Poloxamer 407 as a Thermogelling and Adhesive Polymer for Rectal Administration of Short-Chain Fatty Acids

Abstract

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 concentrations ranging from 17% to 20%. Their viscosities were measured at room temperature and 37°C, and their gelling temperatures were determined. The adhesive properties of each gel were assessed in vitro at 37°C. 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°C. The higher the concentration, the higher the viscosity (1750 to 49,000 mPa · s), the lower the gelling temperature (27.6°C to 23.4°C), 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°C, possessed adhesive properties, and controlled short-chain fatty acid release.