The design and manufacture of 3D peptide gels for tissue engineering applications

角膜是位于眼睛前部的透明窗口，并且对眼睛的主要功能具有几个必不可少的作用。这些包括控制到达眼睛后部的光量，将光线聚焦到视网膜上，以及建立和保持眼睛形状。它由三个主要层组成：复层上皮、基质和单层内皮。角膜受损会导致失明，最常见的治疗方法是供体角膜置换。可能需要替换角膜的一些病理包括化学烧伤、Steven-Johnson综合征和自身免疫性疾病，如粘膜类天疱疮。这一程序在世界各地广泛使用，但并非没有其局限性。其中包括供体角膜的有限可用性，组织排斥和感染的问题，以及最后的手术费用。人工角膜将能够克服这些限制，因为它们可以由生物相容性合成材料制成，减少组织排斥，它们可以大批量生产，并且可以消除诸如供体角膜筛选的费用。利物浦大学最近的一项研究开发了一种基于聚-E-赖氨酸（pEK）的水凝胶材料，该材料被认为可有效用于抗微生物隐形眼镜。该聚合物基于与双羧基脂肪酸交联的pEK，发现最合适的是辛二酸。建立了最佳单体组合物，发现其对HCE-T细胞无细胞毒性，并且不抑制细胞单层的再上皮化。水凝胶是聚合物交联的水溶胀网络，其保持使其成为生物材料和组织工程应用的理想材料的物理和机械性质。它们的高含水量允许它们被引入生物环境而不影响活力，并且还使它们适合于细胞附着。聚-E-赖氨酸的机械性质具体地可以通过改变聚合物和交联密度以及交联剂的分子长度来定制。例如，增加聚合物密度直接增加最终水凝胶的极限拉伸强度。该项目的目的是生产这种基于pEK的水凝胶的3D大孔形式，该水凝胶先前作为薄膜进行了测试。这种3D多孔凝胶的设计和制造将通过多种途径进行试验。这些包括多孔结构的受控3D打印，水凝胶片段的交联和凝胶浇铸的形式。这将涉及探索几种不同的印刷技术，并确定什么是最适合这种材料。可以进一步改变水凝胶的化学性质，以适应这些不同的技术，并优化细胞附着和反应。在建立合适的制造工艺后，可以改变材料的特性以适应眼睛内的应用，主要焦点是透明度。最后，将对具有这种改良结构的材料进行几项试验，以评估其对细胞掺入和附着的适用性。这种材料将不可避免地用于人工角膜，或者当细胞被整合时，角膜的体外3D组织模型。该项目将在老龄化和慢性病研究所和工程学院之间进行，并将由Rachel威廉姆斯教授和Kate Black博士监督。

The cornea is a transparent window located at the front of the eye and has several roles imperative to the main functions of the eye. These include controlling the amount of light reaching the back of the eye, focusing light onto the retina and establishing and maintaining the eye shape. It is composed of three main layers: a stratified epithelium, the stroma, and a single layered endothelium. A damaged cornea can result in blindness, and the most common treatment for this is donor cornea replacement. Some pathologies where a replacement cornea may be required include chemical burns, Steven-Johnson syndrome and autoimmune diseases such as mucus membrane pemphigoid. This procedure is widely used throughout the world, but is not without its limitations. Amongst these are the limited availability of the donor corneas, issues with tissue rejection and infection and finally, the expense of the procedure. An artificial cornea would be able to combat these limitations, as they could be made of a biocompatible synthetic material reducing tissue rejection, they could be manufactured in large volumes and could eliminate expenses such as donor cornea screening.A recent study at the University of Liverpool developed a poly-E-lysine (pEK) based hydrogel material that was seen to be effective for use in anti-microbial contact lenses. This polymer is based on pEK cross-linked with bis-carboxy fatty acids, the most suitable found to be suberic acid. An optimal monomer composition was established and found to be non-cytotoxic to HCE-T cells and did not inhibit the re-epithelialisation of a cell monolayer. A hydrogel is a water-swollen network of polymer crosslinks, which maintains physical and mechanical properties that make it a desirable material for biomaterial and tissue engineering applications. Their high water content allows them to be introduced into a biological environment without affecting the viability, and also makes them suitable for cell attachment. The mechanical properties of poly-E-lysine specifically can be tailored by altering both the polymer and cross-linking density and the molecular length of the cross linker. For instance, increasing the polymer density directly increases the ultimate tensile strength of the final hydrogel.The aim of this project is to produce a 3D macro-porous form of this pEK based hydrogel previously tested as a thin film. The design and manufacture of this 3D porous gel will be trialled via a number of routes. These include the controlled 3D printing of porous constructs, the crosslinking of hydrogel fragments and forms of gel casting. This will involve exploring several different printing technologies and determining what is the most suitable for this material. The hydrogel chemistry can further be altered to suit these different technologies and to optimise cell attachment and response. Upon establishing a suitable manufacturing process, the properties of the material could be altered to suit applications within the eye, with the main focus being transparency. Finally, several trials will be performed on the material with this modified architecture to assess its suitability for cell incorporation and attachment. This material could inevitably be used for an artificial cornea, or an in vitro 3D tissue model of the cornea when cells are incorporated.This project will take place between the Institute of Ageing and Chronic Disease and the School of Engineering and will be supervised by Professor Rachel Williams and Dr Kate Black.