6-Coumarin-loaded NPs were made dissolving 5 mg of 6-Coumarin (Sigma-Aldrich, Saint Louis, MO, USA) in 300 μl of a solution of 30 mg of PLGA-PEG-Bis-sulfone in THF. This solution was added dropwise to 7 ml of stirring water. The reaction was left to proceed for 3 h and then they were collected and centrifugated to be subsequently used for further analysis.