Effect of nanosized reinforcement particles on mechanical properties of high density polyethylene–hydroxyapatite composites

Abstract

The effect of nanoscaled hydroxyapatite (HA) filler particles on the mechanical properties of the high density polyethylene–hydroxyapatite (HDPE–HA) composite samples has been investigated. Nanosized HA particles with an average size in the range of 40–50 nm were synthesised by mechanical milling method. The composite samples with various amounts of nanoscaled HA particles were produced by mixing the ceramic and high density polyethylene particles using a single screw extrusion system. The results of the mechanical testing on the composite samples showed an increase in the fracture strength and the young's modulus values with increasing volume fraction of HA content in the composite samples. At the same time, there were decreases in both the fracture strain and toughness values with increasing volume fraction of the ceramic filler particles. In addition the comparison of the results obtained in this study with the mechanical properties of the commercially available composite samples (HAPEX) shows that similar mechanical properties can be reached at a much lower ceramic content, if nanoscaled HA particles are used in the fabrication of these composite biomaterials.     

Antibacterial ciprofloxacin HCl incorporated polyurethane composite nanofibers via electrospinning for biomedical applications

We report on the preparation and characterization of polyurethane (PU) composite nanofibers by electrospinning. Two different approaches were adopted to obtain the PU composite nanofibers. In the first approach, a homogeneous solution of 10 wt% PU containing ciprofloxacin HCl (CipHCl) drug was electrospun to obtain PU/Drug composite nanofibers. And in the second approach, the PU with ciprofloxacin HCl drug and ceramic hydroxyapatite (HA) particles were electrospun to obtain the PU/Drug and PU/Drug/HA composite nanofibers. The surface morphology, structure, bonding configuration, optical and thermal properties of the resultant products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and UV–vis spectroscopy. The antibacterial activity was tested against common food borne pathogenic bacteria, namely, Staphylococcus aureus, Escherichia coli by the minimum inhibitory concentration (MIC) method. Our result results demonstrate that these composite nanofibers possess superior characteristics which can utilized for variety of applications.     

多孔n-HA/PVA/CS复合水凝胶的制备与抑菌性能研究

以纳米羟基磷灰石、聚乙烯醇、壳聚糖为原料,采用物理交联法制备复合水凝胶(n-HA/PVA/CS),并测定其含水率、力学强度及微观结构。采用比浊法和平板计数法测定n-HA/PVA/CS复合水凝胶在酸性条件下的最低抑菌浓度和抑菌率,同时对比研究其对革兰氏阴性菌大肠杆菌(E.coli)和革兰氏阳性菌金黄色葡萄球菌(S.aureus)的抑菌性。结果表明,n-HA/PVA/CS复合水凝胶具有均匀分散的三维多孔结构,含水率75%,拉伸强度0.26 MPa。经过2%(质量分数)的醋酸溶液处理的n-HA/PVA/CS复合水凝胶材料对S.aureus和E.coli的最低抑菌质量浓度均为0.5 g/L;在该复合水凝胶质量浓度为2.0 g/L时,对S.aureus的抑菌率为84%,对E.coli的抑菌率达到99%,当其样品质量浓度为2.5 g/L时,对E.coli抑菌率接近100%。n-HA/PVA/CS复合水凝胶可望成为性能优良的人工角膜支架材料。     

Effect of Morphological Characteristics and Biomineralization of 3D-Printed Gelatin/Hyaluronic Acid/Hydroxyapatite Composite Scaffolds on Bone Tissue Regeneration

