Developement of mucoadhesive polymer-coated liposomes for hydration of the oral mucosa

Abstract

Dry mucus in the oral cavity is uncomfortable for patients and can lead to other additional illnesses. Reduced or absence of saliva secretion, caused by the diseases, side effects of drugs, aging, or radiotherapy, can result in issues related to xerostomia and dental health. A system that could contribute to increased hydration of the mucus would reduce the discomfort for the patient. In addition, it would prevent the additional issues related to dry mucus. Liposomes and polymer-coated liposomes are proposed as promising systems for local application in the oral cavity. By using mucoadhesive polymers the residence time of the system at the site of administration in the oral cavity can be prolonged.

The overall aim of this thesis was to prepare and characterise different polymer-coated liposomes and investigate the correlation between the mucoadhesive and potential hydrating properties of the liposomal formulations. Firstly, the polymer concentration necessary for complete coating of positively charged EggPC-DOTAP liposomes was determined using negatively charged pectins (HM-, LM-, and AM-pectin). Negatively charged EggPC-EggPG liposomes were coated with chitosan. The determination of the optimal polymer concentrations was based on the measurements of changes in the size and size distribution, transmittance, and zeta potentials. The stability of the samples was followed for a period of 7 weeks. Also, a method using a Dynamic Vapour Sorption (DVS) Intrinsic instrument based on the dynamic sorption/desorption of water and the change in the mass was developed. Mucin from bovine submaxillary glands in phosphate buffer pH 6.8 was used as model for mucosa in this method, and was dried at room temperature in the aluminium pans. The liposomal formulations obtained from the first part of the study was analysed by the newly developed method. In addition the mucoadhesive properties of the formulations were estimated based on the interaction between the liposomal formulations and mucin in solution.

The DVS Intrinsic method showed potential in investigation of hydration abilities. However, there is still a need for more tuning of the instrument to be able to fully investigate the correlation