Biological evaluation of protein nanocapsules containing doxorubicin

本研究描述了一种天然存在的小热休克蛋白（Hsp），形成一个笼状结构，作为药物载体的应用。通过用半胱氨酸残基取代位于笼内的甘氨酸41以允许与荧光团或药物缀合，在大肠杆菌中表达突变型Hsp笼（HspG 41 C）。HspG 41 C笼被各种癌细胞系吸收，主要通过网格蛋白介导的内吞作用。在酸性细胞器（内体/溶酶体）中检测到笼至少48小时，但在线粒体或细胞核中未检测到笼。为了产生携带抗癌剂阿霉素（DOX）的HspG 41 C笼，使用酸不稳定的腙接头将HspG 41 C笼和DOX缀合。HspG 41 C笼中DOX的释放在pH5.0时加速，而在pH7.2时可忽略不计。HspG 41 C-DOX对Suit-2和HepG 2细胞的杀伤作用略弱于游离DOX，但对Huh-7细胞的杀伤作用几乎相同，考虑到HspG 41 C-DOX释放的DOX相对较低，HspG 41 C-DOX对HepG 2和Suit-2细胞的杀伤活性相当，对Huh-7细胞的杀伤作用略强于游离DOX。

This study describes the applications of a naturally occurring small heat shock protein (Hsp) that forms a cage-like structure to act as a drug carrier. Mutant Hsp cages (HspG41C) were expressed in Escherichia coli by substituting glycine 41 located inside the cage with a cysteine residue to allow conjugation with a fluorophore or a drug. The HspG41C cages were taken up by various cancer cell lines, mainly through clathrin-mediated endocytosis. The cages were detected in acidic organelles (endosomes/lysosomes) for at least 48 hours, but none were detected in the mitochondria or nuclei. To generate HspG41C cages carrying doxorubicin (DOX), an anticancer agent, the HspG41C cages and DOX were conjugated using acid-labile hydrazone linkers. The release of DOX from HspG41C cages was accelerated at pH 5.0,but was negligible at pH 7.2. The cytotoxic effects of HspG41C-DOX against Suit-2 and HepG2 cells were slightly weaker than those of free DOX, but the effects were almost identical in Huh-7 cells.Considering the relatively low release of DOX from HspG41C-DOX, HspG41C-DOX exhibited comparable activity towards HepG2 and Suit-2 cells and slightly stronger cytotoxicity towards Huh-7 cells than free DOX.