Effects of friction stir processing and nano-hydroxyapatite on the microstructure,hardness,degradation rate and in-vitro bioactivity of WE43 alloy for biomedical applications

Nowadays,magnesium alloys are emerging in biomedical implants for their similar properties to natural bones.However,the rapid degradation of magnesium alloys in biological media hinders successful implantation.Refinement of microstructure,as well as reinforcement particles can significantly improve the degradation rate.In this work,multi-pass friction stir processing(FSP)was proposed to synthesize WE43/nano-hydroxyapatite(n HA)surface composite,the microstructure,reinforced particle distribution,micro-hardness,corrosion behavior and in-vitro bioactivity were studied.The subsequent FSP passes of WE43 alloy and WE43/n HA composite refined the grain size which was reduced by 94.29%and 95.92%(2.63 and 1.88μm,respectively)compared to base metal after three passes.This resulted in increasing the microhardness by 120%(90.86 HV0.1)and 135%(105.59 HV0.1)for the WE43 and WE43-n HA,respectively.It is found that increasing FSP passes improved the uniform distribution of n HA particles within the composite matrix which led to improved corrosion resistance and less degradation rate.The corrosion rate of the FSPed WE43/n HA composite after three passes was reduced by 38.2%(4.13 mm/year)and the degradation rate was reduced by 69.7%(2.87 mm/y).This is attributed to secondary phase(Mg24Y5and Mg41Nd5)particle fragmentation and redistribution,as well as a homogeneous distribution of n HA.Additionally,the growing Ca-P and Mg(OH)2layer formed on the surface represented a protective layer that reduced the degradation rate.The wettability test revealed a relatively hydrophilic surface with water contact angle of 49.1±2.2°compared to 71.2±2.1°for base metal.Also,biomineralization test showed that apatite layer grew after immersion 7d in simulated body fluid with atomic ratio of Ca/P 1.60 approaching the stoichiometric ratio(1.67)indicating superior bioactivity of FSPed WE43/n HA composite after three passes.These results raise that the grain refinement by FSP and introduction of n HA particles significantly improved the degradation rate and in-vitro bioactivity of WE43 alloy for biomedical applications.

Preparation and characterization of chitosan/nano-hydroxyapatite composite used as bone substitute materials

Chitosan/nano-hydroxyapatite composites with different weight ratios were prepared through a co-precipitation method using Ca（OH）2, H3PO4 and chitosan as starting materials. The properties of these composites were characterized by means of TEM, IR, XRD, TGA, burn-out tests and universal matertial testing machine. The results showed that the HA synthesized here was poorly crystalline carbonated nanometer crystals and dispersed uniformly in chitosan phase and there was no phase-separation between the two phases. The addition of n-HA resulted in a decrease of decomposing temperature of chitosan. Because of the interactions between chitosan and n-HA, the mechanical properties of these composites were improved, and the maximum value of the compressive strength was measured to be about 120MPa corresponding to the chitosan/n-HA composite with a weight ratio of 30/70.

Melt-Spinning of Nano-Hydroxyapatite/Poly(ε-caprolactone)Composite Fibers for Potential Application in Bone Tissue Engineering

Nano-hydroxyapatite/poly（e-caprolactone） （nHA/PCL） composite materials are among the best candidates for application in bone tissue engineering. As the main technique to fabricate porous scaffolds, electrospilming produce scaffolds with unsatisfactory mechanical strength and limited pore size for cdi infiltration. Micron-sized fiber assembly with higher mechanical strength is qualified to structure hybrid scaffolds. In this study, nHA/PCL monofilament fibers with different mass ratios were fabricated through melt-spinning. Transmission electron microscope （TEM） was used to observe the aggregation between nHA parfides. Other characterizations including scanning electron microscopy （SEM）, attenuated total reflection Fourier transform infrared spectroscopy （ATR.FTIR） and X-ray diffraction （XRD） were done to discuss the morphology, components and crystallization of the nHA/PCL composite fibers, respectively. The influence of nHA/PCL mass ratio on the tensile properties and water contact angle of composite fibers was also studied. The SEM images show the homogeneous dispersion of nano partides in the polymer matrix. Besides, nHA content increases the tensile strength, initial modulus and hydrophillcity of the composite fibers under the premise of spinnability. This kind of fibers is strong enough to fabricate fiber assembly which may have potential application in bone tissue engineering.

