Nano Hydroxyapatite-coated Implants Improve Bone Nanomechanical Properties

To gain a better understanding of the anticancer effects of hydroxyapatite (HAP) nanoparticles in vivo and in vitro, the effects of the interaction of HAP nanoparticles with hepatoma cells were explored. HAP nanoparticles were prepared by homogeneous precipitation and characterized by laser particle analysis and transmission electron microscopy (TEM). HAP nanoparticles were observed to be uniformly distributed, with rod-like shapes and diameters in the range of 42.1–87.1 nm. Overnight attached, suspended, and proliferating Bel-7402 cells were incubated with HAP nanoparticles. Inverted microscopy observation revealed that HAP nanoparticles with a cell membrane showed good adsorption. TEM demonstrated that HAP nanoparticles were present on the surface of cells, continuously taken up by cells through endocytosis, and transported in vesicles close to the nucleus. Fluorescence microscopy showed that the concentrations of intracellular Ca2+ labeled with Fluo-3 calcium fluorescent probe were significantly enhanced. In addition, inverted microscopy observation revealed that suspended cells treated with HAP nanoparticles did not adhere to the culture bottle, resulting in cell death. After the overnight attached cells were treated with HAP nanoparticles for 96 h with increasing doses of HAP nanoparticles, inverted microscopy observation revealed that cell proliferation was slowed and cell-cell adhesion was weakened. Feulgen staining and image analysis indicated that the nuclear DNA content of the cells was markedly reduced, and argyrophilic nucleolar organizer region (AgNOR) staining and image analysis indicated that the number of AgNORs was significantly decreased. Therefore, hepatoma cells brought about the adsorption, uptake, transport and degradation of HAP nanoparticles. In addition, HAP nanoparticles affected hepatoma cells with regard to cell-cell adhesion, cell and extracellular matrix adhesion, and DNA and protein synthesis; thus inhibiting cell proliferation. This understanding of the effects of interaction between HAP nanoparticles and hepatoma cells is useful for further study of the anticancer mechanisms of HAP nanoparticles.

The surface modification of hydroxyapatite (HA) nanoparticles by the ring opening polymerization (ROP) of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) was proposed to prepare the poly(gamma-benzyl-L-glutamate) (PBLG)-grafted HA nanoparticles (PBLG-g-HA) for the first time. HA nanoparticles were firstly treated by 3-aminopropylthriethoxysilane (APS) and then the terminal amino groups of the modified HA particles initiated the ROP of BLG-NCA to obtain PBLG-g-HA. The process was monitored by XPS and FT-IR. The surface grafting amounts of PBLG on HA ranging from 12.1 to 43.1% were characterized by thermal gravimetric analysis (TGA). The powder X-ray diffraction (XRD) analysis confirmed that the ROP only underwent on the surface of HA nanoparticles without changing its bulk properties. The SEM measurement showed that the PBLG-g-HA hybrid could form an interpenetrating net structure in the self-assembly process. The PBLG-g-HA hybrid could maintain higher colloid stability than the pure HA nanoparticles. The in vitro cell cultures suggested the cell adhesion ability of PBLG-g-HA was much higher than that of pure HA.

Green synthesis of hydroxyapatite (HA) nanoparticles was followed using various concentrations of pectin extracted from the culinary banana bract. The effect of pectin concentrations on purity, crystallinity, particle size, and morphology of synthesized HA nanoparticles were studied. The extracted pectin was characterized by proton-1 nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infrared (FT-IR) spectroscopy. FT-IR results revealed that increased concentration (0–0.075 % w/w) of pectin substantially improved the purity level of synthesized HA nanoparticles. In addition, higher concentration of pectin also reduced the crystallinity and size of the synthesized HA nanoparticles, which was confirmed by X-ray diffraction (XRD) and SEM results, respectively. The synthesized HA nanoparticles at increased pectin concentration (HA0.075) evinced high purity, less crystallinity, and discrete uniform shape. Results of TEM images have the credence to reveal the presence of nanosized discrete particles (20–50 nm) with lattice structure of hydroxyapatite.

