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Kamei N, Yamamoto S, Hashimoto H, Nishii M, Miyaura M, Tomada K, Nakase I, Takeda-Morishita M. Optimization of the method for analyzing endocytosis of fluorescently tagged molecules: Impact of incubation in the cell culture medium and cell surface wash with glycine-hydrochloric acid buffer. J Control Release 2019; 310:127-140. [PMID: 31442466 DOI: 10.1016/j.jconrel.2019.08.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/09/2019] [Accepted: 08/19/2019] [Indexed: 10/26/2022]
Abstract
To obtain the therapeutic effect of biological medicines, such as proteins and nucleic acids, these medicines must achieve their intracellular target, such as the cytoplasm, and pass through biological membrane barriers. Endocytosis is an attractive route for the intracellular delivery of such drugs, and various endocytosis inhibitors have been used as tools to study the involvement of endocytosis in the cell internalization of delivery carriers. However, the specificity of these inhibitors has been insufficiently studied, and our preliminary tests could not detect the expected effect of the well-known endocytosis inhibitors. Therefore, the present study aimed to optimize the experimental conditions to precisely analyze cellular internalization via endocytosis. We first found that incubation of model molecules, such as transferrin (Tf) and cholera toxin subunit B (CTB), in cell culture medium (DMEM) could efficiently induce their internalization to HeLa cells compared to that in transport buffer (HBSS). Moreover, we clarified that cell surface wash with glycine-hydrochloric acid buffer before confocal microscopy and flow cytometry strengthened the intracellular fluorescence of Tf, CTB, and dextran tagged with fluorescent probes possibly via the neutralization of endosomal pH. Even under the optimized condition, however, the specificity of endocytosis inhibitors was disputable. The present study suggested the importance of the optimization of the study design with endocytosis inhibitors in analyzing cellular internalization.
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Affiliation(s)
- Noriyasu Kamei
- Laboratory of Drug Delivery Systems, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan.
| | - Satoshi Yamamoto
- Laboratory of Drug Delivery Systems, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan
| | - Hiro Hashimoto
- Laboratory of Drug Delivery Systems, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan
| | - Megumi Nishii
- Laboratory of Drug Delivery Systems, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan
| | - Moe Miyaura
- Laboratory of Drug Delivery Systems, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan
| | - Kiho Tomada
- Laboratory of Drug Delivery Systems, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan
| | - Ikuhiko Nakase
- Laboratory for Cellular Regulation Chemistry, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, 1-2 Gakuen-cho, Naka-ku, Sakai-Shi, Osaka 599-8570, Japan
| | - Mariko Takeda-Morishita
- Laboratory of Drug Delivery Systems, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, 1-1-3 Minatojima, Chuo-ku, Kobe, Hyogo 650-8586, Japan
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