a mechanochemical process, they were composited with reduced graphene oxide. The nanoparticles and nanocomposite samples were extensively investigated by transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Their antibacterial behaviors against Escherichia coli and Staphylococcus aureus were studied. The antibacterial properties of hydroxyapatite nanoparticles were found to be improved more than 2.7 and 3.4 times after zinc doping and further compositing with graphene, respectively. In vitro cell assessment was investigated by a cell viability test and alkaline phosphatase activity using mesenchymal stem cells, and the results showed that hydroxyapatite nanoparticles in the culture medium, in addition to non-toxicity, led to enhanced proliferation of bone marrow stem cells. Furthermore, zinc doping in combination with graphene significantly increased alkaline phosphatase activity and proliferation of mesenchymal stem cells. The antibacterial activity along with cell biocompatibility/bioactivity of zinc-doped hydroxyapatite/graphene nanocomposite are the highly desirable and suitable biological properties for bone tissue engineering successfully achieved in this work.
Highlights
IntroductionBacterial infections caused by orthopedic surgeries (such as implantation of bone scaffold and artificial joints) can lead to allergies, inflammation, and necrosis of tissues in the implanted area [1,2]
Bacterial infections caused by orthopedic surgeries can lead to allergies, inflammation, and necrosis of tissues in the implanted area [1,2]
The ALP enzyme participates in the process of maturation of osteoblast cells and alkalizes the environment, which results in hydrolyzing the phosphomonoesters to inorganic phosphates [45]
Summary
Bacterial infections caused by orthopedic surgeries (such as implantation of bone scaffold and artificial joints) can lead to allergies, inflammation, and necrosis of tissues in the implanted area [1,2]. Using innovative materials to construct implants or bone scaffolds possessing antibacterial properties together with biocompatibility is an attractive solution to control bacterial infections [4,5]. Due to its osteoinductivity and osteoconductivity properties, HA in scaffolds can accelerate new bone tissue formation [11]. Zn affects mitochondrial anaplerotic reactions by decreasing lactate, and increasing intermediates of the Krebs cycle; these increase citrate accumulation and deposition of bone apatite. Genes related to mitochondrial biogenesis, such as ERRα and PGC-1α, are activated to increase anaplerotic reactions to intermediate replenishment of the Krebs cycle [24]. As a result, it causes compounds such as α-ketoglutarate to have high concentrations during osteogenic differentiation. Citrate catabolism reduction results in enhanced citrate accumulation and deposition, a crucial factor in bone-strengthening [26]
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