nHAP对大鼠肝线粒体的生物活性作用

为了探讨羟基磷灰石纳米粒子(nHAP)对大鼠肝线粒体生物活性的影响,将nHAP直接作用于线粒体,在不同浓度和时间下测定线粒体标志酶琥珀酸脱氢酶(SDH)比活性,并与对照组进行比较。结果显示,当nHAP中水含量在10%以下时,线粒体生物活性未发现改变;当nHAP浓度递增时,在等时间段内,对线粒体SDH比活性呈逐步抑制作用;在不等时间段内,nHAP对线粒体SDH比活性的抑制作用与对照组相比较差异有显著性(p<0.05)。因此,nHAP对线粒体SDH比活性的抑制有浓度和时间的依赖性。

Development of collagen and nano-hydroxyapatite-based novel self-healing cartilage

In recent years,research on self-healing polymers for diverse biomedical applications has surged due to their resemblance to the native extracellular matrix.Here,we introduce a novel self-healing hydrogel scaffold made from collagen(Col)and nano-hydroxyapatite(nHA)via a one-pot-synthesis approach under the influence of heating in less than 10 min.Process parameters,including the quantities of Col,guar gum,solvent,nHA,borax,and glycerol in the system were optimized for the minimization of the self-healing time.The synthesized hydrogel and polymers underwent characterization via FTIR,SEM,EDS,TGA,and^(13)C-NMR.Additionally,the hydrogel showed hemocompatibility with only 6.76%hemolysis at 10μg-mL^(-1),while the scaffold maintained cellular metabolic activity at all concentrations for 24 h,with the optimal viability at 1 and 2.5μg-mL^(-1),sustaining 93.5%and 90%viability,respectively.Moreover,the hydrogel scaffold exhibited rapid self-healing within 30 s of damage,alongside a tough and flexible nature,as indicated by its swelling rate,biodegradation under various biological pH solutions,and tensile strength of 0.75 MPa.Hence,the innovative Col and nHA self-healing hydrogel scaffold emerges as an ideal,non-toxic,cost-effective,and easily synthesized material with promising potential in cartilage repair applications.

羟基磷灰石混粉电火花铣削加工316L的效果研究

316L不锈钢是一种制作人体植入物的重要材料。经过调研提出一种羟基磷灰石混粉电火花铣削加工方式,通过因素和水平的变化探究羟基磷灰石混粉电火花铣削加工与混粉电火花成形加工两种加工工艺蚀除316L不锈钢的趋势与不同。试验结果发现,混粉电火花铣削加工能够提高材料去除率,降低电极损耗率、表面粗糙度和表面接触角。证明了该加工方式具有研究意义,并通过单因素试验进一步探究该加工方式正负极性下所呈现的不同加工特性及形成原因。极性试验结果显示,正极性加工能够实现更高的材料去除率,负极性加工则呈现更低的电极损耗率、表面粗糙度和表面接触角。

Nano-hydroxyapatite promotes cell apoptosis by co-activating endoplasmic reticulum stress and mitochondria damage to inhibit glioma growth

Despite a growing body of studies demonstrating the specific antitumor effect of nano-hydroxyapatite(n-HA),the underlying mechanism remained unclear.Endoplasmic reticulum(ER)and mitochondria are two key players in intracellular Ca^(2+)homeostasis and both require Ca^(2+)to participate.Moreover,the ER–mitochondria interplay coordinates the maintenance of cellular Ca^(2+)homeostasis to prevent any negative consequences from excess of Ca^(2+),hence there needs in-depth study of n-HA effect on them.In this study,we fabricated needle-like n-HA to investigate the anti-tumor effectiveness as well as the underlying mechanisms from cellular and molecular perspectives.Data from in vitro experiments indicated that the growth and invasion of glioma cells were obviously reduced with the aid of n-HA.It is interesting to note that the expression of ER stress biomarkers(GRP78,p-IRE1,p-PERK,PERK,and ATF6)were all upregulated after n-HA treatment,along with the activation of the pro-apoptotic transcription factor CHOP,showing that ER stress produced by n-HA triggered cell apoptosis.Moreover,the increased expression level of intracellular reactive oxygen species and the mitochondrial membrane depolarization,as well as the downstream cell apoptotic signaling activation,further demonstrated the pro-apoptotic roles of n-HA induced Ca^(2+)overload through inducing mitochondria damage.The in vivo data provided additional evidence that n-HA caused ER stress and mitochondria damage in cells and effectively restrain the growth of glioma tumors.Collectively,the work showed that n-HA co-activated intracellular ER stress and mitochondria damage are critical triggers for cancer cells apoptosis,offering fresh perspectives on ER-mitochondria targeted anti-tumor therapy.

