Organic/inorganic bioactive materials part IV: <Emphasis Type="Italic">In vitro</Emphasis> assessment of bioactivity of gelatin-calcium phosphate silicate/wollastonite hybrids

Biohybrids consisting of gelatin (G) and calcium phosphate silicate/wollastonite (CPS/W) have not been prepared so far. In this work our results are focused on the possibility of obtaining G-CPS/W bioactive hybrids in vitro. XRD, FTIR, SEM/EDS techniques were employed to characterize the synthesized hybrid materials. FTIR shows that before immersion in 1.5 SBF the “red shift” of COO- band for pure G is observed. The presence of this bond could be attributed to the formation of COO-Ca²⁺ via non-biomimetic route. After immersion in 1.5 SBF, FTIR shows the presence of A- and B-type carbonate containing hydroxyapatite (A/B-CO₃HA). ESD and FTIR show that small amount of calcite (CaCO₃) are present after in vitro test in 1.5 SBF for 3 days. XRD reveals that CO₃HA and small amounts of CaCO₃ can be detected after in vitro test. SEM results obtained for immersed samples show that hydroxyapatite (HA) particles fully covered the surface of the hybrids by a layer composed of spherulites. At higher magnification, very small elongated crystallites could be observed.      

Organic/Inorganic bioactive materials Part II: in vitro bioactivity of Collagen-Calcium Phosphate Silicate/Wollastonite hybrids

In the present study, novel hybrid materials of Collagen (C) and Calcium Phosphate Silicate/Wollastonite (CPS/W) were synthesized. The CPS/W ceramic was prepared via polystep sol-gel method. The dissolution test of CPS/W ceramic was filled with TRIS-HCl buffer. FTIR depicts that hydroxyl carbonate apatite (OHCO₃HA) was observed after 3 days of immersion in TRIS-HCl buffer. Biohybrids of C-CPS/W were produced from diluted hydrochloric acid collagen type I and ceramic powder with different ratios of C and CPS/W equal to 25:75 and 75:25 wt.%. The synthesized hybrids were characterized by FTIR, XRD and SEM. FTIR depicts a “red shift” if amide I could be attributed to the fact that the collagen prefers to chelate Ca²⁺ from partial dissolution of CPS/W ceramic. The growth of B-type carbonate containing hydroxyapatite (B-CO₃HA) on the C-CPS/W hybrids soaked in 1.5SBF was observed. The negatively charged carboxylate groups from the collagen may be responsible for hydroxyapatite (HA) deposition. This fact was confirmed by the “red shift” of carboxylate groups of collagen in FTIR spectra. The formation of HA was observed by FTIR, XRD and SEM.     

Organic / inorganic bioactive materials Part I: Synthesis, structure and in vitro assessment of collagen/silicocarnotite biocoatings

The silicocarnotite, as an inorganic part of the coatings, has been synthesized using a polystep sol-gel method. The chemical composition of the prepared silicocarnotite sol is described as 58.12 CaO, 29.42 P₂O₅, 12.45 SiO₂ (wt%), where Ca/P+Si = 1,67. The acid soluble type I collagen, as an organic part of the obtained coatings, was mixed with silicocarnotite powder in a weight ratio of 25:75 and 75:25 weight ratio without cross-linkage. The acidity of the obtained mixture was readjust with 25% NH₄OH to pH = 9.0. The mixture was then dried at 37°C for 12 h. The growth of B-type carbonate containing hydroxyapatite (B-type CO₃HA) in which CO₃ ²⁺→PO₄ ³⁻ on the surface of collagen/silicocarnotite coatings soaked in 1.5 simulated body fluid (1.5 SBF) was observed. The nucleation of B-type CO₃HA was estimated on the obtained coatings after 3 days immersion in 1.5 SBF. The negatively charged carboxylate groups from the collagen surface may be responsible for the HA deposition. This was confirmed by the “red shift” of carboxylate groups of collagen molecules in the FTIR spectra. After soaking in 1.5 SBF, the morphology of prepared coatings and HA formation was observed by SEM.     

