Properties of Microcrystalline Chitosan-Calcium Phosphate Complex Composite

Nature itself uses materials like, cellulose to provide the structure of plants, chitin as the exoskeleton of several insects and molluscs, collagen for mechanical support in connective tissues and so on. At present, the socioeconomic situation of the modern world has raised the interest in renewable materials being used in regenerative medicine. The composition of MCCh/?-TCP complex in sponge shape is derived from the junction of two or more different materials, containing organic and inorganic materials, including bioactivity and biodegradability as a characteristic. The chemical characteristics of MCCh/?-TCP complex composites showed that both of the components organic and inorganic exist in the material. All sponge preparations, with MCCh/?-TCP have a well-shaped 3-dimentional structure, a highly porous and interconnected and homogenous pore structure to ensure a biological environment conducive to cell attachment and proliferation as well as tissue growth, providing the passage of nutrient flow. These materials can be used in future for medical applications as a base for scaffolds production and as implants in regenerative medicine.

The Effect of Premixed Schedule on the Crystal Formation of Calcium Phosphate Cement-chitosan Composite with Added Tetracycline

In this study, calcium phosphate cements （CPC） were prepared by mixing cement powders of tetracalcium phosphate （TTCP） with a cement liquid of phosphate acid saline solution. Tetracycline （TTC）-CPC, chitosan-CPC and chitosan-TTC-CPC were investigated with different premixed schedule. It was demonstrate that both TTC and chitosan worked on the phase transition and crystal characteristics. TTCP mixed with phosphate acid saline solution had similar features of Fourier transform-infrared spectrometry （FT-IR） no matter it was mixed with chitosan or TTC or both. TTC premixed with cement liquid or powder had significant different features of FT-IR and 876 cm-1 seemed to be a special peak for TTC when TTC was premixed with cement liquid. This was also supported by XRD analysis, which showed that TTC premixed with cement liquid improved phase transition of TTCP to OCP. Chitosan, as organic additive, regulates the regular crystal formation and inhibits the phase transition of TTCP to OCP, except when it is mingled with cement liquid premixed with TTC in field scanning electron microscope. It was concluded that the premixed schedule influences the crystal formation and phase transition, which may be associated with its biocompatibility and bioactivities in vivo.

Surface-modified Biphasic Calcium Phosphate/Poly (L-lactide) Biocomposite

Biphasic calcium phosphate （BCP） powders were prepared by hydrolyzation proc-ess and surface-modified by directly grafted L-lactide （LLA） onto the surface of BCP through a chemical linkage. The grafting ratio of organic groups was 9 wt%. After surface modification, the surface of BCP powders was covered by the lamella-shaped crystal. Poly （L-lactide） was mixed with BCP to form the BCP/PLLA biocomposite. Modified BCP （mBCP） particles could be uniformly dis-persed in PLLA matrix. The compressive strength of the mBCP/PLLA composite is 115 MPa, 28% higher than that of unmodified-BCP/PLLA composite. The improved mechanical strength is attributed to the enhanced adhesion between the inorganic BCP filler and the organic PLLA matrix.

Preparation of a Novel Calcium Phosphate Cement Using N-methylene Phosphonic Chitosan as a Gelling Agent

A modified chitosan （ N-methylene phosphonic Chitosan, NMPC） was synthesized to improve solubility and ability to bind calcium ion. The properties of the raw material chitosan and its derivative NMPC were characterised using FTIR , ^1H- NMR . The aim of this study was to enhance the compressive CPC by reinforcing with NMPC. A formulation consisting of CPC powder , buffer solution and gelling agent was used for preparation of the CPC. CPC powder coasisted of tetracalcium phosphate（ TTCP ） and dicalcium phosphate anhydrous （ DCPA ）. NMPC which acted as the gelling ageut was dissohed into KH2PO4-Na2 HPO4 buffer solution. Each specimen in the mold was sandciched between two fritted glass sides and kept for 24 hours. Compressive strengths were determined, the setting product was identified using X-ray diffraction and scanning electron microscopy was used to investigate the hydroxyapatite particles size and porosity. The experimental results showed that the dominating influence on the compressive strengths of CPC-AMPC was the HA panicle size, its uniformity and appropriate porosity.

