Novel bi-layered nanostructured SiO2/Ag-FHAp coating on biodegradable magnesium alloy for biomedical applications

In this study, a novel bi-layered nanostructured silica (SiO₂)/ silver-doped fluorohydroxyapatite (Ag-FHAp) coating was deposited on biodegradable Mg-1.2Ca-4.5Zn alloy via physical vapor deposition (PVD) combined with electrodeposition (ED). The nano-SiO₂ underlayer had a compact columnar microstructure with thickness of around 1 µm while the Ag-FHAp overlayer presented large plate-like crystals accompanied with small rounded particles with thickness about 10 µm. Potentiodynamic polarization test exhibited that the double layer SiO₂/Ag-FHAp coated Mg alloy has superior corrosion resistance compared to uncoated and single layer SiO₂ coated samples. Contact angle measurement showed that Ag-FHAp coating over nano-SiO₂ layers significantly increased surface wettability which is favorable for the attachment of cells. Cytotoxicity tests indicated that the nanostructured SiO₂/Ag-FHAp coating enabled higher cell viability compared to nano-SiO₂ coating and uncoated samples. In addition, bi-layer and single-layer coatings considerably improved the ability of cell attachment than that of the uncoated samples. The cell viability of coated and uncoated samples increased with increasing incubation time. The double layer SiO₂/Ag-FHAp coated biodegradable Mg alloy possessed high corrosion resistance and cytocompatibility and can be considered as a promising material for implant applications.     

Bioactive HA/TiO2 coating on magnesium alloy for biomedical applications

Magnesium alloys are new class of biodegradable alloys having many favourable properties to overcome the limitations of currently used biomedical alloys. Recently, several coatings have been developed to overcome their higher degradation rate. In this regard, a new attempt has been made to develop Hydroxyapatite and Hydroxyapatite/TiO₂ coatings on magnesium alloys to increase the biocompatibility and reduce the corrosion rate. The coated surfaces were characterized by Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction Analysis (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) Spectroscopy, Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Contact angle measurements proved higher hydrophilic nature of HA/TiO₂ coating compared to HA coating. In-vitro studies showed that HA–TiO₂ coated alloy exhibited higher osteoinduction compared to HA coated alloy. Hydrogen evolution studies and corrosion studies confirmed greater reduction in degradation rate of HA/TiO₂ coated alloy. Vickers microhardness test also showed enhancement in mechanical strength of the composite coated alloy compared to HA coated alloy. Three point bend test depicted better adherence of the HA/TiO₂ coating compared to HA coating on the substrate. Cell culture studies proved higher cell attachment and proliferation on composite coated alloy by controlling the release of magnesium ions into the surrounding body tissue.     

钛植入合金表面电化学沉积掺镁羟基磷灰石涂层

以Ca(NO3)2、(NH4)2HPO4和Mg(NO3)2为原料,采用电化学沉积法在医用钛合金表面制备了掺镁羟基磷灰石涂层,研究了电沉积工艺条件对掺镁羟基磷灰石涂层表面形貌的影响。结果表明,当电流密度为1.0mA/cm2,温度为65°C,pH为4.5,n(Mg):n(Ca)=1:3,电沉积时间为1300s时,得到了均匀致密的晶须状涂层。X射线衍射分析表明,烧结后的掺镁羟基磷灰石涂层中Mg2+取代了Ca2+,使HA涂层的晶格发生了变化。     

Bioactive,luminescent erbium-doped hydroxyapatite nanocrystals for biomedical applications

Diagnosis and imaging play an essential key role in primary detection, screening, and image-guided smart nanomedicine for healthcare solutions. This study illustrates the successful fabrication of luminescent lanthanide (erbium)-doped hydroxyapatite (Er-HAp) by one step facile wet-chemical precipitation method. The chemical compositions, morphology, optical, and biological properties were systematically characterized using relevant different structural, compositional analytical instrumentation and cytotoxicity assays. After erbium doping, synthesized luminescent nano-structured materials exhibited elongated morphology, with well dispersed <50 nm size distribution. The photoluminescence (PL) study confirmed three emission bands assigned to ⁴F_3/2 → ⁴I_15/2 (purple), ⁴F_7/2 → ⁴I_15/2 (blue), and ⁴S_3/2 → ⁴I_15/2 (green) transition states, respectively. In vitro bioactivity and optical imaging studies conducted in osteoblast like MG-63 cells confirmed the nontoxic luminescent behavior of the synthesized nanomaterials.     