Sol-gel bioactive glass-ceramics Part II: Glass-ceramics in the CaO-SiO2-P2O5-MgO system

Ceramics, with basic composition based on the CaO-SiO₂-P₂O₅-MgO system with different Ca+ Mg/P+Si molar ratio (R), were prepared via polystep sol-gel technique. The structure of the obtained ceramic materials has been studied by XRD, FTIR spectroscopy, and SEM. X-ray diffraction showed the presence of akermanite and HA for the sample with R = 1.68 and Mg substituted β-TCP and silicocarnotite for the sample with R = 2.16, after thermal treatment at 1200°C/2 h. The obtained results are in good agreement with FTIR. In vitro test for bioactivity in static condition proved that the carbonate containing hydroxyapatite (CO₃HA) can be formed on the surface of the synthesized samples. CO₃HA consisted of both A- and B-type CO₃²⁻ ions. SEM micrographs depicted different forms of HA particles, precipitated on the surface after soaking in 1.5 simulated body fluid (SBF).      

<Emphasis Type="Italic">In vitro</Emphasis> bioactivity of 70 wt.% SiO<Subscript>2</Subscript> — 30 wt.% CaO sol-gel glass,doped with 1, 3 and 5 wt.% NbF<Subscript>5</Subscript>

The 70SiO₂-30CaO (wt.%) sol-gel glasses doped with 1, 3 and 5 NbF₅ (wt.%) were prepared via polystep sol-gel route. The synthesized glasses were characterized by XRD, FTIR and SEM. Changes in 1.5 SBF solutions were measured by ICP-AES. XRD of the glasses stabilized at 700°C for 6 hours proved the presence of niocalite. FTIR was consistent with XRD data. The in vitro bioactivity study of all glasses prepared were carried out by soaking in 1.5 simulated body fluid (1.5 SBF) at 37°C for 6 and 12 days in static conditions. The FTIR reveals the formation of A-type and B-type carbonate containing hydroxyapatite (CO₃HA) layer. Changes in 1.5 SBF solutions, after 6 days of soaking, show that the Ca concentration increased significantly, compared to the initial Ca content in the 1.5 SBF solution before in vitro test. After 12 days of immersion, the Ca concentration decreased, i.e., the formation of HA phase consumed Ca from 1.5 SBF solution. For all soaking times, the concentration of P is much lower than that the used 1.5 SBF. Based on these results we suggest that Ca and P play an active role in the future of the glasses. SEM depicts that the different morphology of hydroxyapatite can be formed as a function of soaking time.     

In vitro bioactivity of Polyurethane/85S Bioglass composite scaffolds

In the present work Polyurethane (PU)/Bioglass (BG) composite materials were synthesized with different content of BG (10 and 20 mol.%) as filler. The 85S Bioglass was synthesized via polystep sol-gel method. The chemical composition of BG is 85SiO₂-10CaO-5P₂O₅ (wt.%). The synthesis of PU was carried out by a two-step polyaddition reaction. The 85S BG was added in situ during the polymerization reaction. In vitro bioactivity of the prepared composites was examined in the presence of 1.5 SBF for 7 days in static conditions. The structure of synthesized PU/BG composites before and after in vitro test was determined by XRD, FTIR and SEM. XRD of the samples before in vitro test proved that the phase of γCa₂P₂O₇ in the PU/20BG is visible. FTIR revealed the presence of urethane bond between OH-(from BG) and NCO groups (from PU). Based on FTIR results after in vitro test in 1.5 SBF solutions, A/B-carbonate containing hydroxyapatite (CO₃HA) was formed. XRD proved that HA was formed on the surface of the samples, but Ca₂P₂O₇ does not undergo any changes in the 1.5 SBF solution. SEM depicted the nano-HA agglomerated in spherical particles after immersion in 1.5 SBF for 7 days.     

磷酸氢钙水解法合成羟基磷灰石纳米晶

采用磷酸氢钙水解法和水热处理技术在模拟体液(SBF)介质中合成HA纳米晶,利用XRD研究了pH值、水热处理温度等制备工艺对合成HA纳米晶的影响。TEM、EDS和FTIR表征结果表明磷酸钙产物为长100 nm、直径10 nm的棒状含碳酸根羟基磷灰石纳米晶,其Ca/P比为1.69,这表明本工作获得的HA在组成与形态上与骨骼中的HA十分相似。     

Evaluation of a novel nanocrystalline hydroxyapatite powder and a solid hydroxyapatite/Chitosan-Gelatin bioceramic for scaffold preparation used as a bone substitute material

