Hydrogels for combined delivery of novel growth factor mimetics and small molecule ligands for treatment of CNS damage

中枢神经系统（CNS）损伤和疾病是残疾的主要原因，导致认知障碍、感觉功能丧失、瘫痪、慢性疼痛和生活质量严重受损等症状。CNS损伤有多种可能的原因，包括脑或脊髓的创伤性损伤、由血管疾病或中风引起的缺血或缺氧，以及各种先天性或退行性疾病。尽管深入研究了解急性和慢性CNS损伤，但大多数情况下的治疗选择有限。在CNS中应用的药物的配制和递送方面存在重大挑战，这可以通过开发新的制药技术来解决。已知CNS损伤和神经变性可以通过多种小分子配体和生长因子进行积极调节。例如，生长因子如胶质细胞系源性神经营养因子（GDNF）、神经生长因子（NGF）和脑源性神经营养因子（BDNF）已显示在帕金森病和阿尔茨海默病模型中促进神经元再生，在早期临床试验中具有一定前景。1目前，将生长因子递送至CNS依赖于蛋白质的直接输注，或通过基因或细胞疗法生产蛋白质。细胞疗法是将生长因子长期递送到大脑的首选方法，然而需要免疫抑制来防止免疫应答的激活，并且这种方法的成本和复杂性是禁止的。对于CNS损伤的新治疗仍然存在迫切的需求，所述新治疗是安全和有效的，适合于规模化生产，并且不引起不利的宿主免疫和炎症反应。生长因子本身的直接递送消除了对细胞和基因疗法以及治疗中的免疫抑制的需要，但是在将这些蛋白质递送到CNS中存在固有的困难。此外，如果已知负责受体激活的生长因子的结构域，则可以合成这些结构域并将其本身用作治疗。这种方法的可行性先前已经用BDNF和NGF的肽模拟物证明。2，3减小活性剂的大小也具有递送制剂可以负载更高剂量的优点，这意味着在没有细胞或基因疗法或频繁重复给药的情况下，更长期的治疗成为可能。这种方法的一个缺点是，在CNS中的生长因子的剂量是有限的低血脑屏障的渗透性和差的体内半衰期的protein.This项目旨在解决这个问题，通过开发一种水凝胶局部递送制剂的小分子配体和生长因子模拟物，这将促进神经再生和恢复中枢神经系统功能。水凝胶是亲水性和生物相容性的3D聚合物网络，并且可以装载随着聚合物生物降解而随时间缓慢释放的货物。随着时间的推移，货物的稳定释放对这个项目至关重要，因为生长因子受体在暴露于持续高水平的生长因子时会变得脱敏。此外，水凝胶模拟神经系统的结构和机械特性，从而最大限度地减少不良宿主组织反应，使其成为CNS治疗的理想递送系统。将合成与神经再生有关的配体和生长因子模拟物，并将其掺入水凝胶制剂中，以确保活性剂的长期局部释放并防止过早降解。将使用CNS损伤的体外细胞模型对开发的制剂进行表征和测试。

Central nervous system (CNS) damage and disease is a leading cause of disability, resulting in symptoms such as cognitive impairment, loss of sensory function, paralysis, chronic pain and severely impaired quality of life. CNS damage has a variety of possible causes, including traumatic injury to the brain or spinal cord, ischaemia or hypoxia resulting from vascular disorders or stroke, and a wide range of congenital or degenerative diseases. Despite intensive research into understanding both acute and chronic CNS damage, limited treatment options are available for most conditions. There are major challenges around the formulation and delivery of medicines for application in the CNS which can be addressed through the development of new pharmaceutical technology.It is known that CNS damage and neurodegeneration can be positively modulated by a variety of small molecule ligands and growth factors. For example, growth factors such as glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) have been shown to promote neuronal regeneration in models of Parkinson's and Alzheimer's disease with some promise in early clinical tests.1 At present, the delivery of growth factors to the CNS relies on either direct infusion of the protein, or production of the protein via gene or cell therapies. Cell therapies are the method of choice for delivery of growth factors to the brain over long periods, however immunosuppression is required to prevent activation of the immune response and the cost and complexity of this approach is prohibitive. There remains a critical need for new treatments for CNS damage which are safe and effective, suitable for scalable manufacture, and do not cause adverse host immune and inflammatory responses.Direct delivery of growth factors themselves eliminates the need for cell and gene therapies and immunosuppression in treatment, but there are inherent difficulties in delivering these proteins to the CNS. Further, if the domain of the growth factor responsible for receptor activation is known, these could be synthesised and used as therapies themselves. The viability of this approach has previously been demonstrated with peptide mimetics of BDNF and NGF.2,3 Decreasing the size of the active agent also has the advantage that delivery formulations can be loaded with higher doses, meaning that longer-term treatments become possible without cell or gene therapies or frequently repeated dosing. One drawback of this approach is that the dose of growth factor available in the CNS after administration is limited by low blood-brain-barrier permeability and poor in vivo half-life of the proteins.This project aims to address this issue by developing a hydrogel local delivery formulation for small molecule ligands and growth factor mimetics which will promote neural regeneration and restoration of CNS function. Hydrogels are 3D polymeric networks which are hydrophilic and biocompatible, and can be loaded with cargoes which are released slowly over time as the polymer biodegrades. Steady release of cargo over time is essential for this project, because growth factor receptors can become desensitised when exposed to continually high levels of growth factor. Additionally, hydrogels mimic the architecture and mechanical properties of the nervous system which minimises adverse host tissue responses, making them ideal delivery systems for CNS therapies. Ligands and growth factor mimetics with implications in neuroregeneration will be synthesised and incorporated into hydrogel formulations to ensure long-term local release of the active agents and prevent premature degradation. The developed formulations will be characterised and tested using in vitro cellular models of CNS damage.