Most recently we found that solubility of non-sulfonated Cyanine7 amine in water is much higher than for Sulfo-Cyanine7 amine:

Solubility in water: Sulfo-Cyanine7 amine 3.2 mg per ml

Solubility in water: Cyanine7 amine more than 25 mg per ml

Initially sulfonated cyanine dyes were designed to make dyes more soluble in water. But after checking that at our lab we realized that solubility of non-sulfonated amine and hydrazide derivatives could be more efficient due to average charge of dye molecule and also pH used to solubilize the dye.

The average charge of non-sulfonated amine-based dyes is +2, for sulfonated dyes the average charge is 0. As a result non-sulfonated amine-based dyes are more soluble in neutral and slightly basic water-based buffers.