HAP Surface Research Articles

Strontium-containing mineralized phospholipid coatings improve osseointegration in osteoporotic rats.

Surface treatments play an important role in enhancing the osseointegration of Titanium (Ti) and its alloys. This study introduces a method employing biomimetic hydroxyapatite (Hap) deposition guided by molecularly organized phospholipids, affixed to the metal implant surface. Using the Langmuir-Blodgett technique, phospholipids were deposited onto Ti-screws by using CaCl2 or CaCl2/SrCl2 aqueous solution in the subphase of a Langmuir trough in the target proportion (i.e. 10 and 90 mol% of Sr2+ in relation of Ca2+) followed by immersion in phosphate buffer and in supersaturated simulated body fluid. Coating composition and morphology were evaluated using infrared spectroscopy and scanning electron microscopy, respectively, while contact angle measurements assessed coating wettability and surface energy. Randomized screws were then implanted into the tibias of healthy and osteoporotic female rats (G1: Control-Machined, G2: Hap, G3: HapSr10, G4: HapSr90). Osseointegration, assessed 60 days post-implantation, included reverse torque, fluorochrome area, bone tissue-screw contact area, and linear extent of bone-screw contact. Results, grouped by surface treatment (Machined, Hap, HapSr10, HapSr90), revealed that the deposition of Hap, HapSr10, and HapSr90 resulted in thin and rough coatings composed of hydroxyapatite (Hap) on the screw surface with nanoscale pores. The coatings resulted in increased wettability and surface energy of Ti surfaces. The minerals are chemically similar to natural bone apatite as revealed by FTIR analysis. In vivo analyses indicated higher torque values for strontium-containing surfaces in the osteoporotic group (p = 0.02) and, in the control group superior torque for screw removal on the Hap surface (p = 0.023). Hydroxyapatite-treated surfaces enhance morphology, composition, and reactivity, promoting screw osseointegration in healthy and osteoporotic female rats. The incorporation of strontium into the mineral phase has been proposed to not only stimulate osteoblast activity but also reduce osteoclastic resorption, which may explain the improved outcomes observed here in experimental osteoporotic conditions.

Biological and Physicochemical Analysis of Sr-Doped Hydroxyapatite/Chitosan Composite Layers.

In this work results are presented on the evaluation of HAp, HApSr, HAp_CS, and HApSr_CS layers deposited on Ti substrates regarding L929 cell viability and cytotoxicity as well as antimicrobial activity against Staphylococcus aureus, in connection with their physicochemical properties. The HAp and HApSr layers generated by radio-frequency magnetron sputtering technique were further covered with chitosan by a matrix-assisted pulsed laser evaporation technique. During the plasma depositions, the Ti substrates were heated externally by a home-made oven above 100 °C. The HApSr_CS layers generated on the unpolished Ti substrates at 100 °C and 400 °C showed the highest biocompatibility properties and antimicrobial activity against Staphylococcus aureus. The morphology of the layer surfaces, revealed by scanning electron microscopy, is dependent on substrate temperature and substrate surface roughness. The optically polished surfaces of Ti substrates revealed grain-like and microchannel structure morphologies of the layers deposited at 25 °C substrate temperature and 400 °C, respectively. Chitosan has no major influence on HAp and HApSr layer surface morphologies. X-ray photoelectron spectroscopy indicated the presence of Ca 2p3/2 peak characteristic of the HAp structure even in the case of the HApSr_CS samples generated at a 400 °C substrate temperature. Fourier transform infrared spectroscopy investigations showed shifts in the wavenumber positions of the P-O absorption bands as a function of Sr or chitosan presence in the HAp layers generated at 25, 100, and 400 °C substrate temperatures.

