title: Norcyanine dyes with benzo[c,d]indolium moiety: Spectral sensitivity with pH change for fluorescence pH imaging in living cells.
abstract: Fluorescence pH imaging in living cells is a rapidly expanding research direction, however, it relies on the development of pH-sensitive fluorescent imaging agents. Here four norcyanine dyes with benzo[c,d]indolium moiety, exhibiting high spectral sensitivity with pH changes, were synthesized for fluorescence pH imaging in living cells, and characterized by1H NMR,13C NMR, IR, UV-Vis and HRMS. The investigation of their spectral properties in methanol and water showed that the absorption and emission maxima were in the region 488-618nm and 583-651nm, respectively, and four dyes exhibited high photostability. The pH spectral titrations showed that selective dye D1 had pH-dependent absorption spectral changes within the pH range of 2.4 to 9.4, and high fluorescent spectral sensitivity at pH5.0-8.0, with a pKaof 5.0. A cell association study indicated that dye D1 exhibited no or mild cytotoxicity at the application dose and duration, and could be accumulated in cells and mainly distributed in the cytoplasm, giving red fluorescence imaging. In particular, dye D1 could achieve pH-dependent fluorescence imaging in living cells with the increase of pH from 3.0 to 8.0, at excitation wavelength of 543nm and receiving wavelength of 655-755nm, which was valuable for studying the weak acidic, neutral and weak alkaline biological tissue compartments.
authors.affiliation: Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an 710127, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Guan
authors.affiliation: Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an 710127, PR China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Biochemistry, Miami University, 651 E. High St, Oxford, OH 45056, USA.
authors.forename: Borui
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an 710127, PR China. Electronic address: wanglany@nwu.edu.cn.
authors.forename: Lanying
authors.initials: L
authors.lastname: Wang
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000737:chemistry*; D013058:Mass Spectrometry; D013057:Spectrum Analysis
chemical_list: D004396:Coloring Agents; D007211:Indoles
keywords: Benzo[c,d]indolium moiety; Cytotoxicity; Fluorescence pH imaging; Norcyanine dyes; Photophysical properties