The environmental response and stability of pectin and poly-l-lysine multilayers

Oral pectin/oligochitosan microspheres for colon-specific controlled release of quercetin to treat inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, life quality-reducing disease with no cures available yet. To develop an effective medication suitable for long-term use is an urgent but unmet need. Quercetin (QT) is a natural dietary flavonoid with good safety and multifaceted pharmacological activities against inflammation. However, orally administrated quercetin yields unproductive outcomes for IBD treatment because of its poor solubility and extensive metabolism in the gastrointestinal tract. In this work, a colon-targeted QT delivery system (termed COS-CaP-QT) was developed, of which the pectin (PEC)/Ca²⁺ microspheres were prepared and then crosslinked by oligochitosan (COS). The drug release profile of COS-CaP-QT was pH-dependent and colon microenvironment-responsive, and COS-CaP-QT showed preferential distribution in the colon. The mechanism study showed that QT triggered the Notch pathway to regulate the proliferation of T helper 2 (Th2) cells and group 3 innate lymphoid cells (ILC3s) and the inflammatory microenvironment was remodeled. The in vivo therapeutic results revealed that COS-CaP-QT could relieve the colitis symptoms and maintain the colon length and intestinal barrier integrity.

Calcium-oligochitosan-pectin microcarrier for colonic drug delivery

Pectin-based hydrogel microcarriers have shown promise for drug delivery to the colonic region. Microcarriers must remain stable throughout the upper gastrointestinal tract for effective colonic delivery, an issue that traditional pectin-based microcarriers have faced. The positively-charged natural biopolymer oligochitosan and divalent cation Ca²⁺ were used to dually cross-link pectin-based hydrogel microcarriers to improve carrier stability through simulated gastric and intestinal environments. Microcarriers were characterized with Scanning Electron Microscope and Fourier-Transform Infrared analysis. An optical microscope was used to observe the change of microcarrier size and morphology over time in the simulated gastrointestinal environments. Fluorescently-labeled Dextran was used as a model drug for this system. Calcium-Oligochitosan-Pectin microcarriers exhibited relatively small drug release in the upper gastrointestinal regions and were responsive to the high pH and enzymatic activity of simulated colonic environment (over 94% release after 2 h), suggesting great potential for colonic drug delivery.

The effect of poly-L-lysine structure on the pH response of polygalacturonic acid-based multilayers

The effect of poly-L-lysine (PLL) molecular weight and structure on pH stability of polygalacturonic acid (PGaLA)-based multilayer films is studied over a pH cycle 7.0-1.6-7.0. The multilayer assembled with the lowest molecular weight PLL (1 kDa) showed the largest pH response. Only 12% of the mass remained and a preferential loss of PLL was observed. Extensive structural reorganisation of the layer as the pH was increased was due to the PGaLA reionisation leading to extensive net loss of hydrated mass. The multilayers assembled with the higher molecular weight linear PLLs (10 kDa, 200 kDa) showed loss of about 50% of their initial polymer mass. The multilayer assembled with the dendrimer (22 kDa) showed a stronger response to pH compared to the linear higher molecular weight PLLs. Over the pH cycle a loss of about 60% polymer mass and a decrease in the film thickness was observed. Despite having a reduced density at pH 1.6, the density substantially recovered to 0.54 g mL(-1) on return to pH 7.0.

Competitive adsorption of mixed anionic polysaccharides at the surfaces of protein-coated lipid droplets

Charged polysaccharides can improve the stability of protein-coated lipid droplets by forming a protective coating around them. Potentially, the interfacial characteristics of these coatings can be controlled by assembling them from mixed polysaccharides with different molecular characteristics. The purpose of this study was to examine the competitive adsorption of two anionic polysaccharides (carrageenan and pectin) to beta-lactoglobulin coated-lipid droplets. Carrageenan has a higher charge density than pectin, and carrageenan has a linear backbone whereas pectin has a linear backbone with branches. Emulsions (phi = 1 wt % oil, d43 = 0.40 +/- 0.03 microm) were mixed with polysaccharide solutions (0 or 0.04 wt%) at pH 7, then the pH was decreased to promote polysaccharide adsorption. The adsorption of the polysaccharide molecules to the droplet surfaces occurred at a higher pH for carrageenan (pH approximately 5.85) than for pectin (pH approximately 5.45). When polysaccharide mixtures were added at pH 7, the carrageenan molecules preferentially adsorbed to the droplet surfaces when the pH was reduced. At pH 3.5, carrageenan coated droplets had a higher negative charge (zeta = - 38.5 +/- 3.1 mV) than pectin-coated droplets (zeta = - 17.9 +/- 2.0 mV). Carrageenan was much more effective at displacing pectin from the surfaces of pectin-coated droplets, than pectin was at displacing carrageenan from carrageenan-coated droplets. The stability of pectin-coated droplets was better than carrageenan-coated droplets, which was attributed to steric hindrance effects. These results have important implications for the design of delivery systems based on polysaccharide/protein-coated droplets.