Hydroxyapatite Fibers Research Articles

Prediction of properties of silica nanoparticle/hydroxyapatite fiber reinforced Bis-GMA/TEGDMA composites using molecular dynamics

In this study, molecular dynamics simulations have been used to investigate the effects of organic/inorganic components on the properties of silica nanoparticle/hydroxyapatite fiber reinforced Bis-GMA/TEGDMA dental composite materials. Characterization at the atomic scale is highly important for an advancement of the understanding of properties of resin based materials. Various combinations of Bis-GMA/TEGDMA (20–80% by weight) were modelled using molecular dynamics. The silica nanoparticle weight percentage was varied from 0 to 11% and the hydroxyapatite fiber weight percentage was varied from 0 to 12%. It was observed that the radius of gyration, in various blends of resin, lie in the range of 16–17 Å and thus was approximately independent of Bis-GMA/TEGDMA weight percentage. It was found that a small percentage of silica nanoparticle improved the mechanical properties significantly because of an increase in the volumetric hydrogen bonds and polymer chain contraction. As the weight percentage of TEGDMA in dental resin blends was increased from 20 to 80%, the hydrogen bonds per unit volume were found to decrease from 1.3 × 10−3 to 0.3 × 10−3 Å−3. The elastic and shear moduli of dental composites containing varying percentage of hydroxyapatite fibers (0–12%) increased by 8.13 and 10% respectively. In comparison to the hydroxyapatite fibers, the silica nanoparticles provided significant mechanical reinforcement effect. The diffusion coefficient falls approximately by 46%, from 1.15 × 10−11 to 0.62 × 10−11 m2/s with an increase in the silica nanoparticle weight percentage from 0 to 11 %. This indicated a strong dependency on change in chain conformation as well as hydrogen bonds. These findings will be of great importance in improving the understanding of the mechanical and dynamic properties of dental materials at the atomic/nanoscale.

Hydroxyapatite as a Nanomaterial for Advanced Tissue Engineering and Drug Therapy.

Hydroxyapatite (HAp) is a complicated ceramic material that varies between the way it appears in biological systems and how it is synthesized as various calcium phosphates. HAp varies in chemical composition of substituting atoms, crystallinity, grain size and electrical polarization. HAp can form solid to macro-, micro- and nanoporous structures. Also, particulate HAp can have highly porous structure. HAp can be used as coatings for metal implants in thicknesses from hundreds of microns down to hundreds of nanometers. Cotton wool-like HAp fibers can be electrospun compounded with polymers (or without) for tissue engineering (TE) scaffolds. This review describes the features of HAp that may be utilized further in developing novel applications. As a nanomaterial HAp has been applied for drug delivery. The adsorption of proteins and other compounds can be adjusted by modifying HAp composition, electrical polarization and wettability. Of special interest are the bisphosphonates that bind to HAp and thereby can be used to treat bone loss and also couple other drugs to the mineral. A new area for HAp constructs may appear in treating metallosis. HAp coating may function as a scavenger for the ions release from metal implants and thereby inhibit the adverse effects of the ion burden for the body. So far HAp is considered as safe biomaterial but nano HAp may insidiously possess adverse effects especially when ingested by cells and eliciting excess intracellular calcium. Thereby critical approach also for HAp biomaterials is of utmost importance.

Electrophoretic deposition of hydroxyapatite fiber reinforced hydroxyapatite matrix nanocomposite coatings

Two-component suspensions of hydroxyapatite nanoparticles with spherical (S-HA) and fiber (F-HA) morphologies were prepared in isopropanol using triethanolamine (TEA) as the dispersant. In-situ kinetics of deposition and current density were recorded during EPD at 60V from suspensions with different wt% of F-HA and TEA. f factor decreased against TEA concentration in all suspensions except the one-component suspension of F-HA particles. The detachment of particles from single component F-HA deposits did not occur during EPD due to the mechanical interlocking of F-HA particles in their microstructure. F-HA particles reinforced the coatings and prevented from their cracking during drying by bridging mechanism. S-HA particles infiltrated and filled the pores formed by stacking of the F-HA particles in deposit. S-HA particles were also grafted to F-HA particles in TEA-containing suspensions via hydrogen bonding between TEA molecules adsorbed on the particles. The coating deposited from the suspension with 75wt% of F-HA particles had the best corrosion resistance in SBF solution at 37.5°C.

