Sulfonium-cation-containing aggregation-induced emission block copolymers: self-assembly, multicolor emission, and detection for DNA polyplexes

Abstract

Amphiphilic aggregation-induced emission (AIE) polymers have emerged as highly attractive materials that exhibit the synergistic effect of functional polymeric self-assemblies with AIE luminogens. In this study, we design and synthesize block copolymers containing sulfonium cations and a hydrophobic tetraphenylethene (TPE) unit. These copolymers exhibit distinct self-assembly behaviors with AIE, polyplex formation with DNA, and tunable color emissions. Amphiphilic block copolymer PMTEAMe+Cl--b-PATPE, consisting of 4-(1,2,2-triphenylvinyl)phenyl acrylate (ATPE) and cationized 2-(methylthio)ethyl acrylate (MTEAMe+Cl-), was synthesized via reversible addition–fragmentation chain transfer polymerization, followed by cationization. Self-assembled structures containing TPE-aggregated cores and cationic PMTEAMe+Cl- shells and their emission behaviors were investigated. By introducing charged fluorescent dyes (Rose Bengal and Rhodamine B) into aqueous solutions of amphiphilic PMTEAMe+Cl--b-PATPE, we observed a shift in the emission color from blue to orange/red, which was attributed to the electrostatic interactions and fluorescence resonance energy transfer between the dyes and the copolymers. The emission color and intensity were also governed by polyplex formation between the negatively charged DNA and the positively charged sulfonium segments in the shell, depending on the charged states of the dyes. This system provides a method for efficient visual detection of DNA polyplex formation using multicolor fluorescent coding.