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The aim of this study was the synthesis and in vitro characterization of aminated cellulose as alternative excipient to chitosan. The aldehyde form of cellulose was generated via the oxidative cleavage of vicinal diols by the addition of increasing concentrations of sodium periodate. The insertion of primary amines was achieved by reductive amination with ammonia. The degree of substitution was calculated via primary amino group quantification using a 2,4,6-trinitrobenzenesulfonic acid assay. Mucoadhesiveness was examined by adopting the rotating-cylinder method and tensile studies using porcine intestinal mucosa. Hydration was evaluated at pH 2-11. The successful formation of aldehydes as well as a subsequent introduction of up to 311.61 micromoles per gram of primary amines were proven to correlate with the amount of added periodate. There was a 3- to 14-fold prolongation in the mucosal residence time of the new polymer in comparison to chitosan, as measured by the rotating-cylinder method. Although cationic cellulose did not reach the maximum detachment force of chitosan, the total work of adhesion of the newly synthesized cellulose derivate was higher than that of chitosan. The higher the degree of amination, the higher the degree of hydration in neutral and alkaline aqueous media was. Compared to chitosan, the novel cationic cellulose derivative displays improved mucoadhesive properties as well as sufficient hydration at physiological pH. Therefore, aminated cellulose is a promising alternative to the cationic polymers, such as chitosan, used thus far.

Background: For the development of novel buccoadhesive formulations, their physicochemical properties, strength of the interfacial joint, and residence time on the buccal mucosa are considered as a measure for their in vivo mucoadhesive properties. Focusing on these parameters, the predictive power of established in vitro systems was assessed for mucoadhesive properties in humans using discs as the model solid dosage form. Methods: Compressed into discs, hydroxyethyl cellulose, carboxymethyl cellulose, carbopol, polycarbophil, alginate, and xanthan gum were used as model polymers. Mucosal residence time, maximum detachment force (MDF), and total work of adhesion (TWA) were determined ex vivo on the porcine buccal mucosa and in vivo on healthy volunteers. The impact of detachment velocity, humidification, and experimental set-up employed for tensile studies was examined and correlated to in vivo studies. Results: Ex vivo results for mucosal residence time showed a very high correlation (r = 0.997) with data obtained in vivo. For tensile studies, a set-up optimized for moistening the interface, speed, and alignment of the tensile force provided ex vivo results with very high correlation to in vivo experiments with r = 0.983 obtained for MDF and r = 0.973 for TWA, respectively. Conclusions: Experimental set-ups for the determination of mucosal residence time and tensile studies could be identified as valid methods for the development of intraoral solid dosage forms.

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