One of the goals of tissue engineering is to create composites that can mimic the behavior of bone in terms of various properties and lead to faster healing with minimal side effects. In this regard, in the present study, porous nanocomposite scaffolds based on Poly(Xylitol-Dodecanedioic acid) (PXDDA) and polycaprolactone (PCL) were prepared in the presence and absence of hydroxyapatite (HA) nanoparticles (NPs) using a salt leaching method with sodium chloride as porogen particles. The results of microscopic examination showed that the presence of HA NPs significantly increased the porosity of the polymer-based scaffold and contact angle (CA) tests showed that these NPs greatly improved the hydrophilicity of the samples. In addition, element mapping and XRD analyses indicated good dispersion of the HA NPs in the polymer matrix. The FTIR results also showed that the sample containing 70% PXDDA and 30% PCL with HA NPs had the highest hydroxyl, hydrocarbon, and ester linkages. In addition, compression tests and dynamic mechanical analysis (DMA) showed that the inclusion of the NPs weakened the mechanical properties of the nanocomposite produced. In addition, the results of the MTT test showed that the presence of HA NPs in this polymer matrix reduced toxicity and increased cell viability.

This research focused on anti-tumor effect of pEGFP-C1-p53 (p53) gene-loaded hydroxyapatite (HAp) nanoparticles in vitro and in vivo. Four kinds of HAp nanoparticles, spherical HAp nanoparticles (S-HAp, diameter: 50 nm), needle-like HAp nanoparticles (N-HAp, average length: 110 nm and width: 30 nm), rod-like HAp nanoparticles (R-HAp, average length: 100 nm and width: 30 nm), and short-rod-like HAp nanoparticles (SR-HAp, average length: 40 nm and width: 30 nm), were prepared initially. The HAp nanoparticles with or without being modified by PEI (named HAp and HAp-PEI, respectively) have excellent biocompatibility as shown by MTT assay and crystal violet staining tests. Then, the subsequent MTT, Hocehst staining tests, and Western blot showed that the killing effect of p53-loaded HAp-PEI (HAp-PEI-p53) was effective with fair selectivity toward Hep-3B and HuH-7 cells’ cell lines. Moreover, HAp-PEI-p53 could inhibit the tumor growth in vivo, and the mechanism of tumor growth inhibition was verified by the hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, P53 protein immunohistochemistry, and transmission electron microscope of the tumor cell in vivo. We found that HAp-PEI-p53 has good anti-cancer effect in vitro and in vivo, especially for the S-HAp-PEI-p53. Tumor metastasis could be suppressed significantly by the S-HAp-PEI-p53 and N-HAp-PEI-p53 treatments by the in vivo imaging system. All these results lead to the conclusion that the particle sizes of HAp ranging from 100 to 200 nm are appropriate for cancer gene therapy and may be widely used in anti-cancer investigation.

This study aimed to evaluate the in vivo osseointegration of implants with hydrophobic antimicrobial GL13K-peptide coating in rabbit femoral condyles by micro-CT and histological analysis. Six male Japanese Rabbits (4 months old and weighing 2.5 kg each) were included in this study. Twelve implants (3.75 mm wide, 7 mm long) were randomly distributed in two groups, with six implants in the experimental group coated with GL13K peptide and six implants in the control group without surface coating. Each implant in the test and the control group was randomly implanted in the left or right side of femoral condyles. On one side randomly-selected of the femur, each rabbit received a drill that was left without implant as control for the natural healing of bone. After 3 weeks of healing radiographic evaluation of the implant sites was taken. After 6 weeks of healing, rabbits were sacrificed for evaluation of the short-term osseointegration of the dental implants using digital radiography, micro-CT and histology analysis. To perform evaluation of osseointegration, implant location and group was double blinded for surgeon and histology/radiology researcher. Two rabbits died of wound infection in sites with non-coated implants 2 weeks after surgery. Thus, at least four rabbits per group survived after 6 weeks of healing. The wounds healed without suppuration and inflammation. No implant was loose after 6 weeks of healing. Radiography observations showed good osseointegration after 3 and 6 weeks postoperatively, which proved that the tissues followed a natural healing process. Micro-CT reconstruction and analysis showed that there was no statistically significant difference (P > 0.05) in volume of bone around the implant between implants coated with GL13K peptide and implants without coating. Histomorphometric analysis also showed that the mineralized bone area was no statistically different (P > 0.05) between implants coated with GL13K peptide and implants without coating. This study demonstrates that titanium dental implants with an antimicrobial GL13K coating enables in vivo implant osseointegration at similar bone growth rates than gold-standard non-coated dental implants up to 6 weeks of implantation in rabbit femurs.

