壳聚糖携载质粒纳米微球体外转染兔关节软骨细胞的实验研究

目的:研究携载质粒的不同分子量的壳聚糖纳米微球的包裹率和保护DNA的能力,镜下观察其大小和形态,观察其对原代兔关节软骨细胞的转染效率。方法:利用酶消化法消化3周龄新西兰大白兔的关节软骨,贴壁培养原代兔关节软骨细胞。购买相对分子量在5K和800K之间的八种壳聚糖,利用表达增强型绿色荧光蛋白的质粒(pEGFP)作报告基因,通过复合凝聚法制备壳聚糖-质粒纳米微球。琼脂糖凝胶电泳、紫外分光光度计分析不同N/P比值对不同分子量壳聚糖和质粒的结合能力及包封率的影响;纳米粒度仪、透射电子显微镜和环境扫描电子显微镜考察纳米微球的粒径分布和形态;荧光显微镜观察壳聚糖纳米微球介导pEGFP在体外培养的兔关节软骨细胞中的表达情况;流失细胞仪计算具体转染效率。结果:①N/P值为4及4以上时,各分子量的壳聚糖可完全包裹质粒成球;N/P值为2时,分子量为5K、50K、85K仅部分包裹质粒,其余可完全包裹;N/P值为1时,各壳聚糖均与质粒部分包裹;N/P值为0.25时,各壳聚糖均与质粒完全分离。②纳米粒度仪分析得出:N/P值为4时,各分子量的壳聚糖纳米微球的平均粒径均在1微米以下,③透射电子显微镜和扫描电子显微镜均可观察到球形或不规则形的大小不同的微球。荧光显微镜可大致观察到绿色荧光蛋白在软骨细胞内表达的表达情况。④流式细胞仪得出具体转染效率,分子量为170K、250K和800K的壳聚糖纳米微球的转染效率均高于5K、50K和85K的壳聚糖纳米微球,其中800K的壳聚糖纳米微球与脂质体相当(差异有统计学意义,P<0.05)。结论:与脂质体相比,N/P比值为4时,相对分子量为800k的壳聚糖纳米微球可高效转染原代培养的兔软骨细胞,可以作为今后进一步体外、体内实验的首选转染载体。     

聚乙二醇修饰的壳聚糖包裹DNA的转染效果研究

目的:为探讨聚乙二醇(PEG,MW4000)修饰的壳聚糖用于包裹质粒DNA(Chi-DNA)是否能有效提高口服发送的外源基因在消化道中的表达量.方法:用PEG修饰的壳聚糖包裹不同剂量(10μg,50μg,100μg)的质粒(pCMVβ),形成壳聚糖纳米复合物,通过口服发送后经X-gal染色法检测pCMVβ在小鼠消化道内的表达效果.结果:胃酸消化实验及DNase Ⅰ消化实验均表明经PEG修饰的壳聚糖纳米粒能有效地保护DNA,使其免受胃酸及Dnase Ⅰ的降解.同时在小鼠消化道内的表达量较修饰前明显增加,随着所发送DNA剂量的增加,表达量也相应增加,且包裹10μg质粒的DNA纳米复合物的表达量相当于100μg未修饰复合物的表达水平.结论:经PEG修饰的Chi-DNA纳米复合物有较高的基因转染效果,有望作为基因治疔中高效非病毒口服发送系统的材料.     

氢氧化镁调控BSA-PLGA微球体外释放的研究

目的:探索氢氧化镁对BSA微球体外释放的影响,优化BSA微球的制备工艺。方法:通过水包油包固复乳法制备BSA-PLGA微球。先将BSA与葡聚糖制备成玻璃体颗粒,再将玻璃体颗粒与氢氧化镁包裹进PLGA中,制备成缓释微球。在扫描电镜下观察其形态。然后用Micro BCA法测定其包封率和载药量,并考察其体外释放行为。结果:所制得的微球粒径约60μm,呈较好的球形。添加氢氧化镁后,BSA微球的包封率和载药量都有显著提高。不同含量的氢氧化镁对BSA微球的包封率和载药量影响也不同。在体外释放过程中,载有氢氧化镁的微球14天累积释放量为(85.10±2.67)%,而对照组不到80%。结论:通过调整氢氧化镁的量,可以制得形态完整,大小均匀,突释较小的BSA微球。     

