Novel pectin–4-aminothiophenole conjugate microparticles for colon-specific drug delivery

Within this study metronidazole-containing microparticles based on a pectin–4-aminothiophenol (Pec–ATP) conjugate were developed and investigated regarding their potential for colon-specific drug delivery. Microparticles were produced by spray-drying and subsequent processing. Posteriorly, they were investigated regarding their disintegration behavior, particle size, drug load, release behavior and impact on viability of Caco-2 cells. Microparticles with a mean diameter of 5.16 ± 2.41 µm and a drug load of 1.15 ± 0.03% metronidazole were prepared. Disintegration studies revealed that the stability of Pec–ATP microparticles was significantly improved compared to control microparticles based on unmodified pectin. In vitro release studies without potential colonic release-inducers revealed that 34.4-fold more metronidazole is retarded in Pec–ATP microparticles within 6 h compared to control particles. It could be demonstrated that the retarded amount of metronidazole can be released rapidly under the influence of pectinolytic enzymes or a reducing agent, simulating the colonic environment. Cell viability studies did not reveal a significant difference between native and modified pectin, neither as a solution nor as microparticle suspension. From the improved stability, the described release features and the low toxicity of the investigated microparticles can be concluded that these particles are a promising carrier for colon-specific drug delivery.

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