Development and evaluation of colon-specific releasing nanoemulsion / hydrogel pellets of camptothecin

Camptothecin-loaded nanoemulsion (CPT/NE), sodium alginate, carbomer, and calcium chloride were chosen to prepare camptothecin-loaded nanoemulsion / hydrogel (CPT/NE/HG) pellets. The optimal formulation of CPT/NE/HG pellets was composed of a mixture of the CPT/NE to hydrogel (1 : 1, w/w) followed by solidification with 15.0% CaCl2 solution, and the hydrogel consisted of a mass ratio of 1 : 1 of sodium alginate (1.92%, w/v) and carbomer 934P (2.20%, w/v). The reconstitution of pellets showed that there were nanoemulsions, microemulsions, or mixed micelles existing together in simulated colonic fluid (SCF). The camptothecin released from the CPT/NE/HG pellets was less than 20% in simulated gastric fluid while more than 40% loaded camptothecin was released in SCF, and the release process was confirmed to be first-order kinetics. The in vivo imaging indicated that the CPT/NE/ HG pellets were firstly aggregated in the stomach while most pellets were destructed after reaching the colon. The inhibitory effect of CPT/NE/HG pellets on LoVo cell growth was significantly stronger than that of the CPT solution.