Hydroxyapatite Fibers: A Review of Synthesis Methods

Hydroxyapatite (HA) exhibits excellent biocompatibility, bioactivity, osteoconductivity, non-toxicity and so on, making it a perfect candidate for biomedical applications. However, HA is not qualified to be used in load-bearing sites due to its poor flexural strength and fracture toughness. Design, synthesis and application of fibrous HA is a promising strategy to overcome the inherent brittleness. This review provides a brief description of HA and hydroxyapatite fiber (HAF), then introduces different synthesis methods of HAF and highlights the inherent merits and drawbacks involved in each method. Finally, the future perspectives in this active research area are given. The purpose of this review is to acquaint the reader with this promising new field of biomaterials research and with emphasis on recent techniques to obtain continuous, uniform and long HAF.

Flexible hydroxyapatite fiber precipitated by urea through a hydrothermal route

Flexible hydroxyapatite fiber (HAF) with high crystallinity is hydrothermally fabricated through the precipitation of urea. By the analysis of field emission scanning electron microscopy, fourier transform infrared spectrometry and X-ray diffraction, a comprehensive composition and morphological characterization of the products is established. The optimal initial pH lies in the range of 3·0–4·0 for synthesizing ribbon-like fibers with lengths larger than 200 μm. The variation in hydrothermal temperatures from 160 to 200°C shows little effect on the constitution of the products, which are all carbonated hydroxyapatite. The formation of HAF is through a fractal growth of two splittings. The HAF paper formed by suction filtration suggests that the obtained HAF is flexible. Also, the phase and morphology transformation of the precursor and the thermal stability of calcium (Ca)–phosphorus (P) fibers are investigated. HAF is formed by the precursor of octacalcium phosphate fibers and is more stable than it. Bone mesenchymal stem cell culture studies indicate that HAF has potential biocompatibility.

Fabrication of Hydroxyapatite Nanofiber via Electrospinning as a Carrier for Protein.

Hydroxyapatite (HAp) nanoscale fibers were produced by combining electrospinning and a sol–gel system. The fibers were electrospun from a mixture of polymer-calcium phosphate (CaP) sol, then subjected to heat treatment. XRD, FTIR, SEM and TEM with HRTEM analyses confirmed HAp nanofibers with the average fiber diameters varied from 80 to 110 nm can be produced. The effects of concentrations of CaP sol and thermal treatment on the structure of nanofiber were studied. Decreasing the concentration of sol in the mixture can produce HAp fibers with smaller diameters; while higher concentrations of the sol resulted in HAp ceramic fibers with porous structures. The possibility of using HAp nanofiber particles as a controlled release carrier of protein was examined. The amount of protein adsorbed onto HAp fibers decreased as the concentration of the sol and the temperature of heat treatment increased. The sustained release of Bovine serum albumin (BSA) from HAp nanofiber was observed. The study provides information relevant to the fabrication and bioapplication of ceramic nanofiber.

Biomimetic, Osteoconductive Non-mulberry Silk Fiber Reinforced Tricomposite Scaffolds for Bone Tissue Engineering.

