Fluorescent molecular logic gates for pH and pE for cell imaging applications

Abstract

Novel molecules for sensing pH and redox potential (pE) were designed and synthesised starting from the asymmetrical 1,8-naphltalimide fluorophore. Attachment of a proton receptor and/or electron donor at either the N-imide or 4-position resulted in the molecular engineering of several positional isomers. Three novel pH-pE molecules of various modular designs were synthesised including 'fluorophore-spacer1-receptor-spacer2-electron-donor', 'electron -donor-spacer1-fluorophore-spacer2-receptor', and 'electron-donor1-spacer1-receptor1-spacer2-fluorophore-spacer2-receptor2-spacer4-electron-donor2' prototype. The receptor was either N-methylethylenediamine or piperazine, whilst the electron-donor was forrocene, both of which were connected via methylene or ethylene spacers. In addition, two model fluoroscent pH indicators were designed and studied, based on a 'fluorsphore-spacer-receptor' format, whilst a third fluorescent pH indicator was synthesised with a 'receptor1-spacer1-fluorophore-spacer2-receptor2' modular format.