Preparation and Compressive Strength of Calcium Phosphate Bone Cement Containing N,O-carboxymethyl Chitosan

N, O-carboxymethyl chitosan （ CMCTS ）, a kind of biodegradable organic substance, was added to calcium phosphate bone cement （CPC） to prodnce a composite more similar in composition to human bone. The compressive strength of the new material was inereased by 10 times compared with conventional CPC.

Microanalyses of the hydroxyl-poly-calcium sodium phosphate coatings produced by ion beam assisted deposition

Thin calcium phosphate catings on titanium alloy substrates were prepared by Ar^+ ion beam assisted deposition(IBAD) from hydroxyl-poly-calcium sodium phosphate(HPPA) target.The coatings were analyzed by XRD,FTIR,XPS,These analyses revealed that the as-deposited films were amorphous or no apparent crystallinity.No distinct absorption band of the hydroxyl group was observed in FTIR spectra of the coatings but new absorption bands were presented for CO3^-2,The calcium to phosphorous ratio of these catings in different IBAD conditions varied from 0.46 to 3.36.

Hydroxyapatite/β-tricalcium Phosphate Composite for Guiding Bone Tissue Growth into a Titanium Tube in 8 mm Dog Tibia Cavity Defects

We developed a fixation method and evaluate bone regrowth in the cavities of a Ф4 mm× 8 mm titanium（Ti）tube through porous hydroxyapatite（HAP）/β-tricalcium phosphate（β-TCP）composite filling（group A）,chitosan/calcium phosphate composite filling（group B）,and HAP particle modification（group C）.After 2 and 5 months of implantation in dog tibia defects,new bone formation in the three groups was studied by histology and histomorphometry.Group A displayed the most bone regenerated area in both 2 and 5 months post-operation.The chitosan/calcium phosphate composite in group B mostly degraded 2 months after implantation,leading to fibrous tissue invasion after 5 months.By contrast,less bone formation was observed in group C.These results indicated that filling the cavities of metalprostheses with a porous HAP/β-TCP composite can be used for stable long-term fixation in clinicalsettings.

改性聚己二酸/对苯二甲酸丁二醇酯熔融包覆制备缓释肥的研究

绿色缓释肥的研发可缓解化肥的利用率较低所造成的养份浪费和严重的环境污染。本文使用异丙基三(十二烷基苯磺酰基)钛酸酯(TDBSP)改性可生物降解聚己二酸/对苯二甲酸丁二醇酯(PBAT),降低其熔体流动温度,加入环境友好的乙酰柠檬酸三丁酯(ATBC)进行增塑,进一步提高熔体流动性,使PBAT改性材料能够在120℃下用简单的搅拌工艺对复合肥颗粒进行环境友好的无溶剂熔融包覆,在此基础上填充一定量的疏水钙镁磷肥粉提高缓释效果,得到包膜完整且达到缓释要求的缓释复合肥,并对包膜形态进行评估,对缓释肥料的缓释性能进行了测试。钙镁磷肥粉的填充显著增强了缓释性能,在土柱淋溶实验中,24 h的养份释放低于15%,28 d养份累计释放约为80%,养份持续释放达20 d以上,为经济便捷地制备绿色环保的缓释肥提供借鉴,也为拓展PBAT等可降解塑料的应用领域提供思路。

Treatment of cervical cancer by si RNA-loaded chitosan-coated calcium phosphate nanoparticles

