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

角膜是一个透明的窗口，位于眼睛的前面，对眼睛的主要功能有几个必不可少的作用。这些措施包括控制到达眼球后部的光量，将光线聚焦到视网膜上，以及建立和保持眼睛的形状。它由三个主要层组成：复层上皮、间质和单层内皮。角膜受损会导致失明，最常见的治疗方法是供体角膜置换术。可能需要更换角膜的一些病理情况包括化学烧伤、史蒂文-约翰逊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被广泛使用，但也不是没有局限性。其中包括供体角膜的可获得性有限，组织排斥和感染问题，最后是手术费用。人工角膜可以克服这些限制，因为它们可以由生物兼容的合成材料制成，减少组织排斥，可以大量生产，并可以省去供体角膜筛查等费用。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，被认为在抗微生物隐形眼镜中使用效果很好。这种聚合物是以PEK为基础，与双羧基脂肪酸交联，发现最适合的是琥珀酸。确定了最佳单体组成，发现其对HCE-T细胞无细胞毒性，且不抑制细胞单层的再上皮化。水凝胶是一种水膨胀的聚合物交联物网络，它保持了物理和机械性能，使其成为生物材料和组织工程应用的理想材料。它们的高水分含量使它们可以被引入生物环境，而不会影响它们的生存能力，也使它们适合细胞附着。通过改变聚合物和交联剂的密度以及交联剂的分子长度，可以特别定制聚-E-赖氨酸的机械性能。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。该项目的目标是生产这种先前作为薄膜测试的PEK基水凝胶的3D大孔形式。这种3D多孔凝胶的设计和制造将通过多条路线进行试验。这些技术包括多孔结构的受控3D打印、水凝胶碎片的交联化和凝胶浇注的形式。这将涉及探索几种不同的打印技术，并确定哪种技术最适合这种材料。可以进一步改变水凝胶的化学成分，以适应这些不同的技术，并优化细胞的附着和响应。一旦建立了合适的制造工艺，材料的性质就可以改变，以适应眼睛内的应用，主要关注的是透明度。最后，将对具有这种改进的结构的材料进行几次试验，以评估其对细胞结合和附着的适宜性。这种材料将不可避免地被用于人工角膜，或者当细胞被结合时，用于角膜的体外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，并将由雷切尔·威廉姆斯教授和凯特·布莱克博士监督。

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.