Water-soluble near-infrared fluorescent probes enhanced by ionic co-assembly of a four-armed amphiphile with SDBS: Toward application in cell imaging

Near-infrared (NIR) organic fluorescent probes have attracted great deal of attention for application in cell imaging , where the probes demand good water solubility, strong emission and good cytocompatibility. In this study, a conjugate of anthraquinone and tetraphenylethylene is introduced into an amphiphile (denoted by BTPEAQ-10) with four pyridinium terminated aliphatic chains. The assemblies of BTPEAQ-10 show an NIR emission peaked at 670 nm. Ionic co-assembly with sodium dodecyl benzene sulfonate leads to drastic enhancement of the fluorescent emission to 30-fold. Controlling experiments on different surfactants and anionic groups show that both the hydrophilic group and the alkyl chain play critical role to the emission enhancement. Both the assemblies and co-assemblies have good water solubility and cytocompatibility, and were applied in cell imaging . The co-assemblies showed much better contrast of cell imaging due to the higher emission property.