Composite biomaterials as artificial bone graft materials are pushing the present frontiers of bioengineering. In this study, a biomimetic, osteoconductive tricomposite scaffold made of hydroxyapatite (HA) embedded in non-mulberry Antheraea assama (A. assama) silk fibroin fibers and its fibroin solution is explored for its osteogenic potential. Scaffolds were physico-chemically characterized for morphology, porosity, secondary structure conformation, water retention ability, biodegradability, and mechanical property. The results revealed a ∼5-fold increase in scaffold compressive modulus on addition of HA and silk fibers to liquid silk as compared to pure silk scaffolds while maintaining high scaffold porosity (∼90%) with slower degradation rates. X-ray diffraction (XRD) results confirmed deposition of HA crystals on composite scaffolds. Furthermore, the crystallite size of HA within scaffolds was strongly regulated by the intrinsic physical cues of silk fibroin. Fourier transform infrared (FTIR) spectroscopy studies indicated strong interactions between HA and silk fibroin. The fabricated tricomposite scaffolds supported enhanced cellular viability and function (ALP activity) for both MG63 osteosarcoma and human bone marrow stem cells (hBMSCs) as compared to pure silk scaffolds without fiber or HA addition. In addition, higher expression of osteogenic gene markers such as collagen I (Col-I), osteocalcin (OCN), osteopontin (OPN), and bone sialoprotein (BSP) further substantiated the applicability of HA composite silk scaffolds for bone related applications. Immunostaining studies confirmed localization of Col-I and BSP and were in agreement with real-time gene expression results. These findings demonstrate the osteogenic potential of developed biodegradable tricomposite scaffolds with the added advantage of the affordability of its components as bone graft substitute materials.

Fabrication of Gelatin-Based Electrospun Composite Fibers for Anti-Bacterial Properties and Protein Adsorption.

A major goal of biomimetics is the development of chemical compositions and structures that simulate the extracellular matrix. In this study, gelatin-based electrospun composite fibrous membranes were prepared by electrospinning to generate bone scaffold materials. The gelatin-based multicomponent composite fibers were fabricated using co-electrospinning, and the composite fibers of chitosan (CS), gelatin (Gel), hydroxyapatite (HA), and graphene oxide (GO) were successfully fabricated for multi-function characteristics of biomimetic scaffolds. The effect of component concentration on composite fiber morphology, antibacterial properties, and protein adsorption were investigated. Composite fibers exhibited effective antibacterial activity against Staphylococcus aureus and Escherichia coli. The study observed that the composite fibers have higher adsorption capacities of bovine serum albumin (BSA) at pH 5.32–6.00 than at pH 3.90–4.50 or 7.35. The protein adsorption on the surface of the composite fiber increased as the initial BSA concentration increased. The surface of the composite reached adsorption equilibrium at 20 min. These results have specific applications for the development of bone scaffold materials, and broad implications in the field of tissue engineering.

Hierarchical porous hydroxyapatite fibers with a hollow structure as drug delivery carriers

Uniform hierarchical porous hydroxyapatite fibers with a hollow structure were fabricated using a facile ion exchange approach. The bioglass fibers were prepared at 600°C in the air as hard template after the composite fibers were fabricated as precursor with electrospinning method. The bioglass fibers used as hard template were immersed in an aqueous phosphate solution of 0.02M for ion exchange at 37°C. After 7 days or longer, the bioglass fibers were converted to hierarchical porous hydroxyapatite fibers with a hollow structure. The formation process was investigated and the mechanism of formation of the hollow structure was proposed. The hierarchical porous hydroxyapatite fibers with a hollow structure exhibited good drug control release properties. The study presents a new way for the fabrication of hierarchical porous ceramics fibers with a hollow structure and shows the novel fibers have potential application to treatment of bone defect repair.

Synthesis of Micro and Nano-Sized Hydroxyapatite Fibers Through the Microwave Assisted Hydrothermal Method

Synthesis of Micro and Nano-Sized Hydroxyapatite Fibers Through the Microwave Assisted Hydrothermal Method

Rapid production of bioactive hydroxyapatite fibers via electroblowing

Submicron hydroxyapatite fibers were fabricated by electroblowing followed by annealing. Solutions of Ca(NO3)2∙4H2O, triethyl phosphate and polyvinylpyrrolidone dissolved in ethanol and water were used for the electroblowing. The annealed membranes consisted of randomly oriented fibers characterized as hydroxyapatite by X-ray diffraction. Solution blow spinning of hydroxyapatite was also attempted, but the resulting fiber membranes incorporated large beads and were overall of poor quality compared to the electroblown fibers. With electroblowing the hydroxyapatite fibers were prepared at a fast rate of 1.38g/h, a significant improvement over the production rate obtainable in conventional needle electrospinning. In simulated body fluid (SBF) a continuous apatite layer was found to form around the hydroxyapatite fibers in just six hours suggesting high bioactivity. SBF immersion up to 7days led to an increase in densification of the apatite layer and further increase in its thickness. The fibers can thus be considered promising for bone scaffold applications.

