Synthesis, characterization, and computational study of aggregates from amphiphilic calix[6]arenes. Effect of encapsulation on degradation kinetics of curcumin

The aggregation behaviour of two tris(N-phenylureido)-calixarene derivatives, bearing three octyl chains at the lower rim and differing from each other for the absence or presence of ionizable carboxyl groups at the upper rim, has been investigated. Aggregates from both calixarenes have been obtained by the emulsion/solvent evaporation method and characterized by a combination of complementary techniques (DLS, SEM and AFM). Critical aggregation concentration has also been determined. The calixarene not bearing carboxyl groups forms aggregates in which the hydrophilic dye Rhodamine B can be loaded. The aggregate stability toward disassembly was evaluated in terms of rate of spontaneous and TX-100 induced release of entrapped Rhodamine. Both calixarene aggregates entrap the hydrophobic drug curcumin and improve its water solubility. The effect of encapsulation on the kinetics of photodegradation and alkaline hydrolysis of curcumin has been evaluated. Molecular dynamics simulations were also carried out to support the experimental results concerning the morphology of the aggregates.