Structure of synthetic calcium hydroxyapatite particles modified with pyrophosphoric acid

Synthesis, Characterization, Functionalization and Bio-Applications of Hydroxyapatite Nanomaterials: An Overview

Hydroxyapatite (HA) is similar to natural bone regarding composition, and its structure favors in biomedical applications. Continuous research and progress on HA nanomaterials (HA-NMs) have explored novel fabrication approaches coupled with functionalization and characterization methods. These nanomaterials have a significant role in many biomedical areas like sustained drug and gene delivery, bio-imaging, magnetic resonance, cell separation, and hyperthermia treatment due to their promising biocompatibility. This review highlighted the HA-NMs chemical composition, recent progress in synthesis methods, characterization and surface modification methods, ion-doping, and role in biomedical applications. HA-NMs have a substantial role as drug delivery vehicles, coating material, bone implant, coating, ceramic, and composite materials. Here, we try to summarize an overview of HA-NMs with the provision of future directions.

Nanoadsorbents for water and wastewater remediation

Water has a wide-ranging effect on all aspects of human life, such as health and food. However, the water has often become polluted by the waste of our industrial, agricultural, and day-to-day activities due to the impact of humans. Therefore, there is an urgent need for new technologies to remove the contaminants from water and wastewater. Thence, many ways and techniques have been developed for water and wastewater remediation. Among all the methods of water and wastewater remediation techniques, the adsorption process has gained tremendous importance as a suitable water and wastewater remediation. The application of nanoadsorbent materials is a growing solution to solving this environmental problem. The unique physical and chemical properties of nanoadsorbents enhance their application due to its higher in ranking, status, and quality and beneficial in different fields compared to traditional adsorbents. Recently, numerous studies reported that the nanosorbent materials have a great and quite promising effect on water and wastewater treatment such as carbon tube, polymeric, zeolites, metal and metal oxides nanosorbents. Thus, the aim of this review article is to provide new data on the study and the improvement in this specific field, and to provide a version of the uses, benefits and restrictions of nanosorbents in water and wastewater remediation.

Optical and biological properties of polymer-based nanocomposites with improved dispersion of ceramic nanoparticles

This article reports a new process for creating polymer-based nanocomposites with enhanced dispersion of ceramic nanoparticles without using any surfactants, and the resulted changes in their optical and biological properties. Specifically, dispersion of two different ceramic nanoparticles, that is, hydroxyapatite (nHA) and magnesium oxide (nMgO) nanoparticles, in a model biodegradable polymer, namely poly(lactic-co-glycolic acid) (PLGA), was studied. High-power sonication was integrated with dual asymmetric centrifugal (DAC) mixing to improve dispersion of nanoparticles during solvent casting. The polymer/solvent ratio was optimized to improve nanoparticle dispersion in the multistep processing, including enhancing the efficacy of sonication and DAC mixing and reducing nanoparticle sedimentation during solvent-casting. Microstructural characterization confirmed that this new process improved nanoparticle dispersion in nMgO/PLGA and nHA/PLGA nanocomposites. Improved nanoparticle dispersion increased the optical transparency visually and optical transmission quantitatively for both nHA/PLGA and nMgO/PLGA nanocomposites. Improved dispersion of nanoparticles improved the adhesion of bone marrow derived mesenchymal stem cells (BMSCs) on nHA/PLGA but decreased BMSC viability on nMgO/PLGA. This difference is likely because the chemistry of nHA and nMgO had different effects on BMSCs. This study provided a new process for enhancing dispersion of ceramic nanoparticles in a polymer matrix and revealed the effects of dispersion on optical properties and cell responses, which are valuable for engineering optimal ceramic/polymer nanocomposites for different biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2692-2707, 2018.

Development of self-repair nano-rod scaffold materials for implantation of osteosarcoma affected bone tissue

Nano-hydroxyapatite with a xylitol based co-polymer and a capsaicin loaded scaffold was investigated as a natural antioxidant loaded bone implant material on osteosarcoma cells.