The use of porous three-dimensional (3D) composite scaffolds has attracted great attention in bone tissue engineering applications because they closely simulate the major features of the natural extracellular matrix (ECM) of bone. This study aimed to prepare biomimetic composite scaffolds via a simple 3D printing of gelatin/hyaluronic acid (HA)/hydroxyapatite (HAp) and subsequent biomineralization for improved bone tissue regeneration. The resulting scaffolds exhibited uniform structure and homogeneous pore distribution. In addition, the microstructures of the composite scaffolds showed an ECM-mimetic structure with a wrinkled internal surface and a porous hierarchical architecture. The results of bioactivity assays proved that the morphological characteristics and biomineralization of the composite scaffolds influenced cell proliferation and osteogenic differentiation. In particular, the biomineralized gelatin/HA/HAp composite scaffolds with double-layer staggered orthogonal (GEHA20-ZZS) and double-layer alternative structure (GEHA20-45S) showed higher bioactivity than other scaffolds. According to these results, biomineralization has a great influence on the biological activity of cells. Hence, the biomineralized composite scaffolds can be used as new bone scaffolds in bone regeneration.     

Preparation and characterization of aliphatic polyurethane and hydroxyapatite composite scaffold

Novel porous composite scaffolds for tissue engineering were prepared from aliphatic biodegradable polyurethane (PU) elastomer and hydroxyapatite (HA). It was found that the aliphatic PU was possible to load up to 50 wt % HA. The morphology and properties of the scaffolds were characterized by scanning electron microscope, X‐ray diffraction, infrared absorption spectra, mechanical testing, dynamic mechanical analysis, and in vitro degradation measurement. The results indicated that the HA/PU scaffolds had an interconnected porous structure with a pore size mainly ranging from 300 to 900 μm, and 50–200 μm micropores existed on the pores' walls. The average pore size of macropores and micropores are 510 and 100 μm, respectively. The compressive strength of the composite scaffolds showed higher enhancement with increasing HA content. In addition, the polymer matrix was completely composed of aliphatic component and exhibited progressive mass loss in vitro degradation, and the degradation rate depended on the HA content in PU matrix. The porous HA/PU composite may have a good prospect to be used as scaffold for tissue engineering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Alternating Current Electrophoretic Deposition of Antibacterial Bioactive Glass-Chitosan Composite Coatings

Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 μm and 20–80 nm in average diameter. The parameter optimization and characterization of the coatings was conducted by visual inspection and by adhesion strength tests. The optimized coatings were investigated in terms of their hydroxyapatite (HA) forming ability in simulated body fluid (SBF) for up to 21 days. Fourier transform infrared (FTIR) spectroscopy results showed the successful HA formation on the coatings after 21 days. The first investigations were conducted on planar stainless steel sheets. In addition, scaffolds made from a TiAl4V6 alloy were considered to show the feasibility of coating of three dimensional structures by EPD. Because both BG and chitosan are antibacterial materials, the antibacterial properties of the as-produced coatings were investigated using E. coli bacteria cells. It was shown that the BG particle size has a strong influence on the antibacterial properties of the coatings.     

Micromorphology,mechanical, crystallization and permeability properties analysis of HA/PBAT/PLA (HA,hydroxyapatite; PBAT,poly(butylene adipate‐co‐butylene terephthalate); PLA,polylactide) degradability packaging films

In this study, the self‐made nano‐hydroxyapatite (HA) and poly(butylene adipate‐co‐butylene terephthalate) copolyesters (PBAT) were used as fillers, and composite films of HA/PLA (PLA, polylactide) and HA/PBAT/PLA systems were prepared. The micromorphology, mechanical properties, thermal properties, crystallinity, water vapor permeability and oxygen permeability of the composite films were studied. The results show that the self‐made HA has a porous rod‐like structure with a size of 30–50 nm. PBAT was dispersed uniformly in the HA/PLA matrix in the form of spherical particles and formed many pores and holes. The tensile strength, elongation at break and modulus of elasticity of HA/PLA composite films were increased by adding 10 wt% PBAT. The addition of HA and PBAT played a synergistic function in improving the crystallinity of the composite films. The water vapor and oxygen permeabilities of HA/PLA and HA/10%PBAT/PLA composite films can be regulated by adjusting the amount of HA. The results of this study indicate that composite films with higher water vapor and oxygen permeabilities exhibit great potential for applications in green packaging and fresh‐keeping packaging. © 2019 Society of Chemical Industry     

