Change in Pull-Out Force during Resorption of Magnesium Compression Screws for Osteosynthesis of Mandibular Condylar Fractures

Background: Magnesium has been used as degradable fixation material for osteosynthesis, but it seems that mechanical strength is still a current issue in these fixations. The aim of this study was to evaluate the axial pull-out force of compression headless screws made of magnesium alloy during their resorption. Methods: The tests included screws made for osteosynthesis of the mandible head: 2.2 mm diameter magnesium alloy MgYREZr (42 screws) and 2.5 mm diameter polylactic-co-glycolic acid (PLGA) (42 pieces, control). The screws were resorbed in Sørensen’s buffer for 2, 4, 8, 12, and 16 weeks, and force was measured as the screw was pulled out from the polyurethane block. Results: The force needed to pull the screw out was significantly higher for MgYREZr screws than for PLGA ones (p < 0.01). Within eight weeks, the pull-out force for MgYREZr significantly decreased to one third of its initial value (p < 0.01). The dynamics of this decrease were greater than those of the pull-out force for PLGA screws (p < 0.05). After these eight weeks, the values for metal and polymer screws equalized. It seems that the described reduction of force requires taking into account when using magnesium screws. This will provide more stable resorbable metallic osteosynthesis.     

Quaternized chitosan-coated nanofibrous implants loaded with gossypol prepared by electrospinning and their efficacy against Graffi myeloid tumor

Nanofibrous poly(L-lactide-co-D,L-lactide) (coPLA) or coPLA/poly(ethylene glycol) implants loaded with plant polyphenolic compound gossypol (GOS) with anti-tumor activity were fabricated by electrospinning. Implants containing quaternized chitosan (QCh) were prepared by coating of the obtained fibrous materials with a thin film of cross-linked QCh. The morphology of the implants and chemical composition of the implant surface were studied by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). In vitro cytotoxicity assay showed that GOS-loaded nanofibrous implants, both non-coated and QCh-coated displayed about two-fold higher inhibitory activity against Graffi tumor cells than that of free GOS at the 72nd h of incubation. As evidenced by the performed fluorescence microscopy analyses and SEM observations, the anti-tumor activity of the fibrous implants was mainly due to induction of apoptosis. The experiments in which the implants containing both QCh and GOS were placed locally into the tumor site after the tumor extirpation showed an increase in the survival rate and a lower rate of recurrence in the operative field and of metastases in regional lymph nodes. In this case, 40% of hamsters were alive on the 45th day of implantation and they did not show any clinical sign of recurrence in the operative field and metastases in the regional lymph nodes.     

新型可吸收材料PLLA/PLLA-gHA的生物相容性

目的：对新型可吸收材料PLLA/PLLA-gHA的生物相容性进行综合性评价。方法：依据IS0 10993系列标准和GB/T 16886系列标准,对新型可吸收材料PLLA/PLLA-gHA进行急性全身毒性实验、溶血实验、肌肉内种植实验和皮内反应实验。小鼠尾静脉注射新材料浸提液,观察注射后各时相点动物的一般状态、毒性表现等指标以评价急性全身毒性反应。在100g•L^-1新材料浸提液加入新鲜抗凝兔血,用分光光度计测取吸光度并计算溶血率。白兔背部皮下注射新材料浸提液,观测各注射点的红斑和水肿情况。将PLLA/PLLA-gHA板植入白兔竖脊肌内,于各时相点抽取兔静脉血检测血液学指标,在术后第14、 30、 60、 90、 180和360天取材,行大体标本和病理组织切片观察。结果：新型可吸收材料PLLA/PLLA-gHA组白兔一般状态良好,无急性全身毒性反应,实验组与对照组各期血液学指标AST、Scr,比较差异无显著性（P>0.05）,新材料浸提液的溶血率为1.22%,低于标准规定的5%;皮下反应实验,各时相点组织水肿极轻微,无红斑形成;肌内植入PLLA/PLLA-gHA板实验,其早期炎性细胞侵润变化规律与对照组类似,符合一般的炎症变化转归规律,材料周围的包膜随植入时间的延长逐渐变薄,术后第360天时纤维化囊壁向材料内长入,囊壁形成程度为Ⅰ级以下。结论：新型可吸收材料PLLA/PLLA-gHA具有良好的生物相容性和安全性。     

Porous polylactide/β‐tricalcium phosphate composite scaffolds for tissue engineering applications

Porous polylactide/β‐tricalcium phosphate (PLA/β‐TCP) composite scaffolds were fabricated by freeze‐drying. The aim of this study was to characterize these graded porous composite scaffolds in two different PLA concentrations (2 and 3 wt%). Also, three different β‐TCP ratios (5, 10 and 20 wt%) were used to study the effect of β‐TCP on the properties of the polymer. The characterization was carried out by determining the pH, weight change, component ratios, thermal stability, inherent viscosity and microstructure of the scaffolds in 26 weeks of hydrolysis. This study indicated that no considerable change was noticed in the structure of the scaffolds when the β‐TCP filler was added. Also, the amount of β‐TCP did not affect the pore size or the pore distribution in the scaffolds. We observed that the fabrication method improved the thermal stability of the samples. Our results suggest that, from the structural point of view, these scaffolds could have potential for the treatment of osteochondral defects in tissue engineering applications. The porous bottom surface of the scaffold and the increased osteogenic differentiation potential achieved with β‐TCP particles may encourage the growth of bone cells. In addition, the dense surface skin of the scaffold may inhibit the ingrowth of osteoblasts and bone tissue, while simultaneously encouraging the ingrowth of chondrocytes. Copyright © 2010 John Wiley & Sons, Ltd.     