Rapid Hydrothermal Synthesis of Submillimeter Ultralong Flexible Hydroxyapatite Fiber Using Different pH Regulators

Hydroxyapatite fiber (HAF) was fabricated via a one-step hydrothermal route by using urea (CA), acetamide (AA) and propanamide (PA) as pH regulators, respectively, and the reaction time was only 0.5 h. The HAF synthesized by CA as the pH regulator was agglomerated with irregular morphology, while using AA or PA as the pH regulator, the HAF was composed of well-dispersed fibers with lengths larger than 200 μm. Two different morphologies form mainly due to the different hydrolysis rates of the pH regulators. Most of the fibers synthesized by the three pH regulators showed curving appearance, implying their outstanding flexibility. The technique in this paper allows the rapid formation of flexible HAF and may have wider applications in the restorations and reinforcement composites.

Effect of Surfactants on the Morphology of Hydroxyapatite Fibers

Effect of Surfactants on the Morphology of Hydroxyapatite Fibers

Osteoclasts in the interface with electrospun hydroxyapatite

Electrospinning is a method to produce lightweight, resorbable and bioinspired scaffolds for tissue engineering. Here we investigated the influence of electrospun hydroxyapatite fibers (HA) on macrophages and osteoclasts. A mouse macrophage cell line (RAW 264.7) and human bone marrow derived primary osteoclasts (hOC) were cultured with electrospun HA fibers embedded in Matrigel. Cell morphology and the secretion of pro-inflammatory cytokines (IL-6 and TNF-α) were analyzed using macrophages. Both fluorescent microscopy and scanning electron microscopy indicated that the cell morphology differed on the various materials (HA fibers on Matrigel, pure Matrigel and a glass control). Control macrophages were activated with bacterial lipopolysaccharide (LPS) but electrospun HA did not provoke an inflammatory response. Cytokine secretion detected with enzyme-linked immunosorbent assay (ELISA) also supported this observation. LPS, but not HA fibers, stimulated TNF-α and IL-6 secretion by macrophages at the 2 day time point. After 4 days in culture there was an increasing trend in cytokine secretion in the HA fiber samples. Human bone marrow myeloid precursor cells were able to fuse and differentiate on the fibrous mineral scaffold to form functional multinuclear osteoclasts that were able to resorb the HA nanofibers. This indicates that osteoclasts do not necessarily need a continuous bone surface but osteoclast ruffled border membranes can form a resorption interface with a fibrous mineral scaffold.

Interconnectivity of Bioceramic Scaffolds with Different Porous Structures and Their Fluid Velocity Distribution Analyzed by Micro-CT Computer Modeling

Pore interconnectivity is a key parameter for bone tissue engineering scaffolds, which controls penetration of body fluid with proteins and cells, and tissue ingrowth. The present study investigated the porous characteristics of hydroxyapatite (HA) scaffolds prepared via three processes (HA sphere packing, wax sphere-leaching and HA fiber aggregation) by micro-computed tomography (μCT) from following three procedures: (1) modeling of the porous structure by image reconstruction; (2) analysis of porosity along longitudinal direction; and (3) simulation of fluid flow across the scaffold by finite element analysis (FEA). Image analyses revealed that, the scaffolds prepared by the above two methods featured relatively regular porosity distributions, whereas that by HA fiber aggregation had an irregular distribution. Fluid velocity distribution by FEA suggested that scaffolds prepared by HA sphere packing and wax 72 无 机 材 料 学 报 第 30卷 sphere leaching readily allowed penetration of fluid due to their favorable pore interconnectivity. The fluid velocity vector distribution predicted that circular flows dominated near the pore wall in the scaffold prepared by wax sphere leaching. These circular flows may impede the material exchange between cells attached to the pore wall and the body fluid, which may illustrate that the inferior in vivo osteogenic activity of scaffolds prepared by wax sphere leaching when compared with those produced by HA sphere packing.

