Stabilization of Pluronic Gels by Hydrophobically Modified Hydroxyethylcellulose

Hydrophobically modified hydroxyethylcellulose (HM-HEC) of different hydrophobicity has been used to stabilize pluronic gels against dissolution in an aqueous environment. While pluronic by itself dissolves within 1-2 days, the addition of HM-HEC can stabilize part of the gels from dissolving for a period of at least six months. A larger fraction of the gel remains undissolved when utilizing high HM-HEC concentrations and when the degree of hydrophobic modification is increased. The stabilization against fast dissolution makes these systems interesting for drug delivery purposes. The effect of HM-HEC addition on rheological properties of pluronic gels has also been examined. For a low pluronic concentration, the addition of HM-HEC increases the viscosity of the sample, shifts the gel transition to a lower temperature, and reduces the deviscosification of the pluronic gels at high temperatures. When the pluronic concentration is increased, the addition of HM-HEC only affects the sample viscosity at low temperatures. [GRAPHICS]