The articles is about a study of the response of six NIR aza-BODIPY-based and structurally similar fluorophores to polarity and viscosity for incorporation inside Pluronic nanoparticles as switchable fluorescent probes (SFPs). Based on their results, all of these fluorophores were moderately to strongly sensitive to the polarity of the microenvironment. They concluded that attaching amine groups to the fluorophore is not necessary for having strong polarity sensitive probes.