Development of Vascular Inspired Electrospun Hollow Fibre Membranes for use in 3D Tissue Culture

二维(2D)组织培养技术对细胞-细胞和细胞-细胞外基质(ECM)相互作用的模拟不足，破坏了2D组织培养技术的必要性。在厚度超过200m的静态三维组织培养支架中，扩散传质的有效范围很短，会导致组织缺血性损伤和坏死区1-4。在体内，血管系统通过动脉将营养物质和氧气输送到组织中，并在静脉中清除废物代谢物。在组织工程构建的天然血管网络的LEU中，中空纤维膜(HFM)已被用于促进对流质量传输5-7。然而，现有的HFM的刚性和整体式表面破坏了被动的机械提示，同时抑制了多模式机械刺激。静电纺丝是一种能够从聚合物溶液或熔体中拉伸纳米纤维的多功能技术，它使模仿ECM8纤维结构的生物活性材料的开发成为可能。通过这项技术的利用，电纺血管支架(EVSS)已经被开发出来，以详尽地模拟天然血管的形态和机械性能。然而，用于生产EVS的方法将它们的长度限制在较短的部分。最近，电纺也被应用于生产机械性能与肌腱相似的柔性长丝。因此，这些技术的结合可能有助于新的长段血管模拟HFM的生产。这些反过来可以用来促进营养和气体的转移，同时保持生理机械提示10，11尽管到目前为止，试验和错误制造主要推动了电动汽车的发展，但几个并发症仍然与它们的使用有关。血管生长和再生建模技术的最新发展为它们的使用提供了希望，以加快确定最佳支架特征12。同时，鉴于生物系统的复杂相互联系的性质，数学建模技术被用来破译决定培养结果、优化培养条件和提高几种细胞类型的培养产量的基本机制13-16。通过结合从每一种模型开发技术中吸取的经验教训，因此有可能开发一种新的模型，从而能够确定电纺HFM生物反应器内的最佳培养条件。考虑到目前的情况，我的研究旨在回答以下问题：1)能否通过静电纺丝以可重复的方式连续制备HF膜，以模拟天然血管的形态和力学特性，并在静态和动态培养条件下促进营养物质向第三级支架的交换？2)此类HFs能否用作生物医学研究的底物，潜在地用于生产用于治疗的生物材料？为了回答这些问题，因此，我的具体目标是：i.通过一种可重复可控的新的连续工艺，生产新型的电纺HFs，以模拟天然血管的形态和机械性能。ii.表征膜的传输特性以及它们在机械载荷下可能发生的变化。建立了一个新的数学模型来描述电纺HFMsIV的输运过程。开发静态和机械动态氢氟化氢生物反应器，几何信息来自于电纺HFM传输模型V。评估静电纺丝在(A)静态和(B)机械动态HF生物反应器结构中用于组织培养的使用本项目属于EPSRC卫生保健技术研究领域，特别是生物材料和组织工程的发展。

The indispensability of two-dimensional (2D) tissue culture techniques is marred by its insufficient mimicry of cell-cell and cell-extracellular matrix (ECM) interactions. In static three-dimensional (3D) tissue culture scaffolds more than 200 m thick, the short effective range of diffusive mass transfer results in ischemic tissue damage and necrotic regions1-4.In vivo, vasculature transports nutrients and oxygen to tissues through arteries and removes waste metabolites in veins. In leu of a native vascular network in tissue engineered constructs, hollow fibre membranes (HFMs) have been utilised to facilitate convective mass transport5-7. The rigidity and monolithic surface of existing HFMs, however, disrupts passive mechanical cues while inhibiting multimodal mechanical stimulation. Electrospinning, a versatile technique enabling the drawing of nano-fibres from polymer solutions or melts, has enabled the development of bioactive materials which mimic the fibrous structure of the ECM8. Through the utilisation of this technique, electrospun vascular scaffolds (EVSs) have been developed to exhaustively mimic the morphology and mechanical properties of native vasculature. The methods used to produce EVSs have, however, limited their length to short sections. Recently electrospinning has also been implemented in the production of long flexible filaments with similar mechanical properties to that of tendon9. The combination of these techniques may thereby facilitate the novel production of long sections of vascular mimetic HFMs. These in turn may be used to facilitate nutrient and gas transfer while maintaining physiological mechanical cues10,11.While trial and error fabrication has predominantly driven EVS development to date, several complications are still associated with their use. Recent developments in vascular growth and regeneration modelling techniques hold promise towards their use to expedite the identification of optimal scaffold characteristics12. Concurrently, in view of the complex interconnected nature of biological systems, mathematical modelling techniques have been used to decipher the underlying mechanisms determining; culture outcomes, optimising culture conditions and improving culture yields of several cell types13-16. By combining lessons learnt from each of these model development techniques it may thereby be possible to develop a novel model to enable the identification of optimal culture conditions within an electrospun HFM bioreactor. Considering this current state of affairs, my research aims to answer the questions: 1) Can HF membranes be fabricated continuously by electrospinning in a reproducible way to mimic the morphological and mechanical properties of native vasculature and facilitate nutrient exchange to a tertiary scaffold in static and dynamic culture conditions?2) Can such HFs be used as a substrate for biomedical research, potentially for the production of biomaterials intended for therapeutic application?To answer these questions, my specific objectives are therefore:I. Produce novel electrospun HFs which mimic the morphology and mechanical properties of native vasculature through a novel continuous process in a reproducible controllable manner.II. Characterise the transport properties of the membranes and how they may change under mechanical loadingIII. Develop a novel mathematical model to describe the transport across the electrospun HFMsIV. Develop a static and mechanically dynamic HF bioreactor, geometrically informed from the electrospun HFM transport modelV. Evaluate the use of the electrospun HFs for tissue culture in (a) static and (b) mechanically dynamic HF bioreactor configurationsThis project falls within the EPSRC Health Care Technologies research area, specifically towards the development of biomaterials and tissue engineering.