Artificially fabricated hydroxyapatite (HAP) shows excellent biocompatibility with various kinds of cells and tissues which makes it an ideal candidate for a bone substitute material. In this study, hydroxyapatite nanoparticles have been prepared by using the wet chemical precipitation method using calcium nitrate tetra-hydrate [Ca(NO₃)₂.4H₂O] and di-ammonium hydrogen phosphate [(NH₄)₂ HPO₄] as precursors. The composite scaffolds have been prepared by a freeze-drying method with hydroxyapatite, chitosan, and gelatin which form a 3D network of interconnected pores. Glutaraldehyde solution has been used in the scaffolds to crosslink the amino groups (|NH₂) of gelatin with the aldehyde groups (|CHO) of chitosan. The X-ray diffraction (XRD) performed on different scaffolds indicates that the incorporation of a certain amount of hydroxyapatite has no influence on the chitosan/gelatin network and at the same time, the organic matrix does not affect the crystallinity of hydroxyapatite. Transmission electron microscope (TEM) images show the needle-like crystal structure of hydroxyapatite nanoparticle. Scanning Electron Microscope (SEM) analysis shows an interconnected porous network in the scaffold where HAP nanoparticles are found to be dispersed in the biopolymer matrix. Fourier transforms infrared spectroscopy (FTIR) confirms the presence of hydroxyl group (OH^-) , phosphate group (PO^3-₄) , carbonate group (CO^2-₃) , imine group (C=N), etc. TGA reveals the thermal stability of the scaffolds. The cytotoxicity of the scaffolds is examined qualitatively by VERO (animal cell) cell and quantitatively by MTTassay. The MTT-assay suggests keeping the weight percentage of glutaraldehyde solution lower than 0.2%. The result found from this study demonstrated that a proper bone replacing scaffold can be made up by controlling the amount of hydroxyapatite, gelatin, and chitosan which will be biocompatible, biodegradable, and biofriendly for any living organism.     

Sol-gel bioactive glass-ceramics Part I: Calcium phosphate silicate/wollastonite glass-ceramics

In this work we present experimental results about synthesis, structure evolution and in vitro bioactivity of new calcium phosphate silicate/wollastonite (CPS/W) glass-ceramics. The samples obtained were synthesized via polystep sol-gel process with different Ca/P+Si molar ratio (R). The structure of the materials obtained was studied by XRD, FTIR spectroscopy and SEM. XRD showed the presence of Ca₁₅(PO₄)₂(SiO₄)₆, β-CaSiO₃ and α-CaSiO₃ for the sample with R=1.89 after thermal treatment at 1200°C/2h. The XRD results are in good agreement with FTIR analysis. SEM denotes that apatite formation can be observed after soaking in simulated body fluid (SBF).      

溶胶-凝胶法制备Ca10(PO4)6(OH)2 /TiO2复合涂层及其在模拟生理体液中的行为

The composite films consisting of hydroxyapatite (HAP) submicron particles embedded in the gel composed of the titania nanoparticles were prepared on commercial Ti6A14V plates with titania buffer layer obtained by a spin-coating technique. The films were calcined in air at various temperatures, and the bioactivities of the films were investigated by immersing them in acellular simulated body fliud (SBF). X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), Field emission-scanning electron microscopy(FESEM) and Energy dispersive X-ray (EDS) analysis were employed to investigate the phase formation and structure of the films before and after immersion, and the variations of Ca and P contents in SBF were measured by Inductively Coupled Plasma Spectroscopy(ICP). The results show that the as-prepared films were dense, homogeneous, all well-crystallized, and there was a close interracial bond between the film and the substrate. The characterisatics of the grown layer on the surfaces of the HAP/TiO2 films after immersion in SBF for different periods of time are specially discussed.     

Synthesis and Kinetic Study of Hydroxy/Fluoroapatite Solid Solution Formation by Decomposition of a Ca‐EDTA Complex

Fluoroapatite/hydroxyapatite (FA/HA) solid solutions were synthesized through the decomposition of a Ca(EDTA) complex in presence of phosphate and fluoride ions. Fluorine content and morphology depend on initial pH value. Phase identification, fluorine content, crystallinity and morphology of the obtained products were studied via chemical analysis, FTIR, SEM, XRD, and EDS. The kinetic study shows a catalytic dependence on pH value. The values of k₀, k_H+ and k_OH are reported.     

