Comparative study of hydroxyapatite, fluor-hydroxyapatite and Si-substituted hydroxyapatite nanoparticles on osteogenic, osteoclastic and antibacterial ability

Design and evaluation of 32P-labeled hydroxyapatite nanoparticles for bone tumor therapy

The clinical diagnosis and treatment of malignant bone tumors are still major clinical challenges due to their high incidence are difficulty. Targeted therapies have become a critical approach to treat bone tumors. In recent years, radiopharmaceuticals have been used widely and have shown potent and efficient results in treating bone tumors, among which ³²P and the labeled radiopharmaceuticals play an essential role. In this study, the ³²P-labeled hydroxyapatite (HA) was prepared through chemical synthesis (³²P-Hap) and physical adsorption (³²P-doped-Hap). The in vitro stability of ³²P-labeled HA was analyzed to assess the superiority of the new-found chemical synthesis. The radiolabeling yield and stability of chemical synthesis (97.6 ± 0.5%) were significantly improved compared with physical adsorption (92.7 ± 0.4%). Furthermore, the CT results corroborate that ³²P-Hap (100 μCi) +DOX group has the highest tumor suppression rate and can effectively reduce bone destruction. The results corroborate the effectiveness of the chemical synthesis and validate the application of ³²P-Hap in bone tumors. Therefore, ³²P-Hap (100 μCi) + DOX may be an effective strategy for bone metastasis treatments.

Hydroxyapatite or Fluorapatite—Which Bioceramic Is Better as a Base for the Production of Bone Scaffold?—A Comprehensive Comparative Study

Hydroxyapatite (HAP) is the most common calcium phosphate ceramic that is used in biomedical applications, e.g., as an inorganic component of bone scaffolds. Nevertheless, fluorapatite (FAP) has gained great attention in the area of bone tissue engineering in recent times. The aim of this study was a comprehensive comparative evaluation of the biomedical potential of fabricated HAP- and FAP-based bone scaffolds, to assess which bioceramic is better for regenerative medicine applications. It was demonstrated that both biomaterials had a macroporous microstructure, with interconnected porosity, and were prone to slow and gradual degradation in a physiological environment and in acidified conditions mimicking the osteoclast-mediated bone resorption process. Surprisingly, FAP-based biomaterial revealed a significantly higher degree of biodegradation than biomaterial containing HAP, which indicated its higher bioabsorbability. Importantly, the biomaterials showed a similar level of biocompatibility and osteoconductivity regardless of the bioceramic type. Both scaffolds had the ability to induce apatite formation on their surfaces, proving their bioactive property, that is crucial for good implant osseointegration. In turn, performed biological experiments showed that tested bone scaffolds were non-toxic and their surfaces promoted cell proliferation and osteogenic differentiation. Moreover, the biomaterials did not exert a stimulatory effect on immune cells, since they did not generate excessive amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS), indicating a low risk of inflammatory response after implantation. In conclusion, based on the obtained results, both FAP- and HAP-based scaffolds have an appropriate microstructure and high biocompatibility, being promising biomaterials for bone regeneration applications. However, FAP-based biomaterial has higher bioabsorbability than the HAP-based scaffold, which is a very important property from the clinical point of view, because it enables a progressive replacement of the bone scaffold with newly formed bone tissue.

The Cytokine and Bone Protein Expression by Ellagic Acid-Hydroxyapatite in Bone Remodelling Model

Objective

Ellagic acid, a phenolic compound with anti-inflammatory potential, can be used to accelerate the bone healing process and affect human health, while hydroxyapatite is the most commonly used bone graft material. Using a combination of the two materials results in reduced inflammation and increased osteogenesis. This study aimed to determine the effects of combining ellagic acid and hydroxyapatite in bone marker remodelling by analysing the expression of tumour necrosis factor-α (TNF-α), interleukin 10 (IL-10), bone morphogenetic 4 protein (BMP-4), and osteopontin (OPN).

Methods

Thirty Wistar rats were used in the study. A defect was created in each animal's femur using a low-speed diamond bur. In the control group, the bone was then treated with polyethylene glycol (PEG). In one of the other groups, the bone was treated with hydroxyapatite, and in the other, with ellagic acid-hydroxyapatite. The femur was biopsied 7 days after the procedure and again 14 days after the procedure, and an indirect immunohistochemical (IHC) examination was performed for TNF-α, IL-10, BMP-4, and OPN expression.

Results

The ellagic acid-hydroxyapatite decreased TNF-α expression in the bone tissue after 7 days and again after 14 days (p < 0.05). On the other hand, it increased IL-10, BMP-4, and OPN expression (p < 0.05) during the same time periods.

Conclusion

Ellagic acid-hydroxyapatite plays a role in bone marker remodelling by decreasing the expression of TNF-α and increasing the expression of IL-10, BMP-4, and OPN. This hydroxyapatite combination can therefore be recommended for use as bone graft material.

Hydrothermal Synthesis of Fluorapatite Coatings over Titanium Implants for Enhanced Osseointegration-An In Vivo Study in the Rabbit

This work aims at the development and characterization of fluorapatite coatings, innovatively prepared by the hydrothermal method, aiming for enhanced osseointegration of titanium implants. Fluoride-containing coatings were prepared and characterized by scanning and transmission electron microscopy, Fourier-transform infrared spectroscopy-attenuated total reflectance, and X-ray photoelectron spectroscopy. The biological response was characterized by microtomographic evaluation and histomorphometric analysis upon orthotopic implantation in a translational rabbit experimental model. Physic-chemical analysis revealed the inclusion of fluoride in the apatite lattice with fluorapatite formation, associated with the presence of citrate species. The in vivo biological assessment of coated implants revealed an enhanced bone formation process-with increased bone-to-implant contact and bone volume. The attained enhancement of the osteogenic process may be attributable to the conjoined modulatory activity of selected fluoride and citrate levels within the produced coatings. In this regard, the production of fluorapatite coatings with citrate, through the hydrothermal method, entails a promising approach for enhanced osseointegration in implant dentistry and orthopedic applications.

Electrodeposited Hydroxyapatite-Based Biocoatings: Recent Progress and Future Challenges

Hydroxyapatite has become an important coating material for bioimplants, following the introduction of synthetic HAp in the 1950s. The HAp coatings require controlled surface roughness/porosity, adequate corrosion resistance and need to show favorable tribological behavior. The deposition rate must be sufficiently fast and the coating technique needs to be applied at different scales on substrates having a diverse structure, composition, size, and shape. A detailed overview of dry and wet coating methods is given. The benefits of electrodeposition include controlled thickness and morphology, ability to coat a wide range of component size/shape and ease of industrial processing. Pulsed current and potential techniques have provided denser and more uniform coatings on different metallic materials/implants. The mechanism of HAp electrodeposition is considered and the effect of operational variables on deposit properties is highlighted. The most recent progress in the field is critically reviewed. Developments in mineral substituted and included particle, composite HAp coatings, including those reinforced by metallic, ceramic and polymeric particles; carbon nanotubes, modified graphenes, chitosan, and heparin, are considered in detail. Technical challenges which deserve further research are identified and a forward look in the field of the electrodeposited HAp coatings is taken.