A novel stereolithography-based three-dimensional (3D) printing technique incorporating hydroxyapatite (HA) nanoparticles into dental photopolymer resin was introduced in this study. The design aimed to address the inadequate mechanical strength of conventional dental photopolymer resins by leveraging the reinforcing properties of HA. The HA concentrations of 0, 1, 3, and 5 wt.% were mixed with the resin to produce four distinct resin-HA (RHA) composites. The composites were evaluated for tensile strength, impact strength, and hardness, wear rate (K), and coefficient of friction (µ). Morphological analysis using scanning electron microscopy (SEM) provided insights into HA distribution and the resulting microstructural changes. The design approach incorporated HA nanoparticles to enhance molecular stiffness and promote a mechanical interlocking effect within the resin matrix. These mechanisms led to significant improvements in the composite's mechanical and tribological properties. The 5 wt.% RHA composite demonstrated the highest tensile strength (66.11 MPa), impact strength (35.2 kJ/m²), and Shore D hardness (79.32). Tribological tests revealed that this composite also exhibited the lowest wear rate and coefficient of friction, correlating with its superior mechanical performance. SEM analysis revealed finer debris and smoother wear tracks in HA-reinforced samples compared to HA-free samples, highlighting the role of HA in improving wear resistance. This study underscores the potential of integrating HA nanoparticles to enhance the performance of 3D-printed dental resins, providing a pathway for developing advanced materials tailored for dental and biomedical applications.

A new phosphorus‐based organic additive (PDA) was designed and successfully synthesized using a three‐component reaction for improvement of the thermal and combustion resistance of polylactic acid (PLA). For compensate for mechanical properties of PLA, hydroxyapatite nanoparticles was modified via in situ surface modification with PDA and was used for preparation of PLA nanocomposites. The structure and morphology as well as thermal, combustion, and mechanical properties of the all PLA systems were investigated. The X‐ray diffraction (XRD) and field‐emission scanning electron microscopy (FE‐SEM) results indicated that the presence of PDA as surface modifier has been necessary for a desirable dispersion of hydroxyapatite (HA) nanoparticles in the PLA matrix. The thermal, combustion, and mechanical properties of the PLA system films were investigated using thermogravimetric analysis (TGA), microscale combustion calorimeter (MCC), and tensile test, respectively. The initial decomposition temperature and char residue of PLA containing 6 mass% of PDA along with 2 mass% HA nanoparticles were increased 20°C and 12% respectively, compared with that of the neat PLA. The peak of heat release rate was decreased from 566 W/g for the neat PLA to 412 W/g for PLA containing 2 mass% of PDA along with 6 mass% HA nanoparticles. By incorporation of only 2 mass% HA nanoparticles and 6 mass% of PDA, the tensile strength was obtained 51 MPa higher than that of the neat PLA.

Stable and single-dispersed hydroxyapatite (HAP) nanoparticles were synthesized with ultrasonic-assisted method. HAP nanoparticles were characterized by dynamic light scattering, XRD (X-ray diffraction) and TEM (Transmission Electron Microscopy). The effect of HAP nanoparticles on the K562 human myelogenous leukemia cell line was investigated by MTT assay and cell count test, and the mechanism was studied through the changes of cell cycle and ultrastructure. The results showed that HAP nanoparticles inhibited the proliferation of K562 cells dramatically in vitro. HAP nanoparticles entered the cytoplasm of K562 cells and the cells were arrested at G2/M phase, thus, the cells died directly.

The change of hydroxyapatite (HAP) nanoparticles in shape and crystal structure after endocytosis into cancer cells was studied. BEL7402 cells were incubated with HAP nanoparticles for 2 hour, 8 hours, 20 hours, respectively. Then, the cells were collected and viewed under a transmission electronic microscope (TEM). Electronic diffraction (ED) attached to TEM was used to detect the properties of the particles. The results show that HAP particles in the cytoplasm can be degraded in cytoplasm. The degradation process is prolonged by more than 20 hours. Thus, it is concluded that HAP nanoparticles would be degraded after kill cells or delivery gene.

