Evaluation and understanding the effect of drug delivery in in vitro systems is fundamental in drug discovery. We present an assay based on real-time electrical impedance spectroscopy (EIS) measurements that can be used to follow the internalisation and cytotoxic effect of a matrix metalloproteinase (MMP)–sensitive liposome formulation loaded with oxaliplatin (OxPt) on colorectal cancer cells. The EIS response identified two different cellular processes: (i) a negative peak in the cell index (CI) within the first 5 h, due to onset of liposome endocytosis, followed by (ii) a subsequent CI increase, due to the reattachment of cells until the onset of cytotoxicity with a decrease in CI. Free OxPt or OxPt-loaded Stealth liposomes did not show this two-stage EIS response; the latter can be due to the fact that Stealth cannot be cleaved by MMPs and thus is not taken up by the cells. Real-time bright-field imaging supported the EIS data, showing variations in cell adherence and cell morphology after exposure to the different liposome formulations. A drastic decrease in cell coverage as well as rounding up of cells during the first 5 h of exposure to OxPt-loaded (MMP)-sensitive liposome formulation is reflected by the first negative EIS response, which indicates the onset of liposome endocytosis.
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We acknowledge Rasmus Eliasen for the help with liposome de-PEGylation.
The authors received funding from the EU for the FP7 project EXCELL (NMP4-SL-2008-214706) and the Horizon 2020 MSCA-ITN project Training4CRM (H2020-MSCA-ITN-2016). Kinga Zór received financial support during the preparation of the manuscript from the Danish National Research Foundation (DNRF122) and Villum Fonden (Grant No. 9301) for Intelligent Drug Delivery and Sensing Using Microcontainer and Nanomechanics (IDUN).
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Caviglia, C., Garbarino, F., Canali, C. et al. Monitoring cell endocytosis of liposomes by real-time electrical impedance spectroscopy. Anal Bioanal Chem 412, 6371–6380 (2020). https://doi.org/10.1007/s00216-020-02592-x
- Real-time monitoring
- Electrical impedance spectroscopy
- Cell morphology
- Matrix metalloproteinase
- Liposome endocytosis