Thermosensitive liposomes with higher phase transition temperature for targeted drug delivery to tumor.

Thermosensitive liposomes (TSL) in combination with local hyperthermia (HT) represent a promising tool for tumor specific drug delivery. The objective of the study was to investigate the influence of phase transition temperature (Tm) on the properties of TSL. High temperature triggered TSL (HTSL), low temperature triggered TSL (LTSL) and non-TSL (NTSL) were prepared and temperature sensitive release properties were extensively compared in different media. Mouse plasma was determined to have similar effect on the release profiles compared to human plasma, in which complete release were obtained at 38 °C and 40 °C for LTSL and HTSL, respectively. The temperature at which complete release achieved was found to be obviously lower than Tm. Brucine, an antitumor alkaloid, was encapsulated into different TSLs. After HT treatment, the viabilities of SMMC 7721 cells were determined to be 21.3±3.8% and 16.8±3.3% for 127 μM brucine LTSL and HTSL, respectively. Treating the tumor-bearing mice with LTSL, HTSL and NTSL led to significantly increased brucine uptake in the heated tumor site compared to the brucine solution group by 2.30, 3.80 and 2.26-fold, respectively. The results of this study suggested that Tm of TSL should be increased to obtain improved drug delivery efficiency to tumor.