Bubbles to Bond Broken Bones: targeted drug delivery for fracture repair

骨折是一个主要的社会问题，每年花费英国经济超过20亿英镑。随着人口平均年龄的增长，预计这一数字今后将显著增加。这一成本的很大一部分可归因于5-10%的骨折无法通过当前的临床干预适当愈合，导致患者需要大手术和广泛的康复。因此，迫切需要开发新的、微创的和具有成本效益的治疗方法。拟议研究的目的是通过调查促进骨愈合的药物靶向递送的潜力来解决这一需求。这将通过使用体外应用于身体的聚焦超声和通过静脉注射递送的载药纳米滴（ND）的组合来实现。ND由挥发性液体颗粒（直径约200 nm）组成，可用于封装一系列不同类型的药物。在小鼠模型的初步工作中，我们已经表明，在暴露于超声波后，它们迅速膨胀形成气体微泡，同时释放其药物有效载荷并刺激细胞摄取。我们还证明，ND可以被设计成在骨折部位积聚。这些观察现在提供了令人兴奋的可能性，远程控制的ND加载药物在骨折部位的交付。我们的方法具有在愈合的正确阶段选择性地将分子递送到损伤部位的优势，并且重要的是，还保留了肉芽和血肿组织，这是良好骨折愈合结果的强阳性调节剂。根据作用的时间和部位，许多分子对骨折愈合都有积极和消极的影响，因此正确的时机是治疗效果的基础。在这个项目中，我们计划首先建立我们已经建立的ND化学品，使蛋白质和小分子能够在不同的时间背景下递送已知是骨折愈合的积极调节剂，例如骨形态发生蛋白（BMP）和WNT蛋白。基于我们的初步数据，我们将同时测试哪些超声参数导致最佳释放、有效载荷摄取和细胞内途径激活，然后评估它们在细胞培养、生物反应器培养和细胞培养的离体系统中的成骨作用。同时，我们将确定哪些超声参数是最佳的，以确保分子在体内释放和激活。最后，我们将结合高分辨率计算机断层扫描、分子和组织学技术，测试优化的ND制剂是否可以促进体内骨折愈合。我们组建了一个世界领先的跨学科团队来进行这项研究，包括超声和药物释放、骨修复、干细胞生物学和纳米颗粒化学方面的专家。此外，我们的研究计划是与专门从事骨折治疗的临床医生密切合作制定的。我们还将与非RCUK公共部门利益相关者Dstl密切合作，他们对我们的技术作为更好地治疗受伤服务人员的手段有浓厚的兴趣，并与商业合作伙伴密切合作，他们将为我们提供临床批准的材料和设备。我们的目标是，通过这些互动，工作成果将对临床实践和商业吸收产生直接影响。最后，我们的研究结果也将广泛的学术和应用相关性的其他医疗条件，控制治疗的时间和地点是很重要的，例如，中风和心血管疾病。

Bone fractures are a major societal problem costing the UK economy more than £2 billion/year. This figure is predicted to increase markedly in the future as the average age of the population increases. A significant portion of this cost can be attributed to the 5-10% of bone fractures that fail to heal appropriately with current clinical interventions, leading to patients requiring major surgery and extensive rehabilitation. Hence there is an urgent need for new, minimally invasive and cost-effective treatments to be developed.The aim of the proposed research is to address this need by investigating the potential for targeted delivery of drugs that promote bone healing. This will be achieved using a combination of focused ultrasound applied externally to the body and drug-loaded nanodroplets (NDs) delivered by intravenous injection. NDs consist of particles (~200nm in diameter) of a volatile liquid that can be used to encapsulate a range of different types of drug. In preliminary work in a mouse model we have shown that upon exposure to ultrasound they undergo rapid expansion to form gas microbubbles, simultaneously releasing their drug payload and stimulating cell uptake. We have also demonstrated that NDs can be engineered to accumulate at bone fracture sites. These observations now provides the exciting possibility of controlling remotely the delivery of ND-loaded drugs at fracture sites. Our approach has the advantage of delivering molecules selectively to the injury site at the correct phase of healing and - importantly - also preserves the granulation and hematoma tissue, which are strong positive regulators of good fracture healing outcomes. Many molecules can have both positive and negative effects on fracture healing depending on the time and site of action, and so correct timing is fundamental to treatment efficacy.In this project, we plan firstly to build on our established ND chemistries to enable the delivery of proteins and small molecules known to be positive regulators of fracture healing in different temporal context, for example bone morphogenetic protein (BMP) and WNT protein. Building on our preliminary data, we will concurrently test what ultrasound parameters result in the optimal release, payload uptake and intracellular pathway activation, before assessing their osteogenic effects in cell culture, bioreactor culture and ex vivo systems of cell culture. In parallel, we will determine which ultrasound parameters are optimal to ensure molecule release and activation in vivo. Finally we will test whether optimised ND preparations can promote fracture healing in vivo using a combination of high resolution computed tomography, molecular and histological techniques.We have assembled a world-leading interdisciplinary team to conduct this research, comprising experts in ultrasound and drug release, bone repair, stem cell biology and nanoparticle chemistry. In addition, our research proposal has been developed in close collaboration with clinicians specialising in bone fracture treatment. We will also work closely with non-RCUK public sector stakeholders, Dstl, who have a strong interest in our technology as a means of better treatment of injured service personnel, and with commercial partners who will provide us with clinically approved materials and equipment. It is our aim that through these interactions, the outcomes of the work will have direct impact upon clinical practice and commercial uptake. Finally our results will also be of wide academic and applied relevance to other medical conditions for which control over timing and location of treatment delivery is important, for example, stroke and cardiovascular disease.