Self-assembled hydrophobin for producing water-soluble and membrane permeable fluorescent dye

Low water solubility and poor membrane permeability are major disadvantages that compromise applications of most fluorescent dyes. To resolve these problems, herein, using Boron-dipyrromethene (BODIPY) as a model fluorescent dye, for the first time, we provide a new strategy for the rapid and efficient production of a water-soluble and membrane-permeable dye by mixing with an amphiphilic protein named hydrophobin. Data shows BODIPY could be effectively solubilized and dispersed in 200 μg/mL hydrophobin by simple mixing and sonication. Subsequent experiments indicated that hydrophobin self-assembled into a protein film on the surface of BODIPY forming stable hydrophobin-BODIPY complexes with a size range of 10-30 nm. Furthermore, we demonstrated hydrophobin-functionalized BODIPY are toxicity free to cells. The hydrophobin-BODIPY complex could pass through both the cell plasma membrane and nuclear membrane efficiently. Our work opens a novel route to modify and functionalize fluorescent dyes and may be developed as a general strategy for broadening their applications.