用壳聚糖纳米磁性微球纯化血红细胞超氧化物歧化酶

本研究旨在用壳聚糖-聚丙烯酸纳米磁性微球纯化血红细胞超氧化物歧化酶。采用了接枝共聚法,以K2S2O8为引发剂,使壳聚糖(CTS)与聚丙烯酸(PAA)进行自由接枝共聚合成含有两性基团(-NH3,-COOH)的壳聚糖-聚丙烯酸纳米微球。化学共沉淀法制备Fe3O4磁流体,以戊二醛为交联剂,制备壳聚糖-聚丙烯酸纳米磁性微球。用傅里叶变换红外光谱仪对磁性微球结构进行检测。JEM-4000EX电镜技术对微球粒径,形貌进行表征。SOD试剂盒测定各步骤Cu-ZnSOD酶活性。结果表明,壳聚糖-聚丙烯酸纳米磁性微球有较好的粒径分布、磁响应性及蛋白吸附特性。纯化后酶比活性达6 727 U/mg,产品得率21.1%,活性回收85.7%。壳聚糖-聚丙烯酸纳米磁性微球经血液纯化血红细胞SOD具有可再生性、易操作性,其纯化效果取决于金属Cu2+的螯合程度。     

纳米磁性壳聚糖微球固定化酵母醇脱氢酶的研究

建立了以纳米级磁性壳聚糖微球(magnetic chitosan microspheres , M-CS)为载体固定化酵母醇脱氢酶(yeast alcohol dehydrogenase,YADH)的方法,优化了YADH的固定化条件,考察了固定化酶的性质。结果表明,M-CS 呈规则的圆球形,粒径在30nm 左右,具有较好的磁响应性。酵母醇脱氢酶固定化适宜条件为:50 mg 磁性壳聚糖微球,加入20mL 0.25 mg/mL 酵母醇脱氢酶(蛋白质含量)磷酸盐缓冲液(0.05 mol/L ,pH 7.0) ,在4 ℃固定2h。M-CS 容易吸附酵母醇脱氢酶,但吸附的酶量受载体与酶的比例、溶液的离子浓度、溶液pH的影响明显,而温度对吸附的酶量的影响则相对较弱。相对于游离的酵母醇脱氢酶,固定化酶的最适温度略有升高,可明显改善其热稳定性、酸碱稳定性、操作稳定性和贮存稳定性。     

新城疫壳聚糖微球疫苗免疫效果的研究

鸡新城疫是由新城疫病毒引起的鸡的一种急性、烈性、高度接触性传染病,是危害养禽业的最严重疫病之一。控制新城疫最根本的措施是进行有效的疫苗接种,目前常用的疫苗是弱毒活疫苗和灭活疫苗,但二者在实际应用中均存在一定的局限性。口服微球疫苗可以诱导较强的粘膜免疫;同时还能够诱导产生系统的体液免疫和细胞免疫,已成为ND疫苗研究的热点。以壳聚糖为囊材,新城疫La Sota抗原液为芯材,戊二醛为交联剂,制备出新城疫壳聚糖微球疫苗,通过了实验室安全检验和效力检验。将新城疫壳聚糖微球疫苗与LaSota活疫苗和新城疫油乳剂灭活苗分别免疫SPF鸡,利用MTT、血凝抑制法(HI)和ELISA等分别检测不同疫苗免疫后的细胞免疫、体液免疫和粘膜免疫抗体IgA,并在当免疫鸡HI抗体降到23的情况下进行了攻毒试验。结果表明,新城疫壳聚糖微球疫苗安全性好,免疫后可刺激机体产生较强的细胞免疫、体液免疫和局粘膜免疫,具有较好的保护作用。     

壳聚糖微球分散体系的抑菌性研究

以乳化交联法制备的壳聚糖微米微球(CMs)为试验材料,研究其对金黄色葡萄球菌和大肠杆菌的抑菌行为,并对其浓度因素、粒径因素和抑菌机理做了探讨。结果表明CMs的抑菌作用随其浓度的增加和粒径的减小而增强。在浓度<0.7 mg/mL时,CMs对细菌的生长具有先抑制后促进的作用;当浓度≥0.7 mg/mL时对细菌有杀灭作用。CMs对两种细菌的最小抑菌浓度和最小杀菌浓度分别为0.8、1.4 mg/mL和1.0、1.8 mg/mL,表明壳聚糖微球对金黄色葡萄球菌和大肠杆菌均具有明显的抑制作用,且金黄色葡萄球菌对微球抑制作用的反应比大肠杆菌更敏感。扫描电子显微镜观察发现,细菌能迅速贴附在CMs表面,并且贴壁后的细菌发生了明显的形态变化,有的甚至完全被破坏。     

