Comparison of binding by smaller micelles (M-Bup-Rhd, 15 nm) and larger liposomes (L-Bup-Rhd, 100 nm), both containing bupivacaine (Bup) and the fluorophore rhodamine (Rhd). (a) Confocal laser scanning microscopy of cells incubated with M-Bup-Rhd or L-Bup-Rhd. Red, rhodamine (Rhd); blue, nuclei (Hoechst33342). Scale bar = 25 μm. (b) Time course of fluorescence in the tail after intravenous regional anesthesia with M-Bup-Rhd or L-Bup-Rhd. (c) Proposed actions of nanoformulations. Adapted from [13] with permission, copyright from American Chemical Society, 2019.