Bioactivity and Antibacterial Behaviors of Nanostructured Lithium-Doped Hydroxyapatite for Bone Scaffold Application

The material for bone scaffold replacement should be biocompatible and antibacterial to prevent scaffold-associated infection. We biofunctionalized the hydroxyapatite (HA) properties by doping it with lithium (Li). The HA and 4 Li-doped HA (0.5, 1.0, 2.0, 4.0 wt.%) samples were investigated to find the most suitable Li content for both aspects. The synthesized nanoparticles, by the mechanical alloying method, were cold-pressed uniaxially and then sintered for 2 h at 1250 °C. Characterization using field-emission scanning electron microscopy (FE-SEM) revealed particle sizes in the range of 60 to 120 nm. The XRD analysis proved the formation of HA and Li-doped HA nanoparticles with crystal sizes ranging from 59 to 89 nm. The bioactivity of samples was investigated in simulated body fluid (SBF), and the growth of apatite formed on surfaces was evaluated using SEM and EDS. Cellular behavior was estimated by MG63 osteoblast-like cells. The results of apatite growth and cell analysis showed that 1.0 wt.% Li doping was optimal to maximize the bioactivity of HA. Antibacterial characteristics against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were performed by colony-forming unit (CFU) tests. The results showed that Li in the structure of HA increases its antibacterial properties. HA biofunctionalized by Li doping can be considered a suitable option for the fabrication of bone scaffolds due to its antibacterial and unique bioactivity properties.     

Effect of carbon nanotube addition on friction coefficient of nanotubes/hydroxyapatite composites

Carbon nanotubes/hydroxyapatite (CNTs/HA) composites with different CNTs contents were synthesized by in situ method and were characterized by XRD, TEM and Raman spectroscopy. Friction coefficients of the composites were tested using UMT-2 friction tester. Effect of various factors including CNTs content, testing time and applied load on friction coefficient was carried out. Results show that the CNTs/HA composites exhibited lower friction coefficient than pure HA and their friction coefficients decreased with increase of CNTs content from 0 to 20 wt.%. Addition of CNTs in composite is beneficial to increase wear resistance of the CNTs/HA composite and to decrease its friction coefficient.     

High performance shape memory foams with isocyanate-modified hydroxyapatite nanoparticles for minimally invasive bone regeneration

This study conducts a comprehensive assessment of shape memory polyurethane (SMPU) composite foams with isocyanate-modified hydroxyapatite (imHA) nanoparticles in terms of their pore structures, mechanical properties, shape memory effects and biocompatibility in vitro. The results obtained in the research reveal the effectiveness of imHA nanoparticles in SMPU foams as inorganic cross-linking fillers, which contribute to the enhancement of mechanical properties and shape memory performance. Pore structures and compressive properties are simultaneously optimized when imHA content increases. The imHA enhanced SMPU foam could be adopted as a promising alternative for overcoming the disadvantages of traditional polymer scaffolds, such as insufficient mechanical properties, inadequate pore structure, low bioactivity and inconvenience in operation for bone regeneration.     

The Synthesis of Urchin‐Like Serried Hydroxyapatite (USHA) and its Reinforcing Effect for Dental Resin Composites

The novel urchin‐like serried hydroxyapatite (USHA) is synthesized by homogeneous hydrothermal precipitation method through adjusting the pH value and temperature. The silanized USHA is thereby used as the reinforcing filler for dental resin composites. The structure and morphology of various HA nanostructures are characterized with X‐ray diffraction, Fourier transform infrared spectroscopy, and field‐emission scanning electron microscope. Thermogravimetric analysis is used to analyze the grafting ratio of 3‐methacryloxypropyl trimethoxysilane on the surface of USHA. Mechanical performance of dental resin composites reinforced with silanized USHA at different filler loadings are measured by a universal mechanical testing machine. The neat resin matrix is served as the control group. Results demonstrate that the optimization of USHA morphology gave a better understanding of the effect of the pH value and temperature on its structure transformation. After trials, USHA with the complete globular structure and the serried whiskers is synthesized at pH value of 12.5 under 105 °C. When the USHA loading is 30 wt%, the corresponding dental composite significantly improved the mechanical properties in comparison with the neat resin, especially for the compressive strength.     

