Characteristics, phase behavior and control release for copolymer–liposome with both pH and temperature sensitivities

A pH- and thermo-sensitive berberine hydrochloride liposome modified by the poly(N-isopropylacrylamide-co-methacrylic acid-co-octadecyl acrylate) was synthesized. The morphology and size were determined by atomic force microscope (AFM) and dynamic light scattering (DLS). The phase transition temperature (Tpm) and phase transition pH (pH*) of the copolymer–liposome were obtained by differential scanning calorimetry (DSC). The results indicate that the size of copolymer–liposome depends on the mass ratios of the copolymer to soya bean lecithin (SPC) and the solution pH value, and the size can reach a maximum value at phase transition pH (pH*). The Tpm and pH* were affected by the mass ratios of the copolymer to SPC and properties of the copolymer. The release of berberine hydrochloride (BH) from the copolymer–liposome was investigated and the maximum release of BH was caused at Tpm and pH* of the copolymer–liposome. The results illustrate that BH released from the liposome is due to the phase transition of the copolymer–liposome, where both Tpm and pH* were acted as switches of the phase transition, and both spacial and temporal releases can be carried out by adjusting the temperature, pH value and release time.