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Mucoadhesive liposomes for vaginal therapy: Chitosan vs pectin

Mucoadhesive drug delivery systems provide enhanced retention at defined sites, including vagina, longer residence time of delivery system-associated drug, offer potential for targeting to particular tissue, and, if with controlled release features, may lead to the reduction in administration frequency and comparable reduction in treatment cost. At the macroscale, vaginal mucus behaves as a non-Newtonian fluid, whereas at the nanoscale, it behaves as a low viscosity flui . One of the very important features, often neglected in the development of delivery systems for vaginal administration, is microviscosity of mucus. In order to optimize mucoadhesive delivery systems for vaginal therapy, in respect to their residence time and stability in vaginal environment, we focused on the properties of mucoadhesive polymer used in delivery system. Chitosan and pectin, two natural origin polymers, were selected due to their confirmed mucoadhesiveness. Both polymers appear in different molecular weights and degrees of deacetylation/metoxylation (DD/DM) which affect their physicochemical properties and are expected to affect mucoadhesiveness of the delivery system. Metronidazole was used as model drug and was entrapped in phosphatidylcoline (PC) liposomes of various sizes. Particle size distributions, entrapment efficiency, stability in simulated vaginal fluid and mucoadhesiveness were determined and compared. PC liposomes of various sizes, containing either chitosan or pectin were found to have higher entrapment efficiency of metronidazole than non-modified PC liposomes. The vesicle size was affected by the presence of mucoadhesive polymer on /in vesicles. Polymer-containing vesicles were larger and more prone to aggregation. Although we could not see difference in vesicle size or entrapment efficiency for vesicles containing chitosan of various molecular weights and DD, for pectin containing vesicles the effect of DM was observed. The stability of the different types of liposomes in simulated vaginal fluid mucoadhesiveness confirmed that polymer type affects vesicle properties. Optimization of chito an- and pectin-containing will be discussed.

Mucoadhesion; Vaginal therapy; Liposomes; Chitosan; Pectin

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