In this study, an anionic conjugated polyelectrolyte, PPET3, which has poly(p-phenylene ethynylene thiophene) (PPET) backbone and carboxylic acid side chains, was synthesized by Pd-catalyzed Sonogashira coupling. Fluorescence quenching experiments showed that the fluorescence emission of PPET3 could be quenched by cytochrome C (cyt C) with high efficiency and specificity through photo-induced electron transfer mechanism. Since the release of cyt C from mitochrondria to cytoplasm is a major process during cell apoptosis, we were intrigued to explore the possibility of using PPET3 to observe this process by cell imaging. The low cytotoxicity of PPET3 makes it a good material for in vivo cell imaging applications. In order to overcome the low cellular uptake and poor endosomal escape, the commercial cationic liposome, Lipofectamine-3000, was chosen to construct a novel CPE-based lipoplex, named as PPET3/Lipo, which enabled non-endocytic membrane entering pathways e.g. membrane fusion. The colocalization experiment of PPET3/Lipo and anti-LAMP1 (lysosome-associated membrane protein 1, a marker for lysosomal membranes) showed an obvious separation of PPET3/Lipo and anti-LAMP1, which suggested that PPET3/Lipo could enter cells by non-endocytic membrane entering pathways. Thus the fluorescence imaging of cyt C in cells could be achieved by efficient endosomal escape of PPET3 in the cytoplasm. As anticipated, the fluorescent intensity of PPET3/Lipo was obviously lower in apoptotic cells than that in normal cells, indicating more cyt C existed in cytoplasm during apoptosis, which was consistent with the western blotting result of cyt C in cytoplasm and mitochrodria at the same condition. These results suggest that PPET3/Lipo could be used as a new fluorescent probe for detection of cyt C and differentiate apoptotic cells from normal cells.

Novel anionic conjugated polyelectrolyte lipoplex and its application for apoptosis imaging

254th National Meeting (2017)

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