Intracellular Postpolymerization Modification via Bioorthogonal Click Chemistry Monitored by Förster Resonance Energy Transfer.

The need for multifunctional polymers in cellular environments arises from their potential applications in cancer treatment, drug delivery, gene delivery, imaging, sensing of different biomolecules, environmental and cellular engineering, etc. However, due to certain limitations, the direct polymerization of multifunctional polymers within cells is not feasible, as it faces many challenges. Therefore, this study emphasizes the synthesis of functionalized molecules outside the cells and subsequent modification of the polymers inside the cells through intracellular postpolymerization modification (iPPM). We investigate Förster resonance energy transfer (FRET) as a technique for confirming the occurrence of postpolymerization reactions in cells in real time without the need for extraction or purification. The FRET reaction consists of 7-nitrobenz-2-oxa-1,3-diazole (NBD) as the FRET donor, integrated as a segment in the polymer backbone, and rhodamine B-polyethylene glycol-dibenzocyclooctyne (RhB-PEG-DBCO) as the FRET acceptor. A copper-free click chemistry method is used as a postpolymerization reaction within cells by the reaction between the azide group on the polymer backbone and DBCO in the FRET acceptor. By employing FRET and a targeted approach, this technique contributes to the development of multifunctional polymers for diverse applications in cellular environments.