Effect of niosome formation with chitosan coating on the stability and absorption of orally administered vesicular ursolic acid

Niosomes are known to improve the bioavailability of drugs. However, niosomes have drawbacks related to stability and absorption in the gastrointestinal tract. Chitosan coating on niosomes can increase their stability in gastrointestinal fluid and absorption after oral administration. This study aimed to evaluate the biopharmaceutical stability and oral absorption of chitosan-coated Ursolic acid niosomes in vivo. Niosomes Ursolic Acid (Nio-UA) were prepared using a thin-layer hydration method, and chitosan was added to produce Niosomes Ursolic Acid with chitosan coating (Nio-UA-CS). The stability of niosomes was evaluated by exposing them to simulated gastrointestinal fluid. The oral absorption and biodistribution were determined in vivo. The results showed that niosome formation increased UA solubility from 1.02 × 10 –4 mg/mL to 23.49 × 10 –3 mg/mL for Nio-UA and 22.34 × 10 –3 mg/mL for Nio-UA-CS and decreased the LogP value of UA from 5.18 ± 0.05 to 1.70 ± 0.22 for Nio-UA and 1.74 ± 0.30 for Nio-UA-CS. Adding chitosan layers increased the stability of the niosome, resulting in the lowest %cumulative calcein release of 7.05 ± 1.77% in Nio-UA-CS after exposure to simulated gastric fluid and 31.53 ± 8.80% after exposure to simulated intestinal fluid. Chitosan-coated niosomes exhibited higher absorption in the duodenum. Moreover, photomicrographs revealed that UA niosomes with a chitosan layer were highly accumulated in the liver 4 h after oral administration. A biodistribution study revealed that chitosan coating increased the plasma concentration of UA and selective hepatic accumulation. Thus, the chitosan layer successfully improved the oral absorption of UA niosomes, providing potential uses of nanoparticles for improving drugs’ bioavailability.