Mei Ling, Fu Ling, Shi Kairong, Zhang Qianyu, Liu Yayuan, Tang Jie, Gao Huile, Zhang Zhirong, He Qin
Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University. No. 17, Block 3, Southern Renmin Road, Chengdu 610041, PR China.
Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University. No. 17, Block 3, Southern Renmin Road, Chengdu 610041, PR China.
Int J Pharm. 2014 Jul 1;468(1-2):26-38. doi: 10.1016/j.ijpharm.2014.04.008. Epub 2014 Apr 5.
Though PEGylation has been widely used to enhance the accumulation of liposomes in tumor tissues through enhanced permeability and retention (EPR) effects, it still inhibits cellular uptake and affects intracellular trafficking of carriers. Active targeting molecules displayed better cell selectivity but were shadowed by the poor tumor penetration effect. Cell penetrating peptides could increase the uptake of the carriers but were limited by their non-specificity. Dual-ligand system may possess a synergistic effect and create a more ideal drug delivery effect. Based on the above factors, we designed a multistage liposome system co-modified with RGD, TAT and cleavable PEG, which combined the advantages of PEG, specific ligand and penetrating peptide. The cleavable PEG could increase the stability and circulation time of liposomes during circulation. After the passive extravasation to tumor tissues, the previously hidden dual ligands on the liposomes were exposed in a controlled manner at the tumor site through exogenous administration of a safe reducing agent L-cysteine. The RGD specifically recognized the integrins overexpressed on various malignant tumors and mediated efficient internalization in the synergistic effect of the RGD and TAT. Invitro cellular uptake and 3D tumor spheroids penetration studies demonstrated that the system could not only be selectively and efficiently taken up by cells overexpress ingintegrins but also penetrate the tumor cells to reach the depths of the avascular tumor spheroids. In vivo imaging and fluorescent images of tumor section further demonstrated that this system achieved profoundly improved distribution within tumor tissues, and the RGD and TAT ligands on C-R/T liposomes produced a strong synergistic effect that promoted the uptake of liposomes into cells after the systemic administration of L-cysteine. The results of this study demonstrated a tremendous potential of this multistage liposomes for efficient delivery to tumor tissue and selective internalization into tumor cells.
尽管聚乙二醇化已被广泛用于通过增强渗透和滞留（EPR）效应来提高脂质体在肿瘤组织中的蓄积，但它仍会抑制细胞摄取并影响载体的细胞内运输。活性靶向分子显示出更好的细胞选择性，但受到较差的肿瘤穿透效果的影响。细胞穿透肽可以增加载体的摄取，但受其非特异性的限制。双配体系统可能具有协同作用，并产生更理想的药物递送效果。基于上述因素，我们设计了一种用RGD、TAT和可裂解聚乙二醇共同修饰的多级脂质体系统，该系统结合了聚乙二醇、特异性配体和穿透肽的优点。可裂解聚乙二醇可以增加脂质体在循环过程中的稳定性和循环时间。在被动渗出到肿瘤组织后，脂质体上先前隐藏的双配体通过外源性给予安全的还原剂L-半胱氨酸以可控方式在肿瘤部位暴露。RGD特异性识别各种恶性肿瘤上过度表达的整合素，并在RGD和TAT的协同作用下介导有效的内化。体外细胞摄取和三维肿瘤球体穿透研究表明，该系统不仅可以被过度表达整合素的细胞选择性地、有效地摄取，而且还可以穿透肿瘤细胞到达无血管肿瘤球体的深处。体内成像和肿瘤切片的荧光图像进一步表明，该系统在肿瘤组织内的分布有了显著改善，并且在全身给予L-半胱氨酸后，C-R/T脂质体上的RGD和TAT配体产生了强烈的协同作用，促进了脂质体进入细胞的摄取。这项研究的结果表明，这种多级脂质体在有效递送至肿瘤组织和选择性内化到肿瘤细胞方面具有巨大潜力。