纳米珍珠粉/壳聚糖-透明质酸支架修复兔股骨远端骨缺损的实验研究

通过体内实验探讨纳米珍珠粉/壳聚糖-透明质酸(NPP/C-HA)复合支架的促成骨能力。采用双侧兔股骨远端骨缺损模型(直径7 mm,深度10 mm),通过大体标本、影像学检查、分子生物学检查及组织学检查来观察骨缺损的修复效果。发现各组均未出现明显不良组织反应;随观察时间增加实验组骨缺损区范围最小,在第8周和第12周数据的差异存在统计学意义(P<0.05);在第4周、6周、8周时实验组BALP含量与其他组比较P<0.05;实验组缺损区边缘出现更多的新生骨,但在骨质成熟度上未见明显差异。结果表明NPP/C-HA支架具有良好的生物相容性及促成骨作用,为进一步研究NPP/C-HA在骨组织工程中的作用提供了实验和理论基础。     

可磷酸化短肽偶联壳聚糖介导IL-1RA与IGF-1共转染对兔关节软骨细胞的作用

探讨可磷酸化短肽偶联壳聚糖(phosphorylatable short peptide coupled chitosan,pSP-CS),介导人白细胞介素 1受体拮抗剂基因(interleukin-1 receptor antagonist protein,IL-1RA)和人胰岛素样生长因子1基因(insulin like growth factor-1,IGF-1) 共转染,对体外培养的兔关节软骨细胞的作用. 将pSP-CS 与共表达质粒pBudCE4.1-IL-1RA+IGF-1、单基因表达质粒pBudCE4.1-IL-1RA、pBudCE4.1-IGF-1和空质粒pBudCE4.1制成pSP-CS/pDNA复合物,转染体外分离培养的正常兔原代关节软骨细胞. ELISA 法检测IL-1RA和IGF-1的表达,以表征pSP CS转染效率;Cell Counting Kit-8 (CCK-8) 法分析软骨细胞的增殖活力;流式细胞仪检测软骨细胞的凋亡;定量PCR检测软骨细胞中基质金属蛋白酶抑制剂-1(matrix metallo proteinase inhibitor-1, Timp-1)、基质金属蛋白酶-3(matrix metalloproteinase-3, Mmp-3)、聚集蛋白聚糖 (Aggrecan) 基因表达. 转基因组IL-1RA和IGF-1有较高的表达水平;各转基因组明显促进细胞增殖、抑制细胞凋亡、下调Mmp-3基因表达、上调Timp 1和Aggrecan基因表达,且双基因组作用明显优于单基因组(P<0.05). 结果表明,pSP-CS可以携带外源基因进入软骨细胞并大量表达, IGF-1与IL-1RA协同作用明显提高体外培养软骨细胞的生物活性, 为今后研究pSP-CS介导多基因体内治疗软骨损伤提供了基础.     

载阿霉素PLGA纳米微球的制备及性质研究

目的:制备新型癌症化疗制剂载阿霉素(Adriamycin)、聚乳酸-羟基乙酸共聚物(PLGA)纳米微球(ADM-PLGA-NP),研究其性质及体外释药特点。方法:以聚乳酸-羟基乙酸共聚物为包封材料,阿霉素为模型药物,采用复乳蒸发法制备ADM-PLGA-NP,扫描电镜观察微球形态,激光粒度分析仪检测粒径分布,紫外分光光度法计算载药率及包封率,体外药物释放实验考察微球对ADM的缓释作用。结果:ADM-PLGA-NP外观呈球形,平均粒径约(237±12.7)nm,载药量及包封率分别为(6.42±1.67)%和(53.82±8.34)%,药物在体外缓慢释放,5 d累积释放量达85%。结论:通过复乳蒸发法制备的ADM-PLGA-NP性质稳定,具有药物缓释性,有望成为一种新型的药物化疗载体。     

Effect of chitosan‐alginate nanoparticles and ultrasound on the efficiency of gene transfection of human cancer cells

Background

Gene therapy has been used to treat a variety of health problems, but transfection inefficiency and the lack of safe vectors have limited clinical progress. Fabrication of a vector that is safe and has high transfection efficiency is crucial for the development of successful gene therapy. The present study aimed to synthesize chitosan‐alginate nanoparticles that can be used as carriers of the pAcGFP1‐C1 plasmid and to use these nanoparticles with an ultrasound protocol to achieve high efficiency gene transfection.

Methods

Chitosan was complexed with alginate and the pAcGFP1‐C1 plasmid at different charge ratios to create chitosan‐alginate‐DNA nanoparticles (CADNs). The average particle size and loading efficiency were measured. Plasmid DNA retardation and integrity were analysed on 1% agarose gels. The effect of CADNs and ultrasound on the efficiency of transfection of cells and subcutaneous tumors was evaluated.

Results

In the CADNs, the average size of incorporated plasmid DNA was 600–650 nm and the loading efficiency was greater than 90%. On the basis of the results of the plasmid DNA protection test, CADNs could protect the transgene from DNase I degradation. The transgene product expression could be enhanced efficiently if cells or tumor tissues were first given CADNs and then treated with ultrasound.