可注射nHA/PU复合多孔骨修复支架制备及表征

兼具良好孔隙率和原位任意塑形固化的可注射复合多孔骨修复材料在临床不规则骨缺损的治疗方面显示出巨大的优势。本研究通过优化双组分设计,以水为发泡剂制备可注射纳米羟基磷灰石/聚氨酯（nHA/PU）复合多孔支架。利用扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、力学测试及Gillmore针测试等手段对制备的支架进行结构形貌、化学组成、力学性能和固化时间表征。结果表明,本研究制备的可注射nHA/PU复合多孔支架孔隙率高、孔隙贯通性好,孔径分布在100~700μm,适宜细胞和组织向孔内生长;添加20% nHA显著提高了PU支架的力学强度,但降低了支架的孔隙率;可注射支架在8h固化,适宜临床操作。本研究制备的可注射nHA/PU复合多孔支架在不规则骨缺损修复领域具有较大的应用潜力。     

Drug loaded electrospun polymer/ceramic composite nanofibrous coatings on titanium for implant related infections

Developing an effective antibacterial surface with the help of drugs that prevent bacterial adhesion, colonization, and proliferation into the surrounding tissues is of great demand. Rifampicin (Rf) is effective antibiotic drug proved has proved its potential in treating bacteria in biofilms, especially against the microbes causing bone infections. Hydroxyapatite (HA), a biocompatible osteoconductive ceramic, has been verified to be a significant material for bioactivity enhancement. Electrospinning is an effective inexpensive method for incorporating nanoparticles into nanofibers with uniform distribution for the drug delivery system for tissue engineering applications. In the current study, for improving bioactivity and antibacterial properties, novel functional polycaprolactone (PCL) composite nanofibers loaded HA and Rf was developed and coated on titanium (Ti). Different characterization techniques such as SEM, EDS, XRD, FITR were used to analyze these PCL/Rf/HA nanocomposites. The results showed that the bioactivity and tensile strength of the composite scaffold increased with the addition of HA nanoparticles. In vitro bioactivity demonstrated that the PCL/HA/Rf composite nanofibers possess enhanced calcium deposition when compared to the pure sample. Cellular interactive responses such as adhesive and proliferation were evaluated using hFOB human fetal osteoblast cell lines. After 6 days of culturing, the cellular properties on Ti sample coated with PCL/HA/Rf was significantly improved. Antibacterial evaluations on the substrates showed that Rf-loaded PCL/HA fibers displayed >3 log reduction against S.aureus MRSA, and S.epidermidis bacterial strain and >2 log reduction against P.aeruginosa bacteria. In vitro drug release study shows initial burst release of Rf, followed by sustained released of 62% at the end of 32 days. The cell viability, adhesion, and proliferation evaluation suggest that the PCL/HA/Rf coated substrate possess good cytocompatibility. Further incorporation of Rf enhanced the antibacterial property of this nanofibrous scaffold.     

梯度多孔载Ag羟基磷灰石陶瓷的制备和性能研究

本文采用添加造孔剂法制备孔隙呈现梯度分布的多孔载Ag羟基磷灰石(Ag-HA)陶瓷。研究了造孔剂分布、烧结温度和载Ag含量对梯度多孔Ag-HA陶瓷孔隙度的影响。分析了烧结产物的物相组成和微观形貌,测量了烧结后梯度多孔Ag-HA陶瓷的压缩性能和抗菌性能。研究结果表明:随着中间层造孔剂含量增加,梯度多孔Ag-HA陶瓷的孔隙度增大,抗压强度减小;随着烧结温度的增大,梯度多孔Ag-HA陶瓷的孔隙度减小,抗压强度增大;当造孔剂分布为20%-10%-20%(质量分数),压制压力为100 MPa,烧结温度为1 150 ℃,Ag含量为2.0%(摩尔分数)时,烧结后梯度多孔2.0Ag-HA陶瓷的孔隙度为24.7%,抗压强度为12.6 MPa。XRD分析表明烧结产物为掺杂Ag离子的HA相。SEM观察表明烧结样品的孔隙呈现梯度分布。梯度多孔Ag-HA陶瓷的抗菌实验表明:随载Ag含量和孔隙度的增大,梯度多孔Ag-HA陶瓷对于大肠杆菌和金黄色葡萄球菌的抑菌圈直径增加,表现出较强的抗菌性能,而纯HA陶瓷未表现出抗菌性能。     

