Temperature-induced unloading of liposomes bound to microgels

Bilayer lipid vesicles (liposomes) composed of zwitter-ionic (electroneutral) egg yolk lecithin and anionic phosphatidylserine were loaded with a water-soluble antitumor antibiotic Dox and electrostatically adsorbed onto the surface of thermo-sensitive microgels synthesized from 3-(N,N-dimethylamino)propylmethacrylamide, N,N-methylenebisacrylamide and 2,2′-azobis(2-methylpropionamidine) dihydrochloride. The resulting saturated microgel-liposomes complex with ultimately adsorbed 40 liposomes retains encapsulated drug in water solution at 25 °C. An increase in temperature induces a collapse of the microgel core and squeezing of the liposome shell, followed by liposome disruption and a release of encapsulated Dox. An intensive Dox leakage begins when temperature reaches 39 °C; a maximum amount of Dox is released within 5 min after starting the temperature trigger. The results are of importance for constricting of thermo-sensitive drug carries and developing protocols for the most productive drug release.