Zn and Ni doped hydroxyapatite: Study of the influence of the type of energy source on the photocatalytic activity and antimicrobial properties

The present work aimed to produce HAp nanoparticles doped with Zn and Ni in order to analyze the incorporation of these elements in the catalytic and antimicrobial properties of HAp. The samples were obtained by the microwave-assisted hydrothermal method in 30 min at 150 °C. XRD and FTIR results showed that HAp was formed without the presence of secondary phases, and Rietveld refinement indicated a reduction in crystallite size after doping. Nanorod-like morphologies were observed by SEM-FEG with reduction in particle size and increase in specific surface area. Furthermore, the hidden gap at 3.26 eV, photoluminescence indicated that there was a predominance of deep defects and XPS showed the presence of dopants on the HAp surface. The catalytic results in the degradation of methylene blue dye indicated that the zinc-doped sample removed 97.85 % under sunlight, 66.81 % under UV light and 70.64 % under ultrasound. After four cycles of reuse under sunlight, good photocatalytic performance was maintained, and inhibition tests indicated that holes and hydroxyls are the active radicals. Antimicrobial activity tests showed that zinc-doped and co-doped samples were efficient in inhibiting Gram-negative bacteria (Escherichia coli). This work brings a promising alternative application for hydroxyapatite in environmental and microbial remediation.

Addressing the issue of surface mechanisms and competitive effects in Cr(VI) reductive-adsorption on tin-hydroxyapatite in the presence of co-ions

Our group recently proposed an innovative sustainable reductant-adsorbent material, tin(II)-hydroxyapatite (Sn/HAP, ca. 10 wt% Sn) for the interfacial Cr(VI) reductive adsorption process. In this study, Cr(VI) removal capacity was evaluated in multi-component solutions containing representative background ions (i.e., CaCl2, Ca(NO3)2, MgSO4, Na2SO4, Fe(NO3)3, AlCl3, Zn(NO3)2, or Mn(NO3)2). Sn/HAP was able to reduce Cr(VI) with complete Cr3+ adsorption on HAP surface, except in the presence of Fe3+ and Al3+ ions. Some metal ions co-existing in solution, such as Fe3+, Al3+, Zn2+, and Mn2+, were also adsorbed on HAP surface. Reuse experiments of the Sn/HAP sample, up to 7 runs, resulted in a total amount of reduced Cr(VI) of ca. 15–18 mg g−1. Fast kinetics of Cr(VI) reductive adsorption at 25 °C in a multi-metal component solution was observed. The pseudo-second order model was in excellent agreement with the experimental kinetic data, leading to a rate constant (k25°C) value of ca. 30 M−1 s−1. The collection of adsorption isotherms of Cr3+ and Fe3+, together with TEM–EDX analysis permitted the unveiling of competitive adsorption phenomena between metal ions. The obtained results demonstrate that Sn/HAP could be an efficient material for the removal of hexavalent chromium in aqueous solutions containing high concentrations of inorganic impurities.

Defect‐induced Synthesis of Highly Dispersed Hydroxyapatite‐Supported Vanadium Oxide for the Oxidative Dehydrogenation of Cyclohexane

AbstractHydroxyapatite (HAP) contains abundant defect sites and easily releases hydroxyl groups to produce new vacancies under calcination at high temperature. The highly dispersed VOx/HAP catalyst was prepared by an impregnation method using these defects as inducement. VOx species with different structures were analysed by XRD, XPS, H2‐TPR, Raman and UV–vis spectroscopy. At low calcination temperatures (500 °C and 600 °C), the V species are mainly V2O5 crystals. At high calcination temperatures (above 700 °C), VOx on the HAP surface fills these defect sites and strongly interacts with HAP to form Ca−O−V or P−O−V bands. These scattered defects improved the dispersion of V species. These highly dispersed VOx/HAP catalysts were used for oxidative dehydrogenation (ODH) of cyclohexane to cyclohexene. The highly dispersed VOx/HAP catalyst showed a high selectivity for cyclohexene, and the selectivity reached 48.2 % when the conversion of cyclohexane was 13.1 % at 410 °C.