Improving chitosan-based composite membrane by introducing a novel hybrid functional nano-hydroxyapatite with carboxymethyl cellulose and phytic acid

A functional hybrid nano-hydroxyapatite(carboxymethyl cellulose-phytic acid-n-HA,CMC-PA-n-HA)was prepared by adding CMC and PA.The results of Fourier transformation infrared spectra,X-ray diffraction,thermal gravimetric analysis and dispersion experiments indicated that the addition of CMC and PA affected the morphology,crystallinity and crystal size of hybrid n-HA,and CMC endowed hybrid n-HA with excellent dispersion.Scanning electron microscope results showed that CMC-PA-n-HA nanoparticle could be uniformly dispersed in chitosan(CS)matrix to obtain composite membrane by casting technology,so that the highest tensile strength of CMC-PA-n-HA/CS composite membrane was 69.64%and 144.45%higher than that of CS membrane and n-HA/CS composite membrane,respectively.Contact angle test showed that CMC-PA-n-HA effectively improved hydrophilicity of the CS membrane.The simulated body fluid immersion results indicated that the CMC-PA-n-HA/CS composite membrane not only exhibited good degradability but also promoted bone-like apatite deposition.The cell proliferation experiments proved that the introduction of PA made the composite membrane have better cell adhesion and proliferation ability.Antibacterial tests demonstrated that PA could effectively improve the antibacterial properties of the composite membrane,which is expected to be applied as guide bone tissue regeneration membrane.

In situ growth of nano-hydroxyapatite on multilayered Ti_(3)C_(2)T_(x) MXene as a drug carrier with superior-performance

Bone defects caused by tumor resection typically require bone repair materials to fill the defect sites.The development of multifunctional bone filling materials with integrated chemotherapy,photohermal therapy,and guided bone regeneration is very necessary and urgently needed.Herein,for the first time,the construction of novel multilayered Ti_(3)C_(2)T_(x) MXene(m-MXene)/nano-hydroxyaptite(nHAp)composites(m-MXene/nHAp)for bone repair is reported.The in situ growth of nHAp on multilayered Ti_(3)C_(2)T_(x) MXene is achieved through a facile hydrothermal method without using any organic additives.Due to the syner-gistic effects of nHAp and m-MXene,the m-MXene/nHAp composites show superior drug carrier perfor-mance with ultra-high drug loading capacity and ultra-long drug sustained release time.The molecular dynamics simulation results indicate that both Ti_(3)C_(2)T_(x) MXene and HAp show many adsorption sites and high binding energy with DOX.Moreover,the m-MXene/nHAp composites possess high photothermal conversion efficiency and excellent photothermal stability.The in situ growth of nano-HAp can signifi-cantly improve the biocompatibility of the m-MXene.The as-prepared multifunctional m-MXene/nHAp composites in this work can be used as bone filling powder and have great potential in bone defect reconstruction caused by bone tumor.

磁性纳米纤维复合材料原位诱导体内成骨的研究(英文)

目的:研究一种新型顺磁性的纳米纤维复合支架γ-Fe2O3/nHAP/PDLLA在弱磁场下体内诱导新骨形成的功效。方法:纳米纤维复合材料支架通过电纺丝方法制成,支架内部的微观结构用扫描电镜(SEM)进行表征。将支架植入兔横突根部骨缺损处并在12周后处死动物,应用组织学方法研究支架在动物体内原位诱导新骨形成和胶原蛋白沉积的情况。结果:与对照的nHAP/PDLLA纳米纤维支架相比,磁性纳米纤维复合支架上有更多的Ⅰ型胶原沉积,新骨的生成量也明显增加。结论:磁性纳米纤维复合支架能够促进骨缺损部位的新骨生成,在引导骨组织再生与修复方面具有应用潜能。