Electrodeposition of ZnO Nanoprism-Zn substituted hydroxyapatite duplex layer coating for carbon fiber

A ZnO nanoprism/Zn substituted hydroxyapatite duplex layer (ZnOnp-ZnHA) coating was prepared on carbon fibers (CF) by two-step electrodeposition method. The ZnOnp-ZnHA coating on CF was characterized by Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Energy dispersive spectrometer, Raman spectra and Thermogravimetric Analysis. The formation mechanism of the duplex layer coating was discussed. The in-vitro bioactivity of the duplex layer coating was investigated by simulated body fluid (SBF) immersion test. The ZnOnp interlayer showed nanoprism morphology with a length of 0.4–0.9 μm and a diameter of 117–220 nm. We found both the CF and the ZnOnp could serve as nucleation sites for ZnHA layer. The ZnHA outer layer showed ball-like morphology with a diameter of 0.6–1.7 μm. The duplex layer coating exhibited suitable in-vitro bioactivity using SBF immersion test method. The ZnOnp-ZnHA duplex layer coated CF may serve as a promising candidate for clinic applications.     

Surfactant-free electrochemical synthesis of fluoridated hydroxyapatite nanorods for biomedical applications

Fluoridated hydroxyapatite (FHA) [Ca₁₀(PO₄)₆F_x(OH)_2−x, x = 0–2] is believed to be a promising calcium phosphate (CaP) to replace pure hydroxyapatite (HA) for next-generation implants, owing to its better biocompatibility, higher antibacterial activity, and lower solubility. Notably, the shape and size of the CaP crystals play key roles in their performance and can influence their applications. One-dimensional (1D) FHA nanorods are important CaP materials which have been widely used in regenerative medicine applications such as restorative dentistry. Unfortunately, the traditional synthesis methods for FHA nanorods either employ surfactants or take a relatively long time. In this study, we aimed to propose a facile synthesis route to fabricate FHA nanorods without any surfactants using an electrochemical deposition method for the first time. This study focused on preparing FHA nanorods without the assistance of any surfactant, unlike the traditional synthesis methods, to avoid chemical impurities. FHA nanorods with lengths of 124–2606 nm, diameters of 28–211 nm, and aspect ratios of 4.4–21.8 were synthesized using the electrochemical method, followed by a heat treatment. For the as-synthesized FHA nanorods, the Ca/P ratio was 1.60 and the atomic concentration of F was 2.06 at.%. An ultrastructure examination revealed that each FHA nanorod possessed long-range order, good crystallinity, and a defect-free lattice with a certain crystallographic plane orientation along the whole rod. In short, we propose a novel, surfactant-free, cost-saving, and more efficient route to synthesize FHA nanorods which can be widely applied in multiple biomedical applications, including drug delivery, bone repair, and restorative dentistry.     

Polyoxymethylene‐homopolymer/hydroxyapatite nanocomposites for biomedical applications

In this article, new polyoxymethylene (POM)/hydroxyapatite (HAp) nanocomposites for bone long‐term implants have been obtained and characterized by using FTIR, WAXD, SEM, TG, DSC, tensile tests, and in vitro evaluation. Characteristic bands both for extended chain crystals (ECC) and folded chain crystals (FCC) were observed in FTIR profiles for both pure POM and POM in POM/HAp nanocomposites. From WAXD analysis it has been found that the addition of HAp does not change the hexagonal system of POM in POM/HAp nanocomposites. Moreover, degree of crystallinity of POM increases with an increase of HAp content up to 1.0% and next decreases with an increase HAp content. It indicates that HAp nanoparticles up to 1.0% content act as effective nucleating sites. Mechanical tests revealed that Young's modulus increases, whereby, elongation at break and tensile strength decrease with increasing hydroxyapatite concentration. Results of in vitro investigations show that an increase of HAp content in POM nanocomposites facilitates formation of apatite layer on the sample surface and improves in vitro stability POM/HAp nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Structural and phase analysis of multi-ion doped hydroxyapatite for biomedical applications

Multi-ion doping in synthetic HA was carried out using high energy planetary ball milling followed by calcination at 1250?°C for 2?h. The influence of Sr⁺², Zn⁺², Ag⁺, and F^- ion doping on crystallinity and crystallite size was analyzed using Taguchi design of experiments (DOE) and optimal concentration of different dopants has been identified to achieve desired crystallinity and crystallite size. The doped HA samples have been characterized using X-ray diffraction and Fourier transform infrared spectroscopy to determine their phase purity, degree of crystallinity, crystallite size and functional groups. Standard Analysis of variance (ANOVA) showed relatively high contribution of Sr⁺² and Zn⁺² doping in changing the crystallinity and crystal size of HA compared to the effect of Ag⁺ and F^- doping. Our analysis demonstrated strong interaction between dopants at binary level doping, while ternary and quaternary doping of elements did not exhibit any interaction in influencing the crystallinity and crystallite size of HA. In general, multi-ion doping in HA found to decrease its crystallinity from 92% to 72% (max.), but enhance the hardness, depending on the type and concentration of doping element. Similarly, a minimum crystallite size of 31?nm was achieved with some binary compositions and other combinations resulted in crystallite sizes up to 59?nm. The compositions that ensure desired crystallinity and crystallite size can also provide high hardness. Our results can be used to tailor the composition of HA in achieving desired functional properties, dependent on crystallinity and crystallite size, such as strength, bioactivity and degradation to suit variety of implant applications.     

