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Porous biodegradable polymeric foams loaded with drugs have potential applications in tissue engineering and sustained delivery systems. A single-step process using supercritical CO2 as a foaming and carrier agent was used for the impregnation of 5-fluorouracil in polylactide and poly­(lactide-co-glycolide) probes. The release of 5-fluorouracil from the probes for 24 h at 37 °C and pH 7.4 was followed by measurement of the amount of drug released to the media and a change of the probe’s weight. In order to gain further insight into the drug-release mechanisms, a mathematical model (not previously described in the literature) is proposed to quantitatively describe the process of drug release. Our model considers that the release process goes through three different steps controlled first by external diffusion, second by internal mass transfer, and third by polymer degradation. The theoretical curves agreed fairly well with the experimental drug-release profiles.

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In drug delivery systems, mathematical modeling plays an important role in elucidating the release mechanisms, the potential applications of a determinate system matrix–drug, or the design of new delivery systems. In this work, we have modeled porous biodegradable foams based on polylactide (PLA) and poly­(lactide-co-glycolide) (PLGA) impregnated with a hydrophobic drug (indomethacin) through a single-step process using supercritical CO2 as foaming agent. The modeling of indomethacin in vitro release was based on a previous model developed to describe accurately the process of release of a hydrophilic drug and consisting of three simpler and more comprehensible stages: external and internal mass transfer as well polymer degradation. It has been modified considering the low aqueous solubility of indomethacin and the variations in the mechanism produced, consequently improving its physical signification. Finally, the solubility of different drugs impregnated and their response in the release profiles were evaluated.

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