Thiolated Cellulose: A Dual-Acting Mucoadhesive and Permeation-Enhancing Polymer

This study aims to design an anionic, thiolated cellulose derivative and to evaluate its mucoadhesive and permeation-enhancing properties utilizing enoxaparin as a model drug. 2-Mercaptosuccinic acid-modified cellulose (cellulose–mercaptosuccinate) was synthesized by the reaction of cellulose with S-acetylmercapto­succinic anhydride. The chemical structure of the target compound was confirmed by FTIR and 1H NMR spectroscopy. The thiol content was determined by Ellman’s test. The conjugate exhibited 215.5 ± 25 μmol/g of thiol groups and 84 ± 16 μmol/g of disulfide bonds. Because of thiolation, mucoadhesion on porcine intestinal mucosa was 9.6-fold enhanced. The apparent permeability (P app) of the model dye Lucifer yellow was up to 2.2-fold improved by 0.5% cellulose–mercaptosuccinate on a Caco-2 cell monolayer. Enoxaparin permeation through rat intestinal mucosa increased 2.4-fold in the presence of 0.5% cellulose–mercaptosuccinate compared with the drug in buffer only. In vivo studies in rats showed an oral bioavailability of 8.98% using cellulose–mercaptosuccinate, which was 12.5-fold higher than that of the aqueous solution of the drug. Results of this study show that the modification of cellulose with 2-mercaptosuccinic acid provides mucoadhesive and permeation-enhancing properties, making this thiolated polymer an attractive excipient for oral drug delivery.