Design and evaluation of pectin-based nanoparticles for overcoming biological barriers as insulin carriers with oral...

This study developed pectin-based nanoparticles (PBNPs) as insulin carriers with oral administration potential, which were prepared from pectin with modified degrees of esterification (DE) and treated with subcritical water to overcome the biological barriers to insulin absorption. The results demonstrated that PBNPs prepared from differently modified pectin exhibited notable variations in their physicochemical properties, including particle size, zeta potential, hydrophilicity/hydrophobicity, and pH responsiveness. These differences contributed to distinct performance characteristics in traversing various biological barriers. In transepithelial transport studies, mildly high-DE pectin nanoparticles (MHEP-NPs) exhibited the highest efficiency in the Caco-2/HT29-MTX Transwell model (with mucus layer), achieving 148.89% of the control group's efficiency. Confocal laser scanning microscopy (CLSM) analysis, flow cytometry, and co-localization of the endoplasmic reticulum further confirmed that all PBNPs were effectively internalized by Caco-2 cells, indicating that PBNPs primarily crossed the intestinal epithelial barrier via the transcellular pathway, with MHEP-NPs exhibiting superior cellular uptake. Transepithelial electrical resistance (TEER) measurements, fluorescein isothiocyanate (FITC)-dextran permeability assays, and immunofluorescence staining of zonula occludens-1 (ZO-1) indicated that PBNPs transiently and reversibly opened partial tight junctions, thereby facilitating the paracellular transport of PBNPs. These findings highlighted the potential of PBNPs, particularly those from DE-modified pectin, as effective and biocompatible insulin carriers with oral administration potential.