Preparation and characterization of zein-based nano-assembled bioadhesive coatings for prolonged gastrointestinal retention of sinapine

Sinapine, a natural rapeseed polyphenol, exhibits antioxidant, anti-inflammatory and anti-tumour properties. However, sinapine is stable under weakly acidic conditions and is easily broken down under alkaline conditions, reducing its bioavailability. We developed a nano-assembled bioadhesive coating (Cca-D) based on zein (corn protein) for sinapine delivery <i>via</i> encapsulation, achieving 89.68% efficiency. The Cca-D complex self-assembled into spherical nanoparticles through hydrogen bonding, demonstrating excellent fluidity and strong adhesion. According to FTIR, lyophilised Cca-D vibrated at 3567.6 cm^-1, suggesting that hydrogen bonding drives the formation of the complex and is not affected by pH. The bio adhesive coagulation coating can protect sinapine from degradation in the gastric environment (with release rates of 0.15% and 0.26% at 30 and 60 minutes, respectively), while allowing for release in the intestinal environment (with release rates of 0.68% and 0.69%, respectively). In addition, the results of cellular experiments showed that the survival rate of Caco-2 cells was more than 95% when the concentration range of the sin-Cca-D complex was 40-80 μg mL^-1, indicating its biocompatibility. Notably, the cellular uptake of sinapine in the sin-Cca-D complex was 10.05%, 11.71%, and 13.18% at low (40 μg mL^-1), medium (60 μg mL^-1), and high (80 μg mL^-1) concentrations, respectively. The generated complexes were able to create a substantial adhesive coating on the colon, according to fluorescence imaging of the mouse digestive tract. This new polymer is expected to be a carrier as a delivery system that can extend the residence time in the gut.