A physiologically stable fluorophore includes a terminal moiety including a terminal reactive site that reacts with a reactive group of a substrate; a stability linker covalently bonded to the terminal moiety; and a bridge moiety covalently bonded to the stability linker such that the stability linker is interposed through chemical bonds between the bridge moiety and the terminal moiety; and a fluorescent moiety covalently bonded to the bridge moiety of the redox moiety and including: an electron bandgap mediator that is covalently bonded to the bridge moiety; a coordinate center covalently bonded to the electron bandgap mediator and that forms a Zwitterionic member with an atom in the electron bandgap mediator; and a steric hinder bonded to the electron bandgap mediator to provide steric hindrance for protection of the coordinate center.