包埋PLGA微球壳聚糖支架的构建及其对蛋白释放的调节

目的制备能缓慢释放蛋白类药物的细胞生长支架。方法采用冷冻干燥制备壳聚糖支架，测定支架的孔隙率和吸水率。以牛血清白蛋白(BSA)为模型药物，制备乳酸-羟乙醇酸共聚物(PLGA)微球，并包埋于壳聚糖支架中，用扫描电镜观察微球和支架的形态，考察药物在各种支架上的体外释放。结果壳聚糖支架为多孔结构，当预冻温度为-70 ℃时，支架的孔隙率和吸水率分别为78.6%±1.5%和85.1%±6.2%。PLGA微球能够较均匀地覆在壳聚糖支架上。单用壳聚糖支架，BSA在24 h累积释放达90%以上，制成PLGA微球后，再包埋于壳聚糖支架中，则药物释放明显缓慢，168 h的累积释放量为33.5%。通过改变壳聚糖的用量和PLGA材料的型号，可以调控药物在复合支架上的释放。结论包埋PLGA微球的壳聚糖支架有望用于组织工程的支架材料和生长因子的缓慢释放。     

球晶制粒技术制备水飞蓟宾缓释微球

目的提高水飞蓟宾的生物利用度。方法采用固体分散载体和阻滞性高分子材料,使用固体分散与球晶制粒相结合的技术制备水飞蓟宾缓释微球。运用差示热分析及X-射线粉末衍射检测水飞蓟宾在微球中分散状态,采用扫描电子显微镜观察微球的形态、表面结构和内部结构,并对微球的特性如平均粒径、粒径分布、松密度进行评价。结果研制微球的大小可由搅拌速度来控制,水飞蓟宾从缓释微球中的释放速度随分散剂的量的增加而增加,阻滞剂可延缓药物的释放。微球中药物的释放速度能够通过调节分散剂和阻滞剂的比例来控制。X射线衍射与差示热分析结果表明:水飞蓟宾以无定型高度分散在微球中。在40℃,相对湿度75%条件下,加速三个月,药物释放与含量不会改变。结论水飞蓟宾缓释微球可通过采用固体分散与球晶制粒相结合的技术一步制成。该制备过程简便、重现性好、成本低,是水不溶性药物制备缓释微球的有效方法。     

喷雾干燥法制备鼻用甲氨蝶呤壳聚糖微球及其特性的考察

目的以壳聚糖为载体材料,甲氨蝶呤为模型药物,制备鼻腔给药甲氨蝶呤壳聚糖微球。方法采用喷雾干燥法制备甲氨蝶呤壳聚糖微球;采用正交设计优化制备工艺,并对药物的包封率、收率、粒径以及释放行为进行考察。结果优化条件下所得微球粒径分布较为均匀,平均粒径为4.0~5.0μm,制成微球后药物可缓慢释放,符合鼻腔给药的要求。结论该方法适用于甲氨蝶呤壳聚糖微球的制备,壳聚糖是良好的鼻用制剂的载体材料,可用于制备脑部靶向鼻黏膜给药制剂。     

bFGF-PLGA缓释微球及其体外释药性能研究

目的以bFGF为缓释药物、PLGA为药物载体制备bFGF-PLGA缓释微球,观察微球表面形态,检测微球物理性能和体外释药行为。方法采用W1/O/W2复乳溶剂挥发法制作微球;通过扫描电镜观察微球的表面形态结构;利用ELISA法测试微球中药物的载药量和包封率,并对微球中药物的体外释放行为进行研究。结果微球表面圆滑均匀,平均粒径(0.75±0.08)μm,载药量[(59.9±1.9)×10-3]%,包封率为(79.9±2.8)%;在为期45 d的体外释放试验中,bFGF累积释放率达到80%。结论bFGF-PLGA微球能够稳定地在较长时间释放药物bFGF,验证了PL-GA微球作为bFGF控制释放载体的可行性。     

多孔微球在医药领域的应用

多孔微球作为一种药物新剂型,在药物新制剂的研发以及新剂型的改造方面应用广泛。多孔微球材料来源丰富,如天然高分子材料,无机材料,合成大分子聚合物等。作为一种新型缓/控释给药载体,微球具有保护药物免遭破坏、与某些细胞组织有特殊的亲和性、控制药物释放速度、延长药物作用时间、减少药物不良反应及降低用药量等优点,还可用于特定组织和器官的药物靶向释放等。由于多孔微球具有巨大的比表面积和孔体积,药物可吸附在多孔微球的表面或进入孔道内部,根据机体需要被做成速释或缓释制剂而发挥药效。该文综述了几种典型的多孔微球材料研究概况及其在生物医药领域中的应用,并对其发展前景进行展望。     

