Mixtures of triblock copolymers E62P39E62 and E137S18E137: Potential for drug delivery from in situ gelling micellar formulations

The gelation behaviour of concentrated micellar solutions of mixtures of a block copolymer of ethylene oxide and styrene oxide (E137S18E137) with one of ethylene oxide and propylene oxide (E62P39E62) has been investigated. Over a wide range of compositions, up to 90 wt.% E137S18E137 in the mixture, gelation resembled that of solutions of E62P39E62 alone, i.e. they gelled on heating from ambient to body temperature. In related experiments, using the aromatic drug griseofulvin as a comparative standard, it was demonstrated that solubilisation efficiency of dilute micellar solutions of the mixtures with 80 wt.% or more E137S18E137 approached that of solutions of E137S18E137 alone. Thus it was shown that the mixed system could have both the satisfactory solubilisation capacity of micellar solutions of E137S18E137 and the desirable gelation characteristics of E62P39E62, and so have potential for use in drug release applications involving in situ gelation.