可电离脂质纳米颗粒(LNP)是用于治疗性核酸的临床上最先进的纳米递送系统。在开发具有增加的体内效力的可电离脂质方面所付出的巨大努力使实验室的LNPs在2018年获得FDA批准patisiran,并正在进行针对SARS-CoV-2的基于mRNA的疫苗的临床试验。尽管有这些成功的故事,RNA递送仍然存在一些挑战,包括所谓的“内体逃逸”。“为了释放RNA分子的治疗活性,必须达到细胞质,因为它们在其他细胞内区室中的积累只会导致功效损失。在LNP中,可电离脂质在酸性pH下形成不稳定的非双层结构的能力被认为是内体逃逸和RNA胞质递送的关键。这激发了旨在设计具有改善的生物降解和安全性的新型可电离脂质的研究激增。在这项工作中,我们描述了装载RNA的LNP跨越多个细胞内屏障的旅程,从细胞外空间到细胞质。在硅分子动力学建模中,体外高分辨率显微镜分析,系统回顾了体内成像数据,以提炼出RNA内体逃逸的调节机制。最后,还提供了与包膜病毒将其遗传物质递送到细胞中所采用的策略的比较。用于内体逃逸定量的多学科分析工具包和受自然启发的设计的组合可以促进具有改进的核酸的胞浆递送的未来LNP的发展。
Ionizable lipid nanoparticles (LNPs) are the most clinically advanced nano-delivery system for therapeutic nucleic acids. The great effort put in the development of ionizable lipids with increased in vivo potency brought LNPs from the laboratory benches to the FDA approval of patisiran in 2018 and the ongoing clinical trials for mRNA-based vaccines against SARS-CoV-2. Despite these success stories, several challenges remain in RNA delivery, including what is known as \"endosomal escape.\" Reaching the cytosol is mandatory for unleashing the therapeutic activity of RNA molecules, as their accumulation in other intracellular compartments would simply result in efficacy loss. In LNPs, the ability of ionizable lipids to form destabilizing non-bilayer structures at acidic pH is recognized as the key for endosomal escape and RNA cytosolic delivery. This is motivating a surge in studies aiming at designing novel ionizable lipids with improved biodegradation and safety profiles. In this work, we describe the journey of RNA-loaded LNPs across multiple intracellular barriers, from the extracellular space to the cytosol. In silico molecular dynamics modeling, in vitro high-resolution microscopy analyses, and in vivo imaging data are systematically reviewed to distill out the regulating mechanisms underlying the endosomal escape of RNA. Finally, a comparison with strategies employed by enveloped viruses to deliver their genetic material into cells is also presented. The combination of a multidisciplinary analytical toolkit for endosomal escape quantification and a nature-inspired design could foster the development of future LNPs with improved cytosolic delivery of nucleic acids.