Comparative in vivo mucoadhesion studies of thiomer formulations using magnetic resonance imaging and fluorescence detection.

The aim of this study was to compare different oral delivery systems based on the thiolated polymer polycarbophil-cysteine (PCP-Cys) and to provide evidence for the validity of the hypothesis that unhydrated polymers provide better mucoadhesion in vivo. To achieve dry polymer application, a new, experimental dosage form named Eutex (made of Eudragit L100-55 and latex) capsule has been developed. Magnetic resonance imaging was used to localize the point of release of the thiolated polymer from the application forms via the positive magnetic resonance signal from a gadolinium complex (Gd-DTPA). In vivo mucoadhesion was determined by ascertaining the residence time of the fluorescence-tagged thiomer on intestinal mucosa after 3 h. Results showed that in comparison to conventional application forms the Eutex capsules led to 1.9-fold higher mucoadhesive properties of PCP-Cys when compared to application with a conventional enteric-coated capsule, and to 1.4-fold higher mucoadhesion when compared to administration with an enteric-coated tablet of the thiomer. The findings of this study should contribute to the understanding of mucoadhesion and mucoadhesion influencing parameters in vivo and should therefore be of considerable interest for the development of future mucoadhesive oral drug delivery dosage forms.