Structural characterization using SAXS and rheological behaviors of pluronic F127 and methylcellulose blends

Abstract

Binary polymeric mixtures containing pluronic F127 (PF) and methylcellulose were prepared to generate new thermosensitive matrices. The small-angle X-ray scattering (SAXS) behavior of PF/MC blends was investigated in relation to the temperature-dependent phase transition and rheological characteristic. Although 11% w/w PF (11PF) cannot form gel, the test tube tilting method and rheological analysis showed that the incorporation of 4% w/w methylcellulose (MC) into 11PF (11PF/MC) enabled the system to form gel upon heating. In addition, adding MC lowered the gelation temperature of 17% w/w PF (17PF). The ordered structure of these gels exhibited a face-centered cubic phase at intermediate temperature above the gelation temperature; the steep upturn of the SAXS curves was observed in the small scattering vector range at high temperatures (55–70 °C). The presence of MC might cause an MC-assisted interconnected network of micelles. At high temperatures, the gelation possibly involved MC-assisted intermicellar organization of PF as well as the gel network of MC. Etidronate sodium was incorporated into the matrices, and the drug did not significantly affect the thermosensitive gelation and the ordered structure of the polymeric systems. Furthermore, this study indicated that 11PF/MC was sol at 25 °C and became gel at body temperature of 37 °C. Therefore, blending PF with MC is a potential strategy for tailoring the thermosensitive performance of the in situ gelling preparation for drug delivery.