In the present study, a chitosan-coated calcium phosphate nanoparticle（CS/CaP/siRNA NP） was developed to deliver si RNA for treatment of cervical cancer. The CS/CaP/siRNA NPs were prepared by the nano-precipitation method. The resulted NPs had a uniform spherical morphology with a size of ～194 nm and a zeta potential of ～＋27 mV. In vitro experiments demonstrated that these NPs could efficiently deliver si EGFR into Hela cells and significantly down-regulate the EGFR expression level, which was probably associated with enhanced cell adhesion of chitosan, leading to extended residence time of cell internalization. Then the internalized CS/CaP/siRNA NPs exhibited pH-responsive disassembly of NPs, resulting in the enhanced release of si RNA and rapid lysosomal escape into cytoplasm. Moreover, in vivo anticancer results showed that the CS/CaP/siRNA NPs had significant inhibitory effects on tumor growth after intratumoral injection in Hela tumor xenografted nude mice, accompanying with no obvious changes of body weight during the whole experimental period. All these results indicated that the CS/CaP/siRNA NPs would have great potential to deliver si RNA for the treatment of cervical cancer via mucosal administration.

In Vitro Biomineralization of Glutaraldehyde Crosslinked Chitosan/Glutamic Acid Films

In vitro biomineralization of glutaraldehyde crosslinked chitosan/glutamic acid films were studied. IR and ESCA （electron spectroscopy for chemical analysis） determinations confirm that chitosan and glutamic acid are successfully crosslinked by glutaraldehyde to form chitosan-glutamic acid surfaces. Composite films were soaked in saturated Ca（OH）2 solution for 8 d and then immersed in simulated body fluid （SBF） for more than 20 d. Morphological characterizations and structure of cal-cium phosphate coatings deposited on the films were studied by SEM, XRD, and EDAX （energy dispersive X-ray analysis）. Initially, the treatment in SBF results in the formation of single-layer cal-cium phosphate particles over the film surface. As immersion time increases, further nucleation and growth produce the simulated calcium-carbonate hydroxyapatite coating. ICP results show Ca/P ratio of calcium phosphate coating is a function of SBF immersion time. The inducing of glutamic acid improves the biomineralization property of chitosan films.

In Vitro Biomineralization of Glutaraldehyde Crosslinked Chitosan Films

The biomimetic approach was applied to study the in vitro biomineralization of series of the chitosan films crosslinked by glutaraldehyde. The deposited calcium phosphate coatings were studied using scanning electron microscopy and energy dispersive X-ray analysis. Initially, the treatment in simulated body fluid (SBF) results in the formation of single layer of calcium phosphate particles over the film surface. As immersion time in SBF increases, further nucleation and growth produce a simulated calcium phosphate coating. The Ca/P molar ratio of the calcium phosphate increases with the immersion time, showing a rapid formation of calcium-deficient phosphate material from the phase of octac1alcium phosphate. The different glutaraldehyde crosslinking degree influences the morphology and magnitude of the calcium phosphate coatings on the surface of the chitosan films.

Delivering MC3T3-E1 cells into injectable calcium phosphate cement through alginate-chitosan microcapsules for bone tissue engineering

Objective： To deliver cells deep into injectable calcium phosphate cement（CPC） through alginate-chitosan（AC） microcapsules and investigate the biological behavior of the cells released from microcapsules into the CPC.Methods： Mouse osteoblastic MC3T3-E1 cells were embedded in alginate and AC microcapsules using an electrostatic droplet generator.The two types of cell-encapsulating microcapsules were then mixed with a CPC paste.MC3T3-E1 cell viability was investigated using a Wst-8 kit,and osteogenic differentiation was demonstrated by an alkaline phosphatase（ALP） activity assay.Cell attachment in CPC was observed by an environment scanning electron microscopy.Results： Both alginate and AC microcapsules were able to release the encapsulated MC3T3-E1 cells when mixed with CPC paste.The released cells attached to the setting CPC scaffolds,survived,differentiated,and formed mineralized nodules.Cells grew in the pores concomitantly created by the AC microcapsules in situ within the CPC.At Day 21,cellular ALP activity in the AC group was approximately four times that at Day 7 and exceeded that of the alginate microcapsule group（P0.05）.Pores formed by the AC microcapsules had a diameter of several hundred microns and were spherical compared with those formed by alginate microcapsules.Conclusions： AC microcapsule is a promising carrier to release seeding cells deep into an injectable CPC scaffold for bone engineering.

