Nanoparticles with Two-Stage Delivery of Tetrodotoxin for Prolonged Duration Local Anesthesia

项目总结 局部麻醉是治疗手术后疼痛的一种临床选择，这种疼痛通常持续5-7年。 持续12周以上的慢性疼痛表型。常规氨基酰胺和氨基酯 局麻药是有效的，但典型的神经阻滞或浸润性神经阻滞的持续时间相对较短。 反映分子清除的时间较短(2-3小时)。除了侵入性导管，还有一种替代方案 商业制剂布比卡因脂质体(Exaprel)被广泛使用。而延长的持续时间 作用超过标准的布比卡因，其持续时间通常不到3-5天。此外， 长期接触布比卡因会增加内在肌肉和神经毒性的风险，以及 心血管和神经系统的全身副作用。我们研究的目标是开发一种局部麻醉剂 一种可从单个神经周围可靠地持续7-14天的局部麻醉的制剂 注射或局部渗透，局部或全身副作用最小。为达致这个目标，我们建议 使用河豚毒素(TTX)，一种钠通道阻滞剂，用于局部麻醉剂配方。与.相比 传统的局部麻醉药TTX在神经阻滞方面的效力大约是后者的1000倍，但它并没有 导致肌肉或神经毒性、癫痫发作或心律失常。TTX临床应用前的最后一个里程碑是解决 它的全身生物利用度，可导致神经阻滞和肌肉无力，导致 横隔膜麻痹，导致呼吸衰竭。以安全的方式使用TTX以延长持续时间 局部麻醉，我们开发了一种两阶段TTX给药系统，它集成了化学渗透 增强剂(CPE)(第一阶段)和控释技术(第二阶段)整合为一个平台。具体来说， TTX将与聚(d，L-丙交酯-乙交酯)-嵌段-聚乙二醇(PLGA-PEGO)共价偶联 通过酯键，得到的PLGA-PEG-TTX偶联物随后将被制造成 纳米粒子。我们假设具有合适亲水性和直径的PLGA-PEG-TTX纳米粒子 可穿透周围神经束膜，实现TTX向神经的靶向递送，减少 全身对TTX的摄取，纳米颗粒将驻留在神经内，充当药物仓库 持续释放恒定量的TTX，随着时间的推移，这足以满足神经阻滞，通过 酯键的水解性。两级TTX递送系统允许安全递送大剂量的 神经TTX高于报告的剂量耐受限度，将TTX毒性降至最低，并大大延长持续时间 局部麻醉。我们将评估坐骨神经阻滞，伤口渗透麻醉，以及 PLGA-PEG-TTX纳米粒在正常大鼠和大鼠原发性疼痛模型中的比较 脂质体布比卡因。该项目的预期结果是，基于TTX的局部麻醉药很可能 甚至更安全，并将提供比快速清除的安全实现更长的神经阻滞 目前正在使用的亲脂性麻醉剂。

PROJECT SUMMARY Local anesthesia is a clinical option for the treatment of post-operative pain that may typically persist for 5-7 days and chronic pain phenotype that lasts longer than 12 weeks. Conventional amino-amide and amino-ester local anesthetics are effective, but the duration of a typical nerve block or infiltrations nerve block is relatively short (2-3 hours) reflecting clearance of the molecule. Aside from an invasive catheter, an alternative commercial formulation of bupivacaine in liposomes (Exaprel) is widely used. While an increased duration of action is achieved over standard bupivacaine, its duration is typically less than 3-5 days. In addition, the extended duration of bupivacaine exposure increases risk of intrinsic muscle and nerve toxicity, as well as cardiovascular and neurologic systemic side effects. The goal of our research is to develop a local anesthetic preparation that can produce a duration of local anesthesia reliably lasting 7-14 days from a single perineural injection or site infiltration with minimal local or systemic side effects. To pursue this goal, we propose to employ tetrodotoxin (TTX), a site 1 sodium-channel blocker, for local anesthetic formulations. Compared with conventional local anesthetics, TTX is around one thousand-fold more potent in nerve block, and it does not cause myo- or neurotoxicity, seizures, or arrhythmias. The final milestone before TTX clinical use is to address its systemic bioavailability, which can cause neural blockade and muscular weakness, resulting in diaphragmatic paralysis, leading to respiratory failure. To use TTX in a safe manner for prolonged duration of local anesthesia, we developed a two-stage TTX delivery system, which integrates the chemical penetration enhancer (CPE) (first stage) and controlled release technology (second stage) into one platform. Specifically, TTX will be covalently conjugated with poly(d,l-lactide-co-glycolide)-block-poly(ethylene glycol) (PLGA-PEG) through ester bonds, and the resulting PLGA-PEG-TTX conjugates will be subsequently fabricated into nanoparticles. We hypothesize that PLGA-PEG-TTX nanoparticles with appropriate hydrophilicity and diameter can penetrate the peripheral nerve perineurium to achieve the targeted TTX delivery to the nerve and reduce the systemic uptake of TTX, and that the nanoparticles will reside inside the nerve and act as a drug depot to continuously release a constant amount of TTX, which is adequate for the nerve block over time, via the hydrolysis of the ester bonds. The two-stage TTX delivery system allows safe delivery of larger doses of perineural TTX than the reported dose tolerance limit, minimizing TTX toxicity, and greatly extending duration of local anesthesia. We will assess sciatic nerve block, wound infiltration anesthesia, and systemic toxicity of the PLGA-PEG-TTX nanoparticles in both normal rats and rat models of primary pain as compared with liposomal bupivacaine. The expected outcome of this project is that TTX-based local anesthetics are likely to be even safer and will provide longer nerve blocks than can be safely achieved with the rapidly cleared lipophilic anesthetics currently in use.