HAP NPs Research Articles

Hybrid scaffolds based on PLGA and silk for bone tissue engineering

Porous silk scaffolds, which are considered to be natural polymers, cannot be used alone because they have a long degradation rate, which makes it difficult for them to be replaced by the surrounding tissue. Scaffolds composed of synthetic polymers, such as PLGA, have a short degradation rate, lack hydrophilicity and their release of toxic by-products makes them difficult to use. The present investigations aimed to study hybrid scaffolds fabricated from PLGA, silk and hydroxyapatite nanoparticles (Hap NPs) for optimized bone tissue engineering. The results from variable-pressure field emission scanning electron microscopy (VP-FE-SEM), equipped with EDS, confirmed that the fabricated scaffolds had a porous architecture, and the location of each component present in the scaffolds was examined. Contact angle measurements confirmed that the introduction of silk and HAp NPs helped to change the hydrophobic nature of PLGA to hydrophilic, which is the main constraint for PLGA used as a biomaterial. Thermo-gravimetric analysis (TGA) and FT-IR spectroscopy confirmed thermal decomposition and different vibrations caused in functional groups of compounds used to fabricate the scaffolds, which reflected improvement in their mechanical properties. After culturing osteoblasts for 1, 7 and 14 days in the presence of scaffolds, their viability was checked by MTT assay. The fluorescent microscopy results revealed that the introduction of silk and HAp NPs had a favourable impact on the infiltration of osteoblasts. In vivo experiments were conducted by implanting scaffolds in rat calvariae for 4 weeks. Histological examinations and micro-CT scans from these experiments revealed beneficial attributes offered by silk fibroin and HAp NPs to PLGA-based scaffolds for bone induction.

Evaluation of cytotoxic, oxidative stress and genotoxic responses of hydroxyapatite nanoparticles on human blood cells

The present study was designed to investigate genotoxic and cytotoxic effects and oxidative damage of increasing concentrations of nano-hydroxyapatite (5, 10, 20, 50, 75, 100, 150, 300, 500 and 1000 ppm) in primary human blood cell cultures. Cell viability was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] assay and lactate dehydrogenase release, while total antioxidant capacity and total oxidative stress levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by sister chromatid exchange, micronuclei, chromosome aberration assays and 8-oxo-2-deoxyguanosine level as indicators of genotoxicity. The results of [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] and lactate dehydrogenase assays showed that the higher concentrations (150, 300, 500 and 1000 ppm) of hydroxyapatite nanoparticles (HAP NPs) decreased cell viability. HAP NPs led to increases of total oxidative stress (300, 500 and 1000 ppm) levels and decreased total antioxidant capacity (150, 300, 500 and 1000 ppm) levels in cultured human blood cells. On the basis of increasing concentrations, HAP NPs caused significant increases of sister chromatid exchange, micronuclei, chromosome aberration rates and 8-oxo-2-deoxyguanosine levels as compared to untreated culture. In conclusion, the obtained in vitro results showed that HAP NPs had dose-dependent effects on inducing oxidative damage, genotoxicity and cytotoxicity in human blood cells.

Evaluating the antibacterial property of gold-coated hydroxyapatite: A molecular biological approach

Hydroxyapatite nanoparticles (HAP NPs) are one of the widely used biocompatible materials. However, information about the reaction between HAP NPs and microorganisms is insufficient. This paper aims to understand the antibacterial property of a new nanocomposite consisting of gold-coated HAP and alginate polymer (namely, Au-HAP@Alg NPs). To the best of our knowledge, we reported the first information regarding to MIC (25mg/mL), DIZ (no visible zone), and IC50 (0.5mg/mL) of Au-HAP@Alg NPs toward the microorganism Escherichia coli TOP10. The real-time gene expression levels of polA, polB, cyd, mdoG, GAPDH, and 16S rRNA were maintained at stable levels up until conditions of 2.5mg/mL Au-HAP@Alg NPs. The results showed that 16S rRNA can be a good reference under these conditions. The expressions of GAPDH, cyd, and mdoG were inhibited obviously under condition of 10mg/mL of Au-HAP@Alg NPs. Our results indicated that the possible antibacterial mechanism of Au-HAP@Alg was through the interaction with these carbohydrate and cell wall-related genes. This novel biocompatible and antibacterial material can potentially be applied in medical and environmental fields.

Structural properties of silver doped hydroxyapatite and their biocompatibility

The aim of this study was to obtain a novel hydroxyapatite-based material with high biocompatibility. The structural properties of the samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The X-ray diffraction studies revealed the characteristic peaks of hydroxyapatite in each sample. Other phases or impurities were not observed. The scanning electron microscopy observations suggest that the doping components have no influence on the surface morphology of the samples, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O) and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) and X-ray Photoelectron Spectroscopy analyses. Nanocrystalline silver doped HAp stimulated viability and potentiated the activation of murine macrophages.

Hydroxyapatite-doped poly(lactic acid) porous film coating for enhanced bioactivity and corrosion behavior of AZ31 Mg alloy for orthopedic applications

The corrosion behavior of magnesium and its alloys in the electrolytic physiological environment is extremely poor; this imposes a limitation for their use in orthopedic applications. In the present study, the effect of spray coating AZ31 magnesium alloy with membrane films of pristine and hydroxyapatite-doped poly(lactic acid) on corrosion behavior and bioactivity is investigated. Polymer concentration was found to have a strong impact on the pore size of the coating layer. However, addition of HAp NPs distinctly stimulated the precipitation of an apatite-like compound upon soaking the samples in a simulated body fluid (SBF). Magnesium coated samples revealed three orders of magnitude less corrosion compared to the naked samples, which indicates a stable electrochemical corrosion resistance. During a 15 days in-vitro test, pH variation, weight loss, and bending strength were lower for the coated samples (with average values of 8.5%, 7.2% and 10%, respectively) than the control sample (10.5%, 15.5%, and 25%, respectively). Moreover, the coated samples showed good bending strength characteristics. Cytocompatibility studies on MC3T3 cells revealed a continuous increase in cell growth with the coated samples. Overall, the suggested strategy might open a new avenue to widen utilization of Mg alloys as implant materials for orthopedic applications.

Characterization of Magnetic Hydroxyapatite Nanocrystallites and Potential Application for MRI Contrast Agent

In this study, synthetic hydroxyapatite nanoparticles (Hap NPs) were rendered magnetic by treatment with iron ions using a wet-chemical process. The magnetized Hap (mHap) NPs were fabricated by the addition of iron precursor in various ratios of Fe:Ca (XFe/ Ca). The physicochemical properties of mHap NPs were evaluated respectively, by X-ray diffraction (XRD) for the crystal structure, Fourier transform infrared (FTIR) spectroscopy for functional groups detection, Energy-Dispersive X-ray Spectroscopy (EDS) for composition analysis , transmission electron microscopy (TEM) for particle morphology characterization, and superconducting quantum interference device (SQUID) for magnetization property. The size distribution of mHap randomly in rod and needle-like shape was in average 80 to 120 nm. We found that the mHap was the result of the hetero-epitaxial growth of magnetite on the Hap crystallites. The magnetic NPs with sphere shape less than 10 nm in diameters were tightly surrounded on Hap crystallites and possessed superparamagnetic property. The magnetization of all groups of mHap NPs increased with the increasing of XFe/ Ca and with no toxic effect to cultured cells. In brief, mHap NPs demonstrated suitable physicochemical properties and good biocompatibility, suggesting that these NPs have potential applications as new biodegradable MRI contrast agent in medicine. Keywords: Nanoparticles, magnetic, contrast agent, hydroxyapatite, Nanocrystallites, wet-chemical process