Improving interface interactions in PLA/HAP composites with hydroxyapatite surface modification

ABSTRACT PLA/HAP composites have attracted significant attention in material science, especially in the field of biomaterials. However, these composites have suffered from unfavorable interface interactions between PLA and HAP interfaces, which limits the applications . In this study, we aimed to improve the interface interactions of PLA/HAP composite by modifying the HAP surface. For this purpose, HAP particles were functionalized with three different silane modifying agents, including (3-Aminopropyl)trimethoxysilane (AMMO), (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and (3-triethoxysilyl)propylsuccinic anhydride (GF-20). The obtained modified HAP (m-HAP) were used to prepare PLA/m-HAP. Interface interactions of composites were characterized by Fourier transform infrared spectrophotometer (FT-IR) and differential scanning calorimetry (DSC). In addition, Vickers hardness tests were performed to reveal the effect of silane modifying agents on hardness before and after the in vitro degradation test.

Topotactic, Vapor-Phase, In Situ Monitored Formation of Ultrathin, Phase-Pure 2D-on-3D Halide Perovskite Surfaces.

Two-dimensional (2D) halide perovskites, HaPs, can provide chemical stability to three-dimensional (3D) HaP surfaces, protecting them from exposure to ambient species and from reacting with contacting layers. Both actions occur with 2D HaPs, with the general stoichiometry R2PbI4 (R: long or bulky organic amine) covering the 3D ones. Adding such covering films can also boost power conversion efficiencies of photovoltaic cells by passivating surface/interface trap states. For maximum benefit, we need conformal ultrathin and phase-pure (n = 1) 2D layers to enable efficient tunneling of photogenerated charge carriers through the 2D film barrier. Conformal coverage of ultrathin (<10 nm) R2PbI4 layers on 3D perovskites is challenging with spin coating; even more so is its upscaling for larger-area devices. We report on vapor-phase cation exchange of the 3D surface with the R2PbI4 molecules and real-time in situ growth monitoring by photoluminescence (PL) to determine limits for forming ultrathin 2D layers. We characterize the 2D growth stages, following the changing PL intensity-time profiles, by combining structural, optical, morphological, and compositional characterizations. Moreover, from quantitative X-ray photoelectron spectroscopy (XPS) analysis on 2D/3D bilayer films, we estimate the smallest width of a 2D cover that we can grow to be <5 nm, roughly the limit for efficient tunneling through a (semi)conjugated organic barrier. We also find that, besides protecting the 3D against ambient humidity-induced degradation, the ultrathin 2D-on-3D film also aids self-repair following photodamage.

How hydroxyapatite governs surface Cu(II) and Fe(III) structuring: Effects in the N2O decomposition under highly oxidant atmosphere

In this work, we present copper- or iron-loaded hydroxyapatite samples as active catalysts in the direct N2O decomposition reaction. Hydroxyapatite, functionalized with increasing amount of Cu(II) or Fe(III) species (from 3 to 9 wt%), were characterized by XRPD, DR UV-Vis, XPS, CO-adsorption followed by FT-IR, TEM-EDS, and tested in the N2O decomposition. Stability tests (550 °C, 72 h), reusability, resistance to sulfur (50 ppm) and to alkali (ca. 1 wt% of K or Ba) completed the study of the catalyst performances. Copper catalysts showed superior performances than iron counterparts. The structural evolution of the metal species with loading plays a critical role in the catalytic behavior. In the case of Fe-catalysts, a gradual Fe-coverage of HAP surface resulted in an increasing trend in the activity. Conversely, for Cu-catalysts high activity and selectivity were associated with a moderate structuration of Cu(II) in the form of nanoparticles with size of around 1.6 nm.

The effect of functionalized hydroxyapatite on the thermal degradation behaviour and flammability of polyoxymethylene copolymer

In this work, the effect of functionalized hydroxyapatite (HAp-g-PEG) on the thermal degradation behaviour and flammability of polyoxymethylene copolymer (POM_C) was investigated. Organic–inorganic hybrid additive, obtained by grafting of poly(ethylene glycol) on HAp surface using 1,6-hexamethylene diisocyanate as a linker, has been incorporated into POM matrix through an extrusion process. TG analyses show that the incorporation of HAp-g-PEG into POM_C leads to the significant improvement in the thermal stability of the polymer matrix. This is an important finding as POM, being an engineering polymer, suffers from a relatively low thermal stability that limits processing options to develop advanced composite materials. Based on TG results kinetic parameters of the thermal degradation process using Friedman isoconversional method and nonlinear regression method have been calculated; an increase in activation energy of POM degradation process after incorporation of HAp-g-PEG has been found. Thermoanalytical analyses (TG-FTIR/MS) show that incorporation of HAp-g-PEG has no significant effect on the composition of the thermal degradation products. Flammability investigations showed small effect of HAp-g-PEG 600 on the burning time and rate, however, there was a significant reduction in the amount of dripping during the material’s burning process.

