Synergistic effects of antitumor efficacy via mixed nano-size micelles of multifunctional Bletilla striata polysaccharide-based copolymer and D-α-tocopheryl polyethylene glycol succinate.

To evaluate if mixed micelles of Dox@FA-BSP-SA/TPGS can allow for the superior antitumor efficiency than Dox@FA-BSP-SA micelles. The complex of doxorubicin (Dox) and sodium cholate was encapsulated into the mixed micelles composed of folate-mediated stearic acid-modified Bletilla striata polysaccharide (FA-BSP-SA) and D-α-tocopheryl polyethylene glycol succinate (TPGS). Its average particle size increased whereas load capacity (LC) and encapsulation efficiency (EE) decreased with the increase of TPGS mass ratio in the mixed micelles. The changes of morphology, particle size and doxorubicin release in vitro demonstrated the pH sensitivity of micelles. FA-BSP-SA/TPGS mixed micelle exhibited average particle size of 147.3 nm, LC of 14.4% and EE of 91.9% for doxorubicin at the weight ratio of 3: 1. The doxorubicin release rate of micelles was faster in pH 5.0 media compared with that in pH 6.0 and 7.4 media. The cytotoxicity in vitro and antitumor efficacy in vivo results of Dox@FA-BSP-SA/TPGS micelle were more superior to that of free doxorubicin and Dox@FA-BSP-SA single micelle. For Dox@FA-BSP-SA/TPGS micelle, the clathrin-mediated endocytosis was the dominant mechanism of intracellular uptake. The FA-BSP-SA/TPGS mixed micelle may be a promising drug delivery system for cancer chemotherapy.