Biocompatibility of Surface-Modified Biphasic Calcium Phosphate/Poly-L-Lactide Biocomposite in vitro and in vivo

The biocompatibility of surface-modified biphasic calcium phosphate （mBCP）/poly-L-Lactide （PLLA） biocomposite was investigated through a series of experiments in vitro and in vivo. Acute toxicity and short term systemic toxicity experiments revealed no toxicity of the materials. Hemolysis assay indicated the good blood compatibility of the composite. In cytotoxicity assay, L929 mouse fibroblasts could well differentiate and proliferate. Animal experiments in vivo were.performed by implanting the materials into rabbits muscle for 8 weeks. The decreasing of inflammatory cells, the building of fibrous tissue layer as well as the growing of blood cells into materials indicated the nontoxicity of the composite. Based on the experiment results, surfacemodified BCP/PLLA biocomposite is proven to have superior biocompatibility, which would be a promising bone repairing material.

壳聚糖对自制磷酸钙骨水泥性能的影响

目的:了解壳聚糖对自制磷酸钙骨水泥(CPC)物理性能、超微结构及生物相容性的影响.方法:分别以50g/L乳酸壳聚糖和1mol/L磷酸氢二钠为液相制备CPC试样,通过防水试验、测定初步凝结时间、抗压强度;扫描电镜观察凝固体超微形态;大鼠肌肉植入及骨髓基质干细胞表面种植试验比较两者差异.结果:复合壳聚糖的CPC在水中更稳定,混合后即刻投入生理盐水3min内不散开;平均初步凝结时间8.38min,对照组23.68min;平均抗压强度6.52MPa;对照组2.08MPa.扫描电镜发现凝固体表面为颗粒状及片状晶体,实验组晶体互相连接,孔隙较对照组少.植入肌袋1wk有轻微炎症反应,4wk后反应减退,12wk后实验组材料变软,对照组外形基本未变.肌肉无坏死.电镜下细胞可在水泥盘上贴附、生长,实验组可见的细胞数较多.结论:CPC-壳聚糖复合物在潮湿条件下更稳定,固化时间缩短,抗压强度提高,生物相容性更好.

聚乙二醇对合成无定形磷酸钙的影响

采用聚乙二醇(PEG)先与钙反应后,再与磷源溶液反应,在低温环境中制得无定形磷酸钙.借助XRD分析讨论了PEG∶CaCl2配比及PEG分子量与形成无定形磷酸钙之间的关系,实验结果表明,PEG∶CaCl2配比为1∶1和PEG分子量为10000是形成稳定无定形磷酸钙的最佳条件.其PEG稳定无定形磷酸钙的作用可理解为:在合成过程中PEG易存在于无定形磷酸钙Ca9(PO4)6团簇之间和吸附在无定形磷酸钙颗粒周围,有效地阻止了无定形磷酸钙向晶态的转变.

微球堆积法制备多孔磷酸钙生物材料

以壳聚糖为原料 ,用乳液凝固法合成了壳聚糖微球。利用造孔剂成孔的特点 ,在有机模具中将壳聚糖微球紧密堆积 ,形成孔隙率至少为 2 6 %的多孔结构的框架 ,再将料浆灌注到框架中 ,充满空隙。干燥后经 6 0 0°C煅烧和12 0 0°C烧结 ,将有机模具及壳聚糖微球烧去 ,获得具有大孔和贯通式微孔的多孔磷酸钙生物材料。材料孔隙率在 6 0～70 %之间 ,大孔直径为 80 μm～ 2 5 0 μm ,孔径可控且分布均匀 ,平均抗压强度为 4 .5 8MPa。

双相磷酸钙多孔陶瓷的制备

以羟基磷灰石为原料 ,壳聚糖微球为成孔剂 ,明胶为分散剂 ,采用注浆法制备多孔双相磷酸钙陶瓷。通过X射线衍射和扫描电子显微镜对烧结体相组成、微观结构、孔径和孔分布进行了分析和观察。结果表明 :起始粉末粒径为 2 60nm的试样 ,在 10 0 0℃～1180℃范围内烧结 ,可获得不同 β -TCP/HA比的双相多孔陶瓷。与单相 β -TCP陶瓷相比 ,β

