Thermoresponsive maleimide-containing polymers with tunable emission for temperature-dependent intracellular imaging

Luminescent systems based on solvatochromic, or aggregation-induced emissive (AIE) dyes have been explored for temperature screening. However, challenges remain regarding the fluorescence properties at higher temperatures and versatility. In this study, we introduced a novel fluorescent copolymer comprising N-isopropylacrylamide as a thermoresponsive unit and amino maleimides with inherent double bonds for subsequent polymerization as luminescent monomers. The resulting copolymers exhibited the combined properties of solvatochromic and AIE dyes. The aminomaleimide copolymer demonstrated significant fluorescence in nonpolar solvents, exhibiting a solvatochromic effect with decreased fluorescence as the solvent polarity transitioned to aqueous media (25 °C). Notably, the aqueous solution of the copolymer exhibited a remarkable increase in the fluorescence intensity with increasing temperature up to 40 °C, thus serving as a higher temperature indicator. Furthermore, this copolymer was used to assess the physiological state of Hella cells by imaging intracellular temperature. This novel copolymer holds promise for various biological applications, providing a valuable method for temperature sensing in biological systems and opening avenues for innovative materials in biotechnology and bioimaging.