Post-substitution of magnesium at CaI of nano-hydroxyapatite surface for highly efficient and selective removal of radioactive 90Sr from groundwater

We have modified the ion-exchange affinity of nano-Hydroxyapatite (Ca5(PO4)3OH, HAP) surface for the rapid and selective adsorption of 90Sr from groundwater. The modification was achieved by the post-substitution of cations (Na+, Mg2+, Cu2+, Ba2+, Fe3+, and Al3+) for parent Ca2+ within surface structure of HAP. The diffraction patterns of modified HAP showed a slight shift of the (002) peak between 25° and 27° 2θ depending the ionic radius of the substituted cation. Magnesium substituted HAP, Mg-HAP, exhibited the highest removal efficiency (>95%) for 10 ppm of Sr2+, which is attributable to the higher ion-exchange affinity of substituted Mg2+ than parent Ca2+ toward Sr2+. The results of various analyses revealed that Mg substitution dominantly occurred at the CaI site of HAP, which enabled the Mg-HAP to adsorb Sr2+ at both of CaI and CaII sites whereas bare HAP could adsorb Sr2+ mainly at CaII site. Adsorption isotherms and the kinetics of Mg-HAP for Sr2+ were evaluated using a bi-Langmuir isotherm and a pseudo-second-order kinetic model, which demonstrated the Mg-HAP exhibited the highest adsorption capacity (64.69 mg/g) and fastest adsorption kinetics (0.161–1.714 g/(mg·min)) than previously modified HAPs. In the presence of competing cations at circumneutral pHs, the enhanced performance of the Mg-HAP led to a greater than 97% reduction of 90Sr (initial radioactivity = 9500 Bq/L) within 1 h. The distribution coefficient of Mg-HAP was 1.3–6.6 × 103 mL/g while that of bare HAP was 1.2–6.6 × 102 mL/g. The findings in the present study highlight that the ion-exchange affinity of CaI and CaII sites on HAP surface plays a key-role in 90Sr uptake. The proposed modification method can simply increase the affinity of HAP surface, therefore, this work can further improve the deployment of an in situ remediation technology for 90Sr contaminated groundwater, i.e., Mg-HAP-based permeable reactive barrier.

A Comparative Study on Hexavalent Chromium Adsorption onto Chitosan and Chitosan-Based Composites.

Chitosan (Cs)-based composites were developed by incorporating silica (Cs–Si), and both silica and hydroxyapatite (Cs–Si–Hap), comparatively tested to sequester hexavalent (Cr(VI)) ions from water. XRD and FT-IR data affirmed the formation of Cs–Si and Cs–Si–Hap composite. Morphological images exhibits homogeneous Cs–Si surface, decorated with SiO2 nanoparticles, while the Cs–Si–Hap surface was non-homogeneous with microstructures, having SiO2 and Hap nanoparticles. Thermal analysis data revealed excellent thermal stability of the developed composites. Significant influence of pH, adsorbent dose, contact time, temperature, and coexisting anions on Cr(VI) adsorption onto composites was observed. Maximum Cr(VI) uptakes on Cs and developed composites were observed at pH 3. The equilibration time for Cr(VI) adsorption on Cs–Si–Hap was 10 min, comparatively better than Cs and Cs–Si. The adsorption data was fitted to pseudo-second-order kinetic and Langmuir isotherm models with respective maximum monolayer adsorption capacities (qm) of 55.5, 64.4, and 212.8 mg/g for Cs, Cs–Si, and Cs–Si–Hap. Regeneration studies showed that composites could be used for three consecutive cycles without losing their adsorption potential.

