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Hydroxyapatite coatings are of great importance in the biological and biomedical coatings fields, especially in the current era of nanotechnology and bioapplications. With a bonelike structure that promotes osseointegration, hydroxyapatite coating can be applied to otherwise bioinactive implants to make their surface bioactive, thus achieving faster healing and recovery. In addition to applications in orthopedic and dental implants, this coating can also be used in drug delivery. Hydroxyapatite Coatings for Biomedical Applications explores developments in the processing and property characterization and applications of hydroxyapatite to provide timely information for active researchers and newcomers alike. In eight carefully reviewed chapters, hydroxyapatite experts from the United States, Japan, Singapore, and China present the latest on topics ranging from deposition processes to biomedical applications in implants and drug delivery. This book discusses: Magnetron sputtering and electrochemical deposition The modification of hydroxyapatite properties by sol–gel deposition to incorporate other elements found in natural bones, such as zinc, magnesium, and fluorine The use of pure hydroxyapatite in drug delivery applications The growth or self-assembly of hydroxyapatite on shape memory alloy Hydroxyapatite composite coatings—with carbon nanotubes, titanium dioxide (TiO2), and others—on the titanium alloy Offering valuable insights and a wealth of data, including numerous tables and figures, this is a rich source of information for research on hydroxyapatite coatings. Each chapter also covers material that provides an accessible stepping stone for those who are new to the field.

Nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) is required for the conversion of extracellular ATP into inorganic pyrophosphate (PP.sub.i ), a recognised inhibitor of hydroxyapatite (HA) crystal formation. A detailed phenotypic assessment of a mouse model lacking NPP1 (Enpp1.sup.-/-) was completed to determine the role of NPP1 in skeletal and soft tissue mineralization in juvenile and adult mice. Histopathological assessment of Enpp1.sup.-/- mice at 22 weeks of age revealed calcification in the aorta and kidney and ectopic cartilage formation in the joints and spine. Radiographic assessment of the hind-limb showed hyper-mineralization in the talocrural joint and hypo-mineralization in the femur and tibia. MicroCT analysis of the tibia and femur disclosed altered trabecular architecture and bone geometry at 6 and 22 weeks of age in Enpp1.sup.-/- mice. Trabecular number, trabecular bone volume, structure model index, trabecular and cortical thickness were all significantly reduced in tibiae and femurs from Enpp1.sup.-/- mice (P<0.05). Bone stiffness as determined by 3-point bending was significantly reduced in Enpp1.sup.-/- tibiae and femurs from 22-week-old mice (P<0.05). Circulating phosphate and calcium levels were reduced (P<0.05) in the Enpp1.sup.-/- null mice. Plasma levels of osteocalcin were significantly decreased at 6 weeks of age (P<0.05) in Enpp1.sup.-/- mice, with no differences noted at 22 weeks of age. Plasma levels of CTx (Ratlaps[TM]) and the phosphaturic hormone FGF-23 were significantly increased in the Enpp1.sup.-/- mice at 22 weeks of age (P<0.05). Fgf-23 messenger RNA expression in cavarial osteoblasts was increased 12-fold in Enpp1.sup.-/- mice compared to controls. These results indicate that Enpp1.sup.-/- mice are characterized by severe disruption to the architecture and mineralization of long-bones, dysregulation of calcium/phosphate homeostasis and changes in Fgf-23 expression. We conclude that NPP1 is essential for normal bone development and control of physiological bone mineralization.

About 80% of wastewater is discarded into the environment without any treatment. In this research work, the metal hydroxyapatite nanoparticles had been synthesized by a wet chemical approach and applied in water treatment applications by using them as adsorbents for the removal of Red 3R dye from an aqueous solution. The obtained products had been characterized by FTIR spectroscopic technique to confirm the synthesis of respective products by ensuring the presence of phosphate and hydroxyl functional groups. Batch experiments were performed and all effective parameters were optimized and their optimized values were 21 mg/g achieved at pH 7.0, adsorbent dose 0.05 g, initial dye concentration 75 mg/L, and contact time 75 min using metal hydroxyapatite nanoparticles. Moreover, the effect of surfactants and electrolytes was also studied. The Red 3R dye adsorption process was explained by the Langmuir isotherm this type of behavior showed the formation of a monolayer of dye molecules on the adsorbent surface and pseudo-second-order kinetic model. The thermodynamic parameters indicated that Red 3R dye adsorption was exothermic and spontaneous. Given the promising adsorption efficiency of metal hydroxyapatite nanoparticles, they might be used as an alternative class of adsorbents for the adsorption of dyes from industrial effluents.

