"chemical Modification of Hyaluronic Acid: Alkylation"

Hydrophobically modified (HM) water-soluble polymers, e.g. cellulose, starch or guar exhibit enhanced solution viscosity and unique rheological behaviour. These properties are explained in terms of intermolecular hydrophobic associations [1]. The general solution viscosity behavior of HM polymers of different hydrophobic chain length (moth frequently in the range of C8 to C24) is characterized by the peak viscosity region observed for a certain alkyl group content (between 1 to 5 wt. %). After reaching the maximum increase in viscosity (peak region) at a certain hydrophobic level, the viscosity dramatically decreases with increasing number of the hydrophobic moieties on the polymer chain. The monomer unit of HA consists of N-acetyl-Dglucosamine and D-glucuronic acid bonded via β(1→3) and β(1→4) interglycosidic bonds [2]. In general, alkzlation of cellulosic derivatives proceeds via corresponding alcoholates. Dialkyl sulfates are not suitable due to their toxicity and carcinogenity. Preparation of alkyl-modified HA chains therefore was achieved upon the alkylation with alkyl halides. In both procedures the selectivity in the attachment of the alkyl chain is limited. The aim of this study was to prepare and characterize physico-chemical properties of aqueous solutions of hydrophobically modified hyaluronic acid derivatives (FM HA).