Recent advances in the synthesis, functionalization and biomedical applications of hydroxyapatite: a review

Hydroxyapatite (HA) is a member of the Ca apatite family.

Synthesis of water-dispersible silicon-containing hydroxyapatite nanoparticles with adjustable degradation rates and their applications as pH-responsive drug carriers

An environmentally friendly method was developed to synthesize water-dispersible Si-HAp nanoparticles with adjustable degradation rates, high loading capacities for anticancer drugs, and sustained and pH-dependent drug release properties.

Direct covalent attachment of Mn(iii) salophen complex to the hydroxyapatite-encapsulated γ-Fe2O3 nanocrystallites: an efficient magnetic and reusable catalyst for oxidation of alcohols

In the present work, the highly efficient oxidation of alcohols catalyzed by manganese(iii) salophen acetate, [Mn(salophen)OAc], supported on hydroxyapatite coated magnetite nanoparticles, HAp–Fe₂O₃, is reported.

Functionalized ceramics for biomedical, biotechnological and environmental applications

Surface functionalization has become of paramount importance and is considered a fundamental tool for the development and design of countless devices and engineered systems for key technological areas in biomedical, biotechnological and environmental applications. In this review, surface functionalization strategies for alumina, zirconia, titania, silica, iron oxide and calcium phosphate are presented and discussed. These materials have become particularly important concerning the aforementioned applications, being not only of great academic, but also of steadily increasing human and commercial, interest. In this review, special emphasis is given to their use as biomaterials, biosensors, biological targets, drug delivery systems, implants, chromatographic supports for biomolecule purification and analysis, and adsorbents for toxic substances and pollutants. The objective of this review is to provide a broad picture of the enormous possibilities offered by surface functionalization and to identify particular challenges regarding surface analysis and characterization.

The role of surface charge on the uptake and biocompatibility of hydroxyapatite nanoparticles with osteoblast cells

The objective of this study is to evaluate the effect of hydroxyapatite (HAP) nanoparticles with different surface charges on the cellular uptake behavior and in vitro cell viability and proliferation of MC3T3-E1 cell lines (osteoblast). The nanoparticles' surface charge was varied by surface modification with two carboxylic acids: 12-aminododecanoic acid (positive) and dodecanedioic acid (negative). The untreated HAP nanoparticles and dodecanoic acid modified HAP nanoparticles (neutral) were used as the control. X-ray diffraction (XRD) revealed that surface modifications by the three carboxylic acids did not change the crystal structure of HAP nanoparticles; Fourier transform infrared spectroscopy (FT-IR) confirmed the adsorption and binding of the carboxylic acids on the HAP nanoparticles' surfaces; and zeta potential measurement confirmed that the chemicals successfully modified the surface charge of HAP nanoparticles in water based solution. Transmission electron microscopy (TEM) images showed that positively charged, negatively charged and untreated HAP nanoparticles, with similar size and shape, all penetrated into the cells and cells had more uptake of HAP nanoparticles with positive charge compared to those with negative charge, which might be attributed to the attractive or repulsive interaction between the negatively charged cell membrane and positively/negatively charged HAP nanoparticles. The neutral HAP nanoparticles could not penetrate the cell membrane due to their larger size. MTT assay and LDH assay results indicated that as compared with the polystyrene control, greater cell viability and cell proliferation were measured on MC3T3-E1 cells treated with the three kinds of HAP nanoparticles (neutral, positive, and untreated), among which positively charged HAP nanoparticles showed the strongest improvement for cell viability and cell proliferation. In summary, the surface charge of HAP nanoparticles can be modified to influence the cellular uptake of HAP nanoparticles and the different uptake also influences the behavior of cells. These in vitro results may also provide useful information for investigations of HAP nanoparticle applications in gene delivery and intracellular drug delivery.

