设计靶向药物递送系统以有效治疗从骨质疏松症到骨不愈合骨缺损的骨疾病仍然是一个重大挑战。以前,纳米颗粒(NPs)自组装的二嵌段共聚物的聚(苯乙烯-alt-马来酸酐)-b-聚(苯乙烯)(PSMA-b-PS)递送Wnt激动剂被证明可以有效地靶向骨骼并通过引入具有高亲和力的肽来改善愈合抗酒石酸酸性磷酸酶(TRAP),在骨重建过程中由破骨细胞沉积的酶。尽管这些有希望的结果,尚未检查控制靶向和随后的药物递送系统(DDS)设计参数的潜在生物学因素,以使合理的设计能够提高骨选择性。因此,这项工作研究了目标配体密度的影响,受伤后的治疗窗口,TRAP结合肽(TBP)的特异性,TRAP沉积的程度,和潜在的遗传因素(例如,小鼠品系差异)在TBP-NP靶向上。基于小鼠股骨骨折模型的体外结合研究和体内生物分布分析的数据表明,TBP-NP-TRAP相互作用和TBP-NP骨积聚是配体密度依赖性的;在体外,TRAP亲和力与配体密度相关,最大为200,000TBP配体/NP,而具有80,000个TBP配体的NP在损伤后第21天显示,与非靶向或混乱对照相比,骨折积累增加了2倍。虽然与骨折后第21天相比,在第3天注射时骨折积聚表现出相似的趋势,在TBP官能化的NPs和对照NPs之间没有观察到显著差异,可能是由于在第3天NPs对TRAP的饱和。利用钙耗尽的饮食,TRAP沉积与TBP-NP骨量呈正相关,证实TRAP-TBP结合导致体内TBP-NP骨积聚。此外,与对照NP相比,TBP-NP在C57BL/6和BALB/c小鼠品系中表现出相似的骨积累,表明TBP-NP的广泛适用性,无论潜在的遗传差异如何。这些研究提供了对TBP-NP设计的见解,机制,和治疗窗口,为利用TRAP的骨折和其他骨相关疾病的NP设计和治疗策略提供信息,如骨髓相关血液病。
Designing targeted drug delivery systems to effectively treat bone diseases ranging from osteoporosis to nonunion bone defects remains a significant challenge. Previously, nanoparticles (NPs) self-assembled from diblock copolymers of poly(styrene-alt-maleic anhydride)-b-poly(styrene) (PSMA-b-PS) delivering a Wnt agonist were shown to effectively target bone and improve healing via the introduction of a peptide with high affinity to tartrate-resistant acid phosphatase (TRAP), an enzyme deposited by the osteoclasts during bone remodeling. Despite these promising results, the underlying biological factors governing targeting and subsequent drug delivery system (DDS) design parameters have not been examined to enable the rational design to improve bone selectivity. Therefore, this work investigated the effect of target ligand density, the treatment window after injury, specificity of TRAP binding peptide (TBP), the extent of TRAP deposition, and underlying genetic factors (e.g., mouse strain differences) on TBP-NP targeting. Data based on in vitro binding studies and in vivo biodistribution analyses using a murine femoral fracture model suggest that TBP-NP-TRAP interactions and TBP-NP bone accumulation were ligand-density-dependent; in vitro, TRAP affinity was correlated with ligand density up to the maximum of 200,000 TBP ligands/NP, while NPs with 80,000 TBP ligands showed 2-fold increase in fracture accumulation at day 21 post injury compared with that of untargeted or scrambled controls. While fracture accumulation exhibited similar trends when injected at day 3 compared to that at day 21 postfracture, there were no significant differences observed between TBP-functionalized and control NPs, possibly due to saturation of TRAP by NPs at day 3. Leveraging a calcium-depletion diet, TRAP deposition and TBP-NP bone accumulation were positively correlated, confirming that TRAP-TBP binding leads to TBP-NP bone accumulation in vivo. Furthermore, TBP-NP exhibited similar bone accumulation in both C57BL/6 and BALB/c mouse strains versus control NPs, suggesting the broad applicability of TBP-NP regardless of the underlying genetic differences. These studies provide insight into TBP-NP design, mechanism, and therapeutic windows, which inform NP design and treatment strategies for fractures and other bone-associated diseases that leverage TRAP, such as marrow-related hematologic diseases.