Biocompatible high internal phase emulsions (HIPEs) have attracted much attention in food and cosmetics due to their unique properties, such as adjustable viscoelasticity, high nutrient load, and long shelf life. Herein, we report an olive oil-in-water high internal phase Pickering emulsion (HIPE) stabilized solely by bare hydroxyapatite (HA) nanoparticles. Compared with other HIPEs, the HIPEs stabilized by HA nanoparticles could be obtained through a one-step emulsification method without chemical modification or other chemical additives. The increase of HA concentration (≥ 0.5 wt%) resulted in increases in both the storage modulus and loss modulus of the HIPEs, indicating the particle network plays an essential role in the HIPEs gel strength. After increasing the oil phase fraction from 80% to 90%, the viscosity of the HIPEs increased from 8316 to 13855 Pa⋅s (shear rate 0.004 s−1) and exhibited as a pseudoplastic fluid. The effect of oil type on the HIPEs was also investigated. The HA nanoparticles may interact with the olefin and carbonyl groups of olive oil, forming interfacial-active particles to stabilize the HIPEs. This method is universal as it occurs with other natural oils (soybean, sunflower, and fish oil), which may have various applications in food, cosmetics, and functional material fields.

Composite scaffolds based on biodegradable natural polymer and osteoconductive hydroxyapatite (HA) nanoparticles can be promising for a variety of tissue engineering (TE) applications. This study addressed the fabrication of three‐dimensional (3D) porous composite scaffolds composed of HA and chitosan fabricated via thermally induced phase separation and freeze‐drying technique. The scaffolds produced were subsequently characterized in terms of microstructure, porosity, and mechanical property. In vitro degradation and in vitro biological evaluation were also investigated. The scaffolds were highly porous and had interconnected pore structures. The pore sizes ranged from several microns to a few hundred microns. The incorporated HA nanoparticles were well mixed and physically coexisted with chitosan in composite scaffold structures. The addition of 10% (w/w) HA nanoparticles to chitosan enhanced the compressive mechanical properties of composite scaffold compared to pure chitosan scaffold. In vitro degradation results in phosphate buffered saline (PBS) showed slower uptake properties of composite scaffolds. Moreover, the scaffolds showed positive response to mouse fibroblast L929 cells attachment. Overall, the findings suggest that HA/chitosan composite scaffolds could be suitable for TE applications.

Elecrtospinning PTMC/Gt/OA-HA composite fiber scaffolds and the biocompatibility with mandibular condylar chondrocytes

In composites of hydroxyapatite (HA) nanoparticles with a polymer matrix, the aggregation of nanoparticles would induce structural defects. In order to improve the dispersibility of HA nanoparticles in poly(ethylene glycol) dimethacrylate (PEGDMA) matrix and enhance mechanical properties of the HA/PEGDMA composite as potential bone substitute material, surface‐grafted HA nanoparticles with poly(ethylene glycol) monomethacrylate (PEGMA) were prepared, and crosslinked with PEGDMA under UV light to form a composite. The structure of HA‐g‐PEGMA was characterized by X‐ray diffraction (XRD) and thermal gravimetric analysis (TGA). The dispersibility of HA‐g‐PEGMA nanoparticles in poly(PEGDMA) was evaluated by SEM. The mechanical properties of the composites were investigated by compressive test. The dispersibility of HA‐g‐PEGMA nanoparticles in poly(PEGDMA) matrix was better than the bare HA. At a 1 wt % content of loading, the strength of composites increased by 14%, and the modulus increased by 9%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

To study the effect of hydroxyapatite (HAP) nanoparticles on human hepatoma cell line BEL-7402 in vitro. The human hepatoma cell line BEL-7402 was cultured and treated with HAP nanoparticles at various concentrations. Growth suppression was detected with MTT colorimetric assay, cell apoptotic alterations were evaluated by cytochemical staining (Hoechst 33258), transmission electron microscopy (TEM), and flow cytometry (FCM). HAP nanoparticles inhibited the growth of hepatoma cells in a dose-dependent manner, with IC(50) values of 29.30 mg/L. Treated with 50-200 mg/L HAP nanoparticles for 48 h, BEL-7402 cells apoptosis with nuclear chromatin condensation and fragmentation as well as cell shrinkage and the formation of apoptotic bodies were observed under cytochemical staining and transmission electron microscopy. FCM analysis showed hypodiploid peaks on histogram, the apoptotic rates at the concentrations of 50, 75, 100, 150 and 200 mg/L of HAP nanoparticles were 20.35+/-2.23 %, 25.35+/-1.92 %, 29.34+/-4.61 %, 44.92+/-3.78 % and 53.64+/-3.49 %, respectively, which were all significantly higher than that of control group 2.23+/-0.14 %. There was a significant correlation between HAP nanoparticle concentration and apoptotic rate (r=0.994, P<0.01). HAP nanoparticles not only inhibit proliferation but also induce apoptosis of human hepatoma cell line BEL-7402 in vitro.