Aim: The purpose of this study was to develop a novel thiolated starch polymer with improved mucoadhesive properties by conjugation of cysteamine to starch as a natural polymer of restricted mucoadhesive properties.
Methods: Aldehyde substructures were integrated into starch via oxidative cleavage of vicinal diols by increasing amounts of sodium periodate followed by covalent attachment of cysteamine to oxidized starch via reductive amination. Thiol groups were quantified via Ellman's reaction and their impact on mucoadhesion was analyzed by rheological investigations, the rotating cylinder method and tensile studies on porcine mucosa.
Results: The total amount of immobilized thiol groups revealed a correlation between degree of oxidation and thiolation. Modified starch demonstrated an up to 1.66-fold increase in water uptake in comparison to native starch. Modification of starch resulted in greatly improved cohesive properties and improvement in mucoadhesion. Rheological investigations revealed a 2- to 4-fold rise in viscosity of mucus. Tensile studies revealed a linear correlation between degree of oxidation/thiolation and enhancement of maximum detachment force and total work adhesion.
Conclusion: In terms of these results, thiolated starch is a new, promising, polymer in the field of mucoadhesive drug delivery systems.
Keywords: Mucoadhesion; Mucoadhesive polysaccharide; Oxidized starch; Starch derivatives; Thiomer.
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