Electrospinning of calcium carbonate fibers and their conversion to nanocrystalline hydroxyapatite

Calcium carbonate (CaCO3) fibers were prepared by electrospinning followed by annealing. Solutions consisting of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and polyvinylpyrrolidone (PVP) dissolved in ethanol or 2-methoxyethanol were used for the fiber preparation. By varying the precursor concentrations in the electrospinning solutions CaCO3 fibers with average diameters from 140 to 290nm were obtained. After calcination the fibers were identified as calcite by X-ray diffraction (XRD). The calcination process was studied in detail with high temperature X-ray diffraction (HTXRD) and thermogravimetric analysis (TGA). The initially weak fiber-to-substrate adhesion was improved by adding a strengthening CaCO3 layer by spin or dip coating Ca(NO3)2/PVP precursor solution on the CaCO3 fibers followed by annealing of the gel formed inside the fiber layer. The CaCO3 fibers were converted to nanocrystalline hydroxyapatite (HA) fibers by treatment in a dilute phosphate solution. The resulting hydroxyapatite had a plate-like crystal structure with resemblance to bone mineral. The calcium carbonate and hydroxyapatite fibers are interesting materials for bone scaffolds and bioactive coatings.

Effect of Hydroxyapatite Fiber Material with Autogenous Bone Graft on Vertical Bone Augmentation

Effect of Hydroxyapatite Fiber Material with Autogenous Bone Graft on Vertical Bone Augmentation

Effect of Density of Hydroxyapatite Fiber Material on Bone Regeneration in Vertical Bone Augmentation Model

Effect of Density of Hydroxyapatite Fiber Material on Bone Regeneration in Vertical Bone Augmentation Model

Preparation and characterization of bioactive composites and fibers for dental applications

ObjectivesThe present study was carried out to create composites and fibers using polyurethane (PU) with hydroxyapatite (HA) that could be used for dental applications. MethodsComposites with varying HA concentration were prepared by solution casting technique. Similarly, PU–HA fibers with varying PU hard and soft segments and fixed HA concentration were also prepared. Various characterization techniques, such as, X-ray diffractometry, differential scanning calorimetry, scanning electron microscopy and Fourier transform infrared spectroscopy in conjunction with photo-acoustic sampling cell were employed to study the composites and fibers for changes in their physicochemical properties before and after immersion in artificial saliva at 37°C for up to 5 days. ResultsThe results indicated formation of amorphous apatite layers with maximum amorphicity in composites containing highest amount of HA with 5 days of immersion in artificial saliva. Similarly, fibers with more PU hard segment resulted in better transformation of crystalline HA to its amorphous state with increasing immersion time thus confirming the bioactive nature of the HA–PU fibers. SignificanceConcentrations of HA and PU hard segment along with the duration of immersion in artificial saliva are two major factors involved in the modification of solid-state properties of HA. The amorphous apatite layer on the surface is known to have tendency to bind with living tissues and hence the use of optimum amount of HA and PU hard segment in composites and fibers, respectively could help in the development of novel dental filling material.

A facile hydrothermal method for synthesis of submillimeter-long octacalcium phosphate and hydroxyapatite as drug carriers with sustained release behaviors

A facile hydrothermal method was employed to synthesize submillimeter-long octacalcium phosphate (OCP) and hydroxyapatite (HAp) crystals as drug carriers. After hydrolysis reaction of urea, calcium phosphate fibers grew preferentially along c-axis due to modulation of crystallization by glutamic acid. With increasing addition of urea, OCP and HAp precipitated with decreased values of crystallite size and aspect ratio. It was found that the conversion of OCP to HAp was completed after hydrothermal treatment at 160°C for 6h. The formation of fibrous crystals and adsorption of water-insoluble drugs were accomplished in one-step synthesis process with presence of ibuprofen molecules. The sustained-release behavior of ibuprofen could be described by a Higuchi model. HAp and OCP fibers might be simultaneously used for high-performance reinforcements to improve mechanical properties of composite materials and sustained-release drug carriers to cure postoperative infection of bone replacement.