To improve the regenerative performance of nano-hydroxyapatite/coralline (nHA/coral) block grafting in a canine mandibular critical-size defect model, nHA/coral blocks were coated with recombinant human vascular endothelial growth factor(165) (rhVEGF) via physical adsorption (3 μg rhVEGF165 per nHA/coral block). After the nHA/coral blocks and VEGF/nHA/coral blocks were randomly implanted into the mandibular box-shaped defects in a split-mouth design, the healing process was evaluated by histological observation and histomorphometric and immunohistological analyses. The histological evaluations revealed the ingrowth of newly formed blood vessels and bone at the periphery and cores of the blocks in both groups at both 3 and 8 weeks postsurgery, respectively. In the histomorphometric analysis, the VEGF/nHA/coral group exhibited a larger quantity of new bone formation at 3 and 8 weeks postsurgery. The percentages of newly formed bone within the entire blocks in the VEGF/nHA/coral group were 27.3% ± 8.1% and 39.3% ± 12.8% at 3 weeks and 8 weeks, respectively, and these values were slightly greater than those of the nHA/coral group (21.7% ± 3.0% and 32.6% ± 10.3%, respectively), but the differences were not significant (P>0.05). The immunohistological evaluations revealed that the neovascular density in the VEGF/nHA/coral group (146 ± 32.9 vessel/mm(2)) was much greater than that in the nHA/coral group (105 ± 51.8 vessel/mm(2)) at the 3-week time point (P<0.05), but no significant difference was observed at the 8-week time point (341 ± 86.1 and 269 ± 50.7 vessel/mm(2), respectively, P>0.05). The present study indicated that nHA/coral blocks might be optimal scaffolds for block grafting in critical-size mandibular defects and that additional VEGF coating via physical adsorption can promote angiogenesis in the early stage of bone healing, which suggests that prevascularized nHA/coral blocks have significant potential as a bioactive material for bone regeneration in large-scale alveolar defects.

A major goal in materials science is to develop bioinspired functional materials based on the precise control of molecular building blocks across length scales. Here we report a protein-mediated mineralization process that takes advantage of disorder–order interplay using elastin-like recombinamers to program organic–inorganic interactions into hierarchically ordered mineralized structures. The materials comprise elongated apatite nanocrystals that are aligned and organized into microscopic prisms, which grow together into spherulite-like structures hundreds of micrometers in diameter that come together to fill macroscopic areas. The structures can be grown over large uneven surfaces and native tissues as acid-resistant membranes or coatings with tuneable hierarchy, stiffness, and hardness. Our study represents a potential strategy for complex materials design that may open opportunities for hard tissue repair and provide insights into the role of molecular disorder in human physiology and pathology. There is evidence that disordered proteins play a role in the mineralization process. Here, the authors report on the development of elastin-like recombinant protein membranes using disordered-ordered interplay to investigate and guide mineralization.

Background Dental caries is a recognized worldwide public health problem. Despite being one of the most effective strategies against dental caries, the excessive use of fluorine may result in a potential risk of developing dental fluorosis especially in children under age of six. The purpose of this work is to analyze a fluorine-free toothpaste containing Biomimetic Hydroxyapatite to assess enamel re-mineralizing and repairing properties. Results The study was performed in vitro and in vivo, comparing the hydroxyapatite toothpaste with two others toothpaste containing different fluorine concentrations. The coating effect of the micro-structured Hydroxyapatite nanoparticles reintegrates the enamel with a biomimetic film reproducing the structure and the morphology of the biologic Hydroxyapatite of the enamel. As demonstrated, the coating is due to the deposit of a new layer of apatite, which presents fewer particles than the natural enamel, not based on the chemical—physical changes occurring in fluorinated toothpastes. Moreover, it shows resistance to brushing as a consequence of chemical bonds between the synthetic and natural crystals of the enamel. Conclusions The use of Biomimetic Hydroxyapatite toothpastes has proven to be a valuable prevention measure against dental caries in primary dentition since it prevents the risk of fluorosis.

