Poloxamer 407 as a thermogelling and adhesive polymer for rectal administration of short-chain fatty acids

Objectives: The purpose of the study was to gel a rectal solution of short-chain fatty acids to decrease the loss of active materials in the colonic lumen and thereby optimize their absorption. Methods: Five thermogels were prepared with poloxamer 407 at concentration ranging from 17% to 20%. Their viscosities were measured at room temperature and 37 degreesC, and their gelling temperatures were determined. The adhesive properties of each gel were assessed in vitro at 37 degreesC. Short-chain fatty acid release was studied using Guyot cells. Results: From the threshold concentration of 17.5%, the solutions, Newtonian at room temperature (50-80 mPa.s), gelled at 37 degreesC. The higher the concentration, the higher the viscosity (1750 to 49,000 mPa.s), the lower the gelling temperature (27.6 degreesC to 23.4 degreesC), and the stronger the work of adhesion (2.2 to 4.5 mJ). Short-chain fatty acid release from the 18% polymer gel was decreased by 60% compared to the rectal solution. Conclusion: The 18% poloxamer 407 concentration provided a solution that was liquid at room temperature, that gelled at 37 degreesC, possessed adhesive properties, and controlled short-chain fatty acid release.