Synthesis and Characterization of a Cationic Thiomer Based on Ethyl Cellulose for Realization of Mucoadhesive Tablets and Nanoparticles

PURPOSE: Ethyl cellulose (EC) based nanoparticles are being extensively studied for their ability to achieve prolonged drug release and improve drug stability. Within this study, the thiolation of unmodified EC using cysteamine as a ligand was carried out to design nanoparticles with mucoadhesive properties and comparatively strong lipophilic properties. METHODS: The thiolation was performed via oxidation and reductive amination, whereas the nanoparticles were generated via the ionic gelation followed by the precipitation method. RESULTS: The number of free thiol groups on EC-cysteamine was in the range of 210–261 µmol per gram of polymer. Tablets based on EC-cysteamine demonstrated mucoadhesive properties 16.7-fold improved compared with those comprising unmodified EC. The mean diameter of the particles was in the range of 94–123 nm and the zeta potential was determined to be −7.97 to −14.70 mV. The nanoparticles remained attached to porcine intestinal mucosa for up to 36% after 3 h of incubation. The formation of nanoparticles improved the stability of EC-cysteamine conjugate against cellulase and provided a zero-order release. Moreover, both EC-cysteamine and the nanoparticles did not show any pronounced cytotoxicity. CONCLUSION: Accordingly, EC-cysteamine nanoparticles could be a specific type of nanoparticulate delivery system with mucoadhesive properties. The amount of free thiol groups within EC-cysteamine nanoparticles together with their lipophilic properties could be further modified and modulated for a desired release behavior.