Diketopyrrolopyrrole-based fluorescence probes for the imaging of lysosomal Zn2+ and identification of prostate cancer in human tissue

• Published in: Chemical science (Cambridge) 2019-06, Vol.10 (22), p.5699-5704
• Main Authors: Du, Chenchen, Fu, Shibo, Wang, Xiaohua, Sedgwick, Adam C, Wei, Zhen, Li, Minjie, Li, Xinqiang, Zhou, Juan, Wang, Zhong, Wang, Hongyu, Sessler, Jonathan L
• Format: Article
• Language: English
• Subjects: Chelation; Electron transfer; Fluorescent indicators; Human tissues; Mass spectra; Medical imaging; Morpholine; NMR; Nuclear magnetic resonance; Prostate; Protonation; Selectivity; Stoichiometry; Titration calorimetry; Toxicity
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c9sc01153f

A series of diketopyrrolopyrrole-based fluorescent probes (DPP-C2, LysoDPP-C2, LysoDPP-C3, and LysoDPP-C4) have been developed for the detection of low pH and Zn2+ in an AND logic fashion. The chelation of Zn2+ or the protonation of a morpholine moiety within these probes results in a partial increase in the fluorescence intensity, an effect ascribed to suppression of one possible photo-induced electron transfer (PET) pathway. In contrast, a large increase in the observed fluorescence intensity is observed at low pH and in the presence of Zn2+; this is rationalized in terms of both possible PET pathways within the probes being blocked. Job plots, fluorescence titration curves, and isothermal titration calorimetry proved consistent with a 1 : 1 Zn2+ complexation stoichiometry. Each probe demonstrated an excellent selectivity towards Zn2+ and the resulting Zn2+ complexes demonstrated pH sensitivity over the 3.5–9 pH range. Fluorescence imaging experiments confirmed that LysoDPP-C4 was capable of imaging lysosomal Zn2+ in live cells. Little evidence of cytotoxicity was seen. LysoDPP-C4 was successfully applied to the bioimaging of nude mice, wherein it was shown capable of imaging the prostate. Histological studies using a human sample revealed that LysoDPP-C4 can discriminate cancerous prostate tissue from healthy prostate tissue.