Hydroxyapatite/nifuroxazide conjugate: Characterization, drug release and antimicrobial activity

Synthetic hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is very similar to the inorganic part of the bones and teeth of mammals. It is a well-known biomaterial with good biocompatibility, osteoconductivity and bioactivity. Nifuroxazide (C12H9N3O5, NFX) is a broad-spectrum antibacterial drug and poorly soluble in water. In order to increase the solubility of NFX, nano-sized HAp powder and raw NFX drug were mixed giving, as a result, a HAp/NFX conjugate. Characterization of the raw materials and the obtained conjugate confirmed the integration of NFX on the HAp surface. An in vitro study of drug release in simulated stomach acid and intestinal fluid showed a much faster release of NFX from HAp surface than those of the raw drug. The HAp/NFX conjugate showed excellent inhibitory effects against Gram-positive bacterium Staphylococcus aureus, Gram-negative bacterium Escherichia coli and yeast Candida albicans, proving the nano-sized HAp powder as a promising drug carrier.

Substitution of Fe in hydroxyapatite as an efficient single-atom catalyst for oxygen reduction reaction in biofuel cells: A first-principles study

Single-atom biological catalysts have attracted enormous attentions for low cost, high stability and catalytic activity in therapeutics and biomedical devices. The properties of Fe atom substituted CaII in HAP surface (Fe@HAP) and Fe adsorbed over HAP surface (Fe/HAP), and the detailed kinetic and thermodynamic behaviors of the oxygen reduction reaction (ORR) processes have been investigated by using the first-principles study. It is found that Fe dopant by substituted CaII ion into HAP surface could be more stably anchored at HAP surface than Fe adsorbate, and the introduced Fe dopant can enormously increase the endogenous ORR catalytic activity of magnetic HAP catalysts. Furthermore, the ORR process on Fe@HAP prefers to the 4e- pathway with the small reaction barrier (0.73 eV) for the rate-limiting step, and the two OH species formed from the hydrogenation of the adsorbed O2 prefer to further hydrogenate into two H2O molecules and their self-dehydrogenation is not preferable according to the transition states simulation, which is also confirmed by the Gibbs free energy calculation. Consequently, our results revealed that the Fe@HAP could be an efficient catalyst as cathode material in the applications of the implantable biofuel cells and shed light on the design of biomaterials for various applications.

Interplay between surface chemistry and osteogenic behaviour of sulphate substituted nano-hydroxyapatite

Surface potential and chemical compositions of the bioceramics are the core of therapeutic effect and are key factors to trigger the interfacial interactions with surrounding hard and soft tissues to repair and regeneration. Ionic substitution in hydroxyapatite (Hap) lattice significantly influences the zeta potential from −16.46 ± 0.66 mV to −6.01 ± 0.68 mV as well as an average nano-rod length from ~40 nm to ~26 nm with respect to SO42− ion content. Moreover, the surface chemistry of Hap is mainly inter-related to SO42− substitution rate at PO42− site. Specifically, nano-sized feature with lowered negative surface potential influences the protein adsorption via their weak repulsive or attractive forces. Bovine serum albumin (BSA) and lysozyme (LSZ) adsorption studies confirmed the increased affinity to active binding sites of Hap's surface. Further, SO42− ion substituted Hap (SNHA) showed improved in vitro biomineralization activity and alkaline phosphatase activity. Expression of osteogenic biomarkers such as collagen I, V, osteopontin and osteocalcin were evaluated in Saos-2 and MC3T3-E1 cells. Gene expression of these markers was influenced by SO42− ion content in Hap (maximum with 10SNHA). Altogether, these data emphasizes that chemical composition and surface properties are dominant aspect in bioceramic development towards bone regeneration.