Characterization of biogenic hydroxyapatite derived from animal bones for biomedical applications

In this work, the viability of producing biogenic hydroxyapatite from bio-waste animal bones, namely bovine (cow), caprine (goat) and galline (chicken), through a heat treatment process has been investigated. The animal bones were locally sourced, cleaned to remove collagen and subsequently heat treated in air atmosphere at different temperatures ranging from 600?°C to 1000?°C. From the range of sintering temperatures investigated, it was found that hydroxyapatite derived from bovine bone showed good thermal stability while those produced from caprine and galline bones exhibited phase instability with traces of tri-calcium phosphate (TCP) being detected after heat treatment beyond 700?°C. The porous nature of the bone samples can be observed from the microstructures obtained and supported by low relative density. Heating the bovine and caprine bones at selected temperatures yielded porous HA body, having hardness values that are comparable with human cortical bone. However, the sintered galline bone sample showed higher porosity levels and low hardness when compared to the other two bone types.     

Electrolytic deposition of fluorine-doped hydroxyapatite/ZrO2 films on titanium for biomedical applications

A novel method of electrolytic fluorine-doped hydroxyapatite/ZrO₂ double-layer coating was conducted on medical titanium in ZrO(NO₃)₂ aqueous solution and subsequently in the mixed solution of Ca(NO₃)₂, NH₄H₂PO₄ and NaF. The microstructure, phase composition, bond strength, dissolution rate and corrosion resistance of the films were studied. Results revealed that the additions of F^? reduced the crystallite and increased the crystallinity of hydroxyapatite, structure of apatite was changed from micro-petal-like crystals to nano-needle-like crystals, which aligned vertically to the substrate. The approximately 10 μm thick layers was much denser and uniform. Addition of ZrO₂ buffer layer could improve the bond strength between the fluorine-doped hydroxyapatite layer and the substrate. The bond strength of the double-layer coating was found to be significantly higher than that of pure hydroxyapatite coating even after soaking in normal saline for two weeks. In physiological solution, the double-layer coating showed lower dissolution rate and stronger corrosion resistance than pure hydroxyapatite coating.     

医用镁合金仿生钝化技术研究进展

在医用镁合金功能化表面改性技术中,仿生钝化具有其他方法无可比拟的优越性。利用仿生钝化技术,可在镁合金表面原位制备兼具优异生物相容性、生物活性和降解控制功能的生物磷灰石膜层,全面满足镁合金生物医用对表面质量的苛刻要求。本文分别从前处理、钝化工艺、钝化后处理等方面,综述了医用镁合金仿生钝化技术的研究进展,并展望了医用镁合金仿生钝化技术的发展趋势。     

Electrophoretic deposition of bioactive glass nanopowders on magnesium based alloy for biomedical applications

To slow down the initial biodegradation rate of magnesium (Mg) alloy, crystalline nano-sized bioactive glass coating was used to deposit on micro-arc oxidized AZ91 samples via electrophoretic deposition (EPD). Zeta potential and conductivity of the bioactive glass suspension were characterized at various pH values to identify the most stable dispersion conditions. The bone-bonding properties of bioactive glass coated samples were evaluated in terms of apatite-forming ability during the immersion in simulated body fluid (SBF) solution. Results revealed that the ability to form a bioactive glass coating via EPD was influenced by the degree of its crystalline phase composition. Moreover, the potentiodynamic polarization tests recorded significant drops in corrosion current density and corrosion rate of the coated samples which implies a good level of corrosion protective behavior. These preliminary results show that this process will enable the development of Mg implants in the later stage of bone healing.     

