*5.5. Ex Vivo Permeation Study*

An earlier study performed by El-Samaligy et al., in 2006, proposed that silymarin liposomal buccal delivery showed steady-state permeation through a chicken buccal mucosa for 6 hrs, and was higher than free drug powder. Hence, the drug permeation study was carried out through chicken buccal mucosa using a Franz diffusion cell. The chicken buccal mucosa was surgically removed from the underlying muscular layer by cutting the loose connective fibers, then cleaned from surface fats and washed with isotonic phosphate buffer at pH 6.8. The buccal mucosa, with the mucosal surface facing up, was placed between the donor and receptor compartments. The receptor compartment was filled with phosphate buffer (pH 6.8) and the diffusion cells were placed on hot plate-multiple magnetic stirrers at 37 ◦C and 150 rpm for 3 h. Samples were withdrawn at different intervals, filtered and replaced by fresh PB, and analyzed spectrophotometrically at wavelength 287 nm. The investigations were carried out in triplicate, and the standard deviation (SD) was determined [18,34].

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/gels9020139/s1, Table S1: Composition of formulated silymarin mucoadhesive gel.

**Author Contributions:** Conceptualization, D.C.V., V.R. and M.K.; data curation, R.D.S., Y.M. and S.S.; formal analysis, R.D.S., S.M., S.S. and M.K.; investigation, D.C.V., R.D.S., Y.M. and M.K.; methodology, D.C.V. and R.D.S.; project administration, V.R. and M.K.; resources, S.M.; software, S.M.; supervision, V.R. and M.K.; validation, V.R.; writing—original draft, D.C.V., R.D.S. and Y.M.; writing—review and editing, V.R. and M.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Data Availability Statement:** The data associated with the manuscript are available from the first and corresponding authors.

**Acknowledgments:** The authors would like to thank Microlabs Pvt. Ltd., Bangalore and Serum Institute of India Pvt Ltd., Pune for providing silymarin.

**Conflicts of Interest:** The authors declare no conflict of interest.
