Synthesis of FA-PEG3350-DSPE. Reagents and conditions: a) succinic anhydride (2 equiv.), triethylamine (4 equiv.), CHCl3, r.t., 24 h; b) (i) N-hydroxylsuccinimide (1.2 equiv.), DMAP (1 equiv.), DCC (1.2 equiv.), r.t., 4 h; (ii) PEG3350-bis-amine (2.2 equiv.), CHCl3, r.t., overnight; c) Folic acid (1 equiv.), DSPE-PEG3350-NH2 (3 equiv.), DCC (3 equiv.), DMSO-Py (10/1, v/v), r.t., 16 h.