Problem of hydroxyapatite dispersion in polymer matrices: a review

This review summarizes recent work on manufacturing biocomposites suitable for bone tissue engineering. There is a great need to engineer multi-phase (i.e. composite) materials that combine the advantages exhibited by each component of the material, with a structure and composition similar to that of natural bone. The discussion concentrates on the preparation of nanocomposites containing hydroxyapatite particles (one of the most widely used bioceramics materials) with polymer matrices. Special attention is paid to the preparation of nanocomposites with individual (non-aggregated) nanoparticles because this is a key problem in nanotechnology industrialization. Controlling the mixing between so two dissimilar phases is a critical challenge in the design of these inorganic-organic systems. Several approaches that may be applied to overcome this problem will be described in this review.

Evaluation of Cu-PPHs as active catalysts for the SCR process to control NOx emissions from heavy duty diesel vehicles

Copper based catalysts supported on mesoporous materials, which were in turn based on a surfactant expanded zirconium phosphate for the formation of silica galleries in the interlayer space, were prepared by the impregnation method. They were then characterised and tested in the selective catalytic reduction of NO with ammonia as active catalysts for the control of the NOx emissions from heavy duty vehicles. Copper catalysts displayed a high catalytic performance, even in the presence of 14% (v/v) of H2O and 100 ppm of SO2. They also displayed improved catalytic behaviour when compared to a CuZSM5 catalyst.

Sorption behavior of Zn(II) ions on synthesized hydroxyapatites

Calcium hydroxyapatite (CaHAP) and barium hydroxyapatite (BaHAP) have been prepared by a wet method from aqueous solutions with cation/P molar ratio of 1.67. The prepared particles were characterized using XRD, IR, TG-DTA and BET-N(2) adsorption measurements. The potential of the synthesized hydroxyapatites to remove Zn(II) from aqueous solutions was investigated in batch reactor under different experimental conditions. Both hydroxyapatites remove Zn(II) from aqueous solutions with an efficiency higher than 98% at initial pH around 6-8. The data reveal that the initial uptake was rapid and equilibrium was established in 20 and 60 min for CaHAP and BaHAP. The sorption process follows the pseudo-first-order kinetic with a rate constant (k(ads)) equals to 1.06x10(-2) and 1.91x10(-2) min(-1) for CaHAP and BaHAP, respectively. Zn(II) removal was quantitatively evaluated using Langmuir isotherm model and the monolayer sorption capacity (Q(max)) shows the values 102.04 and 36.62 mg g(-1) for CaHAP and BaHAP clarifying the high affinity of these novel sorbents for Zn(II) ions. Kinetically, the prepared apatites are feasible sorbents retain Zn(II) ions through a favorable and spontaneous sorption process. The possibility of metal recovery and regeneration of hydroxyapatites were investigated using several eluting agents include hydrochloric acids, double distilled water, calcium chloride, barium hydroxide, and copper chloride. Different desorption levels were obtained with the different adsorbents and the maximum recovery yield was achieved with copper chloride.

Surface modification of hydroxyapatite nanocrystals by grafting polymers containing phosphonic acid groups

A novel approach for the surface modification of hydroxyapatite (HAp) nanocrystals is described by grafting polymerization of vinyl phosphonic acid (VPA) using a redox initiating system in an aqueous media. Fourier transform infrared (FT-IR) and XRD analyses confirmed the modification reaction on HAp surfaces. Inductively coupled plasma mass spectroscopy (ICP MS) showed that the Ca/P molar ratio decreased from 1.67 to 1.36 with increasing the feed VPA amount. Zeta potentials of unmodified HAp and modified HAp in phosphate-buffered saline (PBS) solutions (pH 7.4, ionic strength = 10 mM) were negative and decreased with increasing the amount of grafted PVPA. Transmission electron microscopy (TEM) measurements and time-dependent phase monitoring indicated that the colloidal stability of modified HAp over unmodified HAp in water dramatically increased and tended to exist as single nanocrystals without aggregation.