Molecular Dynamics Study of the Diffusivity of a Hydrophobic Drug Cucurbitacin B in Pseudo-poly(ethylene oxide-b-caprolactone) Micelle Environments

Isobaric–isothermal molecular dynamics simulation was used to study the diffusion of a hydrophobic drug Cucurbitacin B (CuB) in pseudomicelle environments consisting of poly(ethylene oxide-b-caprolactone) (PEO-b-PCL) swollen by various amounts of water. Two PEO-b-PCL configurations, linear and branched, with the same total molecular weight were used. For the branched configuration, the block copolymer contained one linear block of PEO with the same molecular weight as that of the PEO block used in the linear configuration but with one end connecting to three PCL blocks with the same chain length, hereafter denoted PEO-b-3PCL. Regardless of the configuration, the simulation results showed that the diffusivity of CuB was insensitive to the water concentration up to ∼8 wt % while that of water decreased with an increasing water concentration. The diffusivity of CuB (10–8 cm2/s) was 3 orders of magnitude lower than that of water (10–5 cm2/s). This is attributed to the fact that CuB relied on the wiggling moti...