Abstract
A carboxymethyl derivative of scleroglucan (Scl-CM) with a 65±5% carboxylic group degree of derivatization (DD) was recently synthesized and characterized. Aqueous solutions of the polymer underwent to a sharp transition toward a gel like behaviour in the presence of divalent ions such as Ca+2. Physical hydrogels with different Scl-CM/Ca+2 ratios were prepared and characterized for their rheological behaviour. Their potential as drug delivery systems was also evaluated. To this end three non steroidal anti-inflammatory drugs (NSAIDs) were loaded into the hydrogels obtained with 2% w/v solution of Scl-CM and 0.05 and 0.1 M CaCl2. The release rate of the drugs was critically related to the salt concentration. By an appropriate combination of the hydrogels prepared using different amounts of salt, it was possible to obtain a system able to release diclofenac with zero-order kinetics. Primary skin irritation tests showed a good biocompatibility of the new polymer, as well as of its hydrogels. These results suggest a potential of the new hydrogels for the development of modified delivery systems in topical formulations.
Highlights
Polysaccharides and their derivatives represent a class of polymers widely used in pharmaceutical formulations
Scleroglucan is a neutral homopolysaccharide that can be modified by reaction with choloroacetic acid in basic media as previously reported [11,13]
Experiments performed in medium at pH=5.5, miming skin conditions, showed a release rate only slightly slower than that obtained in phosphate buffer (PB) solution, as already reported for acyclovir [11]
Summary
Polysaccharides and their derivatives represent a class of polymers widely used in pharmaceutical formulations. In particular they find employment as starting materials for the preparation of hydrogels, three-dimensional networks able to retain large amounts of water or biological fluids. As a consequence, these systems show a consistence very similar to natural living tissues that allows their use for several biomedical applications [1,2,3,4]. It consists of a backbone of (1→3)-β-linked glucose residues substituted with single (1→6)-β-D-glucopyranosyl residues on every third backbone unit. The controlled oxidation of Scl produces the opening of the glucose in the side chain with the formation of the aldehyde derivative [8] that can be further oxidized to the corresponding carboxylic acid (Sclerox)
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