Cellulose-nanofiber/polygalacturonic acid coatings with high oxygen barrier and targeted release properties

A bio-inspired coating consisting of pectin (polygalacturonic acid) and cationic cellulose nanofibers were successfully produced by the layer-by-layer method. The build-up and the morphology of the resulting coatings were studied with spectroscopic ellipsometry and atomic force microscopy, respectively. The coating was able to survive the exposure of a simulated gastric fluid, but was partially degraded upon exposure to pectinase enzyme, which simulate the action of the microbial symbionts present in the human colon. Prior to exposure, the oxygen permeability coefficient of the coating (0.033 ml (STP) mm  m−2 day−1 atm−1 at 23 °C and 20% RH) was in the same order of magnitude as for ethylene vinyl alcohol films (0.001-0.01 ml (STP) mm m−2 day−1 atm−1). However, after exposure to the mimicked gastrointestinal (GI) tract conditions, the contribution of coating to the overall barrier properties was not measurable.