Hydroxyapatite coating on porous polyurethane facilitated by tetraethoxysilane

Biomimetic growth of calcium phosphate compounds on porous polyurethane (PU) treated with tetraethoxysilane (TEOS) and soaked in simulated body fluid (SBF) solution was studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), and Fourier transformed infrared spectroscopy–attenuated total reflectance (FTIR–ATR). Polyurethane was treated with TEOS in order to produce silanol groups which stimulated the growth of hydroxyapatite when immersed in SBF solution. Polyurethanes that were not treated with TEOS did not show calcium phosphate growth upon immersion in SBF solution. The Ca and P determined by EDAX and inductively coupled plasma spectroscopy (ICP) analysis revealed that the surface layer was not stoichiometric hydroxyapatite, but carbonated, containing hydroxyapatite with a Ca/P ratio of 1.5–1.6. This was confirmed by FTIR–ATR.     

离子热合成形貌可控的羟基磷灰石超细粉体

室温离子液体作为溶剂,以离子热合成法合成了羟基磷灰石超细粉体。当改变不同的离子液体作为溶剂时,可以相应调整羟基磷灰石的形貌。对羟基磷灰石分别采用X-射线粉末衍射（XRD）,扫描电子显微镜（SEM）,傅立叶变换红外光谱仪（FTIR）等进行表征。实验结果表明：所得到的羟基磷灰石为部分CO₃^2-取代的羟基磷灰石,在选用EmimBF₄为溶剂时所合成样品颗粒的尺寸、形貌更加规则、均一。与水作为溶剂相比,以离子液体BmimBr作为溶剂所合成的羟基磷灰石材料对有机染料碱性品红的饱和吸附量为43.78mg·g^-1,具有较好的吸附性能。     

离子热合成形貌可控的羟基磷灰石超细粉体

室温离子液体作为溶剂,以离子热合成法合成了羟基磷灰石超细粉体。当改变不同的离子液体作为溶剂时,可以相应调整羟基磷灰石的形貌。对羟基磷灰石分别采用X-射线粉末衍射(XRD),扫描电子显微镜(SEM),傅立叶变换红外光谱仪(FTIR)等进行表征。实验结果表明:所得到的羟基磷灰石为部分CO32-取代的羟基磷灰石,在选用EmimBF4为溶剂时所合成样品颗粒的尺寸、形貌更加规则、均一。与水作为溶剂相比,以离子液体BmimBr作为溶剂所合成的羟基磷灰石材料对有机染料碱性品红的饱和吸附量为43.78 mg·g-1,具有较好的吸附性能。     

Biomimetic approach towards the preparation of hydroxyapatite and hydroxyapatite/chitosan/β-cyclodextrin nanoparticles: application to controlled drug release

Hydroxyapatite (HAp) and hydroxyapatite/chitosan/β-cyclodextrin (HAp/CS/β-CD) nanoparticles were successfully prepared in the modified simulated body fluid (SBF) solution at the physiological conditions (pH 7.4, temperature?=?37 °C). CS/β-CD nanoparticles acted as templates for the synthesis of HAp/CS/β-CD nanoparticles to improve the nanoarchitecture of HAp and its crystallinity.The nanoparticles were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Kneading and coprecipitation methods were applied to prepare the inclusion complex involving β-CD and p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin), a photosensitizer for anti-cancer drugs. The 1:1 stoichiometric ratio of the formed inclusion complex was characterized by a formation constant of 7.216?×?10² mol^?1 dm³ and analyzed by ¹H NMR, FTIR, and UV–Vis. The p-THPP delivery release in vitro was in this order: HAp/CS/β-CD?<?CS/β-CD?<?<?HAp/β-CD?<?β-CD, hinting at a better controlled release by HAp/CS/β-CD nanoparticles.     

Synthesis and Characterization of Polyvinylferrocene/Polypyrrole Composites

Conducting polymer composites of polyvinylferrocene and polypyrrole (PVF/PPy) were synthesized chemically by the in situ polymerization of pyrrole in the presence of PVF using FeCl₃ as oxidant. Acetic (CH₃COOH) and boric (H₃BO₃) acids were used as the synthesis medium. Effects of the synthesis medium on the properties of the PVF/PPy composite were investigated. The PVF/PPy composites and homopolymers were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and magnetic susceptibility techniques. Conductivity measurements were performed using the four‐probe technique. We found that the conductivities of PVF/PPy‐H₃BO₃ (1.19 S cm^?1) and PVF/PPy‐CH₃COOH (4.5×10^?1 S cm^?1) increased relative to those of the homopolymers of PPy‐H₃BO₃ (2.1×10^?2 S cm^?1) and PPy‐CH₃COOH (1.2×10^?2 S cm^?1) due to the interaction of PVF with the pyrrole moiety. The stability of all homopolymers and composites were investigated by thermogravimetric analysis and by conductivity measurements during heating‐cooling cycles. There was a small drop in conductivity caused by the annealing of PVF/PPy composites at 70°C. The conductivity of all samples increased with temperature and exhibited stable electrical behavior with increasing temperature. TGA analysis of samples showed that the composites were more stable than the homopolymers or PVF separately. The magnetic susceptibility values of samples were negative, except for PVF/PPy‐H₃BO₃. Morphology changes of the composites investigated by scanning electron microscopy (SEM), attributed to synthesis conditions, have a significant effect on their conductivity.     