Modifications of Hydroxyapatite properties by nanosecond Nd: YAG laser pulses

Lasers unique characteristics can be utilized to enhance hydroxyapatite (HAp) properties by modifying its surface features; namely microhardness and morphology. Laser treatment is a promising route to enhance surface properties of HAp coatings and HAp components. Hydroxyapatite pressed pellets were laser-treated by Q-Switched Nd: YAG nanosecond laser pulses with different laser fluences to alter their surface specifications. A significant increase in laser-treated microhardness was observed compared to the control sample. The use of lasers demonstrated clear improvement of the HAP surface against demineralization. Digital Micro Vickers hardness tester, Atomic Force Microscope, and Scanning Electron Microscope were employed to investigate structural changes and laser-treated depth. New aspects for delaying HAp surface abrasion were explored; showing reduced wear after laser treatment.

Photoemission Spectroscopy Characterization of Halide Perovskites

AbstractControlling the surface and interface properties of halide perovskites (HaPs) materials is key to improve performance and stability of HaP‐based optoelectronic devices such as solar cells. Here, an overview is given on the use of different photoemission spectroscopy (PES) techniques as a tool kit to investigate chemical and electronic properties of surfaces and interfaces in research on HaP compounds. The primary focus of the article is X‐ray photoelectron spectroscopy (XPS), hard X‐ray photoemission spectroscopy (HAXPES), ultraviolet photoemission spectroscopy (UPS), and inverse photoemission spectroscopy (IPES), highlighting the importance of good practices during PES measurements. Starting from the working principles of PES, critical measurement conditions are discussed. In particular, the exposure of the HaP surface to vacuum and high energy radiation can cause accelerated ageing, degradation, and also ionic migration in the sample. The impact of these changes on the electronic and chemical properties is discussed, followed by an analysis of the specific challenges encountered when performing PES measurements of HaPs. These include the deviation from pristine surface conditions, determination of “soft” band edges, and assessment of band bending. The review concludes by emphasizing good practices for PES measurements of HaP samples and outlining the scope of operando type measurements to capture the transient behavior of HaPs in the experiment.

A new in situ enhancement of the hydroxyapatite surface by Tyramine: Preparation and interfacial properties

The grafting of biogenic monoamine can provide an effective route to modify the surface properties of apatite materials. This study presents the modification of the hydroxyapatite surface by Tyramine prepared by hydrothermal reaction. The nanoparticles of Tyramine grafted hydroxyapatite were characterized by x-ray diffraction, infrared spectroscopy, solid-state NMR spectroscopy, thermal analysis, TEM microscopy, and measurements of the specific surface area (SBET). In situ grafting of Tyramine onto the HAp surface reduces crystal growth through the formation of organic-inorganic hybrid nanoparticles, thereby developing a multifunctional surface, thus providing a good compatibility with surface interaction for cell-modified HAp. To better illustrate the surface properties of the prepared biomaterials, the interaction of methyl-orange with the modified HAp was studied using a modified method developed within the framework of this work. Effect of the grafting rate on the adsorption performance was examined. The adsorption kinetics were well described by a second order model, which is remarkably influenced by the Tyramine grafting rate.

Comparative Study on Factors Governing Binding Mechanisms in Polylactic Acid-Hydroxyapatite and Polyethylene-Hydroxyapatite Systems via Molecular Dynamics Simulations.

