Hg2+ rhodamine fluorescent probe bearing flexible ɑ-amino acid hydrazines and its photoactivation under UV light

The regulation factors of rhodamine spirolactam switch has captured great attention because of its great potential applications in super-resolution image and fluorescent probe fields. Herein, we developed two Hg2+ rhodamine probe bearing flexible ɑ-amino acid hydrazines, Rh-SH and Rh-MH, to investigate photo-operated rhodamine switch induced by Hg2+. The Hg2+ binding process with Rh-SH containing serine hydrazines moiety was more sensitive to UV light, owing to weak affinity with Hg2+. On the contrary, UV light had little effect on Hg2+ binding process of Rh-MH bearing methionine hydrazine group. The strong Hg2+ binding affinity of Rh-MH demonstrated a higher sensitivity to Hg2+, and detection limit of Rh-MH was 2.32 × 10−6 M. Probe Rh-MH can also map the distribution of Hg2+ in mitochondria of MCF-7 cells. The modulation of binding affinity of flexible ɑ-amino acid hydrazine with Hg2+ might provide new opportunity and strategy to photo-promoted ring switch of rhodamine spirolactam.