The encapsulation and release properties of poly(ethylen oxide)/poly(acrylic acid) micelles with respect to α-tocopheryl acetate

PH-responsive micelles that were formed by asymmetric MOPEO-b-PAAc diblock copolymers with chemically complementary methoxypoly(ethylene oxide)/poly(acrylic acid) blocks were used as nanocarriers to study the encapsulation/release processes of the poorly soluble homologue of alpha-tocopheryl acetate, known as the analogue of Vitamin E. These nanocarriers showed the high encapsulation degree of alpha-TOCA (near 100%) which did not depend on the encapsulation pathway (in situ or ex situ). The effect of various factors such as the time, the solution pH and the addition of NaCl on the state and behavior of alpha-TOCA solutions, micellar dispersions of the diblock copolymer and their micellar compositions were studied and discussed. A methodology for correctly determining the degree of alpha-TOCA encapsulation and release by the copolymer micelles was described. A gradual release of alpha-TOCA from micellar nanocarriers in the dialysis of micellar compositions against deionized water and a significant decrease in alpha-TOCA release in physiological solution and, especially, in water with pH =9 was established.