Micellar nanocontainers based on PAAm-b-PEO-b-PAAm triblock copolymers for poorly soluble drugs

Micellization of asymmetric triblock copolymers (TBCs) contained chemically complementary poly(ethylene oxide) (Mn = 6, 14 and 35 kDa) and polyacrylamide of different chain length (PAAm-b-PEO-b-PAAm) was studied using visible spectroscopy, static light scattering, photography and transmission electron microscopy. The formation of “hairy-type” and “flower-like” micelles consequently in aqueous and aqueous/ethanol (30/70 v/v) solutions was established. An unusual morphology of the “hairy-type” micelles was found in aqueous solutions of TBC, which comprised the lengthiest PEO and PAAm blocks. Significant encapsulation of a model crystalline drug prednisolon (PS) by the “hairy” micelles due to hydrogen bonds and hydrophobic interactions was determined by ultraviolet–visible spectroscopy and Fourier transform infrared spectroscopy. This resulted in the appearance of “snow-flakes-like” micellar structures. The possibility of regulating crystalline properties of the drug in micellar nanocontainers was shown with differential scanning calorimetry and wide-angle X-ray scattering.

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► Micellization of PAAm-b-PEO-b-PAAm with asymmetric complementary blocks is proved.
► The ‘‘hairy-type’’ micelles of spherical and cubic-like morphology are formed in water.
► The “hairy” micelles are transformed to the “flower-like” ones at ethanol addition.
► Significant encapsulation of insoluble drug prednisolon by “hairy” micelles is found.
► We showed a real possibility to regulate the drug crystallization in nanocontainers.