Morphology,wettability, and mechanical properties of polycaprolactone/hydroxyapatite composite scaffolds with interconnected pore structures fabricated by a mini‐deposition system

A new mini‐deposition system (MDS) was developed to fabricate scaffolds with interconnected pore structures and anatomical geometry for bone tissue engineering. Polycaprolactone/hydroxyapatite (PCL/HA) composites with varying hydroxyapatite (HA) content were adopted to manufacture scaffolds by using MDS with a porosity of 54.6%, a pore size of 716 μm in the x‐y plane, and 116 μm in the z direction. The water uptake ratio and compressive modulus of PCL/HA composite scaffold increase from 8 to 39% and from 26.5 to 49.8 MPa, respectively, as the HA content increases from 0 to 40%. PCL/HA composite scaffolds have better wettability and mechanical properties than pure PCL scaffold. A PCL/HA composite scaffold for mandible bone repair was successfully fabricated with both interconnected pore structures and anatomical shape to demonstrate the versatility of MDS. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

3D porous HA/TCP composite scaffolds for bone tissue engineering

Calcium phosphates (apatites) are considered as a research frontier for bone regeneration applications by virtue of similarity to the mineral constituent of bone, suitable biocompatibility and remarkable osteogenesis ability. In this regard, the biodegradability and mechanical properties of monophasic apatites, typically hydroxyapatite (HA) and tricalcium phosphate (TCP), are imperfect and do not fulfill some requirements. To overcome these drawbacks, 3D porous HA/TCP composite scaffolds prepared by conventional and more recently, 3D printing techniques have shown to be promising since their bioperformance is adjustable by the HA/TCP ratio and pores. Despite the publication of several reviews on either 3D porous scaffolds or biphasic calcium phosphates (BCPs), no review paper has to our knowledge focused on 3D porous BCP scaffolds. This paper comprehensively reviews the production methods, properties, applications and modification approaches of 3D porous HA/TCP composite scaffolds for the first time. In addition, new insights are introduced towards developing HA/TCP scaffolds with more impressive bioperformance for further tissue engineering applications, including those with different interior and exterior frameworks, patient-specific specifications and drugs (or other biological factors) loading.     

Chitosan graft copolymers‐HA/DBM biocomposites: Preparation,characterization, and in vitro evaluation

The combination of biopolymer with a bioactive component takes advantage of the osteoconductivity and osteoinductivity properties. The studies on composites containing hydroxyapatite (HA), demineralized bone matrix (DBM) fillers and chitosan biopolymer are still conducted. In the present study, the bioactive fillers were loaded onto p(HEMA‐MMA) grafted chitosan copolymer to produce a novel biocomposites having osteoinductive and osteoconductive properties. The produced composites were assessed by TGA, XRD, FTIR, and SEM techniques to prove the interaction between both matrices. In vitro behavior of these composites was performed in SBF to verify the formation of apatite layer onto their surfaces and its enhancement. The results confirmed the formation of thick apatite layer containing carbonate ions onto the surface of biocomposites especially these containing HA‐DBM mixture and pMMA having bone cement formation in their structure. These a novel biocomposites have unique bioactivity properties can be applied in bone implants and tissue engineering applications as scaffolds in future. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of pH and carbon nanotube content on the corrosion behavior of electrophoretically deposited chitosan–hydroxyapatite–carbon nanotube composite coatings