壳聚糖纤维/磷酸钙骨水泥复合材料人工骨的降解性能

提出添加壳聚糖纤维改善自固化磷酸钙骨水泥的降解性能。根据单一材料均匀降解假设和狗股骨远端松质骨区缺损修复试验研究壳聚糖纤维/骨水泥复合材料人工骨的降解性能。理论分析发现添加的纤维使得人工骨降解量与时间呈现非线性的二次函数关系;纤维质量分数的增减是人工骨降解率的关键影响因素。骨缺损修复试验结果显示人工骨残留材料率与时间形成高阶函数关系,且其试验曲线与骨组织工程理想曲线相似。分析认为,壳聚糖纤维降解速度高于骨水泥造成人工骨在缺损修复的过程中出现多孔结构,进而在促进新生骨组织生长的同时改变了该人工骨的降解规律,结合纤维质量分数的控制,有可能使人工骨的降解速率与骨组织生长相匹配。

壳聚糖纤维及明胶联合增强的磷配钙骨水泥理化性能及生物相容性研究

[目的]探讨壳聚糖纤维联合明胶对磷酸钙骨水泥理化性能及生物相容性的影响。[方法]将不同比例的壳聚糖纤维、明胶和磷酸钙骨水泥复合,通过测定复合物抗弯曲强度、分析固化体相组成、观察超微结构及抽提液体外细胞反应,了解壳聚糖纤维-明胶-磷酸钙骨水泥复合材料的理化性能及细胞毒性。[结果]壳聚糖纤维体积比对抗弯强度影响显著(P<0.05),体积比增加到30%,强度为(9.04±2.63)MPa(对照组为(2.48±0.62)MPa,P<0.05)。X线衍射观察各复合物在31°和35°之间均可见与标准羟基磷灰石一致的衍射峰,与对照组相比较,明胶组、10%纤维组和30%纤维组羟基磷灰石特征衍射峰强度相对高,羟基磷灰石相比例增加,磷酸四钙相比例减少。扫描电镜显示各实验组微孔数少于对照组,纤维分散较好,并被水泥湿化。诱导后的大鼠骨髓基质细胞可在复合物表面生长,短期抽提实验证实实验组和阴性对照组细胞增殖显著高于阳性对照(P<0.05),实验组和阴性对照组间无统计学差异。[结论]添加壳聚糖纤维和明胶在一定程度上提高了骨水泥强度,加速骨水泥向羟基磷灰石转化,新型复合材料无细胞毒性。

复合壳聚糖微球-丝素基载药α-磷酸三钙骨水泥的细胞相容性及毒性

背景:磷酸钙骨水泥具有良好的生物相容性和骨传导性,已被应用于临床,但其不良的力学性能和缺乏骨诱导性限制了其进一步发展和应用。目的:制备壳聚糖微球-丝素基载药α-磷酸三钙骨水泥,验证其细胞相容性及细胞毒性。方法:分别以含体积分数10%胎牛血清和1%双抗的α-MEM培养基、苯酚、100%及50%复合壳聚糖微球-丝素基载药α-磷酸三钙骨水泥材料的浸提液培养MC3T3-E1细胞,采用MTT法评估细胞生长增殖情况,采用乳酸脱氢酶活性检测法判断复合壳聚糖微球-丝素基载药α-磷酸三钙骨水泥材料的毒性。将MC3T3-E1细胞系与复合壳聚糖微球-丝素基载药α-磷酸三钙骨水泥材料共培养,扫描电镜观察细胞在材料表面的附着及生长。结果与结论:复合壳聚糖微球-丝素基载药α-磷酸三钙骨水泥材料浸提液对MC3T3-E1细胞的生长增殖无明显影响,无明显细胞毒性。MC3T3-E1细胞在复合壳聚糖微球-丝素基载药α-磷酸三钙骨水泥材料表面生长良好,伸展充分,在材料表面伸出伪足,与材料贴附紧密,表明壳聚糖微球-丝素基载药α-磷酸三钙骨水泥细胞相容性良好。