Conclusions

The use of CADNs combined with an ultrasound regimen is a promising method for safe and effective gene therapy. Copyright © 2009 John Wiley & Sons, Ltd.

     

Subculture of rabbit articular chondrocytes within a collagen gel: growth and analysis of differentiation

Primary cultures of rabbit articular chondrocytes have been subcultured within three-dimensional (3D) collagen gels. Under these conditions, the cells remained viable and divided, but with a lower proliferation rate than that observed in control monolayer cultures. Flow cytometric analysis of progression of the cells into the cell cycle has confirmed and extended these findings. Also the cellular volume was decreased in 3D-culture, being in the same range as thein vivo size of cartilage cells. Specific staining for proteoglycans and type II collagen immunolocalization on sections of gels showed the expression of differentiated phenotypes and revealed the accumulation of these matrix components in the immediate surroundings of the cells. The use of Ultroser G (a serum substitute) improved the conditions for 3D- culture of rabbit articular chondrocytes.     

A depth-dependent model of the pericellular microenvironment of chondrocytes in articular cartilage

Experimental studies suggest that the magnitude of chondrocyte deformation is much smaller than expected based on the material properties of extracellular matrix (ECM) and cells, and that this result could be explained by a structural unit, the chondron, that is thought to protect chondrocytes from large deformations in situ. We extended an existing numerical model of chondrocyte, ECM and pericellular matrix (PCM) to include depth-dependent structural information. Our results suggest that superficial zone chondrocytes, which lack a pericellular capsule (PC), are relatively stiff, and therefore are protected from excessive deformations, whereas middle and deep zone chondrocytes are softer but are protected by the PC that limits cell deformations in these regions. We conclude that cell deformations sensitively depend on the immediate structural environment of the PCM in a depth-dependent manner, and that the functional stiffness of chondrocytes in situ is much larger than experiments on isolated cells would suggest.     

Characterization of subpopulated articular chondrocytes separated by Percoll density gradient

The aim of this study was to develop a method for fractionation of articular chondrocytes from the entire thickness of the tissue. Isolated chondrocytes from rabbit articular cartilage fractionated by centrifugation in a discontinuous Percoll gradient resulted in four cell fractions with two differing properties. The lowest-density fraction consisted mainly of large cells with small nuclei proliferated actively, maintained the chondrocytic phenotype, and secreted larger amounts of proteoglycan. In contrast, the highest-density fraction consisted of small cells with large nuclei proliferated slowly, did not express the chondrocytic phenotype, and produced larger amounts of interleukin 1-induced nitric oxide. Comparing our results with other previous reports, we find that fraction 1 cells are likely originated from the deep layer of the articular cartilage, whereas fraction 4 cells are tentatively categorized as chondrocytes from the superficial layer of cartilage. Centrifugal fractionation of articular chondrocytes via Percoll density gradient permits clear separation of these heterogeneous cells into different phenotypic populations and allows distinguishing of cells from the different layers of articular cartilage. This simple novel method will provide ready separation of articular chondrocytes for the investigation of the pathogenesis of articular cartilage.     

Human articular chondrocytes express three facilitative glucose transporter isoforms: GLUT1, GLUT3 and GLUT9

Glucose is an important metabolite and a structural precursor for articular cartilage and its transport has significant consequences for cartilage development and functional integrity. In this study the expression of facilitative glucose transporters (GLUTs) in human chondrocytes was investigated. Results showed that at least three GLUT isoforms (GLUT1, GLUT3 and GLUT9) are expressed by normal chondrocytes. Given the central role of glucose in chondrocyte physiology and metabolism, its regular provision via GLUTs will influence the metabolic activity and survival of chondrocytes in cartilage matrices.     

Cytotoxicity of D-penicillamine in association with several heavy metals against cultured rabbit articular chondrocytes

The potentiation or antagonistic effects of Cu, Hg, Pb and Cd salts in the presence of a long-acting anti-rheumatic drug, D-penicillamine (D.P.) were studied on cultured chondrocytes. CuSO₄ (10^–4M), HgCl₂ (10^–5M), Pb(CH₃COO)₂ (10^–3M) and D.P. (10^–3M) when used alone caused a small decrease in cell proliferation. The addition of D.P. with Cu, Hg or Pb salts resulted in a marked increase in the extent of growth inhibition. In contrast, CdCl₂ (10^–5M) produced an important growth inhibitory effect, and D.P. antagonized CdCl₂ action. The CuSO₄ D.P. toxicity was probably due to production of H₂O₂ in situ. To verify this hypothesis, catalase, responsible for H₂O₂ metabolism was used, and was found to partially reverse the inhibitory effect of CuSO₄-D.P.