Structural and therapeutic properties of Pluronic® P123/F127 micellar systems and their modulation by salt and essential oil

Abstract

Pluronics P123 and F127 mixed micellar system has been studied extensively for drug delivery applications because of its non-toxic nature, good solubilization capacity of lipophilic substances and its effectiveness against multi drug resistance (MDR) cancer cells. The constituent pluronics of this system have large difference in their hydrophilic lipophilic balance (HLB) and consequently are strikingly different in their self-assembly characteristics. In this work, we show how the properties of this system compare vis-à-vis the aqueous systems of its constituent pluronics and how pluronics P123 and F127 behave as drug delivery agents in antimicrobial and wound healing applications. DLS, SANS, ITC and rheological studies show that aggregation characteristics in the mixed micellar system is dictated by P123 up to its mole fraction of as low as 0.30. Thus, like pure aqueous P123 solutions, the mixed micellar systems exhibit spherical-to-worm like micelles-to-vesicular structural transitions in the presence of additives like NaCl and tea tree essential oil (TTO), and the dynamics of such structural transitions remains slow at the room temperature. TTO is chosen as additive as it exhibits anticancer, antimicrobial and wound healing properties and like water structure making salt NaCl, it brings about micellar structural changes in aqueous surfactant systems by increasing the hydrophobicity of the surfactant aggregates. ITC and phytochemical solubilization studies suggest that the mixed micellar system does not exhibit synergism in aggregation and lipophile solubilization characteristics. Our antimicrobial and wound healing studies quite interestingly reveal that hydrophobic pluronic P123 remains more effective than F127 as carrier for antimicrobial agent, whereas pluronic F127 based liquid crystalline hydrogel stands superior as topical drug delivery matrix than its P123 counterpart because of its better wound healing abilities. The observed results give insight into the structural and therapeutic properties of P123/F127 system, which were not understood hitherto.