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

二维（2D）组织培养技术的不可或缺性因其对细胞-细胞和细胞-细胞外基质（ECM）相互作用的模拟不足而受到损害。在厚度超过200 m的静态三维（3D）组织培养支架中，扩散传质的有效范围较短，导致缺血性组织损伤和坏死区域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，并在静脉中清除代谢废物。在组织工程构建体中的天然血管网络的leu中，中空纤维膜（HFM）已被用于促进对流质量运输5 -7。然而，现有HFM的刚性和整体表面破坏了被动机械提示，同时抑制了多模态机械刺激。静电纺丝是一种多功能技术，可以从聚合物溶液或熔体中拉伸纳米纤维，从而能够开发出模仿ECM纤维结构的生物活性材料8。通过利用这种技术，电纺血管支架（EVS）已被开发为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为短段。最近，静电纺丝也被用于生产具有与肌腱相似的机械性能的长柔性细丝9。这些技术的组合可以由此促进血管模拟HFM的长切片的新生产。这些反过来可以用于促进营养和气体转移，同时保持生理机械线索10，11。尽管迄今为止，试错制造主要推动了EVS的发展，但仍有一些并发症与其使用有关。血管生长和再生建模技术的最新发展有望用于加快最佳支架特性的鉴定12。同时，鉴于生物系统的复杂的相互关联的性质，数学建模技术已被用于破译决定培养结果、优化培养条件和提高几种细胞类型的培养产率的潜在机制13 -16。通过结合从这些模型开发技术中的每一种中吸取的经验教训，从而可以开发新的模型，以能够鉴定电纺HFM生物反应器内的最佳培养条件。考虑到这种现状，我的研究旨在回答以下问题：1）HF膜能否通过静电纺丝以可重复的方式连续制造，以模拟天然血管的形态和机械特性，并在静态和动态培养条件下促进营养交换到三级支架？2)这种HF是否可以用作生物医学研究的基质，可能用于生产用于治疗应用的生物材料？为了回答这些问题，我的具体目标是：以可再现的可控方式通过新型连续工艺生产新型电纺HF，其模拟天然脉管系统的形态和机械特性。表征膜的传输特性以及它们在机械负载下如何变化III.开发一种新的数学模型来描述通过静电纺丝HFMsIV的运输。开发静态和机械动态HF生物反应器，从静电纺丝HFM传输模型V几何学上获知。评价在（a）静态和（B）机械动态HF生物反应器配置中使用电纺HF进行组织培养。该项目福尔斯属于EPSRC医疗保健技术研究领域，特别是生物材料和组织工程的开发。

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.