Development of a Mucoadhesive and In Situ Gelling Formulation Based on κ-Carrageenan for Application on Oral Mucosa and Esophagus Walls. I. A Functional In Vitro Characterization.

Oral mucositis and esophagitis represent the most frequent and clinically significant complications of cytoreductive chemotherapy and radiotherapy, which severely compromise the patient quality of life. The local application of polymeric gels could protect the injured tissues, alleviating the most painful symptoms. The present work aims at developing in situ gelling formulations for the treatment of oral mucositis and esophagitis. To reach these targets, κ-carrageenan (κ-CG) was selected as a polymer having wound healing properties and able to gelify in the presence of saliva ions, while hydroxypropyl cellulose (HPC) was used to improve the mucoadhesive properties of the formulations. CaCl₂ was identified as a salt able to enhance the interaction between κ-CG and saliva ions. Different salt and polymer concentrations were investigated in order to obtain a formulation having the following features: (i) low viscosity at room temperature to facilitate administration, (ii) marked elastic properties at 37 °C, functional to a protective action towards damaged tissues, and (iii) mucoadhesive properties. Prototypes characterized by different κ-CG, HPC, and CaCl₂ concentrations were subjected to a thorough rheological characterization and to in vitro mucoadhesion and washability tests. The overall results pointed out the ability of the developed formulations to produce a gel able to interact with saliva ions and to adhere to the biological substrates.