Compositional tailoring is gaining more attention in the development of advanced biomimetic nanomaterials. In this study, we aimed to prepare advanced multi-substituted hydroxyapatites (ms-HAPs), which show similarity with the inorganic phase of bones and might have therapeutic potential for bone regeneration. Novel nano hydroxyapatites substituted simultaneously with divalent cations: Mg (1.5%), Zn (0.2%), Sr (5% and 10%), and Si (0.2%) as orthosilicate (SiO ) were designed and successfully synthesized for the first time. The ms-HAPs were obtained via a wet-chemistry precipitation route without the use of surfactants, which is a safe and ecologically friendly method. The composition of synthesized materials was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The materials were characterized by X-ray powder diffraction (XRD), FT-IR and FT-Raman spectroscopy, BET measurements and by imaging techniques using high-resolution TEM (HR-TEM), FE-SEM coupled with EDX, and atomic force microscopy (AFM). The ion release was measured in water and in simulated body fluid (SBF). Characterization methods confirmed the presence of the unique phase of pure stoichiometric HAP structure and high compositional purity of all synthesized nanomaterials. The doping elements influenced the crystallite size, the crystallinity, lattice parameters, morphology, particle size and shape, specific surface area, and porosity. Results showed a decrease in both nanoparticle size and crystallinity degree, coupled with an increase in specific surface area of these advanced ms-HAP materials, in comparison with pure stoichiometric HAP. The release of biologically important ions was confirmed in different liquid media, both in static and simulated dynamic conditions. The incorporation of the four substituting elements into the HAP structure is demonstrated. Synthesized nanostructured ms-HAP materials might inherit the in vivo effects of substituting functional elements and properties of hydroxyapatite for bone healing and regeneration. Results revealed a rational tailoring approach for the design of a next generation of bioactive ms-HAPs as promising candidates for bone regeneration.

Augmentation of the face tissues with different products has been practiced in aesthetic medicine for the last decades. During the last 15 years, a lot of different commercial forms of calcium hydroxylapatite (CaHA) for soft-tissue augmentation appeared on the market. Most of them use the similar concentrations of a synthetic form of CaHA with the same size of CaHA particles of 25-45 μm and the carboxymethyl cellulose gel as a carrier. To explain the observed effect of CaHA on the skin, some authors supposed that it induces neocollagenogenesis; however, temporary increase of collagens I and III caused by CaHA cannot explain the long-term improvement of the skin quality. Also, whereas CaHA is mainly injected subcutaneously, there were no reliable investigations of the influence of CaHA on the structure and physiology of subcutaneous white adipose tissue (sWAT). In our opinion, all the main conclusions concerning the collagen-stimulating properties of 30% CaHA (particle size >25 μm) are at least doubtful and based on misunderstanding, which provides a potential for erroneous interpretation in the future. Additionally, there is no clear understanding of the mechanism of elimination of CaHA with large (25-45 μm) particle sizes from the soft tissues. We believe that this mechanism should be the non-fermented hydrolysis and that the speed of such elimination is dependent on the form of particles, the quality of their surface, and on the level of particle conglomeration. Skin aging leads to various microscopic and mesoscopic structural changes within single skin layers as well as in the interactions between these layers. These skin modifications also affect the interactions between the cells and extracellular matrix (ECM). We propose that CaHA may affect formation and secretion of exosomes producing a long-ranged effect on the skin, but it’s strongly related with concentration and size of the CaHA particles.

Hydroxyapatite (HAP) has been the gold standard in the biomedical field due to its composition and similarity to human bone. Properties such as shape, size, morphology, and ionic substitution can be tailored through the use of different synthesis techniques and compounds. Regardless of the ability to determine its physicochemical properties, a conclusion for the correlation with the biological response it is yet to be found. Hence, a special focus on the most desirable properties for an appropriate biological response needs to be addressed. This review provides an overview of the fundamental properties of hydroxyapatite nanoparticles and the characterization of physicochemical properties involved in their biological response and role as a drug delivery system. A summary of the main chemical properties and applications of hydroxyapatite, the advantages of using nanoparticles, and the influence of shape, size, functional group, morphology, and crystalline phase in the biological response is presented. A special emphasis was placed on the analysis of chemical and physical interactions of the nanoparticles and the cargo, which was explained through the use of spectroscopic and physical techniques such as FTIR, Raman, XRD, SEM, DLS, and BET. We discuss the properties tailored for hydroxyapatite nanoparticles for a specific biomolecule based on the compilation of studies performed on proteins, peptides, drugs, and genetic material.

In the last few years, the preservation of cultural heritage has become an important issue globally, due to the fact that artifacts and monuments are continually threatened by degradation. It is thus very important to find adequate consolidators that are capable of saving and maintaining the natural aspect of these objects. This study aims to provide an updated survey of the main nanomaterials used for the conservation and restoration of cultural heritage. In the last few years, besides the classic nanomaterials used in this field, such as metal nanoparticles (copper and silver) and metal oxides (zinc and aluminum), hydroxyapatite and carbonated derivatives, tubular nanomaterials (such as carbon nanotubes) have been used as a potential consolidate material of cultural heritage. Tubular nanomaterials have attracted attention for use in different fields due to their structures, as well as their ability to present multiple walls. These nanotubes have the necessary properties in preserving cultural heritage, such as superior mechanical and elastic strength (even higher than steel), high hydrophobicity (with a contact angle up to 140°), optical properties (high photodegradation protection), large specific surface area (from 50 to 1315 m2/g, depending on the number of walls) for absorption of other nanomaterials and relatively good biocompatibility.