Differential scanning calorimetry

Prodrug-loaded liposome samples were prepared at 20 mg/mL in deionized water for each compound with increasing prodrug concentrations without extrusion. Deionized water was used as the calibration standard. 10 µL from each liposome suspension were transferred and sealed in an aluminum DSC pan then measurements began at room temperature then heated from 15 °C to 55 °C at 5 °C/min. All liposome suspensions used for DSC analysis were prepared in deionized water, instead of sodium buffer, to prevent undesired interactions; moreover, the samples were not extruded. A Q2000 differential scanning calorimeter (Thermal Analysis Instruments, New Castle, DE) and TA Universal Analysis 2000 software were used to obtain measurements.