影响聚酯微球中药物释放的因素

聚酯材料因其原料易得、容易加工、生物相容性好、具有可生物降解性等优点,已经成为当今药物载体材料中的一大研究热点。现综合国内外的有关报道对可生物降解聚酯材料作为药物载体制备微球制剂的研究进展进行了综述。针对目前限制聚酯材料微球制剂临床应用存在的问题,从聚合物、药物、制备工艺、附加剂、辐射灭菌5个方面对影响聚乳酸(PLA)和聚乳酸乙醇酸共聚物(PLGA)缓释微球中药物释放的因素进行了重点介绍,为研究聚酯微球中药物的释放提供思路。     

聚乳酸、聚乳酸乙醇酸共聚物微球的制备及体外释放影响因素研究进展

目的:对近年来以PLA、PLGA为载体的微球剂的研究进展进行综述。方法:查阅近10年来有关PLA、PLGA微球研究的国内外文献,介绍此类微球的制备方法和影响其体外释放等性质的主要因素。结果:PLA、PLGA的性质、药物的性质及微球的制备工艺等对微球的体外释放等性质均有重要的影响。结论:对以PLA、PLGA为载体制备的药物微球,有待于更进一步的研究和开发     

双氯芬酸钠/海藻酸钠微球的制备与体外释药行为考察

目的以海藻酸钠为载体材料,双氯芬酸钠为模型药物,制备载药微球并考察其性质及体外释放行为。方法本文采用海藻酸钠为药物载体,采用喷雾干燥法制备双氯芬酸钠/海藻酸钠微球。考察于双氯芬酸钠/海藻酸钠投料比对载药微球理化性质的影响。采用扫描电镜对所得到的微球进行形貌观察。同时考察其体外药物释放行为。结果所得到的载药微球形态呈不规则的扁平状,粒径分布较为均匀。通过控制投料比,可以得到不同粒径(5.64～9.58μm),载药量(5.76～18.43%)和包封率(35.45～43.92%)的载药微球。体外药物释放行为结果显示微球在含有0.5%氯化钙的PBS(pH=7.4)溶液的药物释放时间可以持续96h,具有一定的缓释效果。结论通过喷雾干燥法制备的双氯芬酸钠/海藻酸钠载药微球具有较高载药量和一定的药物缓释效果。     

芹菜素壳聚糖微球的制备及体外释药研究

目的以芹菜素为模型药物、脱乙酰壳聚糖为药物载体,制备芹菜素壳聚糖微球,并测定微球中芹菜素的体外释放度。方法采用复乳-乳化化学交联法制备微球,正交试验优化微球制备的工艺,高效液相色谱法检测芹菜素含量。结果最佳工艺制备4批微球,形态良好,微球圆整,平均载药量为8.54%,平均包封率为69.69%,平均粒径为84.33μm。微球在pH 6.8和pH 7.4的磷酸盐缓冲液中释放36 h。结论所选制备工艺稳定,适用于芹菜素壳聚糖微球的制备,体外药物释放结果显示,微球具有良好的缓释效果。     

吲达帕胺肠溶微球的制备及影响因素考察

目的制备吲达帕胺肠溶微球及影响因素考察。方法以羟丙甲纤维素酞酸酯(HPMCP)为肠溶载体材料,采用乳化溶剂扩散法制备吲达帕胺肠溶微球,对影响微球的成型性、收率、载药量、包封率及其释药性能等因素进行了考察。结果微球形态圆整,架桥剂和乳化剂是其成型主要影响因素;载药量14.85%,包封率76.30%,药物在模拟肠液中累计释放度符合要求,载体材料用量控制药物释放速度。结论本方法适宜制备吲达帕胺肠溶微球,工艺简单,体外肠溶释放性良好。     

Controlled Release of Chitosan and Sericin from the Microspheres-Embedded Wound Dressing for the Prolonged Anti-microbial and Wound Healing Efficacy