Synthesis of nanocrystalline REBO3 (RE=Y, Nd, Sm, Eu, Gd, Ho) and YBO3:Eu using a borohydride-based solution precursor route

A solution precursor route has been used to synthesize a series of nanocrystalline rare-earth borates. Amorphous precursor powders are precipitated during an aqueous reaction between RE³⁺ and NaBH₄, and the isolated powders can be annealed in air at 700 °C to form YBO₃, NdBO₃, SmBO₃, EuBO₃, GdBO₃, and HoBO₃. YBO₃:Eu formed using this strategy shows red-orange emission properties that are similar to high-quality nanocrystals prepared by other methods. The materials have been characterized by FTIR spectroscopy, powder XRD, SEM, DSC, UV-Vis fluorimetry, and TEM with EDS and element mapping.     

Nanostructured Graphene/TiO2 Hybrids as High‐Performance Anodes for Microbial Fuel Cells

A new nanostructured graphene/TiO₂ (G/TiO₂) hybrid was synthesized by a facile microwave‐assisted solvothermal process in which amorphous TiO₂ was assembled on graphene in situ. The resulting G/TiO₂ hybrids were characterized by XRD, SEM, TEM, Raman spectroscopy, and N₂ adsorption/desorption analysis. The electrochemical properties of the hybrids as anode materials for Shewanella‐inoculated microbial fuel cells (MFCs) were studied for the first time, and they proved to be effective in improving MFC performance. The significantly improved bacterial attachment and extracellular electron‐transfer efficiency could be attributed to the high specific surface area, active groups, large pore volume, and excellent conductivity of the nanostructured G/TiO₂ hybrid, and this suggests that it could be a promising candidate for high‐performance MFCs.     

AgI/h-MoO3异质结的构筑及其模拟燃油光催化氧化脱硫活性

利用沉积法获得了异质结AgI/h-MoO₃光催化剂,通过X射线衍射（XRD）、扫描电子显微镜（SEM）、光电子能谱（EDS）、X射线光电子能谱（XPS）、紫外-可见漫反射吸收光谱（UV-Vis-DRS）、光致发光（PL）、电化学阻抗（EIS）等方法对其物相组成、形貌、光吸收特性、光电化学性能等进行了表征。以噻吩的正辛烷溶液模拟催化裂化（FCC）汽油为探针考察了AgI/h-MoO₃光催化氧化脱硫活性,结果表明,AgI/h-MoO₃-18异质结在催化剂浓度为1.5 g·L^-1,可见光照射2 h后,光催化氧化脱硫活性达98%。利用XRD、XPS、UV-Vis-DRS揭示了AgI/h-MoO₃光照后生成少量的金属Ag,使其结构转变为Z型AgI/Ag/h-MoO₃,有利于光生电子（e^-）转移。利用活性物种捕获实验、循环实验研究了AgI/h-MoO₃光催化氧化脱硫机理及其稳定性,实验结果表明：AgI/h-MoO₃不仅具有较高的光催化氧化脱硫活性,而且还有良好的稳定性。     

碳酸钙晶须合成过程中可溶性磷酸盐的作用机理研究

以可溶性磷酸盐为控制剂,一步碳化法制备了文石相碳酸钙晶须。借助于XRD和FTIR,分析了可溶性磷酸盐在碳酸钙晶须合成过程中的作用机理。研究结果表明：通入CO₂进行碳化反应前,可溶性磷酸盐与Ca(OH)₂反应生成了热力学上最稳定的磷酸钙化合物——羟基磷灰石;在通入CO₂初期,[CO₃^2-(OH)]进入到羟基磷灰石的晶格,部分替代[PO₄^3-],生成碳酸羟基磷灰石,然后以此为结晶中心诱导文石相的异相成核,Ca²⁺、CO₃^2-不断叠加,进而生长为碳酸钙晶须。