In the first stage, chitosan (CH)–hydroxyapatite (HA)-multiwalled carbon nanotube (MWCNT) composite coatings were synthesized by electrophoretic deposition technique (EPD) on 316L stainless steel substrates at different levels of pH and characterized by X-ray diffraction (XRD), Raman spectroscopy, FTIR and field emission scanning electron microscopy (FESEM). A smooth distribution of HA and MWCNT particles in a chitosan matrix with strong interfacial bonding was obtained. In the next stage, effects of pH and MWCNT content of the suspension on the corrosion behavior and deposition mechanism were studied. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) curves revealed that increasing pH level of the suspension increases the corrosion protection properties of the deposited composite coating in simulated body fluid (SBF). Furthermore, Nyquist plots showed that increasing MWCNT content of the suspension resulted in higher amounts of R_p, but because of the capillary properties of MWCNTs and degradability of the chitosan matrix, corrosion protection level of the coatings containing HA–CH–MWCNT was lower than those of coatings containing solely HA–CH. Amperometric curves in different pH levels of the suspension revealed that the system is diffusion controlled at elevated pH values.     

Preparation and characterization of a poly(methyl methacrylate) based composite bone cement containing poly(acrylate‐co‐silane) modified hydroxyapatite nanoparticles

The purpose of this study was to study the mechanical properties of poly(methyl methacrylate) (PMMA)‐based bone cement incorporated with hydroxyapatite (HA) nanoparticles after surface modification by poly(methyl methacrylate‐co‐γ‐methacryloxypropyl timethoxysilane) [P(MMA‐co‐MPS)]. PMMA and P(MMA‐co‐MPS) were synthesized via free‐radical polymerization. P(MMA‐co‐MPS)‐modified hydroxyapatite (m‐HA) was prepared via a dehydration process between silane and HA; the bone cement was then prepared via the in situ free‐radical polymerization of methyl methacrylate in the presence of PMMA and P(MMA‐co‐MPS)–m‐HA. Fourier transform infrared (FTIR) spectroscopy, ¹H‐NMR, and gel permeation chromatography were used to characterize the P(MMA‐co‐MPS). Thermogravimetric analysis and FTIR were used as quantitative analysis methods to measure the content of P(MMA‐co‐MPS) on the surface of HA. The effect of the proportion of m‐HA in the PMMA‐based bone cement on the mechanical properties was studied with a universal material testing machine. A 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay was also carried out to determine the cytotoxicity of the composite bone cement. The results showed that the surface modification of HA greatly improved the interaction between the inorganic and organic interfaces; this enhanced the mechanical properties of bone cement for potential clinical applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40587.     

Study on the properties of crosslinking of poly(ethylene oxide) and hydroxyapatite–poly(ethylene oxide) composite

This study covers the crosslinking of poly(ethylene oxide) (PEO) and its composite with calcium hydroxyapatite (HA), their mechanical and swelling properties, and morphology. Sheets of the composites of PEO (two different grades with M_v: 5 × 10⁶ and 2 × 10⁵) and HA and neat PEO were prepared by compression molding. The prepared composite and PEO (0.1‐mm‐thick) sheets were crosslinked with exposure of UV‐irradiation in the presence of a photoinitiator, acetophenone (AP). This simple method for crosslinking, induced by UV‐irradiation in the presence of AP, yielded PEO with gel content up to 90%. Gel content, equilibrium swelling ratio, and mechanical and morphological properties of the low molecular weight polyethylene oxide (LMPEO)–HA crosslinked and uncrosslinked composites were evaluated. Although the inclusion of HA into LMPEO inhibits the extent of crosslinking, the LMPEO–HA composite with 20% HA by weight shows the highest gel content, with appreciable equilibrium swelling and mechanical strength. The growth of HA in simulated body fluid solutions on fractured surfaces of LMPEO and also LMPEO–HA was found to be very favorable within short times. The dimensional stability of these samples was found to be satisfactory after swelling and deposition experiments. The good compatibility between the filler hydroxyapatite and poly(ethylene oxide) makes this composite a useful tissue‐adhesive material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 488–496, 2003