One approach in wound dressing development is to incorporate active molecules or drugs in the dressing. In order to reduce the frequency of dressing changes as well as to prolong wound healing efficacy, wound dressings that can sustain the release of the active molecules should be developed. In our previous work, we developed chitosan/sericin (CH/SS) microspheres that released sericin in a controlled rate. However, the difficulty of applying the microspheres that easily diffuse and quickly degrade onto the wound was its limitations. In this study, we aimed to develop wound dressing materials which are easier to apply and to provide extended release of sericin. Different amounts of CH/SS microspheres were embedded into various compositions of polyvinyl alcohol/gelatin (PVA/G) scaffolds and fabricated using freeze-drying and glutaraldehyde crosslinking techniques. The obtained CH/SS microspheres-embedded scaffolds with appropriate design and formulation were introduced as a wound dressing material. Sericin was released from the microspheres and the scaffolds in a sustained manner. Furthermore, an optimized formation of the microspheres-embedded scaffolds (2PVA2G+2CHSS) was shown to possess an effective antimicrobial activity against both gram-positive and gram-negative bacteria. These microspheres-embedded scaffolds were not toxic to L929 mouse fibroblast cells, and they did not irritate the tissue when applied to the wound. Finally, probably by the sustained release of sericin, these microspheres-embedded scaffolds could promote wound healing as well as or slightly better than a clinically used wound dressing (Allevyn®) in a mouse model. The antimicrobial CH/SS microspheres-embedded PVA/G scaffolds with sustained release of sericin would appear to be a promising candidate for wound dressing application.     

Surface engineered and drug releasing pre-fabricated scaffolds for tissue engineering

A wide range of polymeric scaffolds have been intensively studied for use as implantable and temporal devices in tissue engineering. Biodegradable and biocompatible scaffolds having a highly open porous structure and good mechanical strength are needed to provide an optimal microenvironment for cell proliferation, migration, and differentiation, and guidance for cellular in-growth from host tissue. A variety of natural and synthetic polymeric scaffolds can be fabricated in the form of a solid foam, nanofibrous matrix, microsphere, or hydrogel. Biodegradable porous scaffolds can be surface engineered to provide an extracellular matrix mimicking environment for better cell adhesion and tissue in-growth. Furthermore, scaffolds can be designed to release bioactive molecules, such as growth factors, DNA, or drugs, in a sustained manner to facilitate tissue regeneration. This paper reviews the current status of surface engineered and drug releasing scaffolds for tissue engineering.     

Biologically active chitosan systems for tissue engineering and regenerative medicine

Biodegradable polymeric scaffolds are widely used as a temporary extracellular matrix in tissue engineering and regenerative medicine. By physical adsorption of biomolecules on scaffold surface, physical entrapment of biomolecules in polymer microspheres or hydrogels, and chemical immobilization of oligopeptides or proteins on biomaterials, biologically active biomaterials and scaffolds can be derived. These bioactive systems show great potential in tissue engineering in rendering bioactivity and/or specificity to scaffolds. This review highlights some of the biologically active chitosan systems for tissue engineering application and the associated strategies to develop such bioactive chitosan systems.     

Ceramic composites as matrices and scaffolds for drug delivery in tissue engineering

Ceramic composites and scaffolds are popular implant materials in the field of dentistry, orthopedics and plastic surgery. For bone tissue engineering especially CaP-ceramics or cements and bioactive glass are suitable implant materials due to their osteoconductive properties. In this review the applicability of these ceramics but also of ceramic/polymer composites for bone tissue engineering is discussed, and in particular their use as drug delivery systems. Overall, the high density and slow biodegradability of ceramics is not beneficial for tissue engineering purposes. To address these issues, macroporosity can be introduced often in combination with osteoinductive growth factors and cells. Ceramics are good carriers for drugs, in which release patterns are strongly dependent on the chemical consistency of the ceramic, type of drug and drug loading. Biodegradable polymers like polylactic acid, gelatin or chitosan are used as matrices for ceramic particles or as adjuvant to calcium phosphate cements. The use of these polymers can introduce a tailored biodegradation/drug release to the ceramic material.     

Chitosan scaffolds with BMP-6 loaded alginate microspheres for periodontal tissue engineering

The aim of this study is to develop an effective growth factor releasing scaffold-microsphere system for promoting periodontal tissue engineering. Bone morphogenetic protein-6 (BMP-6)-loaded alginate microspheres in narrow size distribution were produced by optimising electrospraying conditions. The addition of these microspheres to chitosan gels produced a novel scaffold in which not only the pore sizes and interconnectivity were preserved, but also a controlled release vehicle was generated. Loading capacity was adjusted as 50?ng or 100?ng BMP-6 for each scaffold and the controlled release behaviour of BMP-6 from chitosan scaffolds was observed during seven days. Cell culture studies were carried out with rat mesenchymal stem cells derived from bone marrow in three groups; chitosan scaffolds, chitosan scaffolds containing BMP-6-loaded alginate microspheres and chitosan scaffolds with free BMP-6 in culture medium. Results showed that controlled delivery of BMP-6 from alginate microspheres has a significant effect on osteogenic differentiation.     