Biowaste-derived hydroxyapatite reinforced with polyvinyl pyrrolidone/aloevera composite for biomedical applications

The present investigation focuses on the synthesis of crabshell-derived hydroxyapatite (CS-HAP)/ water-soluble synthetic polymer—polyvinylpyrrolidone(PVP)/aloevera(AV)—a natural biopolymer, as a composite for enhanced mechanical, antibacterial and biocompatible properties. The reinforcement of polymer has a significant function in increasing the mechanical property of the composite, whereas the incorporation of AV improves the antibacterial and biocompatibility. Phase composition, morphology, mechanical property, and hydrophilicity of CS-HAP/PVP/AV biocomposite with different concentrations of PVP and AV were examined by Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray (SEM-EDX), Vickers microhardness tests, contact angle, respectively. Furthermore, the antibacterial efficiency of the composite is assessed using Escherichia coli (E coli) and Staphylococcus aureus (S aureus). The biocompatibility of HOS MG 63 cells on the CS-HAP/PVP/AV composite is evaluated by MTT assay test. The obtained results evidence that the as-synthesized composite have appropriate mechanical, antibacterial and biocompatible properties. Overall, the combination of mechanical property of PVP, antibacterial and biocompatible property of AV in CS-HAP/PVP/AV, makes the composite a potential therapeutic material for various biomedical applications.     

Nanocrystalline hydroxyapatite doped with aluminium: A potential carrier for biomedical applications

Biocompatible materials based on hydroxyapatite are potentially attractive for a wide range of medical applications. The effect of aluminium substitution on the biocompatibility of hydroxyapatite (HA) under the physiochemical conditions has been investigated. Various samples of aluminium doped hydroxyapatite (Al-HA) with different concentration (0, 0.5, 1.0, 1.5, 2.0, 2.5 mol%) were successfully synthesised by solution combustion method and characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM), and thermal analysis technique. XRD and TEM results reveal uniform and crystalline nature of Al-HA nanoparticles. The biocompatibility of the Al-HA nanoparticles was studied using L929 cell lines by MTT assays up to 24 h. These Al-HA nanoparticles are biocompatible on cell lines L929 and do not have toxic effects for further possible in vivo applications. The results of these studies confirmed the biocompatibility of Al-HA and demonstrated the suitability for biomedical applications. The present work reveals the importance of structural, morphological, biocompatible properties of Al-HA nanoparticles and predicts the suitability for biomedical applications.     

Biodegradable zinc-based materials with a polymer coating designed for biomedical applications

Over the last decades, biodegradable metals have gained popularity for biomedical applications due to their ability to assist in tissue healing. These materials degrade in vivo, while the corrosion products formed are either absorbed or excreted by the body, and no further surgical intervention is required for removal. Intensive research has been carried out mainly on degradable biomaterials based on Mg and Fe. In recent years, zinc-based degradable biomaterials have been explored by the biomedical community for their intrinsic physiological relevance, desirable biocompatibility, intermediate degradation rate, tuneable mechanical properties and pro-regeneration properties. Since pure Zn does not exhibit sufficient mechanical properties for orthopedic applications, various Zn alloys with better properties are being developed. In this work, the combined effect of minor Fe addition to Zn and a polyethyleneglycol (PEG) coating on the surface morphology, degradation, cytotoxicity and mechanical properties of Zn-based materials was studied. There are several studies regarding the influence of the production of Zn alloys, but the effect of polymer coating on the properties of Zn-based materials has not been reported yet. A positive effect of Fe addition and polymer coating on the degradation rate and mechanical properties was observed. However, a reduction in biocompatibility was also detected.     

氧化石墨烯/羟基磷灰石涂层对镁合金耐腐蚀性的影响

采用仿生法在改性模拟体液中于镁合金表面制备了羟基磷灰石(HA)涂层和氧化石墨烯/羟基磷灰石(GO/HA)复合涂层。利用扫描电子显微镜(SEM)和X射线衍射(XRD)对两种涂层进行了形貌和结构表征,通过析氢量测量、极化曲线和交流阻抗等方法分别研究了裸镁合金、含HA涂层及GO/HA涂层镁合金在pH为7.4的模拟体液(SBF)和3.5%NaCl溶液中的腐蚀行为。结果表明,氧化石墨烯增加了羟基磷灰石涂层的致密性,含GO/HA复合涂层的AZ91镁合金耐腐蚀性能最好,相对于裸镁合金,其腐蚀电流密度降低了一个数量级,析氢量降低了52%。     

Nanostructured hollow hydroxyapatite fabrication by carbon templating for enhanced drug delivery and biomedical applications

