Cysteine-based amphiphilic peptide-polymer conjugates via thiol-mediated radical polymerization: Synthesis, self-assembly, RNA polyplexation and N-terminus fluorescent labeling for cell imaging

Publication date: 10 March 2017
Source:Polymer, Volume 112
Author(s): Madhab Dule, Mrinmoy Biswas, Yajnaseni Biswas, Kuheli Mandal, Nikhil R. Jana, Tarun K. Mandal
A water-soluble amphiphilic peptide-poly (1-vinylimidazole) [Boc-Cys (PVim)-Trp-OMe] bioconjugate is synthesized by 'grafting from' technique based on thiol-mediated radical polymerization. The attachment of fluorescein isothiocyanate (FITC) at the N-terminus of the peptide moiety of the bioconjugate results in the generation of fluorescent bioconjugate [FITC-Cys (PVim)-Trp-OMe]. MALDI-TOF-MS analysis confirms the attachment dipeptide moiety as well as FITC group. Owing to the amphiphilic nature, the [Boc-Cys (PVim)-Trp-OMe] bioconjugate undergoes spontaneous self-assembly into primary micelles and their subsequent secondary aggregation into spherical micellar aggregates (nanospheres) in water. The aqueous FITC-Cys (PVim)-Trp-OMe bioconjugate solution emits green light and exhibits a fluorescence emission with a maximum at 520 nm. The amphiphilicity of the fluorescent bioconjuagte molecules also triggers their self-assembly into micelles and micellar aggregates (nanospheres) with hydrophobic FITC-tagged dipeptide core and hydrophilic PVim cell in water. Further, the highly stable and non-toxic fluorescent bioconjugates are used for imaging of Chinese Hamster Ovary (CHO) cells. Finally, the polyplex formation between the untagged cationic Boc-Cys (PVim)-Trp-OMe bioconjugate and ribonucleic acid (RNA) at pH 5.5 is studied by fluorescence spectroscopy.

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