摘要
Precisely designed protein-based nanodrugs, as a kind of colloidal drug system, have attracted significant attention in tumor therapy because of their refined drug loading ratio, controlled delivery efficacy and natural biocompatibility. However, most drugs are conjugated to the protein carriers randomly without specific binding sites. Moreover, such sites could easily be replaced by lipophilic molecules in the physiological environment and result in low delivery efficiency. With strong and specific binding locations especially comparatively narrow spatial binding sites and nonflexible structure, hemin (FePPIX)-free hemoglobin or apohemoglobin (apoHb), as a natural metalloporphyrin protein carrier, represents great potential in bioapplication. Therefore, we herein introduce a folate acid (FA) modified, zinc-substituted hemoglobin (ZnPHb-FA) as a naturally occurring protein matrix-based photosensitizer for cancer photodynamic therapy (PDT). Noncovalent inserted ZnPPIX molecules in apoHb possess an extremely stable property and significant recovered photoproperties with superior biocompatibility and phototoxicity, both in vitro and in vivo. This stability was verified by molecular docking analysis and calculation of binding constant, representing a total of five drug binding sites of apoHb for ZnPPIX molecules, four of which are energetically favorable (△G value of -11.9 kcal/mol), and one which is energetically acceptable (△G value of -9 kcal/mol). Folate acid modification has been shown to efficiently enhance the internalization and retention time of ZnPHb nanodrug. ZnPHb-FA is also an efficient depressor of hemin oxygenase-1 (HO-1), which could, in turn, lower the antioxidant ability of cancer cells by decreasing the production of biiirublin. Results in vitro and in vivo both indicated that the firmly combination of apoHb and ZnPPIX described here represents a novel and efficient protein nanodrug systems for cancer therapy.
基金
supported by the National Natural Science Foundation of China (Nos.21522501, 21521063, 31701249, and 31601125)
Hunan Provincial Natural Science Foundation of China (Nos.2018JJ1007 and 2018JJ3037)
the keypoint research and invention program of Hunan province (No.2017DK2011)
the Science and Technology Development Fund of Macao S.A.R (FDCT, 196/2017/A3).