Fabrication of nanostructured materials with multifunctional properties and improved biocompatibility have immense potential for biomedical applications. The novelty of this research is to synthesize nanostructured hollow hydroxyapatite (H-HAp) for enhanced drug delivery applications. The nano hollow structure synthesis mechanism involves the controlled precipitation of calcium and phosphate ions over a pre-synthesized nano carbon template, followed by calcination to eliminate the core carbon structure. The synthesized nano-structured H-HAp was analyzed to determine its chemical, elemental, structural, and morphological characteristics by different spectroscopic, gravimetric, and electron microscopy techniques. The potential advances of H-HAp nanoparticles in biological applications were studied by using MDA-MB-231 breast cancer cell lines, and drug kinetics experiments. The cytotoxicity and the efficacy of H-HAp as a drug carrier agent were studied by MTT and fluorescence staining assay. The comparative drug loading/releasing kinetics were studied using nanostructured H-HAp and HAp with the model drug doxorubicin (DOX) and bovine serum albumin (BSA) protein. The synthesized nanostructured materials show relatively enhanced drug (DOX = ∼53.33%) and protein (BSA = ∼43.06%) loading capacities compared to conventional HAp (DOX = ∼46% and BSA = ∼23.62%). The H-HAp nanostructured system shows a pH-dependent sustained in vitro release behavior of model drug molecules. The novelty of this study relies on its facile synthesis mechanism to fabricate a hollow nano HAp structure, which differs from limited reported articles based mostly on microstructure H-HAp for biomedical applications.     

Synthesis and characterization of ceramic - polymer composites containing bioactive synthetic hydroxyapatite for biomedical applications

Presented research involved preparation of hydroxyapatite and synthesis of composites based on gelatin, albumin and polyvinylpyrrolidone (PVP) modified with the obtained compound. Hydroxyapatite was attained as a product of two-stage processing of pig bones. Applied procedure involved hydrolysis of the raw material in acidic environment and double calcination. Molar ratio Ca/P of hydroxyapatite has been determined and its chemical structure has been characterized using X-ray diffraction and FT-IR spectroscopy. Ratio Ca/P calculated on the basis of conducted research was 1.50?±?0.05. Thus prepared material met the ISO requirements, which assume that the Ca/P ratio should be in the range 1.5–2.0, which qualifies the material for further studies. Next, series of polymer matrix on the basis of gelatin, albumin and polyvinylpyrrolidone (PVP) has been synthesized and subjected to some analyzes. On the basis of the conducted studies, matrixes with the most favorable features such as desirable strength, flexibility and crosslinking degree were modified with previously prepared hydroxyapatite. Surface morphology and elemental composition of the composites have been analyzed using SEM-EDS method. Additionally, sorption capacity of modified composites and their behavior in simulated body fluids have been determined. Based on the conducted research it can be concluded that pig bones represent a good material for preparation of hydroxyapatite. Furthermore, composites based on proteins of natural origin modified with attained hydroxyapatite constitute a promising material that can be used for biomedical purposes.     

Nanomechanical and tribological behavior of hydroxyapatite reinforced ultrahigh molecular weight polyethylene nanocomposites for biomedical applications

A hydroxyapatite (HA) particulate reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite is fabricated by internal mixer at 180°C and using of paraffin oil as a processing aid to overcome the high viscosity of melted UHMWPE. The reinforcing effects of nano‐HA are investigated on nanomechanical properties of HA/UHMWPE nanocomposites by nanoindentation and nanoscratching methods. Results show that the nanocomposite with 50 wt % nano‐HA exhibits a Young's modulus and hardness of 362.5% and 200% higher, and a friction coefficient of 38.86% lower than that of pure UHMWPE, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42052.     

Morphological and thermal characterization of zirconia/hydroxyapatite composites prepared via sol-gel for biomedical applications

The thermal behavior of pure ZrO₂ and hydroxyapatite (denoted as Z and HAp, respectively), as well as three composites with different content of Z and HAp (Z90HAp10, Z70HAp30 and Z50HAp50) prepared via sol-gel method has been studied by thermogravimetry (TG) and first-order derivative of TG up to 1200?°C under inert gas atmosphere. Dehydration, loss of alcohol and acetylacetone and a multi-step thermal decomposition processes has been identified by analyzing the gases evolved in each step by Fourier transform infrared spectroscopy (FTIR). Fresh samples of Z-rich composites undergo an abrupt ejection of material from the crucible around 200?°C with noticeable increase of the sample temperature. During the occurrence of this phenomenon FTIR spectra demonstrated the evolution of gases (CO, CO₂, acetone and ethylene) due to the simultaneous decomposition of acetylacetone and ethanol, not present in the samples calcined at 120?°C. As far as the structural study is concerned, pure Z crystallizes at 1000?°C in the monoclinic system, but the presence of HAp in the composite materials enables the crystallization of Z in the tetragonal phase. Finally, the amorphization degree increases with increasing the content of Z in all the composites treated at 600 and 1000?°C.