Concentration and temperature-sensitive assembling behavior of polyethyleneimine–cinnamic acid conjugate and its release-controlling property in monoolein cubic phase

Temperature-responsive monoolein (MO) cubic phase was prepared by including polyethyleneimine (PEI) and cinnamic acid (CA) in the cubic phase. PEI/CA aqueous solution exhibited reversible upper critical solution temperature (UCST) behavior. CA and PEI was included in the cubic phase so that the concentrations were the same as those in PEI/CA solution which exhibited reversible UCST behavior from 32 °C to 50 °C. The maximum release degree of methylene blue observed above UCST (12.5% at 45 °C and 13.1% at 50 °C) was apparently higher than the maximum release degree below UCST (4.1% at 25 °C and 4.3% at 30 °C).

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