羟基磷灰石/丝素蛋白复合纤维的制备及其矿化研究

在以静电纺丝法制备羟基磷灰石(HAP)/丝素蛋白(SF)复合纤维的前提下,采用同轴共纺法获得了以HAP为"芯"、SF为"皮"的双组分电纺纤维(电纺膜),并通过扫描和透射电镜、红外光谱以及X射线衍射等手段对电纺纤维进行了表征.结果表明,HAP均存在于上述两种方法制备的纳米纤维中,但同轴共纺法不仅可以避免HAP/SF共混电纺时pH值对丝素蛋白结构的影响,并且能大大提高电纺膜中HAP的含量.同时,我们还分别以SF纤维、HAP/SF复合纤维和HAP/SF"皮-芯"纤维作为有机基质,对羟基磷灰石在其上的矿化过程进行了探索,结果表明含较多羟基磷灰石的HAP/SF"皮-芯"纤维更有利于矿化的进行。

转海蓬子Na^+/H^+逆向运输蛋白基因番茄的耐盐性研究

以转海蓬子Na+/H+逆向运输蛋白基因(Nhap)的番茄(Lycopersicon esculentum Mill.)阳性植株和对照植株为材料,测定叶片相对含水量、质膜透性、K+/Na+比值和叶绿素含量4项耐盐指标.结果表明:在盐胁迫条件下,转基因植株的相对含水量、K+/Na+比值和叶绿素含量明显高于对照植株,而叶片质膜透性明显低于对照植株,说明Nhap基因已经在番茄转化植株体内表达,提高了转基因植株的耐盐性.

静电纺丝素/BMP-2支架在骨组织工程中的应用研究

丝素(SF)与骨形态形成蛋白(BMP-2)共混及添加纳米级羟基磷灰石(nHAP)后,通过静电纺丝制得纤维支架,培养人骨髓间质干细胞(hMSCs)研究体外骨形成。BMP-2在静电纺丝过程中能保持生物活性。hMSCs在SF/PEO/BMP-2、SF/PEO/nHAP、SF/PEO/BMP-2/nHAP上于成骨介质中静态培养31天,对照组为SF/PEO及PEO浸出。结果表明静电纺丝素基支架能促进hMSCs向成骨生长和分化。相比对照组,含有BMP-2的支架促进钙沉积和骨样标志的转录水平,说明该支架是BMP-2的有效传输体系。X衍射分析表明,与对照组相比,SF/BMP-2中的沉积磷灰石结晶度高;nHAP微粒进入纤维支架并促进了骨组织的形成。同时含有BMP-2、nHAP的支架钙沉积最高并促进BMP-2转录水平。静电纺丝素基支架在骨组织工程中具有良好的应用前景,此外电纺丝微弱的水溶性过程给不稳定细胞因子的传输和其它成分进入该体系提供了条件。

动物骨源羟磷灰石负载Co3O4用于N2O催化分解

通过焙烧猪骨和鸡骨获得羟磷灰石(nHAP)载体,并采用浸渍法制备Co3O4/nHAP催化剂。采用XRD、N2物理吸附-脱附、FT-IR和H2-TPR等对催化剂进行表征,在连续流动微反装置上考察催化剂催化分解N2O的性能。结果表明,相比于鸡骨源Co3O4/nHAP催化剂,以猪骨源HAP为载体的催化剂因其较大的比表面积以及较小的Co3O4粒径尺寸,提供了更多的活性位点。特别是猪骨源Co3O4/nHAP催化剂中适量的K、Na等元素促进了Co^3+到Co^2+的还原,削弱了Co-O键,使催化剂的催化活性显著提高。

Nano-hydroxyapatite accelerates vascular calcification via lysosome impairment and autophagy dysfunction in smooth muscle cells

