Fig. 2
Drug release study of O-CS-DOX NDs in vitro. a The influences of pH values on the encapsulation efficiency (EE) and loading efficiency (LE) of O-CS-DOX NDs within 2 h. b Doxorubicin release from O-CS-DOX NDs in pH 7.4 and 6.3 at 37 ℃ for 72 h. c, d Release of doxorubicin from O-CS-DOX NDs without ultrasound (control) and with ultrasound exposure at pH 7.4, at 37 ℃ for 10 min. The intensity of O-CS-DOX NDs + US1 group is 1.0 W/cm2 and that of O-CS-DOX NDs + US2 group is 1.5 W/cm2, asterisks (*) denote significant differences (*p < 0.05, **p < 0.01)