Preparation of adriamycin-loaded temperature/pH sensitive self-assembly block copolymer micelles

The dialysis method was employed to load adriamycin into the micells formed by temperature  and pH sensitive polyhistidine-co-DL-lactide-co-glycolide-polyethylene glycol poly DL-lactide-co-glycolide-co- histidine (OLH-b-PLGA-b-PEG-b-PLGA-b-OLH).  The critical micelle concentration (CMC) of the copolymer was measured with pyrene fluorescent probe method under different temperatures.  The entrapment rate and drug-loading rate were determined with dialysis method.  The diameter, morphology and surface potential of the copolymer micelles were investigated by corresponding instruments, respectively.  The release behavior of adriamycin from copolymer micelles and the pH sensitivity were studied.  The CMC of the copolymers ranged from 0.022 4 to 0.001 7 μg·mL⁻¹.  The entrapment rate and drug-loading rate were 92.8% and 15.7%, respectively.  The micelles have a mean diameter of (61.7 ± 13.4) nm, and zeta potential was −9.88 mV.  The in vitro adriamycin release rate increased with the pH dropping from 7.4 to 5.0.  The results indicated that the CMC of the copolymers  decreased as the raising of temperature, drug release behavior from the micells possessed clearly pH sensitivity, and the copolymers may have a potential in targeted delivery system for anticancer drugs.