A temporal gene delivery system based on fibrin microspheres

Combining complementary nonviral gene delivery vehicles such as tissue engineering scaffolds and liposomes not only is a promising avenue for development of safe and effective gene delivery system but also provides an opportunity to design dynamic extended release systems with spatiotemporal control. However, the DNA loading capacity of scaffolds such as fibrin is limited. Fibrin microspheres carrying DNA complexes can be utilized to extend the capacity of fibrin scaffold. Here, in a proof of concept study, the feasibility of fibrin microspheres for extending gene delivery capacity is described. Toward this goal, fibrin microspheres encapsulating lipoplexes were fabricated. The structural and functional integrity of DNA was assessed respectively by gel electrophoresis and an in vivo pilot study, using endothelial nitric oxide synthase (eNOS) as a model therapeutic gene in a rabbit ear ulcer model of compromised wound healing. The results confirmed structural integrity and successful delivery and functional integrity, assessed qualitatively by angiogenic effect of eNOS. Finally, as a step toward development of a "fibrin in fibrin" temporal release system, fibrin microspheres were shown to degrade and release DNA differentially compared to fibrin scaffold. It can thus be concluded that fibrin microspheres can be utilized for gene delivery to extend the capacity of a fibrin scaffold and can form a component of a "fibrin in fibrin" temporal release system.     

Encapsulation of adipogenic factors to promote differentiation of adipose-derived stem cells

Insulin and dexamethasone were encapsulated in poly(lactic-co-glycolic acid) (PLGA) microspheres to induce adipogenesis for potential applications in soft tissue reconstruction. Release kinetics and bioactivity of the drugs were examined. Surface morphology and diameter of the PLGA microspheres was evaluated using scanning electron microscopy. The release of insulin was determined using ELISA whereas the release of dexamethasone was evaluated spectrophotometrically. The activity of the drugs was assessed by releasing the drugs in the presence of human adipose-derived stem cells. The ability of the cells cultured with microspheres to differentiate into adipocytes was evaluated using Oil Red O stains. Cells treated with the dexamethasone and insulin microspheres demonstrated a significant increase in lipid inclusions compared with control groups. Insulin and dexamethasone microspheres can reproduce the adipogenic effect exerted by differentiation medium, and may represent a clinically relevant method of stimulating adipogenesis in tissue engineering therapies.     

Dexamethasone loaded multi-layer poly-l-lactic acid/pluronic P123 composite electrospun nanofiber scaffolds for bone tissue engineering and drug delivery

In tissue engineering, it is common to mix drugs that can control proliferation and differentiation of cells into polymeric solutions as part of composite to get bioactive scaffolds. However, direct incorporation of drugs might potentially result in undesired burst release. To overcome this problem, here we developed electrospun multilayer drug loaded poly-l-lactic acid/pluronic P123 (PLLA–P123) composite scaffolds. The drug was loaded into the middle layer. The surface, the mechanical and physiochemical properties of the scaffolds were evaluated. The drug release profiles were monitored. Finally, the osteogenic proliferation and differentiation potential were determined. The scaffolds fabricated here have appropriate surface properties, but with different mechanical strength and osteogenic proliferation and differentiation. Multi-layer scaffolds where the drug was in the middle layer and PLLA-plasma and PLLA–P123 with cover layer showed the best osteogenic proliferation and differentiation than the other groups of scaffolds. The drug release profiles of the scaffolds were completely different: single layer scaffolds showed burst release within the first day, while multilayer scaffolds showed controlled release. Therefore, the multilayer drug loaded scaffolds prepared have dual benefits can provide both better osteogenesis and controlled release of drugs and bioactive molecules at the implant site.     

人牙周膜细胞接种于纳米-羟基磷灰石上的形态学研究

目的观察人牙周膜细胞接种于三维多孔纳米-羟基磷灰石上的组织形态学表现。方法将原代培养的人牙周膜细胞接种于三维多孔纳米-羟基磷灰石上，培养15天后，采用扫描电子显微镜观察细胞的生长情况，探讨两者的复合情况。结果作为种子细胞的人牙周膜细胞接种到支架材料上后，细胞粘附充分，生长旺盛，并有钙结节和少量胶原纤维形成。结论三维多孔纳米羟基磷灰石支架材料是一种比较符合牙周组织工程学条件的支架材料。