人源抗VEGFR-2／As2O3-PEG-PLA隐形纳米粒的构建及质量控制研究

目的：探讨三氧化二砷（As2O3）纳米新剂型的制备和质量控制。方法以聚乙醇化聚乳酸（PEG‐PLA）为载体材料,W／O／W型超声乳化制备As2O3纳米粒,同时偶联具有肝癌靶向作用的VEGFR‐2,最终得到人源抗VEGFR‐2／As2O3‐PEG‐PLA纳米粒。对其粒径分布、Zata电位、载药量和包封率进行测定,通过透射电镜（TEM）观察其表观形态,同时考察其体外释药和稳定性。选择24只肝癌裸鼠,随机分为VEGFR‐2／As2O3‐PEG‐PLA组及As2O3‐PEG‐PLA组,通过尾静脉注射纳米粒,高效液相色谱法测定As2O3在两组裸鼠体内的分布;免疫组化及蛋白质印迹法（Westernblot）检测血管内皮细胞生长因子（VEGF）表达量。结果本实验制得的As2O3纳米制剂VEGFR‐2／As2O3‐PEG‐PLA粒径为（141．9±13．2）nm,Zata电位为（10．2±1．1）mV;经TEM观察呈圆形或椭圆形颗,粒状、大小较一致,分散性较好;载药量为（5．51±1．83）％,包封率为（62．12±5．98）％。体外释放发现其具有缓释效果,半数释放时间t1／2分别为10h;初步稳定性考察结果发现该制剂稳定性良好。与As2O3‐PEG‐PLA组比较,VEGFR‐2／As2O3‐PEG‐PLA组中肿瘤、肝组织的As2O3浓度较高,心、血液、肾组织的As2O3浓度较低（P＜0．05）,且肿瘤组织中VEGFR‐2阳性率及蛋白表达较低。结论以PEG‐PLA为载体材料制备得到As2O3纳米制剂,且偶联具有肝癌靶向作用的VEGFR‐2,最终得到粒径分布均匀,包封率和载药量高,稳定性良好的纳米制剂,且初步证实在肝癌裸鼠体内具有良好的靶向作用。     

树脂包覆率对微胶囊包覆聚磷酸铵阻燃聚乳酸性能的影响

通过原位聚合法,以密胺树脂（MF）为壁材,制备了微胶囊包覆聚磷酸铵（MCAPP）,然后密炼将MCAPP与聚乳酸（PLA）熔融共混,得到微胶囊包覆聚磷酸铵阻燃聚乳酸,并研究了不同树脂包覆率的MCAPP对共混物形貌结构、加工性能、热性能、力学性能以及阻燃性能的影响。结果表明,在原位聚合过程中,当MF质量分数为17.2%时,MCAPP树脂包覆率可达13.2%,共混物中PLA结晶度提高,降解程度最低,同时阻燃效果最佳,极限氧指数可达39.4%,并且垂直燃烧等级达到UL94 V0级。     

可生物降解高分子超细纤维PLA药物缓释体作用于脑胶质瘤的体外研究

目的比较可生物降解药物缓释体与单纯抗瘤药物体外抗胶质瘤细胞的作用。方法通过MTT法筛选药物敏感浓度后，应用化学电纺锤工艺将聚乳酸（PLA）与卡氮芥、阿霉素、紫杉醇制成缓释体，并应用高效液相色谱仪测定其缓释率，筛选缓释效果好的缓释体。体外利用L929细胞在空载体浸出液培养后测定吸光度值（OD值），计算相对增殖率（RGR），按六级评分标准评价空载体毒性，0～1级无毒性；利用C6胶质瘤细胞在药物缓释体中培养后计算细胞抑制率（IR）验证药物缓释体的缓释杀瘤效果。结果卡氮芥-PLA缓释体、阿霉素-PLA缓释体缓释平稳，紫杉醇-PLA缓释体缓释效果差并有暴释。空载体毒性为0～1级。卡氮芥-PLA缓释体平稳释放后细胞抑制率为12．3％。结论载体材料无毒性作用，卡氮芥-PLA缓释体缓释效果好，体外杀瘤平稳、持续杀瘤．可进一步通过体内动物实验验证其有效性．     

Protein Precoating of Polylactide Microspheres Containing a Lipophilic Immunopotentiator for Enhancement of Macrophage Phagocytosis and Activation

Biodegradable microspheres containing a lipophilic muramyl dipeptide, MDP-B30, were prepared from a L-lactic acid–glycolic acid copolymer. The effect of precoating the microspheres with water-soluble polymers including proteins on the antitumor activity of mouse peritoneal macrophages (M) was investigated. Macrophages activated by phagocytosis of the microspheres exhibited growth inhibitory activity toward Meth-A tumor cells. The activity correlated with the extent of M phagocytosis of the microspheres. M phagocytosis was greatly augmented by gelatin precoating of the microspheres, resulting in a significant increase of in vitro antitumor activity of M by the microspheres. However, potentiation of M activity by gelatin precoating was minimal after intraperitoneal injection of the microspheres, but cross-linking of the coated gelatin with glutaraldehyde afforded potentiation of the antitumor activity in vivo.