Vascular calcification(VC)is a common characteristic of aging,diabetes,chronic renal failure,and atherosclerosis.The basic component of VC is hydroxyapatite(HAp).Nano-sized HAp(nHAp)has been identified to play an essential role in the development of pathological calcification of vasculature.However,whether nHAp can induce calcification in vivo and the mechanism of nHAp in the progression of VC remains unclear.We discovered that nHAp existed both in vascular smooth muscle cells(VSMCs)and their extracellular matrix(ECM)in the calcified arteries from patients.Synthetic nHAp had similar morphological and chemical properties as natural nHAp recovered from calcified artery.nHAp stimulated osteogenic differentiation and accelerated mineralization of VSMCs in vitro.Synthetic nHAp could also directly induce VC in vivo.Mechanistically,nHAp was internalized into lysosome,which impaired lysosome vacuolar H+-ATPase for its acidification,therefore blocked autophagic flux in VSMCs.Lysosomal re-acidification by cyclic-3′,5′-adenosine monophosphate(cAMP)significantly enhanced autophagic degradation and attenuated nHAp-induced calcification.The accumulated autophagosomes and autolysosomes were converted into calcium-containing exosomes which were secreted into ECM and accelerated vascular calcium deposit.Inhibition of exosome release in VSMCs decreased calcium deposition.Altogether,our results demonstrated a repressive effect of nHAp on lysosomal acidification,which inhibited autophagic degradation and promoted a conversion of the accumulated autophagic vacuoles into exosomes that were loaded with undissolved nHAp,Ca^(2+),Pi and ALP.These exosomes bud off the plasma membrane,deposit within ECM,and form calcium nodules.Vascular calcification was thus accelerated by nHAP through blockage of autophagic flux in VSMCs.

Biocompatibility of nano-hydroxyapatite/Mg-Zn-Ca alloy composite scaffolds to human umbilical cord mesenchymal stem cells from Wharton's jelly in vitro

Seeding cells and scaffolds play pivotal roles in bone tissue engineering and regenerative medicine.Wharton’s jelly-derived mesenchymal stem cells(WJCs)from human umbilical cord represent attractive and promising seeding cells in tissue regeneration and engineering for treatment applications.This study was carried out to explore the biocompatibility of scaffolds to seeding cells in vitro.Rod-like nano-hydroxyapatite(RN-HA)and flake-like micro-hydroxyapatite(FM-HA)coatings were prepared on Mg-Zn-Ca alloy substrates using micro-arc oxidation and electrochemical deposition.WJCs were utilized to investigate the cellular biocompatibility of Mg-Zn-Ca alloys after different surface modifications by observing the cell adhesion,morphology,proliferation,and osteoblastic differentiation.The in vitro results indicated that the RN-HA coating group was more suitable for cell proliferation and cell osteoblastic differentiation than the FM-HA group,demonstrating better biocompatibility.Our results suggested that the RN-HA coating on Mg-Zn-Ca alloy substrates might be of great potential in bone tissue engineering.

Comparative evaluation of the physicochemical properties of nano-hydroxyapatite/collagen and natural bone ceramic/collagen scaffolds and their osteogenesis-promoting effect on MC3T3-E1 cells

The use of various types of calcium phosphate has been reported in the preparation of repairing materials for bone defects.However,the physicochemical and biological properties among them might be vastly different.In this study,we prepared two types of calcium phosphates,nano-hydroxyapatite(nHA)and natural bone ceramic(NBC),into 3D scaffolds by mixing with type I collagen(CoL),resulting in the nHA/CoL and NBC/CoL scaffolds.We then evaluated and compared the physicochemical and biological properties of these two calcium phosphates and their composite scaffold with CoL.Scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared spectroscopy(FTIR),X-ray diffraction spectroscopy(XRD)and compressive tests were used to,respectively,characterize the morphology,composition,distribution and the effect of nHA and NBC to collagen.Next,we examined the biological properties of the scaffolds using cytotoxicity testing,flow cytometry,immunofluorescence staining,biocompatibility testing,CCK-8 assays and RT-PCR.The results reflected that the Ca2t released from nHA and NBC could bind chemically with collagen and affect its physicochemical properties,including the infrared absorption spectrum and compression modulus,among others.Furthermore,the two kinds of scaffolds could promote the expression of osteo-relative genes,but showed different gene induction properties.In short,NBC/CoL could promote the expression of early osteogenic genes,while nHA/CoL could upregulate late osteogenic genes.Conclusively,these two composite scaffolds could provide MC3T3-E1 cells with a biomimetic surface for adhesion,proliferation and the formation of mineralized extracellular matrices.Moreover,nHA/CoL and NBC/CoL had different effects on the period and extent ofMC3T3-E1 cell mineralization.

