Conjugated polymer nanoparticles based on carbazole for detecting ferric ion (III) with a large Stokes shift and high sensitivity and the application in cell imaging

The deficiency and excess of Fe3+ will lead to biological disorders and even many diseases. So, measuring the levels of Fe3+ in human body has drawn great attentions for health monitoring. Fluorescence method has been broadly applied because of high sensitivity, real-time detection and intracellular imaging. In this work, a new lipidic conjugated polymer, poly[3-{2-[2,5-Bis-(2-ethyl-hexyloxy)-4-propenyl-phenyl]-vinyl}-9-butyl-6-methyl-9H-carbazole] (PBMC), has been synthesized and used to prepare the conjugated polymer nanoparticles (CPNs-PBMC) by coprecipitation with poly (styrene-co-maleic anhydride) (PSMA). The CPNs-PBMC exhibited large Stokes shift (141 nm), small average diameter (43.96 nm), low toxicity and excellent photostability. Meanwhile, the CPNs-PBMC was highly sensitive to Fe3+ and has a lower detection limit of 0.63 nmol/L. The sensing mechanism was based on aggregation-induced fluorescence quenching of CPNs-PBMC in the presence of Fe3+ because of chelation and electrostatic interaction. Furthermore, the critical micelle concentration was measured by fluorescence method. More interestingly, the fluorescence of CPNs-PBMC could be circularly quenched and recovered using Fe3+ and EDTA, which may supply a possible control by logic gate. Furthermore, the fluorescence imaging showed that CPNs-PBMC could detect Fe3+ in living cells.