Biodistribution of Fracture-Targeted GSK3β Inhibitor-Loaded Micelles for Improved Fracture Healing
作者:Stewart A. Low、Chris V. Galliford、Jiyuan Yang、Philip S. Low、Jindřich Kopeček
DOI:10.1021/acs.biomac.5b00777
日期:2015.10.12
Bone fractures constitute a major cause of morbidity and mortality especially in the elderly. Complications associated with osteoporosis drugs and the age of the patient slow bone turnover and render such fractures difficult to heal. Increasing the speed of fracture repair by administration of a fracture-targeted bone anabolic agent could find considerable application. Aspartic acid oligopeptides are negatively charged molecules at physiological pH that adsorb to hydroxyapatite, the mineral portion of bone. This general adsorption is the strongest where bone turnover is highest or where hydroxyapatite is freshly exposed. Importantly, both of these conditions are prominent at fracture sites. GSK3β inhibitors are potent anabolic agents that can promote tissue repair when concentrated in a damaged tissue. Unfortunately, they can also cause significant toxicity when administered systemically and are furthermore difficult to deliver due to their strong hydrophobicity. In this paper, we solve both problems by conjugating the hydrophobic GSK3β inhibitor to a hydrophilic aspartic acid octapeptide using a hydrolyzable bond, thereby generating a bone fracture-targeted water-soluble form of the drug. The resulting amphiphile is shown to assemble into micelles, extending its circulation time while maintaining its fracture-targeting abilities. For measurement of pharmacokinetics, an 125I was introduced at the location of the bromine in the GSK3β inhibitor to minimize any structural differences. Biodistribution studies demonstrate a greater than 4-fold increase in fracture accumulation over healthy bone.
骨折是导致主要疾病和死亡的原因,尤其是在老年人中。与骨质疏松药物相关的并发症以及患者的年龄减缓了骨代谢,使得这些骨折的愈合变得困难。通过使用针对骨折的骨生长促进剂来提高骨折愈合的速度可能具有相当大的应用潜力。天冬氨酸寡肽在生理pH下是带负电荷的分子,能够吸附到羟基磷灰石上,羟基磷灰石是骨的矿物成分。这种一般性吸附在骨代谢最高或者羟基磷灰石新鲜暴露的地方最强。重要的是,这两种情况在骨折部位都非常突出。GSK3β抑制剂是一种强效的合成药物,能够在损伤组织中促进组织修复。不幸的是,它们在系统性给药时可能会引起显著的毒性,并且由于其强烈的疏水性,给药也相当困难。在本文中,我们通过将疏水性的GSK3β抑制剂与亲水性的天冬氨酸八肽通过可水解的键结合,从而解决了这两个问题,生成了一种针对骨折的水溶性药物形式。所产生的两性分子显示出能够聚集成微胶束,延长其循环时间,同时保持其针对骨折的靶向能力。为了测量药代动力学,我们在GSK3β抑制剂的溴位置引入了125I,以最小化任何结构差异。生物分布研究表明,骨折部位的积累相较于健康骨骼增加了超过4倍。