新型纳米HAP复合改性材料制备及其防龋性能研究

目的:探讨酪蛋白磷酸多肽(CPP)纳米羟基磷灰石(nHAP)(CPP-nHAP)溶液对正畸邻面去釉(IPR)后釉质表面防龋作用的最佳浓度。方法:将粒径为20 nm的nHAP溶液与不同浓度的CPP碱性溶液反应,制备出CPP浓度分别为1%、3%、5%,nHAP浓度为10%的CPP-nHAP溶液。对溶液抽滤、冷冻干燥后,通过傅立叶变换红外光谱仪对其结构与表征进行分析。收集新鲜前磨牙50颗,制备IPR标本100个,随机分为5组(n=20),对标本进行1%、3%、5%的CPP-nHAP溶液以及多乐氟4种不同再矿化处理,预留一组不做任何处理,进行体外pH循环实验,用显微硬度仪测量实验前后釉质表面硬度,扫描电镜观察釉质表面形态并用X射线能谱仪分析釉质表面钙磷比值。结果:制备的浓度为1%、3%、5%的CPP-nHAP溶液为性状稳定的乳白色悬浊液。防龋实验后各组釉质表面显微硬度值、钙磷比值均有显著性差异(P<0.05),两两比较,浓度为3%的CPP-nHAP溶液组防龋实验后显微硬度值最大,钙磷比值与5%组无显著性差异(P>0.05),大于其他组(P<0.05),浓度为1%的CPP-nHAP溶液显微硬度值与多乐氟组无显著性差异(P>0.05)。结论:3种不同浓度的CPP和10%nHAP CPP-nHAP溶液在IPR后均能达到防龋效果。CPP浓度为1%的CPP-nHAP溶液防龋效果与多乐氟相当,CPP浓度为3%、5%的CPP-nHAP的防龋效果优于多乐氟组,其中3%组的防龋效果最好。

Magnesium/Nano-hydroxyapatite Composite for Bone Reconstruction: The Effect of Processing Method

Nano-ceramic particles can serve as reinforcing agents for metallic materials to improve their mechanical properties.However,it is important to ensure chemical compatibility between the matrix and particles.In the present study,magnesium composites with and without nano-hydroxyapatite(nHA)particles were fabricated for bone reconstruction applications.Two different techniques were used,Conventional Sintering(CS)of powder compacts and Spark Plasma Sintering(SPS)of pre-compacted powder.Results showed that a 10 wt%addition of nHA particles to magnesium,followed by SPS improved the compression strength by 27%.CS did not lead to any significant improvement compared to SPS processing.X-ray diffraction data after CS revealed the formation of unfavorable phases due to chemical reactions between nHA particles and the magnesium matrix,while these phases were absent after SPS processing.The mechanical properties of the specimens fabricated by CS were much inferior to those processed using SPS.The shorter processing time associated with SPS leaded to reduced interaction between nHA particles and the Mg-matrix,compared to CS.

Preparation and evaluation of nano-hydroxyapatite/poly(styrene-divinylbenzene) porous microsphere for aspirin carrier

A novel vehicle for the delivery of aspirin （ASA） was prepared from porous nano-hydroxyapafite/poly（styrene-divinylbenzene） [nano-HAP/P（St-DVB）] composite microspheres by grafting nano-HAP [Ca10（PO4）6（OH）2] onto porous P（St-DVB） micro- spheres. Four types of porous composite microspheres were prepared, each with different nano-HAP contents. The ASA-loaded composite microspheres prepared with 10% and 15% nano-HAP （mass ratio） exhibited excellent buoyancy with relatively short instantaneous floating time （within l0 min） and a long sustained floating time （12 h） in simulated gastric juice. They also offered good sustained release of ASA （up to 8 h）. Furthermore, these composite microspheres displayed good buff- ering capacity that prevented the buildup of acidity caused by hydrolysis of ASA, keeping the pH of gastric juice within the normal range （pH 0.9 to 1.5）. The results showed that porous nano-HAP/P（St-DVB） composite microspheres prepared with 10% and 15% nano-HAP could be used as a novel drug carrier for ASA, providing a sustained release dose without leading to stomach irritation, a side effect that is often associated with ASA medication.