Binding mechanisms in polylactic acid-hydroxyapatite (PLA-HAp) and polyethylene-hydroxyapatite (PE-HAp) systems are comparatively elucidated on HAp (110) surfaces in unprecedented detail using molecular dynamics simulations conducted with the systematically varying number of monomers (N) between 10 and 400 at 310 K (NVT). Although PE seems to gradually cover the HAp surface more effectively compared to PLA, evident from the corresponding radius of gyration and occupied area values, the interface density and total binding energy in PLA-HAp systems is higher compared to those of PE-HAp systems. It is shown that a linear relationship between the binding energy and the surface area occupied by the monomer exists, consistent with our finding that binding energy converges to a limiting value with respect to monomer size on a constant surface area. The major constituent of the total binding energy is, rather surprisingly, shown to be the energy change in the bulk structure in HAp upon interaction; the next most important contributor is found to be the energy corresponding to surface-polymer interactions. The interplay between mainly these two contributors, acting in different fashions in two systems investigated here, seems to control the total binding energies. Increasing monomer size N initially results in enhanced densification of the interface in the HAp-PLA system up until N ≈ 200 with the positioning of mainly ═O units of PLA onto the HAp surface, consistent with the increasing Ca-O coordination numbers. Further increases in PLA size (N > 200) result in decreasing intensities of the peaks in the concentration profile consistent with the decreasing surface-polymer interaction energies while increased stabilization of the energy of the bulk is pronounced in this region. On the other hand, increasing N leads to a constantly increasing concentration at the interface in PE-HAp systems; -H atoms of the PE chain are positioned closer to the HAp surface than are -C atoms. These changes are coupled with increasing surface-polymer interaction energies in PE-HAp complexes, while slight destabilization in the energy of the bulk is observed for N > 100. A detailed examination of binding mechanisms in these technologically important systems as presented here is essential in material discovery; this valuable information, that will not be available from experiments can be attained through molecular simulations. The current study, to the best of our knowledge, comprises one of the first steps in achieving this goal for PLA/PE-HAp systems.

Mechanism study of metal ion adsorption on porous hydroxyapatite: experiments and modeling

In this study, low-cost biomaterial hydroxyapatite (N-Hap) prepared from bovine bones was tested for its potential to sorb copper Cu2+ and Fe3+ from aqueous solution and was compared with commercial hydroxyapatite (C-Hap). The structural characterization of N-Hap and C-Hap were carried out by Fourier transform infrared (FTIR) analysis, textural analysis (BET), morphology, and elemental analysis via scanning electron microscopy (SEM-EDX). The results obtained show that SEM images confirmed the formation of porous N-Hap with various morphologies and the average particle size ranges from 50 to 100 nm and the CaP ratio is 1.657. The presence of functional groups on N-Hap surface was confirmed by FTIR analysis. The specific surface areas of N-Hap and C-Hap are found to be 46.87 and 40.98 m2/g, respectively. Adsorption of two metals Cu2+ and Fe3+ was fast, with equilibrium attained within 30 min. Copper ions exhibited the greatest adsorption on both adsorbents because of their size and pH conditions. Metallic ion removal efficiency was favored at a slightly acidic solution pH and low temperature. The equilibrium and kinetic data were found to fit well the Langmuir model and the pseudo second order model with intraparticle diffusion. Thermodynamic parameters (ΔHads &lt; 0 and ΔGads &lt; 0) involved the exothermic, spontaneous, and physical adsorption process. The adsorption interaction of Cu2+ and Fe3+ with Hap surface was investigated by theoretical density functional theory (DFT) calculations. Therefore, the porous hydroxyapatite N-Hap displays potential as a new biocompatible adsorbent, and its use seems to be an interesting solution for the treatment of industrial wastewater.

Understanding the Role of Shape and Composition of Star-Shaped Polymers and their Ability to Both Bind and Prevent Bacteria Attachment on Oral Relevant Surfaces.

In this study, we have prepared a series of 4- and 6-arm star-shaped polymers with varying molecular weight and hydrophobicity in order to provide insight into the role and relationship that shape and composition have on the binding and protecting of oral relevant surfaces (hydroxyapatite, HAP) from bacteria colonization. Star-shaped acrylic acid polymers were prepared by free-radical polymerization in the presence of chain transfer agents with thiol groups, and their binding to the HAP surfaces and subsequent bacteria repulsion was measured. We observed that binding was dependent on both polymer shape and hydrophobicity (star vs. linear), but their relative efficacy to reduce oral bacteria attachment from surfaces was dependent on their hydrophobicity only. We further measured the macroscopic effects of these materials to modify the mucin-coated HAP surfaces through contact angle experiments; the degree of angle change was dependent on the relative hydrophobicity of the materials suggesting future in vivo efficacy. The results from this study highlight that star-shaped polymers represent a new material platform for the development of dental applications to control bacterial adhesion which can lead to tooth decay, with various compositional and structural aspects of materials being vital to effectively design oral care products.