Development of new bioactive composite materials for bone regeneration

开发新的生物活性骨再生复合材料本项目旨在开发新的肌肉骨骼替代材料，以满足关键的临床需求。随着婴儿潮一代进入骨科干预和骨质疏松症的高峰年龄范围，护理婴儿潮一代的经济和社会负担可以通过基于新生物材料的治疗来解决。开发的材料也将使生物陶瓷治疗发展在市场上的类似材料的竞争优势。正如Stevens博士最近在Science（Stevens和乔治，Science 2005）中所强调的，由纳米纤维构建的三维基质允许细胞在具有与其天然细胞外基质相似规模的特征的环境中生长。纳米纤维结构似乎更有可能呈现刺激细胞表达合适表型的线索，以将其自身组织成生理相关的组织样结构。传统的大孔聚合物或陶瓷支架缺乏这些形貌线索。这种模仿自然基质的“仿生”结构的概念-生物材料和组织工程界的一个关键研究目标-只能通过涉及生物和物理科学输入的跨学科研究来实现。该项目涉及基于聚γ-谷氨酸（PgGA）的静电纺丝纳米纤维支架的制造。与用于纳米纤维的其他材料相比，PgGA具有许多优点：高强度、酶可降解性和非免疫原性。在结构上，它的β片层结构类似于其他高强度天然纤维，如丝心蛋白或丝，但它可以以一小部分的成本生产。细菌产生的PgGA可以产生几乎100%的结晶高强度纤维。Stevens博士实验室中定制设计的静电纺丝设备可以与这种聚合物一起使用，以生产高强度的纳米纤维基质。然后，这种基质可以与BioCeramic Therapeutics内部开发的生物活性陶瓷相结合，以产生用于生物活性组织工程支架的纳米纤维增强复合材料。我们将研究原代成骨细胞（HOBs）和SaOs-2矿化成骨细胞系与支架的相互作用。最初的细胞试验将检查对材料的反应，并将集中于材料支持细胞分化的能力。纤维/生物活性玻璃复合材料提供了许多独特的机会来研究纳米纤维和表面化学对细胞活性的影响。使用静电纺丝系统，可以制造化学性质相似但厚度不同的纤维，以控制纳米级形貌。此外，通过聚合物主链的官能化控制聚合物化学将控制蛋白质吸附到材料上。将通过接种细胞、测量代谢活性、碱性磷酸酶活性和标志物（如骨钙素）的产生来评估体外细胞与材料的相互作用。最终矿化将通过使用四环素染色标记细胞沉积的钙离子来测量。将使用骨钙蛋白、osterix碱性磷酸酶和胶原蛋白I的实时RT-PCR分析来测量细胞通过分化途径的进展。工作方案：静电纺丝PgGA：IC（第0-6个月）电纺纤维的表征：IC（第3-12个月）生物陶瓷BCT的制造和表征（第12-18个月）纤维功能化：IC（18-21个月）纤维/生物陶瓷复合材料工程：BCT + IC（第22-28个月）纤维和复合材料的体外细胞生物相容性试验：IC（第29-36个月）纤维材料的放大和无菌制造：BCT + IC（第37-42个月）合作安排：帝国理工学院的博士学位将由Molly Stevens博士与BioCeramic Therapeutics Ltd合作协调

Development of New Bioactive Composite Materials for Bone Regeneration This project aims to develop new musculoskeletal replacement materials to meet critical clinical needs. The economic and social burden of caring for the baby boomer generation as it enters the peak age range for orthopaedic interventions and osteoporosis can be addressed with new biomaterials based treatments. The materials developed will also allow BioCeramic Therapeutics to develop a competitive advantage over similar materials in the marketplace. As highlighted by Dr Stevens recently in Science (Stevens and George, Science 2005), a three dimensional matrix constructed of nanofibres allows cells to grow in an environment with features on a similar scale to their natural extracellular matrices. Nanofibrous structures appear more likely to present cues which stimulate cells to express a suitable phenotype to organise themselves into physiologically relevant tissue-like structures. Conventional macroporous polymer or ceramic scaffolds lack these topographical cues. This concept of 'biomimetic' structures which mimic natural matrices - a key research goal of the biomaterials and tissue engineering community- can only be achieved through interdisciplinary research involving input from biological and physical sciences. The project involves the fabrication of an electrospun nanofibrous scaffold based on poly-gamma-glutamic acid (PgGA). PgGA has a number of advantages over other materials used for nanofibres; high strength, enzymatic degradability and is non-immunogenic. Structurally, its beta sheet structure is similar to other high strength natural fibres such as fibroin or silk, but it can be produced at a fraction of the cost. Bacterially produced PgGA can generate an almost 100% crystalline high strength fibre. The custom-designed electrospinning apparatus in Dr Stevens' laboratory can be used with this polymer to produce a high strength nanofibrous matrix. This matrix can then be combined with bioactive ceramics developed in-house at BioCeramic Therapeutics to generate nanofibre reinforced composite materials for bioactive tissue engineering scaffolds. We will examine the interaction of primary osteoblasts (HOBs) and a SaOs-2 mineralizing osteoblast cell line, with the scaffolds. Initial cell assays will examine responses to the materials, and will concentrate on the capacity of the materials to support cell differentiation. The fibre/bioactive glass composites offer a number of unique opportunities to examine both the influence of nanoscale fibres and surface chemistry on cell activity. Using the electrospinning system, fibres of similar chemistry but varying thicknesses can be fabricated, to control nanoscale topography. Additionally, control of polymer chemistry through functionalisation of the polymer backbone will control protein adsorption to the material. Cell interactions with the materials in vitro will be assessed by seeding cells, measuring metabolic activity, activity of the enzyme alkaline phosphatase and production of markers such as osteocalcin. Final mineralisation will be measured by labeling calcium ions deposited by cells using tetracycline staining. Progression of cells through the differentiation pathway will be measured using real-time RT-PCR analysis of osteocalcin, osterix alkaline phosphatase and collagen I. Work Programme: Electrospinning PgGA: IC (Month 0-6) Characterisation of electrospun fibres: IC (Month 3-12) Manufacture and characterisation of bioceramic BCT (Month 12-18) Functionalisation of fibres: IC (Month 18-21) Engineering of fibre/bioceramic composites: BCT + IC (Month 22-28) In vitro cell biocompatibility assays on fibres and composites: IC (Month 29-36) Scale-up and sterile manufacture of fibre materials: BCT + IC (Month 37-42) Collaborative arrangements: The PhD at Imperial College will be coordinated by Dr Molly Stevens in collaboration with BioCeramic Therapeutics Ltd